Synthesis, crystal structures, and properties of oxovanadium(IV)-lanthanide(III) heteronuclear complexes

A new series of oxovanadium(IV)-lanthanide(m) heteronuclear complexes [Yb(H2O)(8)]2[(VO)(2)- (TTHA)](3)-21H(2)O (1), {[Ho(H2O)(7)-(VO)(2)(TTHA)][(VO)(2)(TTHA)]0.5}(.) 8.5 H2O (2), {[Gd(H2O)(7)(VO)(2)- (TTHA)] [(VO)(2)(TTHA)](0.5)}(.)8.5 H2O (3), 1[Eu(H2O)(7)][(VO)(2)(TTHA)](1.5)](.) 10.5H(2)0 (4), and [Pr-2(H2O)(6)(SO4)]- [(VO)(2)(TTHA)] (5) (H(6)TTHA=triethylenetetraaminehexaacetic acid) were prepared by using the bulky flexible organic acid H(6)TTHA as structure-directing agent. X-ray crystallographic studies reveal that they contain the same [(VO)2(TTHA)]2- unit as building block, but the Ln(3+) ion lies in different coordination environments. Although the lanthanide ions always exhibit similar chemical behavior, the structures of the complexes are not homologous. Compound 1 is composed of a [Yb(H2O)(8)](3+) ion and a [(VO)(2)(TTHA)](2-) ion. Compounds 2 and 3 are isomorphous; both contain a trinuclear [Ln(H2O)(7)(VO)(2)(TTHA)](+) (Ln= Ho for 2 and Gd for 3) ion and a [(VO)2(TTHA)]2- ion. Compound 4 is an extended one-dimensional chain, in which each Eu3+ ion links two [(VO)(2)(TTHA)](2)- ions. For 5, the structure is further assembled into a three-dimensional network with an interesting framework topology comprising V2Pr2 and V4Pr2 heterometallic lattices. Moreover, 4 and 5 are the first oxovanadium(IV)-lanthanide(III) coordination polymers and thus enlarge the realm of 3d-4f complexes. The IR, UV/Vis, and EPR spectra and the magnetic properties of the heterometallic complexes were studied. Notably, 2 shows unusual ferromagnetic interactions between the VO2+ and Ho3+ ions.