Substituent and solvent effects on the dipole moments and photophysical properties of two azo sulfonamide dyes

Absorption and emission spectra of two azo sulfonamide dyes with different substituent, and size of lateral groups have been studied in different solvents. The solvatochromic method was used to investigate the dipole moments of these dyes in ground and excited states. In order to understand the effect of specific and non-specific interactions on the spectral behavior of these dyes and to conceive nature and extend of solvent–solute interactions, the dyes spectral features were analyzed by the linear solvation energy relationships concept.

► The dipolarity/polarizability and hydrogen bonding contribute into azo sulfonamide interactions predominantly.
► Investigated azo sulfonamide dyes show large dipole moment change on excitation.
► The azo sulfonamide dyes structural configuration can change through excitation.
► TICT increases planarity and polarity of azo sulfonamide dyes upon excitation.