Spectroscopic Study of a Typical Polyaromatic Hydrocarbon (Naphthalene) and a Biological π Acceptor (Folic acid) complex

Abstract

The complexation between folic acid and a typical polyaromatic hydrocarbon, naphthalene, was investigated using FTIR and UV spectra. Appearance of a new IR band at 2376 cm−1 demonstrates that NH2–C=N moiety on pterin ring in folic acid is protonated when naphthalene is introduced. The emergence of two charge transfer bands at 235 nm and 296 nm in UV difference spectra show the presence of π-π complexation between folic acid and naphthalene. These experiments confirm that naphthalene could combine with the pterin ring of folic acid through π-π donor–acceptor interaction and induce the protonation process in folic acid upon strengthening electron accepting ability of pterin ring. The results suggest that complexation between naphthalene and folic acid necessarily changes their charge distribution and the surroundings. It is inferred that not only biotransformation process of folic acid, but also the toxicity of polyaromatic hydrocarbons could be changed