The reasons for the unusually small Bi−Te−Bi bond angle of 86.6° observed in the crystal strucure of (Et2Bi)2Te are investigated by quantum chemical calculations. With the help of coupled cluster theory at the CCSD(T) level it is demonstrated that the structure of an isolated monomer should have a bond angle larger than 90°, despite a Bi−Bi distance in good agreement with the value of 4.09 Å found in the crystal structure. The discrepancy is resolved by a lengthening of the Bi−Te bond in the crystal, which is shown to be caused by partial electron transfer from neighbouring molecules to the Bi−Te σ* orbital. Through symmetry-adapted perturbation theory at the DFT-SAPT level it is shown that London dispersion interactions are highly important for the packing of molecules in the solid state and, in turn, for the small Bi−Te−Bi bond angle. © 2022 The Authors. ChemPlusChem published by Wiley-VCH GmbH.

Five peri-substituted naphthalene and acenaphthalene complexes (Ph2Pn)2Naph (E=Sb 1, Bi 3), (Ph2Sb)2Acenaph (2), (Ph2Bi)(Me3Sn)Naph (4) and (PhBiNaph)2 (5) were synthesized and characterized in solution (1H, 13C NMR, IR) and in the solid-state (sc-XRD). 1–5 show different types of noncovalent intermolecular interactions in the solid-state including Naph−H⋅⋅⋅π, π⋅⋅⋅π and Bi⋅⋅⋅π (5) contacts, which were exemplarily (5) quantified by use of density functional theory and local coupled cluster electronic structure theory calculations, demonstrating that the Bi⋅⋅⋅π contact provides the main stabilizing contribution. Symmetry-adapted intermolecular perturbation theory calculations showed that this and other contacts are dominated by London dispersion interactions. © 2021 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH

We present the reaction of a tris(pyrazolyl) beryllium scorpionate (TpBe) complex with a weakly coordinating anion (WCA), which yields the heteroleptic complex TpBeOC(CF3)3 1 (TpBeORF). The product 1 has been characterized by multinuclear NMR spectroscopy (1H, 9Be, 13C) and single-crystal X-ray diffraction (scXRD). Quantum chemical calculations (DFT, NPA, LOL) were performed to study the bonding nature in 1. © 2020 Walter de Gruyter GmbH, Berlin/Boston 2020.

Apart from fair dealing for the purposes of research for non-commercial purposes or for private study, criticism or review, as permitted under the Copyright, Designs and Patents Act 1988 and the Copyright and Related Rights Regulations 2003, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry or the copyright owner, or in the case of reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the address printed on this page. Whilst this material has been produced with all due care, The Royal Society of Chemistry cannot be held responsible or liable for its accuracy and completeness, nor for any consequences arising from any errors or the use of the information contained in this publication. The publication of advertisements does not constitute any endorsement by The Royal Society of Chemistry or Authors of any products advertised. The views and opinions advanced by contributors do not necessarily reflect those of The Royal Society of Chemistry which shall not be liable for any resulting loss or damage arising as a result of reliance upon this material. © Janos Angyan, John Dobson, Georg Jansen and Tim Gould 2020.

A new strategy for controlling the liquid crystalline and photophysical properties of supramolecular mesogens assembled via halogen bonding is reported. Changing the degree of fluorination at the halogen-bond donor of the supramolecular liquid crystal allows for the fine-tuning of the halogen bond strength and thereby provides control over the temperature range of the mesophase. At least three fluorine atoms have to be present to ensure efficient polarization of the halogen-bond donor and the formation of a mesophase. In addition, it was found that stilbazole acceptors are superior to their azopyridine counterparts in promoting stable liquid crystalline phases. The halogen-bond-driven supramolecular liquid crystals between fluorinated azobenzenes and stilbazole/azopyridine acceptors show a rich variety of photoinduced processes driven by azobenzene photoisomerization, dictated not only by the photochemical properties of the molecular components but also by the difference between the operation temperature and the clearing point. © 2019 American Chemical Society.

Symmetry Adapted Perturbation Theory (SAPT) has become an important tool when predicting and analyzing intermolecular interactions. Unfortunately, Density Functional Theory (DFT)-SAPT, which uses DFT for the underlying monomers, has some arbitrariness concerning the exchange-correlation potential and the exchange-correlation kernel involved. By using ab initio Brueckner Doubles densities and constructing Kohn-Sham orbitals via the Zhao-Morrison-Parr (ZMP) method, we are able to lift the dependence of DFT-SAPT on DFT exchange-correlation potential models in first order. This way, we can compute the monomers at the coupled-cluster level of theory and utilize SAPT for the intermolecular interaction energy. The resulting ZMP-SAPT approach is tested for small dimer systems involving rare gas atoms, cations, and anions and shown to compare well with the Tang-Toennies model and coupled cluster results. © 2019 Author(s).

Triggered by the observation of a short Bi⋯Bi distance and a BiTeBi bond angle of only 86.6° in the crystal structure of bis(diethylbismuthanyl)tellurane quantum chemical computations on interactions between neighboring Bi atoms in Te(BiR2)2 molecules (R = H, Me, Et) and in (BiH3)2 were undertaken. Bi⋯Bi distances atoms were found to significantly shorten upon inclusion of the d shells of the heavy metal atoms into the electron correlation treatment, and it was confirmed that interaction energies from spin component-scaled second-order Møller–Plesset theory (SCS-MP2) agree well with coupled-cluster singles and doubles theory including perturbative triples (CCSD(T)). Density functional theory-based symmetry-adapted perturbation theory (DFT-SAPT) was used to study the anisotropy of the interplay of dispersion attraction and steric repulsion between the Bi atoms. Finally, geometries and relative stabilities of syn–syn and syn–anti conformers of Te(BiR2)2 (R = H, Me, Et) and interconversion barriers between them were computed. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

In this communication we report the synthesis and characterisation of a novel dianionic compound with aggregation-induced emission properties. This compound was able to recognize spermine via a multivalent electrostatic interaction leading to a restriction of intramolecular rotation enhancing the fluorescence emission. This recognition was investigated in detail using UV-Vis and fluorescence spectroscopy. Furthermore the binding stoichiometry was determined via isothermal titration calorimetry. Besides that the structure of the compound was confirmed by X-ray crystallography. To proof the bivalent binding a singly negatively charged control compound was synthesized showing no specific interaction with the amines screened. Theoretical calculations were performed to get a deeper insight in the molecular structure and the electronic transitions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Spontaneous ion separation of the scorpionate beryllium complex, TpBeI 1 (Tp = 1-trispyrazolylborate), occurs upon treatment with THF, yielding [TpBe(thf)]I 2, which was characterized by heteronuclear NMR spectroscopy (1H, 9Be, 13C) and structurally characterized by single crystal X-ray diffraction. 2 represents a rare example of a structurally characterized monocationic beryllium complex, and to the best of our knowledge, the synthesis of 2 by a solvent-induced ion separation has previously only been observed in the reactions of beryllium dihalides with strong Lewis bases. © 2018 The Royal Society of Chemistry.

A simple model for the study of London dispersion interactions is introduced: two spherical boxes, uniformly charged on their surfaces and each containing a freely moving charged particle. The model, also denominated as “interacting quantum balls” model, is applied to calculate the first three dispersion coefficients involving the ground and several excited s states, where dispersion interactions are the only contribution to the interaction energy. Already the first excited symmetric (1 s- 2 s) + state has a negative C6 dispersion coefficient, corresponding to long range repulsion. In general, a drastic state variation of the dispersion coefficients is observed, depending on the occurence of near-resonance excitation/disexcitation coupling. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

In this account, we describe the synthesis of a series of BINOL-based bis- and trisphosphoric acids 11d/e/f, which commonly feature an unusual phosphoric acid monoester motif. This motif is generated by an acid-catalyzed 5-endo-dig cyclization of the 3-alkynyl-substituted BINOL precursors to give the corresponding Furan-annelated derivatives, followed by phosphorylation of the remaining phenolic alcohols. In the cyclization reaction, we observed an unexpected partial racemization in the bis- and tris-BINOL scaffolds, leading to mixtures of diastereomers that were separated and characterized spectroscopically and by X-ray crystal structure analyses. The cyclization and racemization processes were investigated both experimentally and by DFT-calculations, showing that although the cyclization proceeds faster, the barrier for the acid-catalyzed binaphthyl-racemization is only slightly higher. © 2018 American Chemical Society.

Herein we present the results of a blind challenge to quantum chemical methods in the calculation of dimerization preferences in the low temperature gas phase. The target of study was the first step of the microsolvation of furan, 2-methylfuran and 2,5-dimethylfuran with methanol. The dimers were investigated through IR spectroscopy of a supersonic jet expansion. From the measured bands, it was possible to identify a persistent hydrogen bonding OH-O motif in the predominant species. From the presence of another band, which can be attributed to an OH-π interaction, we were able to assert that the energy gap between the two types of dimers should be less than or close to 1 kJ/mol across the series. These values served as a first evaluation ruler for the 12 entries featured in the challenge. A tentative stricter evaluation of the challenge results is also carried out, combining theoretical and experimental results in order to define a smaller error bar. The process was carried out in a double-blind fashion, with both theory and experimental groups unaware of the results on the other side, with the exception of the 2,5-dimethylfuran system which was featured in an earlier publication. © 2018 Author(s).

Here we report on a novel system based on aromatic thioethers with unique luminescence properties. Fifteen different compounds were investigated in detail on their luminescence properties using UV/Vis absorption and steady-state and time-resolved luminescence spectroscopy. Excited state lifetimes as well as quantum yields were determined, and the toxicity towards HeLa cells was investigated. Besides X-ray analyses also quantum chemical calculations were performed to gain deeper insights in the unique behavior of this facile system. The studied compounds reveal remarkable fluorescence emission ranging from 437 to 588 nm as well as phosphorescence (up to 5 μs). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Protonated methane, CH5+, is not only subject to quasi-rigid vibrational motion which describes its unprotonated parent, CH4, but is dominated by large-amplitude motion even in its quantum ground state. This fluxional behavior leads to hydrogen scrambling which sensitively depends on the underlying flat potential energy surface. Yet, it is largely unknown how fluxional species, such as CH5+, respond to perturbations arising from microsolvation by weakly interacting species, such as those commonly used as tags in messenger-based vibrational action spectroscopies. Here, we construct an intermolecular interaction potential of extrapolated coupled cluster accuracy in order to investigate the microsolvation shell structure of small CH5+ center dot He-n complexes. Having explicitly demonstrated that three-body contributions are essentially negligible, our analytical CH5+ center dot center dot center dot He model potential is kept as simple as possible in order to allow for efficient use in the framework of finite-temperature path integral simulations. It is a strictly pairwise additive site-site potential without explicit angular dependence, but critically involves additional pseudo-sites in addition to the usual atom-based interaction sites. The parameterized potential is shown to accurately describe the microsolvation of all low-lying stationary points on the potential energy surface, namely the e-C-s, s-C-s, C-2v, and C-4v structures. Based on path integral Monte Carlo simulations at ultralow temperature, about 1 K, we disclose that the many-body helium density in three-dimensional space, and thus the microsolvation pattern, depends sensitively on the combination of the solute structure and the number of attached He atoms.

Aromatic ethers such as diphenyl ether (DPE) represent molecules with different docking sites for alcohols leading to competing OH-O and OH-π interactions. In a multi-spectroscopic approach in combination with quantum chemical calculations the complex of DPE with tert-butyl alcohol (t-BuOH) is investigated in the electronic ground state (S0) and the electronically excited state (S1). FTIR, microwave as well as mass- and isomer-selective IR/R2PI spectra are recorded, revealing co-existing OH-O and OH-π isomers in the S0 state. Surprisingly, they are predicted to be of almost equal stability in contrast to the previously investigated DPE-MeOH complex, where the OH-π structure is preferred by both theory and experiment. The tert-butyl group in t-BuOH allows for a simultaneous optimization of hydrogen-bonding and dispersion interactions, which provides a sensitive meeting point between theory and experiment. In the electronically excited state of DPE-t-BuOH, vibrational spectra could be recorded separately for both isomers using UV/IR/UV spectroscopy. In the S1 state the same structural binding motifs are obtained as in the S0 state with the OH-O bond being weakened for the OH-O arrangement and the OH-π interaction being strengthened in the case of the OH-π isomer compared to the S0 state. © the Owner Societies 2017.

Single deprotonation of the bis(iminophosphorano)methane ligand (PhN=PPh2)2CH2 (5-H2) with 1 equiv of p-tBu-benzylpotassium followed by reaction with zinc(II) chloride led to the formation of the homoleptic complex ((PhN=PPh2)2CH)2Zn, (5-H)2Zn. Deprotonation of 5-H2 with 2 equiv of p-tBu-benzylpotassium gave known potassium compound (5-K2)2 which reacted further with zinc(II) chloride to the dimeric carbene complex [(PhN=PPh2)2CZn]2 ((5-Zn)2). Crystal structures of (5-H)2Zn and (5-Zn)2 are compared to those of closely related Ca and Mg compounds. To analyze the charge distribution of these zinc complexes, density functional theory calculations on simple model systems were employed. Although the Zn-C bond in (5-Zn)2 is highly ionic (81%) it is significantly more covalent than that in a similar dimeric Ca carbene complex (91% ionic). © 2017 American Chemical Society.

[Ph4P]2[Be(N3)4] (1) and [PNP]2[Be(N3)4] (2; PNP=Ph3PNPPh3) were synthesized by reacting Be(N3)2 with [Ph4P]N3 and [PNP]N3. Compound 1 represents the first structurally characterized homoleptic beryllium azide. The electronic structure and bonding situation in the tetraazidoberyllate dianion [Be(N3)4]2− were investigated by quantum-chemical calculations (NPA, ELF, LOL). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Naph2Sb21 was synthesized by a reaction of 1,8-dilithionaphthalene NaphLi2 with SbCl3 and its solid state structure is reported on. 1 shows intermolecular interactions in the solid state, which were studied by quantum chemical calculations with dispersion corrected density functional theory, supermolecular ab initio approaches and symmetry adapted perturbation theory. The same methods were employed to compare the solid state interactions in the crystal of 1 to those in real (for E = P) and hypothetical (for E = As and Bi) crystal structures of Naph2E2. Dispersion interactions were found to provide the most important stabilising contribution in all cases, seconded by electrostatic attraction between pnictogen atoms and π-systems of neighbouring naphthyl groups. © 2017 The Royal Society of Chemistry.

[(MeLDippZn)2(μ-η2:η2-PhN6Ph)] (3), which was synthesized by reaction of MeLDipp 2Zn2 with PhN3, reacts with two equivalents of Me2Zn to give [(MeZn)2(μ-η2:η2-PhN6Ph)] (2). The reaction of 2 with pyridine gave [(MeZn)2(μ-η2:η2-PhN6Ph)(Py)2] (4), while reactions with H-acidic ligands (MeLMesH, MeLPhH) occurred with elimination of methane and formation of [(MeLMesZn)2(μ-η2:η2-PhN6Ph)] (1) and [(MeLPhZn)2(μ-η2:η2-PhN6Ph)] (5). The reaction of 1 with two equivalents of MeLi yielded the heterobimetallic hexazene complex [(MeZn)(μ-η2:η2-PhN6Ph)(Li)], which was found to undergo stepwise reaction with Me2AlCl to give [MeZn(μ-η2:η2-PhN6Ph)AlMe2] and finally [(Me2Al)2(μ-η2:η2-PhN6Ph)(thf)2] (6). Compounds 3-6 were characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction. Quantum chemical calculations were performed in order to investigate the electronic structure of 4′ and 6′ in more detail and to identify the absorption bands of the hexazene unit. © 2016 American Chemical Society.

Starting from the general expression for the ground state correlation energy in the adiabatic-connection fluctuation-dissipation theorem (ACFDT) framework, it is shown that the dielectric matrix formulation, which is usually applied to calculate the direct random phase approximation (dRPA) correlation energy, can be used for alternative RPA expressions including exchange effects. Within this famework, the ACFDT analog of the second order screened exchange (SOSEX) approximation leads to a logarithmic formula for the correlation energy similar to the direct RPA expression. Alternatively, the contribution of the exchange can be included in the kernel used to evaluate the response functions. In this case, the use of an approximate kernel is crucial to simplify the formalism and to obtain a correlation energy in logarithmic form. Technical details of the implementation of these methods are discussed, and it is shown that one can take advantage of density fitting or Cholesky decomposition techniques to improve the computational efficiency; a discussion on the numerical quadrature made on the frequency variable is also provided. A series of test calculations on atomic correlation energies and molecular reaction energies shows that exchange effects are instrumental for improvement over direct RPA results. © 2016 American Chemical Society.

The controlled hydrolysis of TpBeCl {Tp = trispyrazolylborate [HB(C3N2H3)3]–} with H2O and D2O in the presence of N,N-diisopropylethylamine (DIPEA) yields the trimeric beryllium hydroxide scorpionate complexes [Be3(µ-OX)3(Tp)3] (X = H: 1, D: 2) quantitatively. The complexes contain six-membered Be3O3 rings according to single-crystal X-ray diffraction studies and theoretical calculations. Temperature-dependent 1H and 9Be NMR spectroscopy established that 1 has a dynamic structure in solution. In addition, the structure of [Be3(µ-OH)3(Br)3(thf)6], which was obtained from hydrolysis of a solution of BeBr2 in tetrahydrofuran and CHCl3, is reported. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Three new data sets for intermolecular interactions, AHB21 for anion-neutral dimers, CHB6 for cation-neutral dimers, and IL16 for ion pairs, are assembled here, with complete-basis CCSD(T) results for each. These benchmarks are then used to evaluate the accuracy of the single-exchange approximation that is used for exchange energies in symmetry-adapted perturbation theory (SAPT), and the accuracy of SAPT based on wave function and density-functional descriptions of the monomers is evaluated. High-level SAPT calculations afford poor results for these data sets, and this includes the recently proposed "gold", "silver", and "bronze standards" of SAPT, namely, SAPT2+(3)-δMP2/aug-cc-pVTZ, SAPT2+/aug-cc-pVDZ, and sSAPT0/jun-cc-pVDZ, respectively [ Parker, T. M., et al., J. Chem. Phys. 2014, 140, 094106 ]. Especially poor results are obtained for symmetric shared-proton systems of the form X-···H+···X-, for X = F, Cl, or OH. For the anionic data set, the SAPT2+(CCD)-δMP2/aug-cc-pVTZ method exhibits the best performance, with a mean absolute error (MAE) of 0.3 kcal/mol and a maximum error of 0.7 kcal/mol. For the cationic data set, the highest-level SAPT method, SAPT2+3-δMP2/aug-cc-pVQZ, outperforms the rest of the SAPT methods, with a MAE of 0.2 kcal/mol and a maximum error of 0.4 kcal/mol. For the ion-pair data set, the SAPT2+3-δMP2/aug-cc-pVTZ performs the best among all SAPT methods with a MAE of 0.3 kcal/mol and a maximum error of 0.9 kcal/mol. Overall, SAPT2+3-δMP2/aug-cc-pVTZ affords a small and balanced MAE (<0.5 kcal/mol) for all three data sets, with an overall MAE of 0.4 kcal/mol. Despite the breakdown of perturbation theory for ionic systems at short-range, SAPT can still be saved given two corrections: a "δHF" correction, which requires a supermolecular Hartree-Fock calculation to incorporate polarization effects beyond second order, and a "δMP2" correction, which requires a supermolecular MP2 calculation to account for higher-order induction-dispersion coupling. These corrections serve to remove artifacts introduced by the single exchange approximation in the exchange-induction and exchange-dispersion interactions, and obviate the need for ad hoc scaling of the first- and second-order exchange energies. Finally, some density-functional and MP2-based electronic structure methods are assessed as well, and we find that the best density-functional method for computing binding energies in these data sets is B97M-V/aug-cc-pVTZ, which affords a MAE of 0.4 kcal/mol, whereas complete-basis MP2 affords an MAE of 0.3 kcal/mol. © 2015 American Chemical Society.

The solid state structure of Be[N(SiMe3)2]2 (1) was determined by in situ crystallisation and the bonding situation investigated by quantum chemical calculations. The Be-N bond is predominantly ionic, but some evidence for the presence of a partial Be-N double bond character was found. © The Royal Society of Chemistry 2015.

The zinc hexazene complex MeL<inf>2</inf>Zn<inf>2</inf>(μ-1,6-Ph<inf>2</inf>-N<inf>6</inf>) 1 (MeL = HC[C(Me)N(2,4,6-Me<inf>3</inf>C<inf>6</inf>H<inf>2</inf>)]<inf>2</inf>) is a suitable hexazene transfer reagent in reactions with main group metal and transition metal complexes containing M-Me units. The reactions proceed with elimination of MeLZnMe and the resulting complexes were characterized by NMR and IR spectroscopy and single crystal X-ray diffraction (5, 8). Quantum chemical calculations were performed to investigate the electronic structure of 5′ and 8′ in more detail and to identify the absorption bands of the hexazene unit. © 2015 The Royal Society of Chemistry.

The iodonium pseudohalide compounds, [(C6F5) 2I][X] (X = SCN and CN) were synthesized by means of fluoride substitution in [(C6F5)2I][F] with the Lewis acidic reagents (CH3)3Si-NCS and (CH3) 3Si-CN. The isolated iodonium pseudohalides are intrinsically unstable solids. Decomposition resulted in equimolar amounts of C 6F5I and C6F5SCN or C 6F5I and C6F5CN, respectively. In case of [(C6F5)2I][SCN] single crystals could be grown from CH2Cl2. The crystal structure revealed a dimer with an eight membered ring formed by two ambident anions bridging the iodine atoms of two cations by N and S coordination. The favored dimerization of [(C6F5)2I][SCN] and [(C6F 5)2I][CN] in the gas phase is supported by ab initio computations. © 2014 Published by Elsevier B.V.

Quantum chemistry applies the fundamental physical theory of quantum mechanics to the description of chemical substances and their reactions. A clear task - but not so easy to fulfill. The paper first describes a few of the aspects of quantum mechanics which may seem exotic yet form a part of the world of electrons and atomic nuclei. Then a number of basic approximations will be discussed which help us to find our way in this world. And here and there it will be indicated how this allows to develop quantum chemical methods in the form of computer programs, the results of which help to understand and predict the properties and behaviour of chemical systems. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA.

Two zinc hexazene complexes L<inf>2</inf>Zn<inf>2</inf>(μ-1,6-R <inf>2</inf>-N<inf>6</inf>) (L = HC[C(Me)N(2,4,6-Me<inf>3</inf>C <inf>6</inf>H<inf>2</inf>)]<inf>2</inf>; R = Ph (3), Dipp = 2,6-i-Pr <inf>2</inf>C<inf>6</inf>H<inf>3</inf> (4)), were synthesized by reaction of the Zn(i) complex L<inf>2</inf>Zn<inf>2</inf> (1) with phenyl azide and 2,6-diisopropylphenyl azide, respectively. 3 represents the second structurally characterized transition metal hexazene complex. In contrast, reactions of 1 with Me<inf>3</inf>MN<inf>3</inf> (M = Si, Sn) yielded the azido complex [LZn(μ-N<inf>3</inf>)]<inf>2</inf> (2) and Me<inf>3</inf>M-MMe<inf>3</inf>. © 2014 The Royal Society of Chemistry.

The combination of symmetry-adapted perturbation theory (SAPT) of intermolecular interactions with a density functional theory (DFT) description of the underlying molecular properties, known as DFT-SAPT or SAPT(DFT), is reviewed, with a focus on methodology. A theoretical formalism avoiding an overlap expansion and the single-exchange approximation for the second-order exchange contributions is presented, and ways to include higher order contributions are discussed. The influence of the exchange-correlation potential and kernel underlying any DFT-SAPT calculation will be explicated. Enhancements of the computational efficiency through density fitting are described and comparisons to coupled cluster theory and experiment benchmark the performance of the method. © 2013 John Wiley & Sons, Ltd.

Diethylstibanyl- and diethylbismuthanyl telluranes Et2MTeEt (M = Sb 1, Bi 2) as well as tBu3Sb (3) were structurally characterized by single-crystal X-ray diffraction. Single crystals of 1-3 were grown by using an IR-laser-assisted technique. Compounds 1 and 2 form short intermolecular E···Te interactions in the solid state, which were further investigated with dispersion-corrected density functional theory. Single crystals of Et2M-TeEt (M = Sb 1, Bi 2) as well as tBu3Sb (3) were grown by using an IR-laser-assisted technique. Compounds 1 and 2 form short intermolecular E···Te interactions in the solid state, which were further investigated with dispersion-corrected density functional theory. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Triethylchalcogenostiboranes Et3SbE (E = S 1, Se 2) were synthesized and their solid state structures were determined. The Sb-Se bond length is the shortest ever reported. Short Sb⋯E contacts were not observed. According to quantum chemical calculations, the bonding situation in 1 and 2 is best described as a polarized Sb-E single bond. This journal is © the Partner Organisations 2014.

In recent years, the treatment of wounds with honey has received an increasing amount of attention from healthcare professionals in Germany and Austria. We conducted a prospective observational multicentre study using Medihoney dressings in 10 hospitals nine in Germany and one in Austria. Wound-associated parameters were monitored systematically at least three times in all patients. Data derived from the treatment of 121 wounds of various aetiologies over a period of 2 years were analysed. Almost half of the patients were younger than 18 years old, and 32% of the study population was oncology patients. Overall, wound size decreased significantly during the study period and many wounds healed after relatively short time periods. Similarly, perceived pain levels decreased significantly, and the wounds showed noticeably less slough/necrosis. In general, our findings show honey to be an effective and feasible treatment option for professional wound care. In addition, our study showed a relationship between pain and slough/necrosis at the time of recruitment and during wound healing. Future comparative trials are still needed to evaluate the extent to which the positive observations made in this and other studies can definitely be attributed to the effects of honey in wound care.

It is shown that the exchange-dispersion energy contribution of symmetry-adapted intermolecular perturbation theory (SAPT) can be evaluated without invoking the single-exchange approximation in the case of single-determinant ground-state references. A succinct expression is derived which allows for efficient implementation. Making use of the corresponding exchange-induction contribution, obtained recently, this enables DFT-SAPT calculations, i.e., SAPT based on a density-functional theory description of the monomers, without an expansion in orders of the intermonomer overlap S. The approach is used to test the quality of the S 2 or single-exchange approximation for the systems He2, Ar2, N2-Ne, H2O-Ar, (H2O)2 and LiF, i.e., van der Waals and hydrogen-bridged complexes as well as an ionic molecule. While employing the S 2 approximation for the exchange-dispersion contribution is found to have minor impact on total SAPT interaction energies, its use to evaluate the exchange-induction contribution significantly affects the quality of the repulsive branches of the potential energy curves for the interacting partners. Adding appropriate Hartree-Fock level estimates of higher-order induction plus exchange-induction energies, however, restores good agreement with complete basis set limit coupled-cluster results. © 2013 Taylor and Francis Group, LLC.

Two trialkylbismuthines BiR3 (R = Me (1), i-Pr (2)) were structurally characterized by single-crystal X-ray diffraction. Single crystals were grown using an IR-laser-assisted technique. 1 forms short intermolecular Bi···Bi interactions in the solid state, which were further investigated through quantum chemical computations with ab initio coupled cluster and dispersion-corrected density functional methods. © 2013 American Chemical Society.

Coordination of a strong σ-base has been shown to be an effective method for the stabilization of low valent main group element complexes. This general method was now used for the synthesis of the divalent germanium diazide. IPrGe(N3)21 represents the first neutral homoleptic germanium diazide that could be structurally characterized. © 2013 American Chemical Society.

Isomer- and mass-selective UV and IR-UV double resonance spectra of the BA3, B2A, and B2A2 clusters of benzene (B) and acetylene (A) are presented. Cluster structures are assigned by comparison with the UV and IR spectra of benzene, the benzene dimer, as well as the BA, BA2, and B2A clusters. The intermolecular vibrations of BA are identified by dispersed fluorescence spectroscopy. Assignment of the cluster structures is supported by quantum chemical calculations of IR spectra with spin-component scaled second-order Møller-Plesset (SCS-MP2) theory. Initial propositions for various structures of the BA3 and B2A2 aggregates are generated with model potentials based on density functional theory combined with the symmetry-adapted perturbation theory (DFT-SAPT) approach. Shape and relative cluster stabilities are then confirmed with SCS-MP2. T-shaped geometries are the dominant structural motifs. Higher-energy isomers are also observed. The detected cluster structures are correlated with possible cluster formation pathways and their role as crystallization seeds is discussed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Delicate crystals: ClN3 adopts a polymeric structure in the solid state (see picture; N blue, Cl green) with short intermolecular Cl×××Cl distances, as was observed for the elemental halogen. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Here the interactions of furan with HZ (Z = CCH, CCF, CN, Cl, and F) are studied using a variety of electron correlation methods (MP2, CCSD(T), DFT-SAPT) and correlation-consistent triple- and quadruple-ζbasis sets including complete basis set (CBS) extrapolation. For Fu-HF all methods agree that a n-type structure with a hydrogen bridge between the oxygen lone-pair of furan and the hydrogen atom of HF is the global minimum structure. It is found to be significantly more stable than a πtype structure where the hydrogen atom of HF points toward the πsystem of furan. For the other four dimers MP2 and DFT-SAPT predict the π-type structure to be somewhat more stable, while CCSD(T) favors the n-type structure as the global minimum for Fu-HCl and predicts both structures as nearly isoenergetic for Fu-HCCH and Fu-HCCF. From a geometrical point of view, the Fu-HCN dimer structures are more related to those of the Fu-HCl complex than to Fu-HCCH. The different behavior of HCCF and HF upon complexation with furan evidence the effect of the presence of a π system in the aggregation of fluorine derivatives. It is shown that aggregates of furan cannot be understood by means of dipole-dipole and electrostatic analysis only. Yet, through a combined and detailed analysis of DFT-SAPT energy contributions and resonance effects on the molecular charge distributions a consistent explanation of the aggregation of furan with both πelectron rich molecules and halogen hydrides is provided. © 2012 American Chemical Society.

Two neutral group 15-pentaazides dmap-As(N 3) 5 (1) and dmap-Sb(N 3) 5 (2) were synthesized and structurally characterized for the first time (dmap = 4-dimethylaminopyridine). Base-stabilization was confirmed to be very suitable for the kinetic stabilization of highly explosive covalent main group polyazides. © 2012 American Chemical Society.

An approach to evaluate the second-order exchange-induction energies of symmetry-adapted intermolecular perturbation theory (SAPT) for single-determinant ground-state monomer wavefunctions has been derived. This approach is correct to all orders of the intermonomer overlap, that is, it takes multiple electron exchange between the monomers into account. The resulting formulae can be written in a compact way and implemented efficiently. Here, the method is employed to investigate the performance of the S 2- or single-exchange approximation at the Hartree-Fock-SAPT level. The list of test systems comprises the prototypical van der Waals- and hydrogen-bridge complexes Ne 2, Ar-HF, and (H 2O) 2, but also the systems HeCl -, NeNa + and Li +F - involving closed-shell ions. It was found that the errors introduced by the S 2-approximation are more pronounced for the second-order exchange-induction energy than for the first-order exchange energy. While these errors tend to be negligible throughout the well region of complexes such as the neon dimer, they start to be significant in the repulsive part of the well regions of systems such as the water dimer, and in particular for the ionic lithium fluoride molecule. The consequences of these findings for the Hartree-Fock level estimate of higher-order induction plus exchange-induction energies, which is frequently employed in SAPT are also discussed. © 2012 Springer-Verlag.

The interactions in the complexes of tetracyanothylene (TCNE) with benzene and p-xylene, often classified as weak electron donor-acceptor (EDA) complexes, are investigated by a range of quantum chemical methods including intermolecular perturbation theory at the DFT-SAPT (symmetry-adapted perturbation theory combined with density functional theory) level and explicitly correlated coupled-cluster theory at the CCSD(T)-F12 level. The DFT-SAPT interaction energies for TCNE-benzene and TCNE-p-xylene are estimated to be -35.7 and -44.9 kJ mol -1, respectively, at the complete basis set limit. The best estimates for the CCSD(T) interaction energy are -37.5 and -46.0 kJ mol -1, respectively. It is shown that the second-order dispersion term provides the most important attractive contribution to the interaction energy, followed by the first-order electrostatic term. The sum of second- and higher-order induction and exchange-induction energies is found to provide nearly 40 % of the total interaction energy. After addition of vibrational, rigid-rotor, and translational contributions, the computed internal energy changes on complex formation approach results from gas-phase spectrophotometry at elevated temperatures within experimental uncertainties, while the corresponding entropy changes differ substantially. Complexes of tetracyanoethylene with benzene and p-xylene (see picture), often classified as weak electron donor-acceptor complexes, are investigated by a range of quantum chemical methods including intermolecular perturbation theory at the DFT-SAPT level and explicitly correlated coupled-cluster theory at the CCSD(T)-F12 level. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In this paper we further explore and develop the quantum continuum mechanics (QCM) of Tao [Phys. Rev. Lett. 103, 086401 (2009)] with the aim of making it simpler to use in practice. Our simplifications relate to the non-interacting part of the QCM equations, and primarily refer to practical implementations in which the groundstate stress tensor is approximated by its Kohn-Sham (KS) version. We use the simplified approach to directly prove the exactness of QCM for one-electron systems via an orthonormal formulation. This proof sheds light on certain physical considerations contained in the QCM theory and their implication on QCM-based approximations. The one-electron proof then motivates an approximation to the QCM (exact under certain conditions) expanded on the wavefunctions of the KS equations. Particular attention is paid to the relationships between transitions from occupied to unoccupied KS orbitals and their approximations under the QCM. We also demonstrate the simplified QCM semianalytically on an example system. © 2012 American Institute of Physics.

A new twist: The single-crystal structural analysis of BrN 3 is described. In contrast to IN 3, which forms chains, BrN 3 forms a helical structure in the solid state (see picture). Such a structural feature has not been previously observed in covalent p-block azide chemistry. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Amidinatobismuth(III) diazides LBi(N 3) 2 {L 1 = [tBuC(NiPr) 2] (2), L 2 = [tBuC(NDipp) 2] (3, Dipp = 2,6-iPr 2-C 6H 3)} were synthesized in high yields by metathesis reactions of the corresponding halide-substituted complexes L 1BiI 2 (1) and L 2BiCl 2 with AgN 3. Compounds 1-3 were characterized by using elemental analyses, multinuclear NMR ( 1H, 13C), and IR spectroscopy as well as by using single-crystal X-ray diffraction (for 2, 3). © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tout au contraire: Both tautomeric forms of a methanetrisamidine were structurally characterized for the first time by X-ray diffraction and by ab initio calculations (see structures; gray C, red H, blue N). Their reactivity as proton acceptors and multianionic ligands was demonstrated. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We explore different variants of the random phase approximation to the correlation energy derived from closed-shell ring-diagram approximations to coupled cluster doubles theory. We implement these variants in range-separated density-functional theory, i.e., by combining the long-range random phase approximations with short-range density-functional approximations. We perform tests on the rare-gas dimers He2, Ne2, and Ar2, and on the weakly interacting molecular complexes of the S22 set of Jurečka [P. Jurečka, J. Šponer, J. Černý, and P. Hobza, Phys. Chem. Chem. Phys. 8, 1985 (2006)10.1039/b600027d]. The two best variants correspond to the ones originally proposed by Szabo and Ostlund [A. Szabo and N. S. Ostlund, J. Chem. Phys. 67, 4351 (1977)10.1063/1.434580]. With range separation, they reach mean absolute errors on the equilibrium interaction energies of the S22 set of about 0.4 kcal/mol, corresponding to mean absolute percentage errors of about 4, with the aug-cc-pVDZ basis set. © 2011 American Institute of Physics.

The infrared spectroscopy of molecules, complexes, and molecular aggregates dissolved in superfluid helium clusters, commonly called HElium NanoDroplet Isolation (HENDI) spectroscopy, is an established, powerful experimental technique for extracting high resolution ro-vibrational spectra at ultra-low temperatures. Realistic quantum simulations of such systems, in particular in cases where the solute is undergoing a chemical reaction, require accurate solute-helium potentials which are also simple enough to be efficiently evaluated over the vast number of steps required in typical Monte Carlo or molecular dynamics sampling. This precludes using global potential energy surfaces as often parameterized for small complexes in the realm of high-resolution spectroscopic investigations that, in view of the computational effort imposed, are focused on the intermolecular interaction of rigid molecules with helium. Simple Lennard-Jones-like pair potentials, on the other hand, fall short in providing the required flexibility and accuracy in order to account for chemical reactions of the solute molecule. Here, a general scheme of constructing sufficiently accurate site-site potentials for use in typical quantum simulations is presented. This scheme employs atom-based grids, accounts for local and global minima, and is applied to the special case of a HCl(H 2O)4 cluster solvated by helium. As a first step, accurate interaction energies of a helium atom with a set of representative configurations sampled from a trajectory following the dissociation of the HCl(H2O)4 cluster were computed using an efficient combination of density functional theory and symmetry-adapted perturbation theory, i.e. the DFT-SAPT approach. For each of the sampled cluster configurations, a helium atom was placed at several hundred positions distributed in space, leading to an overall number of about 400000 such quantum chemical calculations. The resulting total interaction energies, decomposed into several energetic contributions, served to fit a site-site potential, where the sites are located at the atomic positions and, additionally, pseudo-sites are distributed along the lines joining pairs of atom sites within the molecular cluster. This approach ensures that this solute-helium potential is able to describe both undissociated molecular and dissociated (zwitter-) ionic configurations, as well as the interconnecting reaction pathway without re-adjusting partial charges or other parameters depending on the particular configuration. Test calculations of the larger HCl(H2O)5 cluster interacting with helium demonstrate the transferability of the derived site-site potential. This specific potential can be readily used in quantum simulations of such HCl/water clusters in bulk helium or helium nanodroplets, whereas the underlying construction procedure can be generalized to other molecular solutes in other atomic solvents such as those encountered in rare gas matrix isolation spectroscopy. © the Owner Societies 2011.

We explore several random phase approximation (RPA) correlation energy variants within the adiabatic-connection fluctuation-dissipation theorem approach. These variants differ in the way the exchange interactions are treated. One of these variants, named dRPA-II, is original to this work and closely resembles the second-order screened exchange (SOSEX) method. We discuss and clarify the connections among different RPA formulations. We derive the spin-adapted forms of all the variants for closed-shell systems and test them on a few atomic and molecular systems with and without range separation of the electron-electron interaction. © 2011 American Chemical Society.

We study the combined effects of counterpoise correction and basis set extrapolation on the second-order Møller-Plesset (MP2) geometries of three hydrogen bonded dimers, namely (NH3)2, (H 2O)2 and (HF)2. For (NH3) 2, we study three characteristic structures on its potential energy surface. In addition, we look at the basis set convergence when diffuse functions on the hydrogen atoms are left out, as well as the errors introduced by including core correlation with valence-only correlation-consistent basis sets. Overall, the counterpoise-corrected and extrapolated geometries appear to be very reliable and are in convincing agreement with the geometries from explicitly correlated MP2-F12 calculations. Obtaining geometries with errors of less than 0.001 Ångstrom and 0.5 degrees compared to the basis set limit is, however, even with these advanced methods a difficult task. © the Owner Societies 2011.

We report the definition and refinement of a new first principles potential for the acetylene dimer. The ab initio calculations were performed with the DFT-SAPT combination of symmetry-adapted intermolecular perturbation method and density functional theory, and fitted to a model site-site functional form. Comparison of the calculated microwave spectrum with experimental data revealed that the barriers to isomerization were too low. This potential was refined by fitting the model parameters in order to reproduce the observed transitions, an excellent agreement within ∼1 MHz being achieved. © 2011 American Institute of Physics.

Synthesis of group 15-triazides E(N3)3 (E = Sb 1, Bi 2) and Py2-Bi(N3)33 (Py = pyridine). Single crystals of 1 were in situ grown by an IR-laser-assisted technique on the diffractometer. The structure of 3, which represents the first structurally characterized neutral Bi-triazide, is influenced by crystal packing effects according to DFT calculations. © 2011 The Royal Society of Chemistry.

The synthesis of antimony polyazides and structural characterization of the pentaazidoantimonite [Sb(N3)5]2- dianion, which is without precedent in Group 15 polyazide chemistry, is reported (see scheme). © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The structures of a series of decaphenyl metallocenes (Ph 5Cp)2M, which model superbulky metallocenes, are calculated by means of density functional theory including a semi-empirical correction for dispersion interactions (DFT+D). Through a detailed investigation of the calcocene it is shown that the interactions between the phenyl substituents of the two cyclopentadienyl ligands lead to a preference of S10 symmetrical structures and that dispersion interactions contribute to the overall stability of superbulky metallocenes. Whereas the Ph substituents of the two ligands bend away from each other with standard DFT, inclusion of the dispersion correction reproduces the experimentally observed slight inclination towards each other. The experimentally observed linear correlation between the out-of-plane bending angle of the phenyl substituents and the size of the metal atom M (M = Fe, Ni, Cr, W, Ca, Yb, Sn, Sm, Sr, Ba) is also confirmed at the DFT+D level. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The novel surprisingly colorful dark blue and orange-red molecular clips 1 and 2 containing a central p-benzoquinone spacer-unit and anthracene or napththalene sidewalls were synthesized by DDQ oxidation of the corresponding colorless hydroquinone clips 7 and 8. The colors of the quinone clips result from broad absorption bands in the visible range (1, λ<inf>max</inf> = 537 nm and 2, λ<inf>max</inf> = 423 and λ<inf>shoulder</inf> =515 nm) showing bathochromic shifts of 112 and 90 nm, respectively, compared to the similarly tetraalkyl-substituted duroquinone 31, even though the clips 1 and 2 only contain insulated π systems as chromophores, a central tetraalkyl-substituted p-benzoquinone spacer-unit and two anthracene or two naphthalene sidewalls. To elucidate the electronic properties of these clips, we prepared the compound 3, the anti-configured isomer of clip 2, and the benzene-, naphthalene-, and anthracene-substituted quinones 4, 5, and 6, the so-called "half-clips". The "half-clips" 6 and 5 show a similar color change and the same trend in the UV/vis absorption spectra as the anthracene and naphthalene clip 1 and 2. This finding already rules out that the color of these systems is a result of "through-space" π-π interactions between the aromatic sidewalls in the molecular clips 1 and 2. Quantum chemical ab initio calculations provide good evidence that the bathochromic shift of the absorption band at the longest wavelength observed in the UV/vis spectra of the clip quinones 2, 3, and 1 and the "half- clip" quinones 4, 5, and 6 with an increasing number of rings in the anellated aromatic unit (from benzene to anthracene) is the result of an increasing configuration interaction between a n → π* excitation of the quinoid component and a π → π* excitation with intramolecular charge transfer (CT) character. The initial π orbitals involved here and in higher lying transitions mainly stem from through-space interactions between π orbitals of the aromatic sidewalls and π orbitals of the quinone moiety with varying degree of mixing. The configuration interaction in the excited states can be considered to be a homoconjugation, that is, the relevant charge transfer states are formed across an allegedly insulating aliphatic bridge. The UV/vis spectra of the molecular clips 1-3, the "half-clips" 4-6, and the quinones 32 and 33 simulated by means of quantum chemical ab initio calculations agree well with the experimental spectra. © 2010 American Chemical Society.

The correlation energy in the direct random phase approximation (dRPA) can be written, among other possibilities, either in terms of the interaction strength averaged correlation density matrix, or in terms of the coupled cluster doubles amplitudes obtained in the direct ring approximation (drCCD). Although the corresponding dRPA correlation density matrix on the one hand, and the drCCD amplitude matrix on the other hand, differ significantly, they yield identical energies. Similarly, the analogous RPA and rCCD correlation energies calculated from antisymmetrized two-electron integrals are identical to each other despite very different underlying working equations. In the present communication, a direct correspondence between amplitudes and densities is established and investigated with perturbation theory arguments. Our analysis also sheds some light on the properties of recently proposed RPA/rCCD variants which use antisymmetrized integrals in part of the equations and nonantisymmetrized integrals in others. © 2010 American Institute of Physics.