Single molecule magnet behavior and luminescence of {Ln} and {LnZn} complexes

A series of tetranuclear coordination clusters [Ln 4 L 2 (HL) 2 (μ 3 -OH) 2 (NO 3 ) 2 ](NO 3 ) 2 [Ln = Dy ( 1 ·3CH 3 CN·5H 2 O), Gd ( 2 ·4CH 3 CN·5H 2 O), H 2 L = 6,6′-dimethoxy-2,2′-[2,2-dimethylpropane-1,3-diylbis-(nitrilomethylidyne)] diphenol] and dinuclear complexes [LnZnL(NO 3 ) 3 (H 2 O)]·2CH 3 CN [Ln = Dy ( 3 ), Er ( 4 ), Yb ( 5 ), Lu ( 6 )] were prepared and characterized. Static magnetic measurements revealed the presence of ferromagnetic interactions between the Dy( iii ) ions and weak antiferromagnetic couplings between the Gd( iii ) ions in 1 and 2 . Dynamic magnetic studies showed that complexes 1 and 3 exhibit slow magnetic relaxation under a zero static field as expected for single molecule magnet (SMM) behavior, whereas complex 4 is a field-induced SMM. Clear hysteresis loops were observed for 1 and 3 at 2 K, verifying their SMM behavior. Luminescence investigations demonstrated that complexes 1 and 2 show ligand-based emission and can act as luminescence thermometers below 100 K, whereas complexes 3 and 5 display the characteristic emission of lanthanide ions. From the high-resolution emission spectra of 3 and 5 , the energy gaps between the ground state and excited states of Dy( iii ) and Yb( iii ) ions were determined. Two tetranuclear coordination clusters and four dinuclear heterometallic complexes have been synthesized and their structural analyses, magnetic investigations as well as luminescence studies are reported herein.