| Inspirted by the reasonable hydrolytic metalloenzyme models, we chose the pyrazole-based system to synthesize3,5-Bis[N,N-di(2-pyridylmethyl)-aminomethyl]pyrazole (HL1). HL1was used as the first llgand, and carbanyl group、 P2O74-and PO43-were acted as the second ligands, respectively. An array of bi-, tetra-and penta-nuclear copper and zinc complexes were synthesized, nine of which were structurally characterized by FT-IR, UV-Vis, FS, EA and X-ray crystallography, respectively.In this paper,3,5-Bis[N,N-di(2-pyridylmethyl)-aminomethyl]pyrazole (HL1) was used as first ligand and two dinuclear Cu(II) complexes,[Cu2(L1)(N3)](ClO4)2-H2O (1) and [Cu2(L1)(iso)](ClO4)2-0.5CH3OH (2), were obtained where NaN3and monocarbolylic acid isonicotinate (iso-) were the second ligands. Three tetranuclear Cu(II) complexes,[Cu4(L1)2(fuma)](ClO4)4-2CH3OH-3H2O (3),[Cu4(L1)2(pta)](ClO4)4-2CH3OH (4) and [Cu4(L1)2(PO4)](ClO4)3(5), were synthesized and characterized, where dicarboxylic acids fuma or pta, was the anoin of fumaric acid or terephthalic acid. When pyrophosphate acted as the second ligand, the penta-nuclear complex [Cu5(L1)2L2((μ-P2O7)](ClO4)4-CH3OH (6) was obtained and characterized. In these compounds, the two Cu(II) ions were bridged by one pyrazolate of L-to form a pyrazolato bridged dinuclear [CU2L1]3+unit. For complexes1and2, the structures show two Cu(II) atoms bridged by two pyrazolate N atoms of L1and by the second ligand to form a double bridged dinuclear core. The coordination geometries of two metal centers are different, distorted tetragonal pyramid for one and distorted trigonal bipyramid for the other. In complex3and4, two dinuclear units [Cu2L1]3+are connected by four O atoms in fuma anion and pta anion to form tetranuclear complexes, in which the four Cu(II) ions are in the same plane. Cul-Cu4in the two complexes exhibit distorted trigonal bipyramidal coordination. Two [CU2L1]3+are bridged by a central tetradentate PO43-group to form a novel tetranuclear complex5, which contains an unusual μ4-phopate bridge. The four Cu2+in two dinuclear moieties have somewhat different geometries:Cu(1), Cu(2) and Cu(4) exhibit a distorted trigonal bipyramidal coordination whereas Cu(3) show a distorted square pyramidal geometry. Because of the extensive exsistence in living organism of phopate, the synthesis of complex5is of great significance in modelling active sites of phosphate hydrolytic enzymes. In the study, we firstly prepared a penta-nuclear coper(II) complex6. Firstly,114-P2O74-coonect two [Cu2L1]3+and four metal ions exhibit distorted trigonal bipyramidal coordination. Then the two free O atoms of pyrophosphate coordinate [CuL2]+, where L2is the anion of2,2’-dipicolylamine. So two [Cu2L1]3+and [CuL2]+are connected by U6-P2O74-into a penta-nuclear motif. Cu(5) in [CuL2]+show a distorted square pyramidal geometry. It is shoule be noted that complex6and the coordination mode of μ6-P2O7-are first reported.Three Zn(II) complexes [Zn2(L1)(iso)](ClO4)2(7),[Zn4(L1)2(pta)](ClO4)4·2CH3H(8) and [Zn5(L1)2L2(μ-P2O7)](ClO4)4-CH3OH (9) have the same second ligands with the complex2、4and6, respectively and their structures are similar. Different from4, four Zn(II) are in the same plane and each two in diagonal position are completely equivalent. Complex9was obtained by the same synthetic procedure of6and copperperchlorate hydrate was replaced by Zinc perchlorate hexahydrate. Complex9and6have identical coordination structure. In all the reported pyrophosphate-bridged complexes, the first ligands are small molecular, such as pyridine and phenanthroline. In the basis of overcoming the difficulty of pyrophosphate hydrolysis, my study synthesized two pyrophosphate-bridging complexes6and9in which the N-donar pyrazole-based ligand is the first ligand. |
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