Structural and photophysical properties of lanthanide complexes with N'- (2- methoxybenzylidene) - 2-pyridinecarbohydrazide Schiff base ligand: Catalyzed oxidation of anilines with hydrogen peroxide

• LaL (NO 3 ) 3 .xH 2 O and LnL 2 (NO 3 ) 3 .xH 2 O complexes are synthesized. • Complexes are characterized and screened for fluorescence nature. • Complexes catalyze the oxidation of aniline and its derivatives. • Sm and Eu complexes converted aniline selectively to nitroso-benzene. Several lanthanide (III) complexes { Ln : La, 1; Sm, 2; Eu, 3; Gd, 4; Tb, 5; Dy, 6 } with the Schiff base ligand, N'-​(2-​methoxybenzylidene)​-​2-pyridinecarbohydrazide, L , have been synthesized. These complexes having general formula LaL (NO 3 ) 3 .xH 2 O and LnL 2 (NO 3 ) 3 .xH 2 O, and the ligand L have been characterized by elemental analysis, spectral analysis (IR, 1 H and 13 C NMR), molar conductivity and thermogravimetric analysis. In the proposed structure of complex 1 , La(III) ion is ten coordinate. Six coordination sites are satisfied by three bi-dentate nitrate ions, one site is occupied by H 2 O and the remaining three positions are occupied by ONO belonging to one neutral L . In contrast the lanthanide ion in the proposed structures of complexes 2 - 6, is twelve coordinated by two three bi-dentate ONO L and three bi-dentate nitrate anions. The photophysical properties of L and 1 – 6 in DMF solution have been investigated and reported. Complexes 1 - 6 catalyze the oxidation of aniline 1a and its derivatives 1b - 1 g using H 2 O 2 as an oxygen source at an ambient conditions. Aniline is selectively converted to nitroso-benzene in the presence of complexes 2 and 3 . Complexes 4 – 6 gave mixtures of nitrozo- and azoxybenzenes. With complex 1 a mixture of nitroso-, azoxy- and azobenzenes were obtained. Among the substrates tested, the best result was obtained in the case of 1e with 78.6% conversion and 100% selectivity for the nitroso-benzene in the presence of 4 as a catalyst.