An Atropisomeric Chiral 2,2'-bipyridyl-3,3'-dicarboxylic Acid and Corresponding Platinum(II) Complex


Abstract: 2,2'-Bipyridyl-3,3'-dicarboxylic acid (H_2BDC) spontaneously resolves on crystallization from water, giving monohydrated crystals of the space group P2_12_12_1. In any individual crystal, all the atropisomeric-skewed molecules are of one hand; however, on dissolution in water, optical activity is lost. Strong hydrogen bonding leads to a helical structure, via O--H ... N links, and 3 further strong bonds between water and carboxylate groups produce a framework structure. The pK_a values measured for H_2BDC (3.18 \pm 0.04 and 4.59 \pm 0.02 at 20 \pm 1 °C, in dilute aqueous solution) agree with the zwitterionic form. The reaction of H_2BDC with potassium tetrachloroplatinate(II) in water gives Pt(H_2BDC)Cl_2 . H_2O. The complex was characterized by elemental analysis and spectroscopic techniques.

Keywords: Platinum complexes, 3,3'-dicarboxyl-2,2'-bipyridine ligand, Crystal structure, Spontaneous resolution, Hydrogen bonding

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