Improved synthesis of 4,4′-bipyridine-2-carboxylic acid and its use in the construction of novel metal and mixed-metal coordination polymers

Abstract

An improved synthesis of 4,4′-bipyridine-2-carboxylic acid (ppcaH) has significantly increased the yield and thus enabled the preparation of four new coordination compounds that contain copper, cobalt, and vanadium or molybdenum oxide. Each structure was synthesized solvothermally and characterized by both powder and single-crystal X-ray diffraction. Cu(ppca) 2 ( 1) is a discrete molecular complex that crystallizes in the P2 1/ c space group, a = 5.0749(4) Å, b = 25.442(2) Å, c = 7.2536(6) Å. Co(ppca)(SCN)(H 2O) ( 2) is a H-bonded 2D coordination polymer that crystallizes in the P2 1/ c space group, a = 11.0716(4) Å, b = 11.2327(4) Å, c = 10.2073(4) Å. [Cu(ppca)(Hppca)] 2[H 2Mo 4O 14] ( 3) and Co(ppca) 2(V 2O 6)(H 2O) ( 4) are mixed-metal coordination polymers that crystallize in the P 1 ¯ and Pbca space groups, respectively. Complex ( 3) is a 2D framework that contains an H 2Mo 4O 14 2− anion, a = 8.4019(6) Å, b = 8.6990(6) Å, c = 16.8513(12) Å, while ( 4) is a highly ordered H-bonded 3D mixed-metal coordination polymer whose vanadate cluster species was generated in situ using a tetramethyl ammonium hydroxide and acetic acid buffer solution, a = 18.0118(8) Å, b = 11.2664(5) Å, c = 25.3385(11) Å.