We present nanosecond transient resonance Raman experiments that investigate the photoproduct species formed following A-band and B-band excitation of bromoiodomethane in room temperature cyclohexane solutions. Density functional theory calculations were also performed for several species that have been proposed as photoproducts for photodissociation of bromoiodomethane in the condensed phase. Comparison of the experimental resonance Raman spectra to density functional theory computational results and results for the closely related iso-CH2I-I and iso-CH2Br-Br species demonstrated that the iso-CH2I–Br species is mainly responsible for a transient absorption spectrum that appears after either A-band or B-band photoexcitation of bromoiodomethane in cyclohexane solution. This is in contrast to previous results for low temperature (12 K) solids where mainly the iso-CH2Br-I species was observed following A-band photoexcitation of bromoiodomethane. Further density functional theory computational results indicate that the iso CH2I–Br species is noticeably more stable than the iso-CH2Br-I species by about 4.1kcal/mol. This suggests that although both iso-CH2I–Br and iso-CH2Br–I species may be initially produced following ultraviolet excitation of bromoiodomethane in cyclohexane solution, only the more stable isomer has a sufficiently long lifetime to be observed in our nanosecond time-scale transient resonance Raman experiments. We compare results for the bromoiodomethane ultraviolet photodissociation/photoisomerization reactions in the condensed phase to those of the closely related diiodomethane system and discuss a probable mechanism for the formation of the iso-bromoiodomethane species in the condensed phase.

We have obtained Raman spectra for neat liquid iodocyclopentane and for two types of solid phases. Ab initio calculations were done to help elucidate the Raman band assignments to either the axial or equatorial conformations of iodocyclopentane. The liquid Raman spectrum displays bands for both axial and equatorial conformations of iodocyclopentane while the two solid phases exhibit a strong preference for either the axial conformation for the annealed solid phase or the equatorial conformation for the unannealed solid phase. We discuss the possible utility for using this phase-dependent conformation selection to examine the conformation dependence of solid-state photochemical reactions.

Resonance Raman spectra of 1,2-diiodoethane in cyclohexane solution have been obtained in the A-band absorption. A resonance Raman intensity analysis was done to examine the short-time photodissociation dynamics of 1, 2-diiodoethane. Significant bond length and bond angle changes were found for both C-I bonds and the C-C bond as well as the CCI and HCH bond angles. Comparison of the Franck–Condon region dynamics of 1,2-diiodoethane with diiodomethane suggests that the degree of coupling of the two C-I chromophores depends on both the relative geometry of the C-I bonds and their relative separation.

We examine the chemical reactions of the isodiiodomethane (CH2I-I),

Resonance Raman spectra of l-chloro-2-iodoethane in cyclohexane solution are presented for three excitation wavelengths. The fundamentals, overtones and combination bands of the nominal CCCI bend (v10), the nominal C I stretch (v9), and the C-C1 stretch (v8) vibrational modes can account for most of the resonance Raman intensity. The resonance Raman spectra and associated short-time photodissociation dynamics of I-chloro-2-iodoethane are compared with iodoethane and this suggests that the chloroethyl radical receives more internal excitation than the ethyl radical from the A-band photodissociation in as much as the initial dynamics determines the internal excitation of the alkyl radical photoproducts.