Spectroscopic studies on newly synthesized 5-(2-hydroxy-5-methoxy-phenyl)-2-phenyl-2H-pyridazin-3-one molecule

Abstract

Spectroscopic studies on newly synthesized biologically active pyridazin-3(2H)-one derivative 5-(2-hydroxy-5-methoxy-phenyl)-2-phenyl-2H-pyridazin-3-one (HMPP) molecule have been studied at room temperature in various solvents of different polarities. Theoretically, the ground state dipole moment was calculated using the Gaussian-09 program and experimentally by Guggenheim and Higasi methods. Calculated ground state dipole moment value by these three methods is well correlated. It is an inference that the molecular geometry is taken for HMPP molecule under theoretical and two experimental methods are similar. The excited state dipole moment (μe) was calculated using solvatochromic shift method which involves two equations proposed by Bakshiev's and Kawski-Chamma-Viallet's. The change in dipole moment (∆μ) was calculated both from solvatochromic shift method and microscopic solvent polarity parameter (ETN)later on the value is compared. We found that the excited state dipole moment (μe) is greater than the ground state dipole moment (μg) which indicates that the excited state is more polar than the ground state. Further, we studied the solvent effect on the spectral characteristics using the methods as suggested by Kamlet and Catalan. Furthermore, we studied the fluorescence quenching of HMPP molecule using aniline as a quencher in different solvents at room temperature, with a view to understanding the role of the activation process in a quenching mechanism. The probability of quenching per encounter (p) is determined in all solvents. Lastly, activation energy (Ea) of quenching was calculated using the literature value of activation energy for diffusion (Ed) and experimentally calculated value of p. The magnitude of these parameters indicates that the quenching phenomenon in HMPP molecule is due to an activation process.