Pentanuclear 3d鈥?f Heterometal Complexes of MII3LnIII2 (M = Ni, Cu, Zn and Ln = Nd, Gd, Tb) Combinations: Syntheses, Structures, Magnetism, and Photolumines

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• 作者：Manoranjan Maity ; Mithun Chandra Majee ; Sanchita Kundu ; Swarna Kamal Samanta ; E. Carolina Sa帽udo ; Sanjib Ghosh ; Muktimoy Chaudhury
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：October 19, 2015
• 年：2015
• 卷：54
• 期：20
• 页码：9715-9726
• 全文大小：674K
• ISSN：1520-510X

文摘

A new family of pentanuclear 3d鈥?f heterometal complexes of general composition [Ln^III₂(M^IIL)₃(渭₃-O)₃H](ClO₄)路xH₂O (1鈥?b>5) [Ln = Nd, M = Zn, 1; Nd, Ni, 2; Nd, Cu, 3; Gd, Cu, 4; Tb, Cu, 5] have been synthesized in moderate yields (50鈥?0%) following a self-assembly reaction involving the hexadentate phenol-based ligand, viz., N,N-bis(2-hydroxy-3-methoxy-5-methylbenzyl)-N^{鈥?/sup>,N鈥?/sup>-diethylethylenediamine (H₂L). Single-crystal X-ray diffraction analyses have been used to characterize these complexes. The compounds are all isostructural, having a 3-fold axis of symmetry that passes through the 4f metal centers. The [MIIL] units in these complexes are acting as bis-bidentate metalloligands and, together with 渭₃-oxido bridging ligands, complete the slightly distorted monocapped square antiprismatic nine-coordination environment around the 4f metal centers. The cationic complexes also contain a H+ ion that occupies the central position at the 3-fold axis. Magnetic properties of the copper(II) complexes (3鈥?b>5) show a changeover from antiferromagnetic in 3 to ferromagnetic 3d鈥?f interactions in 4 and 5. For the isotropic CuII鈥揋dIII compound 4, the simulation of magnetic data provides very weak Cu鈥揋d (J₁ = 0.57 cm鈥?) and Gd鈥揋d exchange constants (J₂ = 0.14 cm鈥?). Compound 4 is the only member of this triad, showing a tail of an out-of-phase signal in the ac susceptibility measurement. A large-spin ground state (S = 17/2) and a negative value of D (鈭?.12 cm鈥?) result in a very small barrier (8 cm鈥?) for this compound. Among the three NdIII₂MII₃ (M = ZnII, NiII, and CuII) complexes, only the ZnII analogue (1) displays an NIR luminescence due to the 4F_3/2 鈫?4I_11/2 transition in NdIII when excited at 290 nm. The rest of the compounds do not show such NdIII/TbIII-based emission. The paramagnetic CuII and NiII ions quench the fluorescence in 2鈥?b>5 and thereby lower the population of the triplet state.}