Matrix and time-resolved infrared spectroscopy of chloro-p-nitrophenylcarbene and related species

Chloro-p-nitrophenyldiazirine (2) was deposited in an argon matrix. Photoly sis (350 nm) releases chloro-p-nitrophenylcarbene (1) as a persistent speci es. The IR and UV-vis spectra of carbene 1 were obtained, and the IR spectr um was adequately simulated by density functional theory (DFT) calculations . The carbene has an intense IR vibration at 1206 cm(-1) involving the carb ene carbon and aromatic ring carbon. This band was observed by TRIR spectro scopy upon laser flash photolysis (355 um) of 2 in heptane at ambient tempe rature. The presence of benzene did not influence the frequency of this vib ration. The carbene lifetime as measured by TRIR spectroscopy (approximate to 400 ns) is consistent with previous LFP studies utilizing UV-vis detecti on. Upon LFP of 2 in CCl4 or CF2ClCFCl2 the photogenerated carbene abstract s chlorine atom from solvent to form a,a-dichloro-p-nitrobenzyl radical wit h a TRIR band at 1316 cm(-1). Upon LFP of 2 in acetonitrile; acetone, methy l acetate, pyridine, and tetrahydrofuran ylide species were produced. The y lides had similar TRIR spectra with bands at 1584, 1504, and 1312 cm(-1).