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The microwave spectra of CD 3 C 35 Cl 3 , CD 3 C 35 Cl 2 37 Cl, CD 3 C 35 C1 37 Cl 2 and CD 3 C 37 Cl 3 have been recorded from 18.0 to 40.0 GHz. The observed rotational constants were readily calculated from the structural parameters previously obtained by Holm, Mitzlaff and Hartmann. From the relative intensities of the ground and the excited vibrational states, the torsional modes were found to have frequencies of 276 and 199 cm −1 for the CH 3 CC1 3 and CD 3 CCl 3 molecules, respectively. From these frequencies, a barrier of 5.1 kcal mol −1 was calculated for the internal rotational motion. It is shown that this value is consistent with the determined barriers for other chloro-substituted ethanes and the barriers increase in a predictable manner as would be expected from a significant contribution from non-bonded interactions.

The microwave spectrum of glycolaldehyde, CH 2 OH-CHO, has been measured and the rotational and centrifugal distortion constants of the ground and three vibrational excited states have been obtained. Only one isomer, which has the carbonyl and the hydroxyl groups cis to one another, was identified. The dipole moment was determined to be 2.73 ± 0.04 D from Stark-effect measurements.

Microwave spectra of CHO-COOH and CHO-COOD are reported. The molecule has a planar equilibrium conformation with the two carbonyl groups trans to each other. A weak five-member intramolecular hydrogen bond is formed between the hydroxyl proton of the carboxyl group and the oxygen atom of the carbonyl group thus stabilizing the trans planar form. Other conformations having a statistical weight of 1 ( cis and trans ) are at least 1.3 kcal mol −1 less stable, and rotamers with a statistical weight of 2 ( e.g. , gauche and skew ) have at least 1.7 kcal mol −1 higher energy. Four vibrationally excited states of CHO-COOH have been analyzed and relative intensity measurements yielded 167 ± 12 cm −1 for the C-C torsional mode and 288 ± 26 cm −1 for the lowest in-plane bending mode. The dipole moment was determined to be μ a = 1.85 ± 0.03 D, μ b = 0.20 ± 0.10 D, and μ tot = 1.86 ± 0.04 D. A seven-parameter centrifugal distortion analysis has been carried out for the ground vibrational state of CHO-COOD and for the ground and three vibrationally excited states of CHO-COOH.

The microwave spectrum of thionyl fluoride has been investigated in the spectral region 40–70 GHz. The assignment of many high J transitions gives all rotational constants and quartic and sextic Watson's parameters for the ground state and the excited vibrational state v4.

The semi-empirical cndo, indo and modified cndo-ci methods are applied to an analysis of the ground and excited state electronic properties of vinyl cyanide. The theoretical ionization potential agrees with experiment and the dipole moment is shown to be almost parallel to the nitrile bond. An analysis of the C-H bond populations gives an electronic interpretation of the corresponding stretching frequency differencss. The positions and intensities of ultraviolet absorption bands are correctly reproduced by the cndo-ci calculation and the variations of dipole moment in excited singlets agree with the observed blue-shifts of this spectrum.

The rotational spectrum of methyltrifluorosilane in the ground and the first three excited states of the torsional mode have been investigated in the region of 12.5–40.0 GHz. The rotational transitions for the 13 C isotopic species have also been measured. The following structural parameters have been determined: r (CH) = 1.081 ± 0.004 A, ∠ HCSi = 111°1' ± 30', r (CSi) = 1.812±0.014 A, r (SiF) = 1.574 ± 0.007 A, ∠ FSiC = 112°20'± 1°6'. The structural parameters are compared to the corresponding ones for similar molecules. The dipole moment was determined to be 2.33 ± 0.10 D. From relative intensity measurements, the barrier to internal rotation was found to be 0.93 ± 0.09 kcal mol −1 ; this value is consistent with the values obtained for other methylfluorosilanes.

The polarized medium, infrared and the laser excited lattice mode Raman spectra of oriented single crystal NaNCS, together with the far infrared lattice mode spectrum of a polycrystalline film of the salt, have been measured in the frequency range 40 to 5000 cm −1 . The fundamental modes are interpreted in terms of the → k = 0 factor group selection rules. The spectra essentially support the previously determined space group Pnma-D 2h 16 . Some general observations on the splittings and the symmetries of the combination and overtone modes have been made. The interionic interactions in NaNCS compared with that in KNCS, are discussed.

The microwave spectrum of nitrobenzene has been reinvestigated. Transitions in the ground state and three torsionally excited states have been assigned. It is shown that the nitrobenzene molecule is planar in the ground state. The torsional frequency (50 ± 15 cm −1 ) and the barrier to internal rotation (1000 ±500 cm −1 ) have been derived from the inertial defect and the relative intensity of transitions in torsionally excited states.

Hydrazine derivatives have a wide variety of applications in organic synthesis, material science, medical treatments, as well as the dye-sensitized solar cells (DSSC). In this work, the molecular structure, electronic spectra and first principles investigation for the exo-endo isomerization in (1E,2E)-bis[1-(4-nitrophenyl)ethylidene]hydrazine were studied. The structural interactions and synthon formations have been determined experimentally via Hirshfeld surface analysis (HSA) and two-dimensional fingerprint plots (2D-FP). Furthermore, the solid-state XRD/HSA interactions have been used to explain the physical behavior of the compound. The transition state for the exo-endo isomerization was located using density functional theory (DFT). The activation barrier is estimated to be 110.5 kJ/mol (in vacuo). The endo isomer was found to be slightly more stable than the exo one. The UV-Vis spectra of the two isomers were obtained using time-dependent density functional theory (TDDFT) and compared to the experimental spectra in vacuo, water, and methanol. To explore the potential of the new compound as a DSSC sensitizer, the emission spectrum was also constructed by optimizing the singlet electronic excited state.