R-Substituent-Induced Structural Diversity and Single-Crystal to Single-Crystal Transformation of Coordination Polymers: Synthesis, Luminescence, and Magnetic Behaviors

Four Zn(II) coordination polymers (CPs), namely, [Zn(3-bpdb)(MeO-ip)](n) (1), [Zn(3-bpdb)(EtO-ip)](n) (2), {[Zn(3-bpdb)(n-PrO-ip)].H2O}(n) (3), and [Zn(3-bpdb)(n-BuO-ip)](n) (4), have been first prepared under solvothermal conditions on the basis of four 5-substituted isophthalic acid ligands including 5-methoxy-1,3-benzenedicarboxylate (MeO-H(2)ip), 5-ethoxy-1,3-benzenedicarboxylate (EtO-H2ip), 5-propoxy-1,3-benzenedicarboxylate (n-PrO-H(2)ip), and 5-butoxy-1,3-benzenedicarboxylate (n-BuO-H(2)ip) with the help of 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpdb) as a secondary ligand. CPs 1 and 2 exhibit double pillared layered three-dimensional (3D) structures with non-interpenetrated fsc topology. CP 3 possesses a two-dimensional (2D) terrace layered structure with (4(2).6)(4(2).6(7).8) topology, while CP 4 features a one-dimensional (1D) infinite tubular helical chain. Second, when the orange-yellow crystals of 4 were immersed in the mother liquor at room temperature, vivid bright yellow crystals of {[Zn(3-bpdb)(n-BuO-ip)].2H(2)O}(n) (5) with a 2D terrace layered structure and bright yellow crystals of {[Zn(3-bpdb)(n-BuO-ip)(H2O)].1.5H(2)O}n (6) with a single-layered 2D (4,4) grid network were obtained on the 8th and 20th days by single-crystal-to-single-crystal (SCSC) phase transformation, respectively. These structural transformations were thoroughly studied by powder X-ray diffraction (PXRD) analysis and field-emission scanning electron microscopy (FE-SEM) along with single-crystal X-ray diffraction. In order to clarify the structure control factors in this series of CPs, similar reactions with 14 were continuously carried out, except that Zn(NO3)(2).6H(2)O was replaced by Co(NO3)(2).6H(2)O, and four Co(II)-based CPs formulated as [Co(3-bpdb)(MeO-ip)](n) (7), [Co(3-bpdb)(EtO-ip)](n) (8), {[Co(3-bpdb)(n-PrO-ip)].H2O}(n) (9), and [Co(3-bpdb)(n-BuO-ip)](n) (10) were purposefully constructed. The whole structures of 710 are isostructural with 13 and 5, respectively. The present results reveal that substitutions of isophthalic acid ligands with different lengths exert significant effects on the architecture of the CPs. Besides, the fluorescent properties of 16 were also investigated. The magnetic measurements indicate that CP 7 exhibits weak antiferromagnetic interactions, and CPs 810 exhibit weak ferromagnetic interactions within the binuclear (Co-II)(2) units. Magnetostructure relationships were investigated as well.

Automated summary

This study presents the synthesis and structural features of four zinc(II) and cobalt(II) based coordination polymers. The different lengths of isophthalic acid ligands resulted in distinct topologies, leading to varied optical and magnetic properties in the materials.