Benzophenone based photostable fluorescent monoazo disperse dyes: Synthesis, AIE, viscosity, UPF and TD-DFT study

Abstract

Synthesis of a parallel series of hydrophobic azo dyes (4-hydroxy benzophenone and corresponding 4-methoxy benzophenone series) and a comprehensive systematic spectroscopic study in solvents of varying polarity and viscosity is presented. This includes glycerol-dimethylsulfoxide, toluene–polyethylene glycol 400 and toluene–paraffin oil viscous mixtures. Emission intensities of dyes (hydrazone forms) were enhanced by 47–96 folds in viscous solvent media compared to the non-viscous media. So, role of hydrogen bonding in the emission enhancement were verified for 4-hydroxy benzophenone series with 4-methoxy benzophenone series. Polarity alteration effect on spectroscopic properties of dyes in various viscous combinations has been correlated by solvent polarity graphs. Density Functional Theory (DFT), Time Dependent Density Functional Theory (TD-DFT), HOMO–LUMO energy gap and Electrophilicity-index estimations are in good contract with the experimental interpretations. Dyes on PET fibers showed excellent light fastness. Moreover, all the dyes on dyed fabrics exhibited good sublimation fastness and color values. Ultraviolet A/Ultraviolet B blocking and Ultraviolet Protection Factor (UPF) of all the dyes range 15–50 and are in good agreement with light fastness.