TIME-RESOLVED IR SPECTROMETRIC DETECTION SYSTEM FOR KINETIC AND STRUCTURAL STUDIES OF REACTIVE INTERMEDIATES AT AMBIENT TEMPERATURE

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The goal of this study is to build a time-resolved IR detection system for laser flash photolysis (LFP). It is designed to be compact and suited for kinetic and structural studies of gain high cost-performance. The operational software for our LFP system is also modified so that it can be synchronized with the IR detection system. So far, intermediates with sufficient extinction coefficients and the lifetime of some hundred seconds can be readily detected.On the other hand, time-resolved spectroscopic studies of reactive intermediates are also carried out with UV-VIS detection. We are interested in this particular carbene and have attempted to generate benzocyclobutenylidene from precursors in order to investigate its reactivity. LFP (XeCl, 308 nm) of N-(2-phenylazyridyl)imine of benzocyclobutenone results in transient species with its absorption maximum around 450 nm. After these transients disappeared with the lifetime of 1 μs, a longer-lived species was observed as a weak absorption at 510 nm with the lifetime of 660 μs. We assign the former transient as being due to benzocyclobutenylidene based on the observed reactivity toward alkenes and alcohols. The latter 510 nm transient can be assigned as diazobenzocyclobutene because this species can be quenched by dipolarophiles such as fumaronitrile.Similar LFP of the same precursor with IR detection allowed us to observe absorption at 2042 cm^<-1>, which can be assigned as being due to diazobenzocyclobutene. The lifetime is 1 ms, which is in good agreement with the observation by UV-VIS detection. Further progress in the instrumental sensitivity and time-resolution is underway so that benzocyclobutenylidene and the pyridine ylide can be observed.