A series of Zn(ii) and Cd(ii) coordination polymers based on flexible bis-[(pyridyl)-benzimidazole] ligand and different carboxylates: syntheses, structures, and photoluminescent properties

Abstract

Eight new coordination polymers, namely, [Zn(m-bdc)(L)] (1), [Zn(NH₂–bdc)(L)] (2), [Zn₃(p-bdc)₃(L)]·2H₂O (3), [Zn₃(btc)₂(L)(H₂O)]·H₂O (4), [Cd(o-bdc)(L)(H₂O)] (5), [Cd(m-bdc)(L)] (6), [Cd(p-bdc)(L)(H₂O)] (7) and [Cd₂(btda)(L)]·H₂O (8) (m-H₂bdc = 1,3-benzenedicarboxylic acid, NH₂–H₂bdc = 5-NH₂–1,3-benzenedicarboxylic acid, p-H₂bdc = 1,4-benzenedicarboxylic acid, H₃btc = 1,3,5-benzenetricarboxylic acid, o-H₂bdc = 1,2-benzenedicarboxylic acid, btda = 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and L = 1,1′-(1,4-butanediyl)-bis[2-(3-pyridyl)benzimidazole]), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compounds 1 and 2 display bilayer structures. The neighboring layers of 2 are further linked by hydrogen-bonding interactions to form a 3D supramolecular architecture. Compound 3 shows a 3D 8-connected (3⁶·4¹⁰·5¹¹·6) topology. Compound 4 exhibits a 3D (3,4)-connected (5·7·8)₂(4²·6·7²·8)₂(4²·5²·6·7)₂(7²·8⁴) net. Compound 5 reveals a layer. The layers are further connected by π–π interactions to give rise to a 3D supramolecular architecture. Compound 6 shows a 3D framework with (3,5)-connected (4²·6)(4·10²)₂(4³·6·8⁴·10²) topology. The structure of compound 7 is a 3D (3,4)-connected framework with (4·8²)(4·9·10)₂(4²·8²·9²·10⁴) topology. Compound 8 displays a 3D (3,4)-connected (4·10²)₂(4²·8²·10²)(4²·8⁴)₂ topology. Their photoluminescent behaviours have been investigated in detail.