LnIII/MnII–LnIII complexes derived from a salicylic azo dye ligand: synthesis, structures, magnetic and fluorescence properties

Abstract

Two Ln^III complexes Ln(HTMSA)₃(H₂O)₂·5.5H₂O (Ln = Dy (1) and Tb (2), H₂TMSA = 5-azotriazolyl-3-methoxysalicylaldehyde) and two Mn^II–Ln^III clusters [Mn(H₂O)₆][MnLn₂(TTMSA)₄(HTTMSA)₂(H₂O)₆]·4H₂O (Ln = Dy (3) and Tb (4), H₂TTMSA = 5-azotetrazolyl-3-methoxysalicylaldehyde) have been synthesized and structurally characterized. Single-crystal X-ray diffraction reveals that 1 and 2 are isostructural complexes in which the Ln^III ions are surrounded by six oxygen atoms from three chelate HTMSA ligands and two oxygen atoms from two coordinated water molecules forming a distorted square-anti-prismatic geometry. In complexes 3 and 4, the Mn^II ions adjust two Ln^III mononuclear anion clusters into tri-nuclear Ln^III–Mn^II–Ln^III anion clusters, with an additional [Mn(H₂O)₆]²⁺ as a counter ion to maintain the electroneutrality of the compound. Magnetic studies reveal that all the complexes 1–4 show nonzero out-of-phase signals, indicating single-molecule magnet behavior. The photoluminescence spectra of all the complexes were investigated and are discussed in detail.