The Ubiquitous Paddle-Wheel Building Block in Two-Dimensional Coordination Polymers with Square Grid Structure


This work describes design of a series of new paddle-wheel binuclear clusters containing 2-D coordination polymers based on ditopic carboxylate linkers, 1,4-benzenedicarboxylate (BDC) or 2-amino,1,4-benzenedicarboxylate (Am-BDC). The strategic use of strongly coordinating base/solvent as blocking ligand to restrict the structure in 2-D space is explored, and the role of organic base on the overall structure formation is further elaborated. The isostructural [Zn(BDC)(Py)]n (1) and [Co(BDC(Py)]n (2) were formed by the use of strong base pyridine (Py) as a blocking ligand whereas reaction using N-methylimidazole (Mim) in place of pyridine gives [Co(BDC)(Mim)]n (3) with similar topology and coordination environment. The use of weak/non-coordinating base such as 2-chloropyrimidine, pyrazine, and tetramethylammoniumhexafluorophosphate [(CH3)4 N(PF6)] gives the DMF-coordinated 2-D frameworks, [Cu(BDC)(DMF)]n (4), [Zn(BDC)(DMF)]n (5), and [Zn(AmBDC)(DMF)]n (6). All the structures crystallize in monoclinic crystal system yielding 2-D nets with square grid 44 topology and solid state 3-D structure via extensive non-covalent supramolecular interactions. Surface area analysis via N2 adsorption of three representative 2-D coordination polymers, 1, 4, and 6, indicate that 4 has a surface area of 450 m2 g?1 which is a signature of microporosity, while 1 and 6 have moderate (161.6 m2 g?1) and negligible (33 m2 g?1) surface areas, respectively.



Second Department

Chemical and Biochemical Engineering

Keywords and Phrases

1,4-benzenedicarboxylate; 2-D coordination polymer; Paddle-wheel; Square grid topology; Transition metal

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Article - Journal

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Publication Date

01 Jul 2016