Vanadium polyoxoanion-bridged macrocyclic metal complexes: from one-dimensional to three-dimensional structures

Abstract

The reactions of four-coordinated transition metal macrocyclic complexes [ML](ClO₄)₂ (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, M = Ni, Cu) with NH₄VO₃ under different conditions gave four coordination polymers of {[(CuL)_0.5(H₂L)_1.5][H₂V₁₀O₂₈]·6H₂O}_n (1·6H₂O), {[NiL]₃[V₁₆O₃₈(H₂O)]·6H₂O}_n (2·6H₂O), {[NiL][VO₃]₂·0.33H₂O}_n (3·0.33H₂O), and {[CuL][VO₃]₂·0.33H₂O}_n (4·0.33H₂O). Single crystal X-ray diffraction analyses reveal that four diverse vanadium polyoxoanions, [H₂V₁₀O₂₈]⁴⁻cluster, [V₁₆O₃₈(H₂O)]⁶⁻ cage, [V₆O₁₈]⁶⁻ ring, and [VO₃]_nⁿ⁻ chain, were obtained from the same reactant NH₄VO₃ under different conditions. In 1, the cluster anion [H₂V₁₀O₂₈]⁴⁻ alternately bridges [CuL]²⁺/[H₂L]²⁺ to form a one-dimensional chain, and the [V₁₆O₃₈(H₂O)]⁶⁻ cage in 2 links three [NiL]²⁺ into a two-dimensional sheet. Compounds 3 and 4 show three-dimensional structures, which are constructed by the connections of hexanuclear [V₆O₁₈]⁶⁻ rings with [NiL]²⁺ in 3, and [VO₃]_nⁿ⁻ chains with [CuL]²⁺ in 4, respectively, generating one-dimensional channels occupied by guest water molecules.