title: 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 (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.
authors.affiliation: Laboratoire de Spectrochimie Infrarouge et Raman (UMR 8516 du CNRS), Université des Sciences et Technologies de Lille, Bat C5, 59655 Villeneuve d'Ascq Cedex, France.
authors.forename: Zuzanna
authors.initials: Z
authors.lastname: Pawlowska
authors.forename: Aude
authors.initials: A
authors.lastname: Lietard
authors.forename: Stéphane
authors.initials: S
authors.lastname: Aloïse
authors.forename: Michel
authors.initials: M
authors.lastname: Sliwa
authors.forename: Abdenacer
authors.initials: A
authors.lastname: Idrissi
authors.forename: Olivier
authors.initials: O
authors.lastname: Poizat
authors.forename: Guy
authors.initials: G
authors.lastname: Buntinx
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Delbaere
authors.forename: Aurélie
authors.initials: A
authors.lastname: Perrier
authors.forename: François
authors.initials: F
authors.lastname: Maurel
authors.forename: Patrice
authors.initials: P
authors.lastname: Jacques
authors.forename: Jiro
authors.initials: J
authors.lastname: Abe