Issue 29, 2011

The excited state dipole moments of betaine pyridinium investigated by an innovative solvatochromic analysis and TDDFT calculations

Abstract

This work reports on the solvatochromic properties of a simple heterocyclic betaine pyridinium, 2-(1-pyridinio)benzimidazolate (SBPa), having promising potentialities in non-linear optics. From advanced PCM-TDDFT calculations, the solvatochromism of SBPa was found to be unusual, involving two different electronic states for absorption (S0 → S2) and emission (S1→S′0). To account for this behavior, we developed an innovative physical treatment which consists in a non-linear fit of the solvatochromic data using the Bilot–Kawski theoretical model and visualizing the least-square coefficient χ2 on a 2D map as a function of the solute polarizability and gas phase absorption energy. In parallel, Kamlet–Taft correlations were undertaken to select a propitious set of electrostatic solvents usable in this treatment. Protic solvents that lead to specific interactions and nonpolar solvents that favor dimerization processes were excluded. From a choice of aprotic solvents with sufficiently high polarity, 4 dipole moments μg(S0) = +9.1 D, μe(S2) = −1.5 D, μe(S1) = 0 D and μg(S′0) = +3.31 D were determined, the 3 former values being in close agreement with TDDFT values, although the solute polarizability values seem underestimated. Anyhow, disregarding this discrepancy, we evaluated the static hyperpolarizability to β(0) = −64 × 10−30 esu from the solvatochromic data in close agreement with DFT calculations.

Graphical abstract: The excited state dipole moments of betaine pyridinium investigated by an innovative solvatochromic analysis and TDDFT calculations

Supplementary files

Article information

Article type
Paper
Submitted
25 Mar 2011
Accepted
30 Apr 2011
First published
22 Jun 2011

Phys. Chem. Chem. Phys., 2011,13, 13185-13195

The excited state dipole moments of betaine pyridinium investigated by an innovative solvatochromic analysis and TDDFT calculations

Z. Pawlowska, A. Lietard, S. Aloïse, M. Sliwa, A. Idrissi, O. Poizat, G. Buntinx, S. Delbaere, A. Perrier, F. Maurel, P. Jacques and J. Abe, Phys. Chem. Chem. Phys., 2011, 13, 13185 DOI: 10.1039/C1CP20920E

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