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An examination is done on the photophysical properties of (oligo)polyfurans. It is found that it is not possible to clearly distinguish whether cis and trans conformers simultaneously exist (most likely for F2), or the magnitude of inter-ring bond twisting but the latter appears to be no more than 20--30 degrees and the virtual molecules at 77 K are clearly more planar than at room temperature.

A new study investigates the photophysical properties of hydroxy-substituted flavothiones.

Research was conducted to examine the reaction quantum yield (phi-PC) and fluorescence quantum yield (phi-F) of a photochromic molecule, flinderine, as a function of the vibronic level excited within a given sequence. A new model is proposed to permit the determination of the molar extinction coefficient of the partially produced colored form, the quantum yield, the photochemical reaction rate constant, the vibrational relaxation rate constant and the nonradiative internal-conversion rate constant. Results indicate a vibronic-level dependence for phi-PC and phi-F.

Photochromic hydrazones of benzaldehyde compounds were studied under microsecond and nanosecond laser flash spectroscopy and they were all found to exhibit anti to syn isomerization. Morover, the lowest excited singlet state of 2-hydroxybenzaldehyde hydrazones featured competing isomerization and protonation mechanisms. In addition, the photophysics and photochemistry of the hydrazone compounds at the excited state were influenced by the nature of the functional groups and the hydrogen-bonding property of the solvent.

The photophysics of several oligomers containing mixed furan, pyrrole, and thiophene heterocyclic systems is reported. The mixed systems contain three rings and five rings of the heterocycles. Comprehensive spectroscopic and photophysical data were obtained and all of the rate constants k[sub F], k[sub IC], and k[sub ISC] were evaluated. The lowest singlet excited state is of ( 1 )B-like origin in any solvent. It is possible to have a reasonable understanding of the photophysics of the mixed ring systems compared to all the thiophene analogs if it is considered that some π-electron decoupling occurs at the site of the pyrrole or furan substitution, although this cannot be the total answer, as is discussed. [ABSTRACT FROM AUTHOR]

The excited-state ring-opening reaction coordinate for 2H-chromene (C) and 2,2-diethyl-2H-chromene (DEC) is determined and an explanation for such an unusual mode-dependent behavior is provided using ab initio CASPT2/CASSCF calculations. It is revealed that excited-state relaxation and decay occur through a multimodal and barrierless reaction coordinate.

A report on the potential of photochromic agents, which are compounds with the ability to undergo light-induced, reversible reactions, to be used as effective photoaffinity ligands is presented. The results demonstrate that chromenes are effective photoaffinity reagents for the cytochrome P450 superfamily of enzymes and probably other proteins as well.

Focuses on the photophysical behavior of 3-chloro-7-methoxy-4-methylcoumarin (CIMMC) as a function of the solvent and temperature. Representative solvents yielded by the triplet formation quantum; Factors that dictate the photophysical behavior of CIMMC; Rate constants and activation energies for the radiationless processes.

The dynamics of three distinctively different optical changes of three different cholesteric liquid crystal mixtures of different pitch doped with a guest molecule are seen for the first time utilizing single laser beam excitation. The guest molecule acted as a light absorber and subsequent fast heat radiator. Two of the three cholesteric mixtures had opposite directions of pitch change from the third with increasing temperature. In the first optical process (also the fastest), just after laser excitation, ≤200 ns, the reflectance band always moved to longer wavelength irrespective of the magnitude of the original pitch or the directional sensitivity of the pitch change to increasing temperature. This nanosecond time domain phenomenon is assigned as originating from formation of a transient grating caused by modulation of the index of refraction associated with heat instantaneously (≤10 ps) released by the guest molecules to their immediate neighborhood. The second process, in the time domain of 30–600 μs, is mainly the result of the characteristic pitch change of the helix of the cholesteric mixtures with corresponding reflection band shift to longer or shorter wavelengths according to the type of mixture. The final process (>1000 μs) is the consequence of the pitch of the cholesteric returning to the original value after the heat is dissipated. [ABSTRACT FROM AUTHOR]