Solvatochromic studies of biologically active iodinated 4-aryloxymethyl coumarins and estimation of dipole moments

• Published in: Journal of molecular liquids 2015-02, Vol.202, p.9-16
• Main Authors: Raghavendra, U.P., Basanagouda, Mahantesha, Melavanki, R.M., Fattepur, R.H., Thipperudrappa, J.
• Format: Article
• Language: English
• Subjects: 4IPMBC; 4IPMMC; Coumarin; Dipole moment; Intramolecular charge transfer; Solvatochromic shift
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2014.12.003

The steady state absorption and emission spectra of biologically active iodinated 4-aryloxymethyl coumarins 4-(4-iodo-phenoxymethyl)-benzo[h]coumarin (4IPMBC) and 4-(4-iodo-phenoxymethyl)-6-methoxy coumarin (4IPMMC) are studied at room temperature in a series of solvents and 1,4-dioxane–acetonitrile solvent mixture. The effect of pure solvents upon the spectral properties are analyzed using Lippert–Mataga polarity function, Reichardt's microscopic solvent polarity parameter, Kamlet's and Catalan's multiple linear regression approaches. General solute–solvent interactions and hydrogen bonding interactions are operative in these systems. However, the contribution of later interaction is less. The solvatochromic data is used to estimate excited state dipole moment using experimentally determined ground state dipole moment. The bathochromic shift of emission spectra and increase in dipole moment after excitation indicate the intramolecular charge transfer (ICT) character in the emitting singlet state. The solvation studies in 1,4-dioxane–acetonitrile solvent mixture suggest that these dyes are preferentially solvated by 1,4-dioxane. [Display omitted] •The effect of solvents on spectral properties of biologically active coumarins is studied.•The double linear correlation of spectral properties with ETN is observed.•The dipole moment of dyes is higher in excited state compared to its value in ground state.