Guanidinium Bis(pyridine-2,6-dicarboxylato-N,O,O)manganese(II)

Numerous complexes of pyridinecarboxylic acids with transition metals have been investigated because of their interesting structural, redox and water oxidation properties. 1,2 Pyridine-2,6-dicarboxylic (dipicolinic) acid has been demonstrated in spores of aerobic and anaerobic bacteria. It is released during the germination of spores of aerobes. Pyridine-2,6-dicarboxylic forms a metal complex with divalent metal ions, especially with manganese and calcium. 3 Also the guanidinium cation has an important role in enzymes; for example, X-ray structural evidence places the guanidinium cation of the conserved arginine 357 residue of CP43 within a few Å to the Mn 4 Ca cluster of the water-oxidizing complex (WOC) in photosystem II. 4 The title complex was synthesized and structurally characterized by single-crystal X-ray diffraction. This complex was solved in the triclinic system, space group P 1 , with the following unit-cell parameters: a = 8.5657(4)Å, b = 10.9848(5)Å, c = 13.1681(6)Å, α = 112.617(1)˚, β = 99.646(1)˚, δ = 90.849(1)˚, Z = 2, V = 1123.28(9)Å 3 . The final R value was R 1 = 0.0344 for 15675 measured reflections.