4-(1H-Imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzaldehyde as a probe in pure solvents: Solvatochromism, electric dipole moment and pH influence

Yulia E Begantsova; Evgeny V Baranov; Sergey A Chesnokov

doi:10.1016/j.saa.2022.121480

4-(1H-Imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzaldehyde as a probe in pure solvents: Solvatochromism, electric dipole moment and pH influence

Spectrochim Acta A Mol Biomol Spectrosc. 2022 Nov 5:280:121480. doi: 10.1016/j.saa.2022.121480. Epub 2022 Jun 17.

Authors

Yulia E Begantsova¹, Evgeny V Baranov², Sergey A Chesnokov²

Affiliations

¹ G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 Tropinin Str., Nizhny Novgorod 603950, Russian Federation. Electronic address: begantsova@mail.ru.
² G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 Tropinin Str., Nizhny Novgorod 603950, Russian Federation.

PMID: 35753103
DOI: 10.1016/j.saa.2022.121480

Abstract

The spectral properties of 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzaldehyde (1) in eleven organic solvents of different polarity have been studied. In order to determine the contributions of specific and non-specific interactions between the considered compound and the solvents, the solvatochromic Lippert-Mataga, McRae, Bakhshiev methods have been applied. The compound demonstrates positive solvatochromism. The dipole moment of the excited state of 1 obtained using the Reichardt method is equal to 10.56/7.08 D for trans- and cis-conformers, respectively, and agrees well with the theoretically calculated value. The influence of the polarizability of 1 on changes in the dipole moments has been analyzed using the Bilot-Kawski method. The multiple linear regression analysis in the framework of the Kamlet-Abboud-Taft and Catalán models has highlighted that the main properties which determine the Stokes shift of 1 are the acidity and dipolarity of the solvent. The variation of pH by additions of acid or base to solution 1 leads to significant changes in absorption and fluorescence spectra, therefore, 1 can be of interest as a solvatochromic probe, being sensitive to acidic/base properties of the environment. It has also been found out that the anion form of 1 is present in the DMSO solution. An addition of N,N-dimethylcyclohexylamine intensifies the dissociation of the considered compound in the DMSO solution and suppresses the fluorescence at a large amine excess.

Keywords: Acidochromism; Anion; Dissociation; Imidazole; NN-dimethylcyclohexylamine; Solvatochromism.