Synthesis and Structural Characterization of 1D and 2D Coordination Polymers based on Flexible 1,3-Adamantanediacetic Acid and Exo-bidentate Organic Linkers

Abstract

Five mixed-linkers based coordination polymers, namely {M(1, 3-Hadc)(bpy)(H2O)(2)}(n) [M = Ni-II (1), Co-II (2)], {Zn(1, 3-adc)(bpy)(0.5)}(n) (3), {Cd(1, 3-Hadc)(2)(bpy)}(n) (4), and {Cu(1, 3-Hadc)(2)(bpp)}(n) (5) [1, 3-H(2)adc = 1, 3-adamantanediacetic acid, bpy = 4, 4-bipyridine, bpp = 1, 3-bis(4-pyridyl)propane] were synthesized by solvent diffusion reactions. Their structures were determined by single-crystal X-ray diffraction analyses. Compounds 1 and 2 are isostructural and they have 1D linear coordination polymer structure that are further interdigitated via hydrogen bonding resulting in 2D extended networks. The dehydrated 1 shows type-I profile for H2O vapor suggesting hydrophilic nature of the framework. In compound 3, a paddle-wheel type secondary building unit (SBU) directs the overall structure to form a 2D square grid type structure. The 2D sheets further stack along the c axis in a AB fashion and leaves no void space. Compound 4 has a hexacoordinate Cd-II and forms a zigzag coordination polymer chain-like structure and these chains form a 2D structure by hydrogen bonding interactions. Compound 5 contains a longer linker bpp compared to bpy and forms a 2D structure similar to that of 4. These results demonstrate that by changing the metal ions coordination mode versatile structures with different dimensionalities and network topologies can be realized in a same mixed linkers system.