Catalytic and electrocatalytic wet oxidation of phenol using two new nickel(II) tetraazamacrocycle complexes under heterogeneous conditions

Abstract

Two new tetraazamacrocycle complexes, namely, 7,16-dinicotinoyl[Ni{Me 4(4-MeBzo) 2[14]tetraeneN 4}] and 7,16-diisonicotinoyl[Ni{Me 4(4-MeBzo) 2[14]tetraeneN 4}] (where [Ni{Me 4(4-MeBzo) 2[14]tetraeneN 4}] = 5,7,12,14-tetramethyldi-4-methylbenzo[ b, i][1,4,8,11]tetraazacyclo-tetradecahexaenatonickel(II)) were synthesized by acylation of [Ni{Me 4(4-MeBzo) 2[14]tetraeneN 4}] and characterized using spectral and microanalytical data. All tetraazamacrocycle complexes were found to catalyze chemical oxidation of phenol by H 2O 2 to catechol and hydroquinone and it is found that 7,16-diisonicotinoyl[Ni{Me 4(4-MeBzo) 2[14]tetraeneN 4}] showed the best performance. Catechol as the major product and hydroquinone as the minor were characterized respectively under optimal values of some parameters such as amount of catalyst, reaction temperature, oxidant and substrate concentration, effect of reaction media and reaction time. Electrocatalytic oxidation of phenol on glassy carbon electrode modified by the synthesized macrocycle complexes has also been studied.