Rotational dynamics of 7-(dimethyl amino)-4-methoxy-1- methyl-1, 8-napthyridin-2(1H)-one in DMSO and acetonitrile solvents

Abstract

Steady-State anisotropy and time-resolved fluorescence decay measurements have been carried out by varying temperatures in DMSO and acetonitrile solvents to study the rotational reorientation dynamics of 7-(dimethylamino)-4-methoxy-1-methyl-1,8-napthyridin-2(1H)-one(Quinolon-390). Experimentally determined rotational re-orientation time values in DMSO are found to be higher than acetonitrile, which implies that Qu-390 experiences more friction in DMSO than acetonitrile. To understand this friction, the theoretically measured rotational reorientation times using Stokes-Einstein’s-Debye (SED), Geirer-Wirtz (GW), and Dote-Kivelson and Schwartz (DKS) models are compared with experimental ones. Theoretically, estimated Qu-390 rotational reorientation times in DMSO and acetonitrile underestimate the experimental values which emphasize that mechanical friction contribution is less and dielectric friction contribution is more. Interestingly the experimental value and stick theoretical value 164 Ps at around 320 K is the same in DMSO.