Nanosecond time-resolved infrared spectroscopy: A comparative view of spectrometers and their applications in organometallic chemistry

Three time-resolved infrared (TRIR) spectrometers are described. These instruments are based on (i) a line-tunable CO laser (2000-1550 cm ^-1), (ii) a continuously tunable semiconductor diode laser (approximately 2250-1900 cm^-1) and (iii) a modified and adapted dispersive IR spectrometer with Nernst glower (or globar) which, in principle, could cover all of the mid-IR region. The spectrometers differ in their inherent signal-to-noise ratio and their response. Although the ultimate performance can be achieved with the CO laser, the instruments are complementary, each with its own advantages. The performances of the three TRIR spectrometers were compared in a number of applications in organometallic photochemistry, including the IR detection of molecules in electronically excited states, the kinetic behaviour of intermediates in the reaction of (η⁵-C₅H ₅)M(CO)₄ compounds (M = V, Nb and Ta), an IR study of the photochemical reaction of CpMn(CO)₃ within polyethylene film and solvent interactions in supercritical xenon solution and the detection of W(CO)₅Xe.