Prabal Kumar Mallick

Raman excitation profiles and excited state molecular configurations of three isomeric phenyl pyridines

Contributions of different electronic states to Raman scattering have been studied by critical analyses of Raman excitation profiles (REPs) of several normal modes of vibration of three isomeric phenyl pyridines. In this context, possible structures and other interesting properties of the three molecules in the excited electronic states have been discussed. Normal mode characteristics are also described. Most likely a singlet state, lying in the vacuum ultraviolet region with respect to the ground state, is found to be playing a very significant role in the scattering phenomena.

Molecular structures in the excited states of 2‐ and 4‐benzylpyridine

Raman excitation profiles of several normal vibrations of 2- and 4-benzylpyridine were measured and analyzed. On the basis of the results, possible structures and other interesting properties of the two molecules in the excited electronic states are discussed. Normal mode characteristics are also described. It seems likely that a singlet state, lying in the vacuum ultraviolet region with respect to the ground state, plays a significant role in the scattering phenomena. Copyright

Raman excitation profile of diphenylamine

Abstract Vibrational analyses have been done on the basis of Raman and FTIR spectra of diphenylamine (DPA) and contributions of the two rings to different normal modes of vibration have been discussed. From the analyses of Raman excitation profiles (REPs) of several vibrational modes, useful information about the geometries of the molecule in different excited states have been obtained. Also vibronic coupling has been found to be important in the case of some Raman bands. Besides an interesting Molecular Orbital (MO) calculation, exploring the structure of DPA in the allowed singlet electronic state ( 1 L a ) , has been presented. Moreover, possible orientations of the two rings with respect to the amine nitrogen atom in the ground and in the 1 L a states have been discussed.

Excited state molecular configuration of biphenyl

Abstract Contributions of different electronic states to Raman scattering have been studied by critical analyses of Raman excitation profiles of several normal modes of vibration of biphenyl. In this context, the possible structure and other interesting properties of the molecule in the excited electronic states have been discussed. It is found that the first allowed transition to the excited state occurs at 248 nm whose major geometry change involves CC stretching vibrations, whereas, for the second allowed transition (corresponding to 205 nm) inter (i.e., substituent-sensitive) and intra (i.e., ring-breathing) ring CC stretching and in plane CCH angle bending modes are important.

N-heteroatomic effect on the photophysics of polyphenyl system : 2,6-diphenyl pyridine

Abstract From the detailed analysis of emission and absorption spectra of 2,6-diphenyl pyridine (DPP), m -terphenyl (MTP) and 2,6-luitidine (LTD) in different solvents, a striking change in absorption and emission characteristics of DPP compared to others could be observed. Consideration of through-space interaction of nonbonding electrons of the N atom and the π electrons of the outer rings becomes significant in explaining the dramatic change of absorption and emission character of the title compound in relation to a polyphenyl, MTP. The lowest excited singlet state of DPP is identified as 1 L a , indicating a crossover of states relative to MTP.

N heteroatomic effect on the photophysics of a polyphenyl system: 2,2′-dipyridylamine

Abstract A detailed investigation of the absorption and emission characteristics of 2,2′-dipyridylamine (DPyA) and diphenylamine (DPA) has been carried out in different polar and non-polar solvents at room temperature (300 K) and at 77K. A dramatic change in both the characteristics has been observed in DPyA in comparison with DPA. Measured fluorescence and phosphorescence lifetimes and critical study of the absorption and emission spectral data suggest that DPyA is more planar than DPA and its lowest-energy singlet state is of 1La type containing a little charge transfer character. Evidence of the presence of a 1 n π ∗ state has been found in DPyA on protonation in the binary mixture of water and sulphuric acid at room temperature.

Excited Electronic States and Raman Spectra of 2-Benzoylpyridine

Raman excitation profiles of several normal modes of 2-benzoylpyridine were measured, and the structural changes encountered on excitations, excited state symmetries, and vibronic couplings among various excited electronic states of the molecule were investigated. Vibrational spectroscopic studies of the molecule were done in detail, and critical investigation on the electronic spectra of the molecule was also carried out. It is shown that the experimentally allowed transitions, corresponding to the band around 262 and 238 nm, occur to the excited states, where the major geometry changes involve both ring CC/CN and CO stretching vibrations. An excited state lying around 185 nm above the ground state was also found to play an important role in the scattering process. All necessary and valuable quantum chemical calculations accompany the presented spectral studies.

Electronic and vibrational spectra of some rare earth trifluoromethanesulfonates crystals

The Raman and infrared spectra of some rare earth (dysprosium and terbium) trifluoromethanesulfonates crystals have been analyzed. Different vibrational frequencies of trifluoromethanesulfonate ions (CF3SO3-) are identified and assigned to different vibrations of the SO3 and CF3 groups. Electronic transitions of R3+ ions (R=Dy, Tb) in these salts have been assigned to transitions from the ground to different energy levels of the ground multiplet. The electronic energy levels of the rare earth ions are also determined theoretically with the help of single electron crystal field theory. They are found to yield results not only in good agreement with the observed spectral data but also in good conformity with those obtained previously from magnetic measurements.

Magnetic measurements, Raman and infrared spectra of metal–ligand complex derived from \(\hbox {CoCl}_{2}\cdot \hbox {6H}_{2}\hbox {O}\) and 2-benzoyl pyridine

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