Construction of 3d-4f mixed-metal complexes based on a binuclear oxovanadium unit: Synthesis, crystal structure, EPR, and magnetic properties

The oxovanadium(IV)-lanthanide(III) heteronuclear complexes, {[Ce(H2O)(7)(VO)(TTHA)(0.5)][(VO)(2)(TTHA)]}center dot 8H(2)O (2), [Pr(H2O)(7)(VO)(3)(TTHA)(1.5)]center dot 10H(2)O (3), and [Nd(H2O)(7)(VO)(3)(TTHA)(1.5)]center dot 10H(2)O (4) (H(6)TTHA = triethylenetetraamine-hexaacetic acid), were prepared based on a binuclear building block of [(VO)(2)(TTHA)](2-) in [VO(H2O)(5)][(VO)(2)TTHA]center dot 4H(2)O (1). The X-ray crystallographic studies show that 1 is an ion-pair complex, containing the [(VO)(2)(TTHA)](2-) unit as a useful building block. Adding the light Ln(3+) ions to this synthesis system, three new 3d-4f mixed-metal-based complexes were obtained. Although the light lanthanide ions always exhibit similar chemical behavior, the structures of 2-4 are not homologous. 2 is exhibited as a one-dimensional coordination polymer, comprising an unusual Ce2V2 heterometallic lattice in the chain structure, which is the second report of a oxovanadium(IV) lanthanide (III) coordination polymer. 3 and 4 are isomorphic, every two of the Ln3+ cations linked three [(VO)(2)(TTHA)](2-) anions, forming an interesting linear octanuclear structure. This kind of heteronuclear linear complex is rather rare, which expands the realm of 3d-4f complexes. Further investigations such as IR spectra, UV-vis spectra, magnetic properties, and EPR spectra were studied, and a detailed discussion is given for this system.