Ln III /Mn II –Ln III complexes derived from a salicylic azo dye ligand: synthesis, structures, magnetic and fluorescence properties

Two Ln III complexes Ln(HTMSA) 3 (H 2 O) 2 ·5.5H 2 O (Ln = Dy (1) and Tb (2), H 2 TMSA = 5-azotriazolyl-3-methoxysalicylaldehyde) and two Mn II –Ln III clusters [Mn(H 2 O) 6 ][MnLn 2 (TTMSA) 4 (HTTMSA) 2 (H 2 O) 6 ]·4H 2 O (Ln = Dy (3) and Tb (4), H 2 TTMSA = 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(H 2 O) 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.