Construction of noninterpenetrating and interpenetrating Co(ii) networks with halogenated carboxylate modulated by auxiliary N-donor co-ligands: structural diversity, electrochemical and photocatalytic properties

Abstract

Six Co(II)-based coordination polymers (CPs) with characteristic frameworks and topologies—namely, [Co(L1)(DCTP)]_n (1), [Co(L2)(DCTP)]_n (2), [Co(L3)(DCTP)]_n (3), {[Co₃(L4)₃(DCTP)₃·H₂O]·H₂O}_n (4), [Co(L5)_1.5(DCTP)]_n (5) and [Co(L6)(DCTP)]_n (6)—were successfully hydrothermally synthesized by employing the halogenated linear ligand 2,5-dichloroterephthalic acid (H₂DCTP). The interpenetrated structures could be rationally modulated by auxiliary N-donor co-ligands containing 1,1′-(1,4-butanediyl)bis-1H-benzimidazole (L1), 1,4-bis(5,6-dimethylbenzimidazol-1-yl)-2-butylene (L2), 1,2-bis(2-methylbenzimidazol-1-ylmethyl)benzene (L3), 1,4-bis(2-methylbenzimidazol-1-ylmethyl)benzene (L4), 1,2-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene (L5) and 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene (L6). These diaphanous crystals were clearly characterized by elemental analysis, infrared (IR) spectra and X-ray powder diffraction (XRPD) as well as single-crystal X-ray diffraction analysis. With the aid of the flexible N-donor co-ligands, CP 1 occupies a non-interpenetrated 2D sheet with the point symbol {4⁴·6²} sql net topology, CP 2 possesses a 3D hexagon-shaped network with the point symbol {6⁶} three-fold interpenetrated sqc6 topology, CP 3 exhibits a 2D layer with the point symbol {4⁴·6²} sql net topology, CP 4 reveals an unusual 3D framework with the point symbol {4²·6³·8} three-fold interpenetrated sra topology, CP 5 has a 3D hexagon-shaped network with the point symbol {6⁶} two-fold interpenetrated sqc6 topology, while CP 6 displays a 3D hexagon-shaped network with the point symbol {6⁶} three-fold interpenetrated sqc6 topology. The diverse structures of CPs 1–6 illustrate that the substitute group and position of the methyl group of the bis(benzimidazole) derivatives play a significant role in the assembly of such interpenetrated frameworks. Moreover, luminescence properties and thermal behavior, as well as the electrochemical and photocatalytic properties of CPs 1–6 on the degradation of methylene blue, are also presented.