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), [H2 -(4,4' -bipy)$]^{2+}$ [($Cr_2O_7$)$]^{2-}$ and a metal organic-inorganic coordination framework (2), [Mn(4,4'-bipy)($Cr _2O_7$)($H_2 O)_2$] (4,4' bipy=4,4' -bipyridine) were successfully synthesized by microwave method. Their characterization was performed by single crystal X-ray crystallography and FTIR spectroscopy. The crystal structure of 1 revealed a diprotonated 4,4' -bipyridium dichromate compound while compound 2 is an onedimensional (1D) polymer in which ($Cr _20_7)^{2-}$ acts as a bridging ligand supporting the formation of infinite {[Mn(4,4' -bipy)($Cr _2O_7)(H_2 O)_2$ ]}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.