Time-resolved infrared spectroscop

Recently, time-resolved infrared spectroscopic measurements revealed evidence for the first direct observation of an acyl nitroso compound in solution [22]. Pho-... 

Weinstein JA, Grills DC, Towrie M et al (2002) Picosecond time-resolved infrared spectroscopic investigation of excited state dynamics in a Pt(II) diimine chromophore. Chem Comm 382-383... 

Colley CS, Grills DC, Besley NA, Jockusch S, Matousek P, Parker AW, Towrie M, Turro NJ, GUI PMW, George MW. Probing the reactivity of photoinitiators for free radical polymerization time-resolved infrared spectroscopic study of benzoyl radicals. J Am Chem Soc 2002 124 14952-14958. 

Quantum cascade laser Each laser of this type has its laser oscillation center somewhere in the region of about 2400-900 cm" and its tunable wavenumber region is over about 60-250 cm". Application of such lasers to time-resolved infrared spectroscopic measurements is fairly recent and will likely increase in future [7]. 

Infrared pulses used for ultrafast time-resolved infrared spectroscopic measurements have been generated mainly by the following three methods ... 

In practice, an electromagnetic pulse with an infinitely short width does not exist, but ultrashort laser pulses are now used for various spectroscopic measurements. Terahertz spectrometry described in Chapter 19 is based on femtosecond laser pulses. In Chapter 20, time-resolved infrared spectroscopic methods using picosecond to femtosecond laser pulses are described. Such ultrashort laser pulses have large spectral widths in the frequency domain. Let us discuss the relation between the pulse width in the time domain and its spectral width expressed in either frequency or wavenumber. 

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... 

A variety of spectroscopic methods has been used to determine the nature of the MLCT excited state in the /ac-XRe(CO)3L system. Time-resolved resonance Raman measurements of /ac-XRe(CO)3(bpy) (X = Cl or Br) have provided clear support for the Re -a- n (bpy) assignment of the lowest energy excited state [44], Intense excited-state Raman lines have been observed that are associated with the radical anion of bpy, and the amount of charge transferred from Re to bpy in the lowest energy excited state has been estimated to be 0.84 [45], Fast time-resolved infrared spectroscopy has been used to obtain the vibrational spectrum of the electronically excited states of/ac-ClRe(CO)3(bpy) and the closely related/ac-XRe(CO)3 (4,4 -bpy)2 (X = Cl or Br) complexes. In each... 

Once the transient species has been formed, it has to be monitored by some form of kinetic spectroscopy, typically with ultraviolet-visible absorption or emission, infrared (time-resolved infrared or TRIR) (74), or resonance Raman (time-resolved resonance Raman or TR3) (80) methods of detection. The transient is usually tracked by a probe beam at a single characteristic frequency, thereby giving direct access to the kinetic dimension. Spectra can then be built up point by point, if necessary, with an appropriate change of probe frequency for each point, although improvements in the sensitivity of multichannel detectors may be expected to lead increasingly to the replacement of the laborious point-by-point method by full two-dimensional methods of spectroscopic assay (that is, with both spectral and kinetic dimensions). 

Two spectroscopic methods that have been used in bioinorganic chemistry but not discussed in the text are time-resolved infrared spectroscopy and time-resolved resonance Raman spectroscopy. Speculate on the types of investigation that might be made with these methods. 

H. Heusmann, J. Kolzer, and G. Mitic, Characterization of Female Breast Ln Vivo by Time Resolved and Spectroscopic Measurements in Near Infrared Spectroseopy, JBiomed. Opt., voL 1, no. 4, 1996, pp. 425-434. 

Other integral methods include in situ spectroscopic techniques, such as time-resolved infrared spectroscopy, which measures concentration or conversion as well as provides information on chemical identities of components in the reactor. In contrast to the chemical sampling method, the infi ared (IR) spectrum of the reacting system may be collected at a much faster pace than that normally possible for the chemical sampling method. Consequently, rate data may be derived with good accuracy by differentiating the IR intensity data with respect to time. 

X-Z Sun, MW George, SG Kazarian, SM Nikiforov, M Poliakoff. Can organometal-lic noble gas compounds be observed in solution at room temperature A time-resolved infrared (TRIR) and UV spectroscopic study of the photochemistry of M(C0)6 (M = Cr, Mo, and W) in supercritical noble gas and CO2 solution. J Am Chem Soc 118 10525-10532, 1996. 

In this book, most chapters deal with FT-IR spectrometry and its applications to various methods of infrared spectroscopic measurements. Only terahertz spectrometry in Chapter 19 and a large part of time-resolved infrared spectrometry in Chapter 20 are laser-based measurements. This shows how widely FT spectrometry is used at present in the measurements of vibrational spectfa. 

For microsecond to nanosecond time-resolved infrared absorption measurements, three types of spectroscopic methods have been developed (i) a method using an infrared laser, (ii) a method using a dispersive spectrometer, and (iii) a method using an FT-IR spectrometer. The time resolution of each of these is limited to the fastest time-response capability of the detector used. 

Spectroscopic methodologies have provided a wealth of information concerning the amination of ketenes. Scaiano and co-workers have measured rate constants for ketene reactions with various classes of amines in acetonitrile. The reaction rate is influenced by the basicity of the amine as well as by steric factors in both the ketene and the amine. Ketene amination has also been studied by time-resolved infrared (TRIR) spectroscopy. The strong ketene IR band near 2100 cm" makes it an excellent candidate for study by this spectroscopic technique. Scaiano, Wagner, Lusztyk, and co-workers provided evidence for the first nucleophilic attack being rate determining and that the transition state involves an enol amide. They further found that the asymmetric stretching IR band of substituted ketenes... 

Probing Metalloproteins Electronic absorption spectroscopy of copper proteins, 226, 1 electronic absorption spectroscopy of nonheme iron proteins, 226, 33 cobalt as probe and label of proteins, 226, 52 biochemical and spectroscopic probes of mercury(ii) coordination environments in proteins, 226, 71 low-temperature optical spectroscopy metalloprotein structure and dynamics, 226, 97 nanosecond transient absorption spectroscopy, 226, 119 nanosecond time-resolved absorption and polarization dichroism spectroscopies, 226, 147 real-time spectroscopic techniques for probing conformational dynamics of heme proteins, 226, 177 variable-temperature magnetic circular dichroism, 226, 199 linear dichroism, 226, 232 infrared spectroscopy, 226, 259 Fourier transform infrared spectroscopy, 226, 289 infrared circular dichroism, 226, 306 Raman and resonance Raman spectroscopy, 226, 319 protein structure from ultraviolet resonance Raman spectroscopy, 226, 374 single-crystal micro-Raman spectroscopy, 226, 397 nanosecond time-resolved resonance Raman spectroscopy, 226, 409 techniques for obtaining resonance Raman spectra of metalloproteins, 226, 431 Raman optical activity, 226, 470 surface-enhanced resonance Raman scattering, 226, 482 luminescence... 

Sakamoto A, Nakamura O, Tasumi M (2008) Picosecond time-resolved polarized infrared spectroscopic study of photoexcited states and their dynamics in oriented poly(p-phenylene-vinylene). J Phys Chem B 112 16437... 

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