Synthesis and characterization of aromatic compounds containing imine and amine groups via oxidative polycondensation

Abstract

In this study, Schiff bases compounds were synthesized from the condensation of 3,5-diaminobenzoic acid and 4,4′-diaminobenzanilit with salicylaldehyde, o-vanillin, 4-hydroxy benzaldehyde, and 2-hydroxy-l-naphthaldehyde. The derived monomers were changed into their polyphenol species by oxidative polycondensation in aqueous alkaline medium by using NaOCl as the oxidant. At the optimum reaction conditions, the yield of 3,5-bis((2-hydroxynaphthalen-1-yl)metyleneamino) benzoic acid was 69%. The structures of the monomers and polymers were confirmed by FTIR, ultraviolet–visible (UV-vis), 1H-NMR, and 13C-NMR analyses. The 1H-NMR and 13C-NMR data showed that polymerization preceded by C–C and C–O couplings of the monomer units (phenylene and oxyphenylene groups). The molecular weight distribution of the product was determined by size exclusion chromatography. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index of P-4,4′-DABAVA were 20,970, 15,420 g mol−1, and 1.36 for NaOCl oxidant, respectively. The CV behaviors electrochemical HOMO, LUMO, and energy gaps (Eg) were investigated using glassy carbon electrode as the working electrode. Optical Eg band gaps were made UV-vis measurements. Solid-state electrical conductivities of both doped and undoped states of the synthesized polyphenols were evaluated showing that conductivity of P-3,5-DABAHNA is better than other polymers. Optical properties were investigated by UV-vis and fluorescence analyses. Maximum fluorescence intensity was obtained from the solution of P-3,5-DABAVA.