Selenium bearing 24- and 28-membered macrocyclic schiff bases: syntheses and electrochemical behavior

In this communication we illustrate an effortless, convenient and less hazardous route for the synthesis of phenol based 24- and 28-membered macrocyclic Schiff bases, [Se2{(CH2)nN=C PhC6H2(OH)(4-CH3) PhC=N(CH2)n}2](where n= 2,LaH2; n = 3, LbH2) of Se2N4O2type have been developed by end-off [2+2] dipodal condensation of 2,6-dibenzoyl-4-methylphenol with the appropriate bis(aminoethyl/ propyl)selenide. The Schiff-bases (LaH2 and LbH2) have been well characterized by mass spectrometry, IR, electronic, 1H,13C{1H} and 77Se{1H} NMR spectroscopy and cyclic voltammetry. Applications of most of such organoselenium compounds have, however, been restricted by difficulties in synthetic methodologies, purification and instabilities of their certain derivatives. To overcome these potential difficulties, sterically bulky substituents and chelating groups in close proximity to selenium have been used. These Schiff-base framework is highly interesting as they can provide insight into competitive coordination behaviour between “hard (N and O)” and “soft (Se)” donors towards the metal center and also stabilize low as well as high oxidation states of a metal atom.