Infrared gas phase intensity measurements. Polar tensors and effective charges of cis-dichloroethylene-d and d2

Abstract

Infrared gas phase intensity measurements, polar tensors, and effective charges of cisdifluoroethylene and its deuterated modifications J. Chem. Phys. 78, 7029 (1983); 10.1063/1.444746Infrared gas phase intensity measurements, polar tensors, and effective charges of vinylidene fluoride and its deuterated modificationsThe gas phase fundamental intensities of cis -dichloroethylene and its dideuterated modification have been measured. Isotopic invariance, the G sum rule and the results of molecular orbital calculations have been used to select preferred experimental values for the dipole moment derivatives and polar tensor elements of these molecules. The F sum rule has been used to determine individual intensity values of the v" v 12 overlapped band system of the dihydrogen molecule. Values of the polar tensor elements for cis dichloroethylene are compared with those previously determined for cis-difluoroethylene. The hydrogen effective charge values in these molecules are essentially identical (0.17 and O.l8e). The polar tensor of cis-dichloroethylene is used to predict the vibrational intensities of trans-dichloroethylene.

Transferability of the cis- and trans-Dichloroethylene Atomic Polar Tensors

“…The values of the polar tensor invariants, atomic mean dipole moment derivatives (p α ), anisotropies (β α 2 ), and effective charges (χ α ) for the new set of preferred signs are shown in Table . These values are similar to the invariant values determined previously . For example, the 0.160 e , 0.047 e , and −0.206 e values found here for p̄ C , p̄ H , and p̄ Cl , respectively, can be compared with 0.182 e , 0.021 e , and −0.203 e values obtained previously.…”

“…The preferred polar tensor element values in Tables −5 are similar to those determined some years ago based on the isotopic invariance criterion and semi-empirical CNDO estimates …”

“…The values of the experimental fundamental infrared intensities, vibrational frequencies, molecular geometries, and definitions of the symmetry coordinates of the cis -compounds were taken from ref . The orientations for cis -C 2 H 2 Cl 2 and cis -C 2 D 2 Cl 2 in the space-fixed Cartesian coordinate system, the atom numbering scheme, and the internal coordinates are identical to those in Figure of ref . The corresponding information for the trans - C 2 H 2 Cl 2 and trans - C 2 D 2 Cl 2 molecules was taken from ref .…”

“…The infrared spectra of the difluoro- and dichloroethylenes in the gas phase are particularly intriguing since the fundamental intensity sums of the cis and trans forms are almost the same. − Preliminary results based on atomic polar tensors (APTs) determined from measured intensities and normal coordinate transformations obtained from force fields calculated from experimental frequencies indicated that the APTs of the cis isomers are transferable to the trans forms. Since the isotopic invariance criterion was not sufficient to remove all the sign ambiguities of the dipole moment derivatives with respect to the normal coordinates of these molecules, ∂ p⃗ /∂ Q j , the APTs used in this transference study were determined on the basis of the signs of derivatives calculated using approximate semiempirical CNDO molecular orbital results.…”

Core Electron Energies, Infrared Intensities, and Atomic Charges

“…To obtain a unique polar tensor from experimental intensity values, therefore, 3 N − 6 sign ambiguities must be removed. Bibliographic references for these polar tensor solutions are indicated in Tables −3. − Errors for the p̄ C values, propagated from experimental intensity error estimates, are also reported where avaliable. Other sources of error for the p̄ C values are either difficult to assess (errors in the normal coordinates) or probably negligible (dipole moment and molecular geometry errors).…”