Synthesis, Crystal Structures, and Properties of Oxovanadium(IV)–Lanthanide(III) Heteronuclear Complexes

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Abstract
A new series of oxovanadium(IV)–lanthanide(III) heteronuclear complexes [Yb(H2O)8]2[(VO)2(TTHA)]3⋅21 H2O (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), {[Eu(H2O)7][(VO)2(TTHA)]1.5}⋅ 10.5 H2O (4), and [Pr2(H2O)6(SO4)2][(VO)2(TTHA)] (5) (H6TTHA=triethylenetetraaminehexaacetic acid) were prepared by using the bulky flexible organic acid H6TTHA as structure‐directing agent. X‐ray crystallographic studies reveal that they contain the same [(VO)2(TTHA)]2− unit as building block, but the Ln3+ 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.