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)]}·8H2O (2), [Pr(H2O)7(VO)3(TTHA)1.5]·10H2O (3), and [Nd(H2O)7(VO)3(TTHA)1.5]·10H2O (4) (H6TTHA = triethylenetetraaminehexaacetic acid), were prepared based on a binuclear building block of [(VO)2(TTHA)]2- in [VO(H2O)5][(VO)2TTHA]·4H2O (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 Ln3+ 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 24 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.