The syntheses and characterization of a series of complexes of the general formula [Cl(bpy‘)Ru(tppz)Ru(bpy‘)Cl](PF6)2, where tppz is tetra-2-pyridylpyrazine and bpy‘ is 2,2‘-bipyridine or substituted 2,2‘-bipyridine, are described. Preparations with 2,2‘-bipyridine or 4,4‘-dimethyl-2,2‘-bipyridine (1 and 2, respectively) give mixtures of two isomers. The isomers of 2 were separated chromatographically and the X-ray crystal structure of the cis isomer was solved. Significant distortion is observed in both the coordination geometry around each ruthenium atom and in the tppz ligand resulting in short intramolecular Ru···Ru and Cl···Cl separations (6.558(1) and 5.880(2) Å, respectively). Ligands containing two bipyridine groups linked through eight- and nine-atom bridges have also been synthesized. The length of the bridge between bipyridine groups allows for the formation of cis complexes 3−5 having the general formula shown above but prevents formation of a trans isomer.

The chelate ligands 1 l-R-dipyrido[3,2-a:2',3'~]phenazine, dppz-R (R = NHz, CH3, H, COOH, NOz) and the Re(dppz-R)(CO)&l (R = NHz, COOH, NO2) complexes were synthesized and characterized by conventional techniques. The influence of the donor and acceptor properties of the R substituents on the ligand properties were studied by spectroscopic techniques such as 'H-NMR and UV-Vis. Theoretical calculations were also achieved, mainly to interpret and understand the experimental spectra.

) is an alternative to hypochlorites (NaOCl, Ca(OCl) 2 ) for fruit and vegetable sanitization to reduce postharvest decays caused, among other fungi, by Botrytis cinerea, Penicillium expansum and Rhizopus stolonifer. Due to economical reasons and because of its explosiveness, the use of chlorine dioxide has been relatively limited. However, the development of stabilized commercial formulations has allowed to reintroduce it. In this study, the efficacy of a new stabilized chlorine dioxide formulation (Tecsa®Clor, Protecsa S.A., Santiago,Chile) to inhibit conidial germination of B. cinerea and P. expansum, and sporangiospore germination of R. stolonifer was demonstrated. The efficacy was dependent primarily on concentration and exposure time but it was also affected by pH. Conidia germination of B. cinerea was inhibited over 98% at concentrations higher than 75 or at 25 µg·mL -1 after 1 or 30 min of contact, respectively. Similarly, over 90% inhibition of conidial germination of P. expansum was achieved with 100 and 25 µ·mL -1 after 1 and 30 min, respectively. Sporangiospores of R. stolonifer were inhibited by 90% at 100 µg·mL -1 for 30 min. The pH of the solution increased as chlorine dioxide concentration increased, and the biological activity decreased considerably at pH higher than 8, after 5 and 15 min of contact. No phytotoxic effects were obtained on pear cv. Packham's Triumph even at 1000 µg·mL -1 after 20-day-exposure at 20 ºC. Therefore the stabilized commercial formulation of chlorine dioxide is an alternative to chlorinate water to treat fruits by immersion in order to control B. cinerea, P. expansum and R. stolonifer during postharvest. For a complete control, concentrations higher than 75 µg·mL -1 should be used at pH between 7 and 8.