Spectroscopy and Photodissociation of Dimethylzinc in Solid Argon. 1. Vacuum UV Luminescence Detection/Synchrotron Radiation Photolysis

Abstract

Absorption spectra of thin-film DMZ/Ar samples, prepared by condensing gaseous mixtures of dimethylzinc (DMZ) with argon at 12 K, were recorded in the region of the first dissociative absorptions of DMZ centered in the gas phase at 200 nm. Large blue shifts are observed in the matrix spectra which can be related to the Rydberg-like characteristics of these excited states of DMZ. The photochemistry of DMZ in an argon matrix was investigated either by subjecting samples to undispersed synchrotron irradiation using a quartz filter to select a wavelength range above 155 nm or to wavelength-specific irradiation. Steady-state and time-resolved luminescence spectroscopy of the dissociation products isolated in solid argon indicate the existence of atomic zinc strongly perturbed by a methyl radical in freshly photolyzed samples, which yields truly isolated atomic zinc upon annealing to 33 K. Dissociation threshold measurements indicate a barrier of 25 kcal/mol for direct cage escape of atomic zinc in the Ar lattice. The increased intensity of Zn( 3 P 1 )/Ar emission observed in photolyzed DMZ/Ar samples relative to pure Zn/Ar samples is explained in terms of the enhanced ISC of atomic zinc in the presence of hydrocarbon species in the former samples. This has been shown by codeposition of atomic zinc with Ar doped with CH 4 and C 2 H 6 .

Vacuum Ultraviolet Spectroscopy and Photochemistry of Zinc Dihydride and Related Molecules in Low-Temperature Matrices

“…Irradiation into any of them resulted (data not shown) in the regeneration of the atomic zinc absorption at 214 nm and depletion of the new molecular bands. This behavior is similar to that observed by us previously in the photochemistry of matrix-isolated dimethylzinc (DMZ). However, in contrast to the dissociation of DMZ, where secondary photolysis never regenerated the starting material, methylzinc hydride species could be regenerated with atomic photolysis.…”

The application of synchrotron radiation and in particular X-ray absorption spectroscopy to matrix isolated species

“…Cl2 in Ar matrices [302]; Me2Zn in argon matrices [303]; CH4 in Kr matrices [304]; CH3OH in solid Ar and Ne [305]; as well as the photochemistry of HCl in rare gas matrices [306][307][308]. SR vac-UV radiation has been used to identify the photoionisation threshold of CS2 [309] and C6F6 [310] in solid Ne, and the valence photoionisation of CH3C(O)SCH3 [311].…”

Matrix-Isolation ESR Studies of the Various Isotopomers of the CH3Zn and ZnH Radicals: Comparisons with ab Initio Theoretical Calculations

“…Greene and co-workers have also reported the reaction of excited metal atoms to form species of the type MH 2 (M = Zn or Cd) isolated in argon matrixes and have performed ab initio calculations on these species; in these experiments, the ZnH radical was observed. Bracken and co-workers , found no evidence for the CH 3 Zn radical from irradiation (down to 155 nm) of (CH 3 ) 2 Zn isolated in an argon matrix at 12 K.…”