Three novel organic–inorganic complexes based on decavanadate [V10O28]6− units: special water layers, open 3D frameworks and yellow/blue luminescences

Abstract

Three unusual polyoxovanadate-based inorganic–organic hybrid complexes, [Zn(Im)₂(DMF)₂]₂[H₂V₁₀O₂₈]·Im·DMF (1), [Zn₃(Htrz)₆(H₂O)₆][V₁₀O₂₈]·10H₂O·Htrz (2) and {[Zn₃(trz)₃(H₂O)₄(DMF)]₂[V₁₀O₂₈]·4H₂O}_n (3) (Im = imidazole, Htrz = 1,2,4-triazole, DMF = N,N′-dimethylammonium) have been synthesized at room temperature via evaporative crystallization, and characterized by single-crystal X-ray diffraction. Complex 1 shows the structure of a discrete [V₁₀O₂₈]⁶⁻ cluster grafted by two [Zn(Im)₂(DMF)₂]²⁺ fragments through two bridged oxygen atoms, representing a rarely observed coordination mode. Complex 2 consists of a linear trinuclear Zn(II) unit bridging six Htrz ligands and a [V₁₀O₂₈]⁶⁻ cluster as the counter anion, where the extensive hydrogen-bonding interactions lead to {Zn₃–V₁₀}_SMF and a special water layer involving (H₂O)₃₆ rings, and consequently forms a unique 3D metal–organic–water supramolecular network. Complex 3 can be described as a 3,4-connected fsc-type network, and is the first example of open coordination 3D framework based on [V₁₀O₂₈]⁶⁻ and the other two different secondary building units, involving mononuclear and binuclear Zn(II)–Htrz motifs. The optical properties of complexes 1–3 in the solid state are investigated at room temperature. The results show that complexes 1 and 3 emit intense blue luminescences attributed to the ligands, while complex 2 exhibits an infrequent fluorescent property, emitting both blue and yellow luminescences at 472 and 603 nm simultaneously. Furthermore, powder X-ray diffraction and thermogravimetric analyses of 1–3 are also investigated, which demonstrate their high purities and thermal stabilities.