Novel pyrazino-phenanthroline based rigid donor-π-acceptor compounds: A detail study of optical properties, acidochromism, solvatochromism and structure-property relationship

Donor-pi-acceptor-pi-auxiliary acceptor type compounds have been designed and synthesized to study their rigidity and structural effects on optical properties. Structural variation is achieved by changing the central pi-conjugated core with naphthalene, acenaphthene and phenanthrene based donor-pi-acceptor compounds containing N, N-diethyl aniline or morpholine as donor and pyrazine ring fused with phenanthroline as acceptor. A detailed study of positive and negative acidochromism is performed. Intramolecular charge transfer, solvatochromism and highly polar excited state of these compounds are elucidated by Lippert-Mataga, Mac-Rae and Reichardt correlations. Multilinear regression analysis using Kamlet-Taft and Catalan parameters is also performed to support the observed solvatochromism in absorption and emission spectra from non-polar to polar solvents. All the spectroscopic results were correlated theoretically by Density Functional Theory (DFT) computations. (C) 2016 Elsevier Ltd. All rights reserved.