Influence of anion on the quadratic nonlinearity and depolarization ratios of scattered second harmonic light from cation-pi complexes

Ramasesha, S and Mukhopadhyay, S and Pandey, Ravindra and Das, Puspendu K and Zyss, Joseph (2012) Influence of anion on the quadratic nonlinearity and depolarization ratios of scattered second harmonic light from cation-pi complexes. In: JOURNAL OF CHEMICAL PHYSICS, 136 (19).

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Abstract

We have investigated quadratic nonlinearity (beta(HRS)) and linear and circular depolarization ratios (D and D', respectively) of a series of 1:1 complexes of tropyliumtetrafluoroborate as a cation and methyl-substituted benzenes as pi-donors by making polarization resolved hyper-Rayleigh scattering measurements in solution. The measured D and D' values are much lower than the values expected from a typical sandwich or a T-shaped geometry of a complex. In the cation-pi complexes studied here, the D value varies from 1.36 to 1.46 and D' from 1.62 to 1.72 depending on the number of methyl substitutions on the benzene ring. In order to probe it further, beta, D and D' were computed using the Zerner intermediate neglect of differential overlap-correction vector self-consistent reaction field technique including single and double configuration interactions in the absence and presence of BF4- anion. In the absence of the anion, the calculated value of D varies from 4.20 to 4.60 and that of D' from 2.45 to 2.72 which disagree with experimental values. However, by arranging three cation-pi BF4- complexes in a trigonal symmetry, the computed values are brought to agreement with experiments. When such an arrangement was not considered, the calculated beta values were lower than the experimental values by more than a factor of two. This unprecedented influence of the otherwise ``unimportant'' anion in solution on the beta value and depolarization ratios of these cation-pi complexes is highlighted and emphasized in this paper. (C) 2012 American Institute of Physics. http://dx.doi.org/10.1063/1.4716020]

Item Type:	Journal Article
Publication:	JOURNAL OF CHEMICAL PHYSICS
Publisher:	AMER INST PHYSICS
Additional Information:	copy right of this article belongs to American Institute of physics
Keywords:	configuration interactions:molecule-photon collisions: negative ions:optical harmonic generation:organic compounds: positive ions:Rayleigh scattering:SCF calculations
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	09 Jul 2012 10:03
Last Modified:	11 Jan 2013 11:24
URI:	http://eprints.iisc.ac.in/id/eprint/44692

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