Microwave-assisted synthesis, spectroscopy, and crystal structures of [(H_2-(4,4'-bipy)]^{2+} [Cr_2O_7]^{2-} and one-dimensional polymeric {[Mn(4,4'-bipy)(Cr_2O_7)(H_2O)_2]\}_n compounds


Abstract: A compound (1), [H_2-(4,4'-bipy)]^{2+}[(Cr_2O_7)]^{2-} and a metal organic-inorganic coordination framework (2), [Mn(4,4'-bipy)(Cr_2O_77)(H_2O)_2] (4,4'-bipy=4,4' -bipyridine) were successfully synthesized by microwave method. Their characterization was performed by single crystal X-ray crystallography and FT-IR spectroscopy. The crystal structure of 1 revealed a diprotonated 4,4'-bipyridium dichromate compound while compound 2 is an onedimensional (1D) polymer in which (Cr_2O_7)^{2-} acts as a bridging ligand supporting the formation of infinite {[Mn(4,4'-bipy)(Cr_2O_7)(H_2O)_2]}_n polymeric chains. The geometry of the 4,4'-bipy ring in 1 is typical coplanar, but twists in 2. In the free molecule 1, dichromate ligand adopts an eclipsed conformation, but adopts a staggered conformation in complex. The principal features of the crystal supramolecularity of 1 and 2 are non-covalent weak interactions which occurred via N-H...O and C-H...O hydrogen bonding.

Keywords: Microwave assisted synthesis, organic-inorganic framework, diprotonated 4,4'-bipyridium, eclipsed conformation

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