Investigation of Optoelectronically Active Coumarin Based Substitute (PM6C and PM7C) Derivatives Using Photophysical...

The solvatochromic effect and dipole moment characteristics of 4-(2-iodo-phenoxymethyl)-6-methoxy-chromen-2-one (PM6C) and 4-(2-iodo-phenoxymethyl)-7-methoxy-chromen-2-one (PM7C) were examined at room temperature using absorption and emission spectra in a series of solvents with increasing polarity. Stokes shift obtained from spectral data is found to be bathochromic in nature for both the molecules, indicating π-π* transitions. The ground state and excited state dipole moments of PM6C and PM7C were determined by the means of Lippert-Mataga, Bakhshiev, Kawaski-Chamma-Viallet, and Reichardt's solvent polarity functions. Excited state dipole moments were found to be larger than the ground state dipole moment due to significant redistribution of the π-electron density in more polar excited state. Computational examination using the density functional theory (DFT) method validates the results calculated through solvent polarity functions. The HOMO and LUMO energy bands obtained by DFT approach are found be in good agreement with cyclic voltammetry data. The energy gap, chemical hardness (ɳ), chemical softness (s), ionization potential (IP), electron affinity (EA), electronegativity (χ), electrophilicity (ω), and chemical potential (µ) of the molecules were estimated using the values of HOMO and LUMO energy bands. The electrical conductivity and charge transport characteristics of the synthesized molecules are studied through A.C Impedance behaviour. This study gives comprehensive understanding of the molecules involvement in an optoelectronic device.