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Abstract:
A series of isostructural d/f molecular compounds Zn(H2L)Ln(NO3)3·CH3OH (Ln = Dy (1), Tb (2) and Sm (3)) were synthesized by the introduction of a designed multifunctional ligand N,N′,N″,N″′-tetra(2-hydroxy-3-methoxy-5-methylbenzyl)-1,4,7,10-tetraazacyclododecan (H4L = C44H60N4O8). In the isostructural molecules, each crystallographically independent Zn²⁺ and Ln³⁺ centers are connected by two phenolic oxygen atoms. For the six-coordinate Zn²⁺ ion, the coordination geometry can be viewed as a regular bicapped square pyramid. While for the ten-coordinate Ln³⁺ ion, if each O,O′-chelated nitrate ligand is seen as a single coordination site, the coordination geometry can be viewed as a distorted pentagonal bipyramid. The fluorescent spectra show that compounds 2 and 3 exhibited characteristic sharp emissions of Tb³⁺ and Sm³⁺, respectively, while compound 1 was found to be a single-component white-light-emitting complex in the solid state. Thermal stabilities of the three compounds were investigated by using thermal gravimetric analysis. In addition, the thermal decomposition of compound 1 was confirmed by temperature-dependent powder X-ray diffraction technique.
