Ultrafast TRIR spectroscopy

Although very detailed, fundamental information is available from ultrafast TRIR methods, significant expertise in femtosecond/picosecond spectroscopy is required to conduct such experiments. TRIR spectroscopy on the nanosecond or slower timescale is a more straightforward experiment. Here, mainly two alternatives exist step-scan FTIR spectroscopy and conventional pump-probe dispersive TRIR spectroscopy, each with their own strengths and weaknesses. Commercial instruments for each of these approaches are currently available. 

Femtosecond TRIR spectroscopy was used to probe vibrational mode coupling to ultrafast electron transfer in [(NC)50sCNRu(NH3)5]. 275 The IR spectrum of (ri2-C6o)Os(CO)(tBuNC)(PPh3)2 includes vCN at 2153 cm 1, with vCO at 1953 cm-1.276... 

The photoinduced Wolff rearrangement of 5-diazo-2,2-dimethyl-l,3-dioxan-4,6-dione has also been examined by TRIR methods [116], These ultrafast measurements, conducted in a PMMA matrix, revealed that the formation of the ketene rearrangement product was complete within 20 ps a carbonyl carbene was not detected in this study. Other applications of TRIR spectroscopy to the study of carbene-related chemistry include investigations of diazirine to diazo rearrangements [117] and of oxygen and sulfur atom transfer reactions [118]. 

Although we have focused on the photochemistry of Rh(Cp )(CO)2 (Cp =Cp or Cp ) so far, the most complete understanding of C-H reactions came in parallel TRIR studies on Rh(Tp )(CO>2 (Tp = HB(3,5 -Me2pyrazol-l-yl)3, and extensive reviews cover this work." We choose this example since this investigation built upon matrix-isolation and liquid Xe studies. A combination of ultrafast TRIR and ns-step-scan FTIR spectroscopy was used to unravel the mechanism of alkane C-H activation by Rh(Tp An alkane complex was formed within the earliest... 

Another method, which allows the structural characterization and elucidation of the reactivity of transient species using infrared spectroscopy, is to observe them in real time, using fast time-resolved infrared (TRIR) spectroscopy. In this section we shall focus on the application of fast (submillisecond) and ultrafast (subnanosecond) TRIR spectroscopy to coordination compounds, and describe experiments that cannot be performed using conventional infrared spectrometers. 

DFT calculations and TRIR data have been reported for a range of /ac-Re(CO)3 complexes containing bipy or dipyridophenazine derivatives.105 Ultrafast two-dimensional transient IR spectroscopy was used to follow photoinduced charge transfer processes in Re(CO)3(dmbpy), where... 

These questions have been recently addressed using ultrafast time-resolved infrared spectroscopy (Fig 3.14), on the example of stretching vibration v(CN) in the ground state, at 2239 cm is clearly seen. Notably, the IR bands in the excited state are much broader, and more intense than... 

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