Matrix and Time-Resolved Infrared Spectroscopy of Chloro-p-nitrophenylcarbene and Related Species

Chloro- p -nitrophenyldiazirine ( 2 ) was deposited in an argon matrix. Photolysis (350 nm) releases chloro- p -nitrophenylcarbene ( 1 ) as a persistent species. The IR and UV−vis spectra of carbene 1 were obtained, and the IR spectrum was adequately simulated by density functional theory (DFT) calculations. The carbene has an intense IR vibration at 1206 cm -1 involving the carbene carbon and aromatic ring carbon. This band was observed by TRIR spectroscopy upon laser flash photolysis (355 nm) of 2 in heptane at ambient temperature. The presence of benzene did not influence the frequency of this vibration. The carbene lifetime as measured by TRIR spectroscopy (≈400 ns) is consistent with previous LFP studies utilizing UV−vis detection. Upon LFP of 2 in CCl 4 or CF 2 ClCFCl 2 the photogenerated carbene abstracts chlorine atom from solvent to form α,α-dichloro- p -nitrobenzyl radical with a TRIR band at 1316 cm -1 . Upon LFP of 2 in acetonitrile, acetone, methyl acetate, pyridine, and tetrahydrofuran ylide species were produced. The ylides had similar TRIR spectra with bands at 1584, 1504, and 1312 cm -1 .