Single molecule magnet behavior and luminescence of {Ln 4 } 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.