Department of Chemistry

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Author: search.filters.author.Chakraborty, ShamikSubject: search.filters.subject.Hydrocarbons

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    Protonated Benzene Dimer: An Experimental and Ab Initio Study
    (ACS, 2009-07-21) Chakraborty, Shamik
    The excitation spectrum of the protonated benzene dimer has been recorded in the 415−600 nm wavelength range. In contrast to the neutral iso-electronic benzene dimer, its absorption spectrum extends in the visible spectral region. This huge spectral shift has been interpreted with ab initio calculations, which indicate that the first excited states should be charge transfer states.
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    Gas-Phase Spectroscopy of Synephrine by Laser Desorption Supersonic Jet Technique
    (ACS, 2011-08-06) Chakraborty, Shamik
    In our previous work, we found that synephrine has six conformers in the gas phase, while adrenaline, which is a catecholamine and has the same side chain as synephrine, has been reported to have only two conformers. To determine the conformational geometries of synephrine, we measured resonance enhanced multiphoton ionization, ultraviolet–ultraviolet hole burning, and infrared dip spectra by utilizing the laser desorption supersonic jet technique. By comparing the observed infrared spectra with theoretical ones, we assigned geometries except for the orientations of the phenolic OH group. Comparison between the determined structures of synephrine and those of 2-methylaminno-1-phenylethanol, which has the same side chain as synephrine but no phenol OH group, leads to the conclusion that the phenolic OH group in synephrine does not affect the conformational flexibility of the side chain. In the case of adrenaline, which is expected to have 12 conformers if there are no interactions between the catecholic OH groups and the side chain, some interactions possibly exist between them because only two conformations are observed. By estimation of the dipole–dipole interaction energy between partial dipole moments of the catecholic OH groups and the side chain, it was concluded that the dipole–dipole interaction stabilizes specific conformers which are actually observed.