Cavitation energies can outperform dispersion interactions.

The accurate dissection of binding energies into their microscopic components is challenging, especially in solution. Here we study the binding of noble gases (He-Xe) with the macrocyclic receptor cucurbit[5]uril in water by displacement of methane and ethane as H NMR probes. We dissect the hydration free energies of the noble gases into an attractive dispersive component and a repulsive one for formation of a cavity in water.

Covalent Co-O-V and Sb-N Bonds Enable Polyoxovanadate Charge Control.

The formation of [{Co(teta)}{Co(tren)(teta)}VSbO(HO)]·ca.9HO [teta = triethylenetetraamine; tren = tris(2-aminoethyl)amine] illustrates a strategy toward reducing the molecular charge of polyoxovanadates, a key challenge in their use as components in single-molecule electronics. Here, a V-O-Co bond to a binuclear Co-centered complex and a Sb-N bond to the terminal N atom of a teta ligand of a mononuclear Co complex allow for full charge compensation of the archetypal molecular magnet [VSbO(HO)].

Group 10-group 14 metal complexes [E-TM](IV): the role of the group 14 site as an L, X and Z-type ligand.

A series of new complexes of a general motif [R2E(μ-N,S)2TM-L] (E: metalloid group 14 element; TM: group 10 metal; R: Cl, Ph, pyS, OH, (N,N,O)-chelating ligands; N,S: 1-methylimidazole-2-thiolate (methimazolyl, mt(-)), pyridine-2-thiolate (pyS(-)); L: PPh3, PCy3, pyS) was synthesised and characterised by single-crystal X-ray diffraction, multi-nuclear NMR spectroscopy ((1)H, (13)C, (31)P, (119)Sn), (119)Sn Mössbauer spectroscopy and quantum chemical calculations. The E-TM bonding situation in these compounds can be described with various resonance structures which comprise E(ii)→TM(ii), E(iii)-TM(i) and E(iv)←TM(0) features. Thus, in these complexes the atoms of the group 14 based ligand sites reveal L-, X- and Z-type ligand characteristics.

Metallophilic Contacts in 2-C6F4PPh2 Bridged Heterobinuclear Complexes: A Crystallographic and Computational Study.

Treatment of the bis(chelate) complex trans-[Pd(κ(2)-2-C6F4PPh2)2] (7) with PMe3 gave trans-[Pd(κC-2-C6F4PPh2)2(PMe3)2] (13) as a mixture of syn- and anti-isomers. Reaction of 13 with CuCl, AgCl, or [AuCl(tht)] (tht = tetrahydrothiophene) gave the heterobinuclear complexes [(Me3P)2Pd(μ-2-C6F4PPh2)2MCl] [M = Cu (14), Ag (15), Au (16)], from which the corresponding salts [(Me3P)2Pd(μ-2-C6F4PPh2)2M]PF6 [M = Cu (17), Ag (18), Au (19)] could be prepared by abstraction of the chloro ligand with TlPF6; 18, as well as its triflato (20) and trifluoroacetato (21) analogues, were also prepared directly from 13 and the appropriate silver salt. Reaction of 13 with [AuCl(PMe3)] gave the zwitterionic complex [(Me3P)PdCl(μ-2-C6F4PPh2)2Au] (24) in which the 2-C6F4PPh2 ligands are in a head-to-head arrangement.

Pyridine-2-thiolate bridged tin-palladium complexes with Sn(PdN2Cl2), Sn(PdN2S2), Sn(PdN2C2) and Sn(Pd2N4) skeletons.

Reactions of tin(IV) complexes of the type Sn(PyS)2X2 (X = Cl, PyS, Ph; PyS = pyridine-2-thiolate) with Pd(PPh3)4 provide easy access to novel heterometallic complexes with Pd-Sn bonds. Electronic characteristics of this connection were analysed by X-ray crystallography, (119)Sn Mössbauer spectroscopy and quantum chemical analyses.

DFTB Parameters for the Periodic Table: Part 1, Electronic Structure.

A parametrization scheme for the electronic part of the density-functional based tight-binding (DFTB) method that covers the periodic table is presented. A semiautomatic parametrization scheme has been developed that uses Kohn-Sham energies and band structure curvatures of real and fictitious homoatomic crystal structures as reference data. A confinement potential is used to tighten the Kohn-Sham orbitals, which includes two free parameters that are used to optimize the performance of the method.

Disilicon complexes with two hexacoordinate Si atoms: paddlewheel-shaped isomers with (ClN4 )Si-Si(S4 Cl) and (ClN2 S2 )Si-Si(S2 N2 Cl) skeletons.

The reaction of 1-methyl-3-trimethylsilylimidazoline-2-thione with hexachlorodisilane proceeds toward substitution of four of the disilane Cl atoms during the formation of disilicon complexes with two neighboring hexacoordinate Si atoms. The N,S-bidentate methimazolide moieties adopt a buttressing role, thus forming paddlewheel-shaped complexes of the type ClSi(μ-mt)4 SiCl (mt=methimazolyl). Most interestingly, three isomers (i.

Phosphorus(V) complexes with acyclic monoaminocarbene ligands via oxidative addition.

(Difluoroorganyl)dimethylamines, RCF2NMe2 (R = H, Ph, tBu), can be used as carbene precursors for phosphorus trifluoride in an oxidative addition reaction. By this method, complexes of sterically nondemanding asymmetric and acyclic carbenes were obtained that are otherwise not accessible.

MFU-4 -- a metal-organic framework for highly effective H(2)/D(2) separation.

The metal-organic framework, MFU-4, possessing small cavities and apertures, is exploited for quantum sieving of hydrogen isotopes. Quantum mechanically, a molecule confined in a small cavity shows an increase in effective size depending on the particle mass, which leads to a faster deuterium adsorption from a H(2)/D(2) isotope mixture.

Ylenes in the M(II)→Si(IV) (M=Si, Ge, Sn) coordination mode.

The reaction of the methimazolyl (mt, i.e., 2-mercapto-1-methylimidazolide) substituted silane Si(mt)(4) with SnCl(2) and GeCl(2) in dioxane affords the paddlewheel-shaped complexes [ClSi(μ-mt)(4)MCl] (M=Sn (1) and Ge (2), respectively).

Hydrogen sieving and storage in fullerene intercalated graphite.

The geometrical properties of recently synthesised C60 intercalated in graphite have been confirmed by density-functional-based computer simulations. The capability of this material to store molecular hydrogen by physisorption is evaluated. While the material can sieve H2 from heavier molecular gases, our free energy calculations indicate that further tuning of the system by reducing the amount of intercalated fullerene cages is necessary to achieve H2 loadings which are interesting for technical applications.

C28 fullerites-structure, electronic properties and intercalates.

Mechanical and electronic properties of hypothetical carbon nanostructures, on the basis of C28 building blocks, hyperdiamond and hyperlonsdaleite, have been investigated with DFT based methods. The low mass density and large internal surface suggest applications as catalyst, nanosieve and gas storage material. We estimate the active volume accessible by H2.

An Efficient a Posteriori Treatment for Dispersion Interaction in Density-Functional-Based Tight Binding.

The performance of density functional theory (DFT) (VWN-LDA, PBE-GGA, and B3LYP hybrid functionals), density-functional-based tight binding (DFTB), and ab initio methods [HF, MP2, CCSD, and CCSD(T)] for the treatment of London dispersion is investigated. Although highly correlated ab initio methods are capable of describing this phenomenon, if they are used with rather large basis sets, DFT methods are found to be inadequate for the description of H2/PAH (polycyclic aromatic hydrocarbon) interactions. As an alternative approach, an a posteriori addition of a van der Waals term to DFTB is proposed.

Graphene nanostructures as tunable storage media for molecular hydrogen.

Many methods have been proposed for efficient storage of molecular hydrogen for fuel cell applications. However, despite intense research efforts, the twin U.S.