Fluorescence of copper(I) and mixed valence copper(I/II) complexes with dipicolinic acid and their catalytic activity on catechol oxidation

The pyridine-2,6-dicarboxylic acid or dipicolinic acid (H(2)DPA) is a unique biomarker for the detection of bacterial spores. Therefore the qualitative and quantitative determination of H(2)DPA is crucial for the timely detection of bacteria. Here, the first analysis of H(2)DPA which is based on the fluorescence of coinage metal complexes is reported. Catechol oxidase, on the other hand, is a copper containing oxidase enzyme that catalyzes the oxidation of ortho-diphenols into ortho-quinones. The catechol oxidation reaction is used in the determination of catecholamines, adrenaline, noradrenaline, dopamine, etc. Therefore, the development of new copper complexes which act as catechol oxidase models can be applied in the detection of these hormonally (adrenaline, noradrenaline, dopamine, etc.) active compounds. Thus, the copper(I) complex of dipicolinic acid (H(2)DPA) with formulae [Cu-I(HDPA)(TPP)(2)] center dot H2O (1) (TPP= triphenylphosphine) and the mixed valence copper(I/II) one with formulae {[Cu-II(DPA)(H(2)DPA)] center dot [Cu-I(TPP)(3)](2)}center dot 2DMSO (2) have been synthesized and characterized by m.p., FT-IR, UV-vis, Fluorescence and H-1 NMR spectroscopic techniques and X-ray crystallography. These complexes (1-2) and the known ones [Cu-II(DPA)(H(2)DPA)] (3) and [Cu2Cl2(TPP)(3)] (4) were used for the evaluation of their fluorescence properties. The excitation wavelengths maxima are observed at 350 nm while they emit at 407-496 nm. The catalytic activities of 1-3 on the oxidation of 3,5-di-tertbutyl-o-catechol to 3,5-di-tert-butyl-o-quinone were also studied spectrophotometrically. The high yields of 2 and 3 suggest their biomimetic behavior with catechol oxidase.