SPECTROSCOPIC INVESTIGATIONS OF THE CRYSTAL STRUCTURES OF SOME SIMPLE MOLECULES (INFRARED, POLARIZED, ORIENTED)

Polarized infrared spectra obtained from oriented samples are useful in determining vibrational assignments and/or crystal structure information. This work summarizes important factors in the growth of such films and describes extensions of the technique to organometallic and inorganic compounds and to the far infrared. Crystal orientation and polymorphism are also considered.;Oriented polycrystalline films of dimethyltin dichloride were grown from the melt and their polarized infrared spectra studied at sub-ambient temperatures. X-ray powder data were collected on the oriented polycrystalline films. Modifications and extensions of a previously reported vibrational assignment are proposed. Factor group splitting and polarization evidence indicate dimethyltin dichloride occupies a C(,2v) site in the crystal. The factor group was found to be D(,2h) for a body-centered orthorhombic crystal with 4 molecules/crystallographic unit cell, suggesting a space group of Imma.;Oriented polycrystalline films of methyltin trichloride were grown from the melt and then polarized infrared spectra studied at sub-ambient temperatures. Modifications and extensions of previously reported vibrational assignments are proposed. Factor group splitting and polarization evidenced indicate methyltin trichloride occupies a C(,s) site in the crystal. The crystal class is most likely orthorhombic with a factor group of either C(,2v) with 2 molecules/Bravais cell or D(,2h) with 4 molecules/Bravais cell.;An existing glove box was reconditioned to exclude H(,2)O from the box atmosphere. Modifications of the glove box are presented, and procedures for operation discussed.;Infrared spectra of liquid and crystalline fumaryl chloride were recorded. Also, the Raman spectrum of liquid fumaryl chloride was obtained. Two conformers exist in equilibrium in the liquid: trans-trans (C(,2h)) and cis-trans (C(,s)). The spectrum of the crystal is that of the trans-trans conformer only. Vibrational assignments of the conformers have been proposed. Oriented polycrystalline films of fumaryl chloride were grown at sub-ambient temperatures and their polarized spectra studied. Results indicate that the trans-trans conformer occupies a C(,i) site in the unit cell. Factor group splitting and polarization evidence are consistent with a factor group of D(,2h) for an orthorhombic crystal with 4 molecules/Bravais cell.