Coordination polymers built with transition metal sulphates and angular 2,5-bis(imidazol-1-yl)thiophene (thim2): synthesis, structure and photoluminescent properties

Abstract

The reactions of angular tritopic ligand 2,5-bis(imidazol-1-yl)thiophene (thim₂) with different metal sulphates afforded six new CPs {[M(thim₂)(SO₄)(H₂O)₂]₂·(thim₂)·(H₂O)}_n [M = Zn (1); Mn (2)], {[Cd(thim₂)(SO₄)(H₂O)]·(H₂O)}_n (3) and {[M(thim₂)₂(SO₄)]·(H₂O)_x}_n [M = Co, x = 7, (4); Ni, x = 7 (5); Cu, x = 6.5 (6)]. CPs 1 and 2 are isostructural with a 1D double chain propagating in a wave like fashion. Whereas, CP 3 exhibits a layered 2D network and in the case of 4–6 an isostructural 3D framework containing a 1D rhombic channel was obtained. In all the CPs there is an interesting sulphate ion binding mode to the metal centers, such as four membered M₂O₄ rings (1 and 2), six membered (Cd₂SO₃) 1-D chain (3) and MSO₄ (4–6) 1-D chain, which is further linked by thim₂ to form inorganic organic hybrid type systems. The stability of CPs (1–6) was monitored by TGA and a solid state photoluminescence study was carried out for 1 and 3 at room temperature.