New p-aminophenol-based dendritic melamines. Iterative synthesis, structure, and electrochemical characterisation

Abstract

Avoiding any protective–deprotective step, the synthesis of new (G-0, -1, -2) dendritic melamines is reported. Their construction consisted of chemoselective S N 2–Ar amination of cyanuric chloride with p -aminophenol (peripheral unit) and piperazine or 4,4′-bipiperidine (linkers). This novel class of amino- s -triazines is primarily investigated by DFT calculations (optimal geometry and electronic structure) in tandem with (VT) 1 H NMR spectroscopy providing details of the rotational diastereomerism about the C( s -triazine)-N(exocyclic) partial double bonds, solvation effects and conformation of the linkers. These data are subsequently exploited in electrochemical investigations (cyclic voltammetry on the Pt electrode/DMSO, 0.1 M KCl). Two reversible electron-transfer phenomena have been observed. Thus, depending on the variable π-deficiency strength of the s -triazine ring acting as the EWG on the adjacent NH group and the ability of the latter to undergo redox processes in tandem with the phenolic p -HO group, two electrochemical pathways are proposed, namely the p-benzoquinonimine route and the electropolymerization route .