Syntheses, supramolecular structures, magnetic and photochromic properties of six lanthanide complexes based on the 5-azotetrazolyl salicylic acid ligand

Abstract

Six lanthanide complexes based on the 5-azotetrazolyl salicylic acid (H₃ASA) ligand of {[Er(H₂ASA)(HASA)(H₂O)₆]·6H₂O} (1), {[Ln(H₂ASA)(HASA)(H₂O)₄]₂·6H₂O} [Ln = Er (2), Ho (3)], [Ln(H₂ASA)(HASA)(H₂O)₄] [Ln = Nd (4), Gd (5)] and {[Dy(ASA)(H₂O)₅]·5H₂O} (6) have been synthesized and characterized by single crystal X-ray diffraction analysis. In 1–6, the carboxyl group acts in different coordinating or bridging modes resulting in a mononuclear structure for 1, two dinuclear structures for 2 and 3 and three one-dimensional structures for 4–6, and the unusual π⁻–π stacking between tetrazolate anions and phenyl rings and various hydrogen bonding interactions are observed. The energies for π⁻–π stacking interactions were calculated and demonstrated at the MP₂ level using the Gaussion 09 suite. The magnetic properties of 2–6 and photochromism for aqueous solutions of 1–6 were investigated.