Nanosecond transient absorption spectroscopy

Kinetics and thermodynamics of electron injection and charge recombination DNA hairpins possessing a stilbenediether electron donor linker observed with neighboring cytosine or thymine bases obtained by femtosecond transient absorption spectroscopy were investigated [12]. 

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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... 

The UV-visible absorption and fluorescence spectra of NKX-2311 in solution are measured. The absorption and fluorescence maxima are located at 490 and 555 nm, respectively. The fluorescence spectrum is shown in Fig. 1. This figure also shows the transient absorption spectrum of NKX-2311 in deuterated methanol (CD3OD) solution measured by the nanosecond laser system. The spectrum is ascribed to the excited singlet state (dye ). The absorption spectrum of the oxidized form of NKX-2311 (dye+) was measured by nanosecond transient absorption spectroscopy after adding electron acceptor, 1,4-benzoquinone, in NKX-2311 solution of CD3OD. As shown in Fig. 1, there are two characteristic peaks at around 875 and 1010 nm. 

Schaniel and coworkers studied the properties of the photoinduced ON and r/ -NO isomers in Na2[Fe(CN)5N0]-2H20 embedded in meso-pores of sihca xerogels by X-ray diffraction, steady-state low-temperature absorption, nanosecond transient absorption spectroscopy, and IR spectroscopy (34). They determined that the electronic structures and activation energies of these / -ON and tf -NO isomers were not dependent on the particle size (statistically distributed molecules or nanoparticles) and as such the isomers were essentially quasi-free inside the pores of the gel (34). 

The mechanism and dynamics of photoinduced charge separation and charge recombination have been investigated in synthetic DNA hairpins possessing donor and acceptor stilbenes (stilbene-4,4 -dicarboxylic acid, bis(3-hydroxypropyl)amide of stilbene-4,4 -dicarboxylic acid, bis(2-hydroxyethyl)stilbene 4,4 -diether) (Figure 11.1) using femtosecond broadband pump-probe spectroscopy, nanosecond transient absorption spectroscopy, and picosecond fluorescence decay measurements [11]. Nanosecond time-resolved spectra of stilbenes attached to DNA are shown in Figure 11.4. 

For the homoleptic compounds M02(O2CC6H4-p-X)4 (X=CsC-H or C=N), fs-TRIR studies showed that for the MLCT Si state the negative charge is delocalised over two tram ligands ligands. NIR emission and nanosecond transient absorption spectroscopy showed that the Ti states are MoMo88, with lifetimes of 56 (X = C=C-H) and 61 (X = C=N) ps. 

The photoinduced electron transfer reactions have also been studied with nanosecond transient absorption spectroscopy [67]. The transient absorption difference spectrum for the reaction of 12a and 4-(methoxycarbonyl)-A/-methylpyr-idinium is shown in Fig. 4. The difference spectrum is characterized by a sharp intense absorption at approximately 390 nm, a Iowa- intensity band at 484 nm, and an intense broad absorption band at approximately 693 nm. The sharp band at around 390 nm is characteristic of pyridinyl radical absorption. The reaction mechanism is depicted in Scheme 1. 

The photoinduced electron transfer behavior has also been confirmed by nanosecond transient absorption spectroscopy [102,103,108,111]. A representative transient absorption difference spectrum recorded 10 ps after laser flash excitation of 24a (0.05 mM) and 4-(methoxycarbonyl)-A[-methylpyridinium hexaflu-orophosphate (13 mM) in degassed acetonitrile (0.1 M "Bu4NPF6) is shown in... 

Several of the aforementioned compounds have now been examined by femtoseconds and nanoseconds, transient absorption spectroscopy in THF solutions. From the decay of the transients, the lifetimes of the photoexcited states SI and T1 have been determined. Representative compounds that have been examined in this manner are given in Table 6.3. 

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