Assembly of a series of zinc coordination polymers based on 5-functionalized isophthalic acids and dipyridyl

Abstract

To investigate the influence of different 5-functionalized isophthalate ligands on the self-assembly and structures of Zn(II)-based coordination polymers (CPs), we selected four 5-functionalized isophthalate ligands coordinated with 4,4′-bipyridyl (bpy) and Zn(II) salt, and four new CPs, namely, {[Zn(EtOip)(bpy)]·2H₂O}_n (1), {[Zn(PrOip)(bpy)]·2H₂O}_n (2), [Zn(ⁿBuOip)(bpy)]_n (3) and [Zn(ⁿPeOip)(bpy)]_n (4) (where EtOip = 5-ethoxyisophthalate, PrOip = 5-n-propoxyisophthalate, ⁿBuOip = 5-n-butoxyisophthalate and ⁿPeOip = 5-n-pentyloxyisophthalate), were prepared under hydrothermal conditions. Moreover, we considered changing the features of the N-ligands (length), which are expected to alter the structural diversities and properties of the resultant CPs. We used 1,2-bis(4-pyridyl)ethene (bpe) to replace bpy; and obtained four new coordination polymers (CPs), namely, {[Zn(EtOip)(bpe)]·H₂O}_n (5), {[Zn(PrOip)(bpe)]·H₂O}_n (6), {[Zn(ⁿBuOip)(bpe)]·0.5DMF}_n (7) and [Zn(ⁿPeOip)(bpe)]_n (8). All of these compounds were characterized by single crystal X-ray diffraction, infrared spectroscopy, elemental analysis and powder X-ray diffraction measurements. Single-crystal X-ray analysis reveals that the structure of complexes 1–4 are very similar, although different functionalized-isophthalate ligands are employed. Complexes 5, 6 and 7 possess a two-dimensional (2D) layered structure, and the 2D framework of complexes 5 and 7 can be rationalized to be a threefold interpenetrating four-connected {4⁴·6²} topological sql network, while 6 exhibits a twofold interpenetrating 4-connected 2D framework. Compound 8 features a 6-connected 3D topology net based on a novel bimetallic unit [(Zn)₂(CO₂)₂] linked by mixed ⁿPeOip and bpe ligands. Moreover, thermal and photoluminescence properties of the synthesized complexes were also studied in detail.