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

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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)]·H 2 O} 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-H 2 ip), 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)(H 2 O)]·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 1 – 4 were continuously carried out, except that Zn(NO 3 ) 2 ·6H 2 O was replaced by Co(NO 3 ) 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)]·H 2 O} n ( 9 ), and [Co(3-bpdb)( n -BuO-ip)] n ( 10 ) were purposefully constructed. The whole structures of 7 – 10 are isostructural with 1 – 3 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 1 – 6 were also investigated. The magnetic measurements indicate that CP 7 exhibits weak antiferromagnetic interactions, and CPs 8 – 10 exhibit weak ferromagnetic interactions within the binuclear (Co II ) 2 units. Magnetostructure relationships were investigated as well.