Royal Society of Chemistry, Physical Chemistry Chemical Physics, 29(13), p. 13185, 2011
DOI: 10.1039/c1cp20920e
Full text: Unavailable
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 (S 0 → S 2 ) and emission (S 1 →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 χ 2 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 μ g (S 0 ) = +9.1 D, μ e (S 2 ) = −1.5 D, μ e (S 1 ) = 0 D and μ g (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.