Synthesis, crystallographic and spectrophotometric studies of charge transfer complex formed between 2,2′-bipyridine and 3,5-dinitrosalicylic acid

Abstract

Crystals of a novel charge transfer compound of 2,2′-bipyridine with 3,5-dinitrosalicylic acid were isolated and studied. 2,2′-Bipyridine used in the reaction belongs to an important class of compounds with broad applications in various fields. The proton-transfer (charge transfer) complex was characterized by elemental analysis, FTIR, 1HNMR, TGA–DTA, ESI-mass spectra, UV–visible and single crystal X-ray analysis. Spectrophotometric studies have been made in various solvents with different polarities. Various important parameters such as formation constant (KCT), molar extinction coefficient (εCT), energy of interaction (ECT), ionization potential (ID), resonance energy (RN), free energy (∆G), resonance energy (RN) oscillator strength (f) and transition dipole moment (μN) were calculated and the effect of polarity on these parameters was also discussed. Spectroscopic studies show formation of 1:1 charge transfer complex between 2,2′-bipyridine and 3,5-dinitrosalicylic acid which is in good agreement with the application of the Benesi–Hildebrand equation. Single-crystal X-ray diffraction data of CT complex indicates that N+H⋯O− type hydrogen bonds are present between donor and acceptor moieties and corroborates the formation of the 1:1 CT complex.