Time-resolved infrared studies

O. S. Jina, X. Z. Sun and M. W. George, Do early and late transition metal noble gas complexes react by different mechanisms A room temperature time-resolved infrared study of (z)5-C5H5)Rh(CO)2 (R = H or Me) in supercritical noble gas solution at room temperature. Dalton Trans., 1773-8 (2003). 

Firth S, Hodges PM, Poliakoff M, Turner JJ. Comparative matrix isolation and time-resolved infrared studies on the photochemistry of MnRe(CO)10 and Re2 (CO)10 evidence for CO-bridged MnRe(CO)9. Inorg Chem 1986 25(25) 4608-4610. 

Time-Resolved Infrared Studies of Ligand Dynamics in Heme Proteins... 

Organometallic COj complexes in supercritical COji a time-resolved infrared study... 

Deeper insight into this mechanism was afforded by femtosecond time-resolved infrared studies that enabled observation of intermediates and the calculation of relative energy barriers. Thus, upon UV irradiation 430 loses CO (<100fs) to afford a 16-electron monocarbonyl complex that is rapidly solvated (barrier-less process) to afford Tp Rh(CO)(RH), which vibrationally cools in 20 ps. Thermal mono-dechelation of the Tp ligand (zlG=4.2kcalmol ) proceeds... 

For instance, cis-trans isomerisation in stilbene is one of the most studied isomerisation processes in organic compounds. It occurs efficiently using 313 nm irradiation. An example of a stilbene-type cis-trans isomerisation on a metal centre was reported for Re(I) [85]. In this example, the process occurs under UV light, and time-resolved infrared studies provided direct evidence for a ligand-based photochemical transient (Fig. 3.17a). 

Samjeske, G., Komatsu, K.-L, Osawa, M. Dynamics of CO oxidation on a polycrystaUine platinum electrode A time-resolved infrared study. J. Phys. Chem. C 2009, 113, 10222-10228. 

Diller R, Malt S, Walker G 0, Cowen B R, Pippenger R, Bogomoini R A and Hochstrasser R M 1995 Femtosecond time-resolved infrared laser study of the J-K transition of bacteriorhodopsin Chem. Rhys. Lett. 241 109-15... 

Time-Resolved Infrared (TRIR) Studies of Organic Reactive Intermediates... 

TIME-RESOLVED INFRARED (TRIR) STUDIES OF ORGANIC REACTIVE INTERMEDIATES... 

Despite the considerable amount of information that has been garnered from more traditional methods of study it is clearly desirable to be able to generate, spectroscopically characterize and follow the reaction kinetics of coordinatively unsaturated species in real time. Since desired timescales for reaction will typically be in the microsecond to sub-microsecond range, a system with a rapid time response will be required. Transient absorption systems employing a visible or UV probe which meet this criterion have been developed and have provided valuable information for metal carbonyl systems [14,15,27]. However, since metal carbonyls are extremely photolabile and their UV-visible absorption spectra are not very structure sensitive, the preferred choice for a spectroscopic probe is time resolved infrared spectroscopy. Unfortunately, infrared detectors are enormously less sensitive and significantly slower... 

Fast time resolved infrared attached to flow and to uv-vis flash photolysis has been an important development for the study of rapid substitution, e.g. in Co2(CO)r in hexane " and... 

Nanosecond time resolved infrared (TRIR) spectroscopy has recently become available to physical organic chemists. This spectroscopy is an attractive tool for studying carbonyl nitrenes. Such work is in progress in several laboratories ... 

Laser flash photolysis methods have also been applied to the study of nitrenium ion trapping rates and hfetimes. This method relies on short laser pulses to create a high transient concentration of the nitrenium ion, and fast detection technology to characterize its spectrum and lifetime The most frequently used detection method is fast UV-vis spectroscopy. This method has the advantage of high sensitivity, but provides very little specific information about the structure of the species being detected. More recently, time-resolved infrared (TRIR) and Raman spectroscopies have been used in conjunction with flash photolysis methods. These provide very detailed structural information, but suffer from lower detection sensitivity. 

Although, relevant information about ferrous hemeproteins kinetics, dynamics and ligand photodissociation pathways has been obtain, less is known about ferric hemeproteins photophysic processes. Recent studies performed with Hbl-CN and Mb-CN at ultrafast time scale, have suggested that some of the transients intermediaries observed after ferrous complexes ligand photodissociation are observed in ferric Mb and Hbl [7], However, time-resolved infrared data shows that the complex remained six coordinated after photoexcitation. In this work we present ultrafast data on ferric Hbl-NO, HM-N3, HM-H2S and metHbl complexes that suggest a mechanism for the photoinduced reduction of Hbl species. 

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