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Issue 2, 2012
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Effect of ring torsion on intramolecular vibrational redistribution dynamics of 1,1′-binaphthyl and 2,2′-binaphthyl

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Abstract

The role of ring torsion in the enhancement of intramolecular vibrational energy redistribution (IVR) in aromatic molecules was investigated by conducting excitation and dispersed fluorescence spectroscopy of 1,1′-binaphthyl (1,1′-BN) and 2,2′-BN. The dispersed fluorescence spectra of 1,1′-BN in the origin region of S1–S0 were well resolved, which presented 25–27 cm−1 gaps of torsional mode in the ground state. The overall profile of the dispersed spectra of 1,1′-BN is similar to that of naphthalene. In contrast, the spectra of 2,2′-BN were not resolved due to the multitude of the active torsional modes. In both cases, dissipative IVR was observed to take place with a relatively small excess vibrational energy: 237.5 cm−1 for 1,1′-BN and 658 cm−1 for 2,2′-BN, which clearly shows that ring torsion efficiently enhances the IVR rate. Ab initio and density functional theory calculations with medium-sized basis sets showed that the torsional potential of 1,1′-BN has a very flat minimum over the range of torsional angles from ca. 60° to 120°, whereas that of 2,2′-BN showed two well-defined potential minima at ca. 40° and 140°, in resemblance to the case of biphenyl. In this work, we propose that aromatic molecules be classified into “strong” and “weak” torsional hindrance cases: molecules with strong hindrance case show shorter torsional progressions and more effective IVR dynamics than do those with weak hindrance.

Graphical abstract: Effect of ring torsion on intramolecular vibrational redistribution dynamics of 1,1′-binaphthyl and 2,2′-binaphthyl

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Publication details

The article was received on 07 Sep 2011, accepted on 07 Nov 2011 and first published on 28 Nov 2011


Article type: Paper
DOI: 10.1039/C1CP22854D
Citation: Phys. Chem. Chem. Phys., 2012,14, 840-848
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    Effect of ring torsion on intramolecular vibrational redistribution dynamics of 1,1′-binaphthyl and 2,2′-binaphthyl

    N. K. Lee, S. Park, M. Yoon, Z. H. Kim and S. K. Kim, Phys. Chem. Chem. Phys., 2012, 14, 840
    DOI: 10.1039/C1CP22854D

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