Spectrophotometric study on the charge-transfer reaction between 4-aminopyridine with 2,5-dihydroxy-p-benzoquinone in methanol and the binary mixture 50% acetonitrile + 50% 1,4-dioxane (v/v)

Abstract

Charge-transfer (CT) reaction between 4-aminopyridine (4APy) as the electron donor with 2,5-dihydroxy-p-benzoquinone (DHBQ) as the electron acceptor has been investigated spectrophotometrically in methanol (MeOH) and a binary mixture composed of 50% acetonitrile and 50% 1,4-dioxane (v/v) (ANDI). The composition of the complex has been investigated utilising Job's and photometric titration methods to be 1:1. Benesi–Hildebrand equation has been applied to estimate the formation constant of the CT reaction (K CT) and the molecular extinction coefficient (ϵ) where they reached high values confirming high stability of the produced complex. The solid CT complex (4APy–DHBQ) was isolated, and elemental analysis proved its formation in 1:1 ratio. A spectral study on the formed complex has been carried out using infrared and 1H NMR measurements, where it included hydrogen bonding beside CT.