NIR luminescent heterodinuclear [ZnII LnIII] complexes: Synthesis, crystal structures and photophysical properties

Abstract

Two series of new 3d-4f heterodinuclear [ZnIILnIII] Schiff base complexes of general formula [Zn(µ-L1)(µ-CH3COO)Ln(NO3)2(S)] [Ln = Pr (1), Nd (2), Sm (3), Gd (4); S = MeOH; H2L1= N,N-bis(3-methoxysalicylidene)-1,4-diaminobutane] and [Zn(µ-L2)(µ-CH3COO)Ln(NO3)2(S)] [Ln= Pr (5), Nd (6), Sm (7), Gd (8), S= MeOH; H2L2= N,N-bis(3-ethoxysalicylidene)-1,4-diaminobutane] are synthesized and fully characterized. Complexes 1, 2, 3, 4, 5 & 7 are structurally characterized by single crystal X-ray crystallography. The crystallographic investigation indicates that the complexes contain 9 and 10-coordinated LnIII ions, while the ZnII ions always display a distorted square-pyramidal geometry. The crystal structure of the complexes are stabilized by inter molecular extended hydrogen bonding and C-H····π interactions resulting in supramolecular frameworks. Luminescence studies for the heterodinuclear compounds containing NdIII & SmIII reveal that the Zn-complex moiety acts as antenna for the emission from LnIII ions. In addition to the ligand-centered emission in the UV–Vis region, complex 2 (having NdIII) exhibits emission in NIR region also, thus resulting a new NIR emitting material. © 2017