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(H<sub>2</sub>O)<sub>7</sub>(VO)(TTHA)<sub>0.5</sub>][(VO)<sub>2</sub>(TTHA)]}·8H<sub>2</sub>O (<b>2</b>), [Pr(H<sub>2</sub>O)<sub>7</sub>(VO)<sub>3</sub>(TTHA)<sub>1.5</sub>]·10H<sub>2</sub>O (<b>3</b>), and [Nd(H<sub>2</sub>O)<sub>7</sub>(VO)<sub>3</sub>(TTHA)<sub>1.5</sub>]·10H<sub>2</sub>O (<b>4</b>) (H<sub>6</sub>TTHA = triethylenetetraaminehexaacetic acid), were prepared based on a binuclear building block of [(VO)<sub>2</sub>(TTHA)]<sup>2-</sup> in [VO(H<sub>2</sub>O)<sub>5</sub>][(VO)<sub>2</sub>TTHA]·4H<sub>2</sub>O (<b>1</b>). The X-ray crystallographic studies show that <b>1</b> is an ion-pair complex, containing the [(VO)<sub>2</sub>(TTHA)]<sup>2-</sup> unit as a useful building block. Adding the light Ln<sup>3+</sup> 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 <b>2</b>−<b>4</b> are not homologous. <b>2</b> is exhibited as a one-dimensional coordination polymer, comprising an unusual Ce<sub>2</sub>V<sub>2</sub> heterometallic lattice in the chain structure, which is the second report of a oxovanadium(IV)−lanthanide(III) coordination polymer. <b>3</b> and <b>4</b> are isomorphic, every two of the Ln<sup>3+</sup> cations linked three [(VO)<sub>2</sub>(TTHA)]<sup>2-</sup> 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.