Abstract
The syntheses and characterization of trans-[Ru IIIClL(1-(3-propylammonium)cyclam)] n+ (L=Cl −, trifluoromethanesulfonate, H 2O; 1-(3-propylammonium)cyclam=1-(3-propylammonium)-1,4,8,11-tetraazacyclotetradecane) are described. The p K a values of the propylammonium branch are 7.6 and 7.8 for the dichloro and chlorohydroxo complexes, respectively. The reduction potentials, E′ 1/2, for the Ru III/II processes are −385 and −240 mV vs Ag/AgCl for the dichloro and chloroaqua complexes, respectively. All compounds have one UV–Vis absorption band in the 300–360 nm assigned as ligand to metal charge transfer, similar to the corresponding cyclam complexes. The complex trans-[Ru IIICl 2(1-(3-propylammonium)cyclam)] 2+ releases one Cl − forming trans-[Ru IIICl(H 2O)(1-(3-propylammonium)cyclam)] 3+ in aqueous solution at pH 1 ( k=8.2×10 −5 s −1; 25 °C); the coordinated water of trans-[Ru IIICl(H 2O)(1-(3-propylammonium)cyclam)] 3+ has a p K a of 3.1. The reduced complex trans-[Ru IICl 2(1-(3-propylammonium)cyclam)] + aquates chloride by pseudo-first-order kinetics with k=0.29 s −1. Those rates are larger than in the corresponding cyclam complexes and are explained on the basis of the decrease of cyclam nitrogenhydrogen bonding interactions with the chloro ligands in the substituted cyclam.
Published Version
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