The IR and Raman spectra and conformations of the ionic liquid 1-ethyl-3-methyl-1H-imidazolium tetrafluoroborate, [EMIM][BF4] (6), were analyzed within the framework of scaled quantum mechanics (SQM). It was shown that SQM successfully reproduced the spectra of the ionic liquid. The computations revealed that normal modes of the EMIM+ (.) BF4- ion pair closely resemble those of the isolated ions EMIM+ and BF4-, except for the antisymmetric BF stretching vibrations of the anion, and the out-of-plane and stretching vibrations of the H-C(2) moiety of the cation. The most plausible explanation for the pronounced changes of the latter vibrations upon ion-pair formation is the H-bonding between H-C(2) and BF4-. However, these weak H-bonds are of minor importance compared with the Coulomb interactions between the ions that keep them closely associated even in dilute CD2Cl2 Solutions. According to the 'gas-phase' computations, in these associates, the BF4- anion is positioned over the imidazolium ring of the EMIM+ cation and has short contacts not only with the H-C(2) of the latter, but also with a proton of the Me-N(3) group.

A new type of macrocycle containing 2-thio-4-aminopyrimidine and 6-methyluracil moieties has been studied by IR and UV spectroscopy. The vibrational spectra, conformations and amine–imine tautomerism of the aminopyrimidine fragments have been analysed within the framework of ab initio MO theory (HF/6-31G**, MP2/6-31G**) and density functional theory (B3LYP/6-31G**). According to experimental and theoretical results, the amino form is preferred in these compounds. Both intra- and intermolecular hydrogen bonds of the type NH⋯N are present in crystals, whereas in solutions, conformational equilibria with free NH groups are also obtained.

The conformations and vibrational spectra of the 2,6-dimethylanisole and n-propyl-2,6-dimethylphenyl ether molecules have been analysed within the framework of density functional theory. The calculated force field (B3LYP/6-31G∗) has been transformed to internal coordinates, and the set of 10 different scaling factors has been applied. The scaled quantum mechanical method reproduces the experimental range of the IR and Raman spectra with high accuracy. According to the computations, the conformational behaviour of the alkyl aryl ethers studied is similar to the related dialkyl ether molecules, i.e. the CO–CC bond prefers the anti conformation, while the OC–CC bond prefers the gauche conformation. The major part of the vibrational spectra of the title compounds can be approximated by the sum of the vibrational modes of their constituent groups, these modes being transferable among the related molecules.

The conformational and normal coordinate analysis of vibrational spectra of the diphenylmethane molecule has been realised within the framework of density functional theory. The calculated force field (B3LYP/6-31G∗) was transformed to nonredundant internal coordinates. It is shown that after assignment of two different scaling factors for aromatic and aliphatic C–H coordinates, the scaled quantum mechanical (SQM) method reproduces the complete experimental range of the IR and Raman spectra with high accuracy (mean deviation: 5.5cm−1). The set of nine different scaling factors will be used in conformational studies of calixarene building blocks.

Data on the interpretation of the IR and Raman spectra based on normal coordinate analysis, on the force constants and on the conformations of the molecules of trivalent tricoordinate phosphorus compounds are summarised. The existing correlations between the spectra and molecular structures are refined and some new correlations are proposed. The bibliography includes 171 references.

A series of complexes (RS)(3)P . CuBr with R = Et, Pr, Bu, i-Pr as well as the complex of (PrS)(3)P . CuSCN were studied by X-ray single-crystal diffraction. Coordination properties of thiophosphites were found to be essentially different from their oxygen and nitrogen analogues and depend on the nature of the metal center, substituents at sulfur atoms, the conditions of reactions and of the crystal growth. All trithiophosphites in the studied copper(I) complexes except the isopropyl derivative exhibit bidentate coordination with both phosphorus and sulfur participating in coordination bonds with copper.Trithiophosphites increase their conformational multiformity upon complexation regardless of the coordination mode, propyl and butyl derivatives being conformationally inhomogeneous in crystals. Unusual cis-conformations about the P-S bond, which are not observed for "free" trialkyltrithiophosphites or their phosphoryl and thiophosphoryl analogues, are realized in the complexes.The complexation results in the significant high-frequency shift of the symmetric and asymmetric PS3 stretching vibrations in the Raman spectra of complexes regardless of the coordination mode and in minor changes of the C-S stretching vibrations in comparison with the spectra of the "free" ligands. (C) 2000 Elsevier Science B.V. All rights reserved.

IR and Raman spectroscopy, normal coordinate analysis, and molecular mechanics were used to study the conformations of R(CH2)2-O-PCl2 molecules (R=Et, OMe). It is shown that in the case of R=Et, that the molecules prefer to exist in more or less extended conformations, R and PCl2 groups being spatially far apart. In contrast, the convoluted conformations are preferred in the case of R=OMe. In these conformations the intramolecular distances between nonbonded P1 and O5 atoms are comparable with the sums of the corresponding van der Waal's radii. The substantial energetical preference of the convoluted conformations in the liquid state is assigned to certain attractive intramolecular 1–5 interactions between the phosphorus and the oxygen atoms. The energy of the interaction may amount to ∼2–4.5kcalmol−1.

Here we report on a new type of chiral molecular propellers - trianhydrides of trithiophosphorous acid and organic thioacids.

A considerable amount of data on IR and Raman spectra, conformations and force constants of the title compounds is summarized. The vibrational origion of group frequencies is emphasized with the discussion of the effects of vibrational interactions. Certain new spectra–structure relationships and refined versions of existing ones are proposed. The force constants of the organophosphorus molecules are discussed, as well as applications of conformational analysis to studies of the intramolecular interactions.

IR and Raman spectroscopy, normal coordinate analysis, and molecular mechanics were used to study the conformations of Cl(CH2)2O–PCl2 molecules. It is shown that gauche conformations of the Cl–CH2–CH2–O residue are energetically preferred in liquid. These are the only conformations remaining in the low temperature crystals, anti conformations being “frozen out”. In these crystals the POCC residue most probably adopts an extended conformation, the OC bond being in anti-position relative to the phosphorus lone pair. In the liquid state the extended conformers coexist with the convoluted conformations. Contrary to what might be expected from molecular mechanics considerations the latter conformers are practically as energetically stable as the former. The gap between experimental measurements and the respective molecular mechanics’ estimation is attributed to certain attractive intramolecular 1–5 interactions between the phosphorus and the chlorine atoms. It is used for rough quantitative evaluation of the energy of these interactions, which amount to ∽10–15kJmol−1.

IR and Raman spectroscopy, normal coordinate analysis, and molecular mechanics were used to study the conformations of the Cl2P–O–(CH2)2SCN molecule. It is shown that in the low temperature crystals the molecule exists in two or more conformations, and in the liquid in at least three conformations. In both liquid and solid phases there exist the conformers with the O…S and/or P…S intramolecular distances comparable with the sums of the corresponding van der Waals radii. The substantial energy preference of the gauche conformation about the CC bond in the liquid state is assigned to certain attractive intramolecular interactions between the sulfur and phosphorus (or oxygen) atoms. The energy of the interaction may amount to about 2–4 kcal mol−1.