Structural diversity and luminescence properties of coordination polymers based on mixed ligands, 2,5-bis(imidazol-1-yl)thiophene (thim2) and aromatic multicarboxylates

Abstract

Seven new CPs, {[Zn(thim₂)(o-BDC)]·(H₂O)₂}_n (1), [Co(thim₂)(m-BDC)]_n (2), {[M(thim₂)(HBTC)]·(H₂O)}_n [M = Co(3) and Zn(4)], {[M(thim₂)(OBA)]·(H₂O)₂}_n [M = Co(5) and Zn(6)], [Mn₂(thim₂)₂(m-BDC)₂(H₂O)]_n (7) [o-H₂BDC = phthalic acid, m-H₂BDC = isophthalic acid, H₃BTC = trimesic acid, H₂OBA = 4,4′oxybis(benzoic acid)], have been prepared by hydro/solvothermal reaction of different metal salts with 2,5-bis(imidazol-1-yl)thiophene (thim₂) in the presence of various multicarboxylic acids. CP 1 exhibits a 2D herringbone pleated network structure. CP 2 reveals a 2D + 2D = 3D polycatenated framework composed of a 2D parallel pleated network. CPs 3 and 4 show isostructural 2D herringbone pleated networks. CPs 5 and 6 are also isostructural and form a 2D layer structure arranged in a ⋯ABAB⋯ pattern in the crystal lattice. CP 7 forms a 3D framework consisting of 1D [Mn₂(m-BDC)₂(H₂O)]_n chains linked by thim₂. The structures of all five type of CPs indicate that different multicarboxylate coligands play an important role in structural variation. The thermal stabilities of all the CPs (1–7) were monitored by TGA. Furthermore, solid state photoluminescence was investigated for 1, 4 and 6 at room temperature.