Influence of chloro⋯chloro interaction and π–π stacking in 3D supramolecular framework construction

Abstract

A series of 1D and 2D coordination polymers have been synthesized under solvothermal conditions using a terminal ligand, 3,5,6-trichlorosalicylic acid (H₂TCSA) and different bipyridine based ligands, 2,2′-bipyridyl (2,2′-BIPY), 4,4′-bipyridyl (4,4′-BIPY), 4,4′-trimethylene bipyridine (TMBP) and trans-1,2-bis(4-pyridyl)-ethylene (TBPE). The major aim of this work was to study the influence of weak interactions in constructing 3D supramolecular frameworks. A two-step crystal engineering strategy has been adopted for generating 3D supramolecular frameworks. Firstly, various lower dimensional coordination networks have been achieved and then 3D supramolecular frameworks were constructed from the self-assembly of these networks via weak intermolecular interactions among the organic parts. The latter was achieved with the usage of ligand systems that are devoid of any conventional hydrogen bonding functional group. On the other hand, employment of a terminal ligand serves the purpose of generating different lower dimensional architectures, ranging from discrete zero dimensional coordination complexes to 1D, 2D coordination polymeric networks. We report herein, two 0D complexes, [Zn(HTCSA)₂(TBPE)₂] (1), [{Zn(TCSA)(2,2′-BIPY)}₄] (2), five 1D coordination polymers, [Zn(TCSA)(4,4′-BIPY)_0.5(DMF)]_n(3), [Zn(HTCSA)₂(4,4′-BIPY)]_n(4), [Zn(HTCSA)₂(TMBP)]_n(5), [Zn(HTCSA)₂(TMBP)]_n (6), [Zn(HTCSA)₂(TBPE)(H₂O)]_n (7), and two 2D polymeric networks, [Zn(TCSA)(4,4′-BIPY)]_n (8) and [{Zn(TCSA)(TBPE)}·(TBPE)]_n (9), and two related cobalt and nickel complexes, [{Co(TCSA)(TBPE)}·(TBPE)]_n (10) and [Ni(HTCSA)(TBPE)_1.5·(NO₃)]_n (11). For all the structures, π–π stacking and halogen bonding were found to be instrumental in bringing the additional dimensions to the self-assembly of the lower dimensional networks and lead to diverse 3D supramolecular frameworks.