The strength of hydrogen bonding to metal-bound ligands can contribute to changes in the redox behaviour of metal centres.

A series of nine tripodal tetradentate ligands based on tris(pyridyl-2-methyl)amine TPA with hydrogen bond donors R in one, two and three of the pyridine 6-positions (R = NH2 amino, L(Am-1,2,3); NHCH2(t)Bu neopentylamino, L(Np-1,2,3); NHCO(t)Bu pivaloylamido, L(Piv-1,2,3)) and TPA are used to investigate the effect of different hydrogen bonding microenvironments on electrochemical properties of their LCuCl complexes. The hydrogen bond donors are rigidly preorganised and suitably oriented for intramolecular N-H..

Molecular structures of the 1,6-disubstituted triptycenes Sb2(C6F4)3 and Bi2(C6F4)3 using gas-phase electron diffraction and ab initio and DFT calculations.

The structures of the D(3h)-symmetric molecules dodecafluoro-1,6-distibatriptycene and dodecafluoro-1,6-dibismatriptycene [Z2(C6F4)3 (Z = Sb, Bi)] have been determined in the gas phase by electron diffraction, using the SARACEN method, with restraints obtained from quantum chemical calculations. Several methods of ab initio and density functional theory geometry calculations have been performed and recommendations made as to their relative suitabilities for determining the structures of such species. Calculations using the MP2 method with a small-core pseudopotential (aug-cc-pVQZ-PP) on the Sb and Bi atoms and the 6-311G* basis set on the light atoms were found to give the closest correlation with the experimental results for both molecules.

An experimental and theoretical study of the molecular structure and vibrational spectra of iodotrimethylsilane (SiIMe3).

The gas-phase molecular structure of iodotrimethylsilane (ITMS) has been determined from electron diffraction data. Infrared and Raman spectra have been completely assigned. The experimental work is supported by ab initio HF and MP2 calculations for the gas-phase structure determination and DFT(B3LYP) calculations, combined with Pulay's SQM method, for the vibrational spectra data.

Molecular structures of Se(SCH3)2 and Te(SCH3)2 using gas-phase electron diffraction and ab initio and DFT geometry optimisations.

The molecular structures of Se(SCH(3))(2) and Te(SCH(3))(2) were investigated using gas-phase electron diffraction (GED) and ab initio and DFT geometry optimisations. While parameters involving H atoms were refined using flexible restraints according to the SARACEN method, parameters that depended only on heavy atoms could be refined without restraints. The GED-determined geometric parameters (r(h1)) are: rSe-S 219.

Gas-phase structures of aminodifluorophosphines determined using electron diffraction data and computational techniques.

The molecular structures of a family of eight aminodifluorophosphines, (PF2)NRR'(R, R' = H, CH3, SiH3, GeH3, PF2), have been redetermined using gas-phase electron diffraction data and high-level ab initio molecular-orbital calculations. The SARACEN method has allowed the application of flexible restraints, giving greater accuracy and precision of structure, while the SHRINK program has allowed curvilinear corrections for vibrational effects to be applied to intramolecular distances. The more accurate structures of these eight compounds show consistent patterns of effects attributable to the various substituents, while conformations are dominated by the requirement that adjacent phosphorus and nitrogen lone pairs of electrons should be orthogonal.

The molecular structure of [Sn(P2C2But2)] using gas-phase electron diffraction and DFT calculations.

The molecular structure of 2,4-di-tert-butyl-eta4-1,3-diphosphacyclobutadiene tin has been determined in the gas phase by electron diffraction using both the DYNAMITE and SARACEN methods. The suitability of many different theoretical methods for the calculation of structures of half-sandwich main-group metal complexes has been investigated, and, by comparison of the results with the experimental structures, suggestions have been made as to the most suitable methods for this class of compound.

Steric and electronic effects on the conformations of n-butane derivatives with trichlorosilyl, silyl and trichloromethyl groups.

The molecular structure and conformation of 1,1,1,4,4,4-hexachloro-1,4-disilabutane in the gas-phase have been determined by electron diffraction and computational methods. The lowest-energy conformation has the trichlorosilyl groups anti to one another. The gauche conformation also has a shallow potential minimum, but lies about 19 kJ mol-1 above the anti form.

The structures of higher boron halides B8X12(X = F, Cl, Br and I) by gas-phase electron diffraction and ab initio calculations.

The structure of B8F12 has been shown by gas electron diffraction and computational methods (up to MP2/6-31+G*) to have the same highly asymmetric form observed in crystalline phases. The structure can be regarded as derived from a central B2 group, bridged by two BF2 groups to give a central B4 core that is folded, not planar, and with a very short bond [164.3 pm calculated, 164.

Determination of sugar structures in solution from residual dipolar coupling constants: methodology and application to methyl beta-D-xylopyranoside.

We have developed methodology for the determination of solution structures of small molecules from residual dipolar coupling constants measured in dilute liquid crystals. The power of the new technique is demonstrated by the determination of the structure of methyl beta-d-xylopyranoside (I) in solution. An oriented sample of I was prepared using a mixture of C(12)E(5) and hexanol in D(2)O.

Dramatic structural effects of a single hydrogen atom in HNPBu t 3.

The molecular structure of tri-tert-butylphosphine imide has been re-determined using the recently developed DYNAMITE method, which allows all assumptions about local symmetry to be removed without increasing the number of refining structural parameters excessively. The imide hydrogen causes the NPBu(t)(3) group to deviate hugely from local C(3) symmetry, with N-P-C angles returned as 99.2(9), 110.

The molecular structure of tetra-tert-butyldiphosphine: an extremely distorted, sterically crowded molecule.

The molecular structure of tetra-tert-butyldiphosphine has been determined in the gas phase by electron diffraction using the new DYNAMITE method and in the crystalline phase by X-ray diffraction. Ab initio methods were employed to gain a greater understanding of the structural preferences of this molecule in the gas phase, and to determine the intrinsic P-P bond energy, using recently described methods. Although the P-P bond is relatively long [GED 226.

Molecular structure of tris(dipivaloylmethanato)lutetium(iii) studied by gas electron diffraction and ab initio and DFT calculations.

Combined gas electron diffraction/mass spectrometry (GED/MS) was used to determine the molecular structure of tris(dipivaloylmethanato)lutetium(III), Lu(dpm)(3)(dpm = 2,2,6,6-tetramethyl-heptane-3,5-dionato). Up to about 520-570 K the vapour consisted only of molecules Lu(dpm)(3). The experimental data recorded at 408(5) K indicate that the molecules have D(3) symmetry.

Dynamic interaction of theory and experiment: total determination of the gas-phase molecular structure of tri-tert-butylphosphine oxide (OPBut3).

A new method to aid the determination of structures of sterically crowded molecules in the gas phase by dynamically linking the gas-phase electron diffraction (GED) refinement process with computational methods has been developed. The procedure involves refining the heavy-atom skeleton of the molecule using the GED data while continually updating the light-atom positions during the refinement using computational methods, in this case molecular mechanics. This removes errors associated with the assumption of local symmetry for the light-atom groups, which can affect the final values of the heavy-atom parameters.

Molecular structure of 1,1,2,2-tetra-tert-butyldisilane: unusual structural motifs in sterically crowded disilanes.

The molecular structure of 1,1,2,2-tetra-tert-butyldisilane has been determined by gas-phase electron diffraction supported by ab initio calculations, in the solution phase by Raman spectroscopy, and in the solid phase by Raman spectroscopy and X-ray crystallography. The gas-phase structure (C2 symmetry) was found to be almost anticlinal, a most unusual and unexpected result. In the favoured conformation, contact between tert-butyl groups at each end of the molecule is avoided by a large deviation of the angles around the silicon atoms from the parent tetrahedral angle of 109.

Strong intramolecular secondary si.N bonds in trifluorosilylhydrazines.

The simple silylhydrazines F(3)SiN(Me)NMe(2) (1), F(2)Si(N(Me)NMe(2))(2) (2), and F(3)SiN(SiMe(3))NMe(2) (3) have been prepared by reaction of SiF(4) with LiN(Me)NMe(2) and LiN(SiMe(3))NMe(2), while F(3)SiN(SnMe(3))NMe(2) (4) was prepared from SiF(4) and (Me(3)Sn)(2)NNMe(2) (5). The compounds were characterized by gas-phase IR and multinuclear NMR spectroscopy ((1)H, (13)C, (14/15)N, (19)F, (29)Si, (119)Sn), as well as by mass spectrometry. The crystal structures of compounds 1-5 were determined by X-ray crystallography.

Highly asymmetric coordination in alkenes: gas-phase structures of trans-1,2-dichloro-1,2-disilylethene and 1-bromo-1-silylethene.

The molecular structures of trans-1,2-dichloro-1,2-disilylethene and 1-bromo-1-silylethene have been determined by gas-phase electron diffraction (GED) and ab initio molecular orbital calculations (MP2/6-311G). Both compounds were found to have highly asymmetric coordination around the carbon atoms with [ab initio (r(e))/GED (r(a))] C=C-Cl [117.0/117.