Design,Synthesis And Properties Of Novel Polynuclear Complexes With Oxamido-bridge

Through condensing N,N'-bis(2-aminoethyl)oxamide and two aldehydes we have synthesized and characterized two new Schiff base ligands with oxamido group ,namely N,N'- bis(2-aminoethyl) oxamido -bis(o- aminobenzaldehyde) (1) and N,N'-bis (2-amin-oethy l)oxamido -bis(3-carboxylsalicylidene) (2). New Cu(II),Ni(II) homobinuclear complexes have been synthesized and characterized. The studies by cyclic voltammetry show that two metal cations have the same electrochemical behavior bridged by the ligand (1) but two Ni(II) centers have the same behavior and two Cu(II) centers have different behavior bridged by the ligand (2).Through condensing o-aminobenzoic acid ,ethyl oxalyl chloride and 1,3 -propylenediamine, a new ligand N-(2-carboxyphenyl)-N'-(3-aminopropyl) oxamide(oxca) has been synthesized. Using mononuclear complex Na[Cu ( oxca)] -1.5H2O as building block we have synthesized five novel binuclear complexes [Cu(oxca)M(phen)2]ClO4-2H20, where phen=l,10-phenanthroline, M= Mn2+, Co2+, Ni2+,Cu2+,Zn2+. They have been characterized through the results obtained from elemental analysis, IR, electronic spectrum et al. The studies by cyclic voltammetry show that within the binuclear complexes "inner" Cu(II) is easy to reduct.The temperature dependence of the magnetic susceptibility of Cu(II)-Mn(II) and Cu(ir)-Ni(H) over the range 4 ~ 300K gave the exchange integral J= -10.56cm"1 and J= -17.08cm"1. It shows that when Cu(II) is under N3O coordination enviroment magnetic exchange interaction is smaller than under the N4 enviroment. Moreover , the change within Cu(II)-Ni(II) is more obvious. The reason is perhaps that O atom has higher electronegativity than N atom and then d-electron of Cu(II) has stronger delocalization.Using Na[Cu(oxca)] -l.SHaO as building block and adopting the strategy of "complexes as ligands" we have designed and synthesized and characterized five trinuclearcomplexes[CuCoxca)]2M-2H20 (M=Mn2\ Co2\ Ni2\ Cu2\ Zn2+) .The,studies by cyclic voltammetry show that within heterotrinuclears two Cu(II) have very different electrochemical behavior except [Cu(oxca)]2Zn-2H2O. The temperature dependence of the magnetic susceptibility of [Cu(oxca)]2Co-2H2O over the range 4 ~ 300K gave the exchange integral J= -28.09cm"1, g-2.13, F=3.81xlO"3.Using Na[Cu(oxca)] -l.SHiO as building block we have synthesized and characterized two rare earth-transition metal heterotetranuclear complexes [Cu(oxca)]3M(H2O)2-5H2O (M=Nd, Gd) . The electrochemical properties have been studied. The temperature dependence of the magnetic susceptibility of [Cu(oxca)]3Gd(H2O)2'5H2O over the range 4 ~ 300K gave the exchange integral J=0.537cm"1,g=1.955, F=5.68X 10~4. The smaller J value indicates that there is a very weak ferromagnetic spin exchange interaction between Cu+ and Gd3+ within heterotetranuclear complex. This may account for the fact that 4f-electrons are shielded by the outer shell electrons.