Antimony(v) complexes with tetradentate ONNO redox-active ligands: optical, electrochemical and photothermal properties

Abstract

New antimony(V) complexes, 1 and 2, containing the redox-active ligands N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (LH₄) and glyoxal-bis(2-hydroxy-3,5-di-tert-butylanil) (L′H₂), respectively, were synthesized and characterized. Single-crystal X-ray diffraction analysis showed that complexes 1 and 2 exhibit distorted pentagonal bipyramidal structures. These complexes contain a tetradentate, redox-active ONNO ligand that, doubly deprotonated, forms a dianion with a nearly planar core. The UV/vis/NIR absorption spectra of 1 and 2 demonstrate intense bands in the 500–1000 nm range attributed to intraligand charge transfer (ILCT). Electrochemical analysis demonstrates the redox-amphoteric properties of complexes 1 and 2. Complex 1 also exhibits efficient photothermal conversion (η = 57%) under 808 nm laser irradiation.