Effect of increasing methoxyphenyl substitution on pyrene pyrazoline enduring green light emitting materials

Abstract

The pyrene pyrazoline derivatives containing mono, di and tri methoxy phenyl substituents were synthesized. Thermal stability and glass transition temperatures changed with progressive substitution of methoxy phenyl group. X-Ray Diffraction pattern revealed their crystalline nature. The photophysical properties of materials exhibited green emission at 510 nm (PP1My), 510 nm (PP2My) and 508 nm (PP3My) in solution and yellow emission at 580 nm (PP1My), 574 nm (PP2My) and 563 nm (PP3My) in solid state. The blue shift in the emission in solid state was owing to aggregation induced by methoxy substituent. The color chromaticity values were calculated for their color purity of green and yellow emissions. Ten different solvents were used to examine solvatochromism and red shifted emission observed in enhancing polarity of solvents and dual emission in cyclohexane were suggested twisted conformation of molecule that led to Intramolecular charge transfer becomes twisted Intramolecular charge transfer. Nonlinear optical properties of pyrazoline derivatives improved when electron donates methoxy groups and polyaromatic luminophore of pyrene were substituted on pyrazoline moiety. The third order nonlinear optical properties were investigated by Z-scan technique at 532 nm and exhibited strong reverse saturable absorption and self-defocusing natures. The optimized geometry evidences that molecules have twisted structures and looks like an antenna molecules. These kinds of molecules are demand in energy applications such as light harvesting solar materials and light emitting materials.