Photophysics of a coumarin based Schiff base in solvents of varying polarities

Saptarshi Ghosh; Nayan Roy; T Sanjoy Singh; Nitin Chattopadhyay

doi:10.1016/j.saa.2017.07.006

Photophysics of a coumarin based Schiff base in solvents of varying polarities

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Jan 5:188:252-257. doi: 10.1016/j.saa.2017.07.006. Epub 2017 Jul 13.

Authors

Saptarshi Ghosh¹, Nayan Roy², T Sanjoy Singh², Nitin Chattopadhyay³

Affiliations

¹ Department of Chemistry, Jadavpur University, Jadavpur, Kolkata 700032, India.
² Department of Chemistry, Assam University, Silchar, Assam 788011, India.
³ Department of Chemistry, Jadavpur University, Jadavpur, Kolkata 700032, India. Electronic address: nitin.chattopadhyay@yahoo.com.

PMID: 28728100
DOI: 10.1016/j.saa.2017.07.006

Abstract

The present work reports detailed photophysics of a coumarin based Schiff base, namely, (E)-7-(((8-hydroxyquinolin-2-yl)methylene)amino)-4-methyl-2H-chromen-2-one (HMC) in different solvents of varying polarity exploiting steady state absorption, fluorescence and time resolved fluorescence spectroscopy. The dominant photophysical features of HMC are discussed in terms of emission from an intramolecular charge transfer (ICT) excited state. Molecular orbital (MO) diagrams as obtained from DFT based computational analysis confirms the occurrence of charge transfer from 8'-hydroxy quinoline moiety of the molecule to the coumarin part. The notable difference in the photophysical response of HMC from its analogous coumarin (C480) lies in a lower magnitude of fluorescence quantum yield of the former, particularly in the solvents of low polarity, which is rationalized by considering the higher rate of non-radiative decay of HMC in apolar solvents. Phosphorescence emission as well as phosphorescence lifetime of HMC has also been reported in 77K frozen matrix.

Keywords: Fluorescence; Intramolecular charge transfer; Molecular orbital; Photophysics; Schiff base.