The surface active properties and antibacterial activity of the compounds, trans-[Rh(L)4Cl2]Cl . nH2O

The antibacterial activity and surfactant activity of the compounds trans-[Rh(L)4-Cl2]Cl . nH2O increase in the order L = pyridine less than 4-methylpyridine less than 4-ethylpyridine less than 4-n-propylpyridine. As surfactants, the compounds are far more effective at reducing the interfacial tension, n-hexadecane/H2O, than the surface tension, H2O/air. The most effective and efficient surfactant in this series, trans-[Rh(4-n-propylpyridine)4Cl2]Cl . H2O, can cause the leakage of intracellular manganese ions from the gram-positive bacteria, Bacillus brevis ATCC 9999, at a concentration of 130 ppm but there is no observable effect on the retention of intracellular manganese ions at the minimum concentration required to prevent growth of this organism (approximately 0.6 ppm at 23 degrees C in nutrient broth). At 130 ppm, trans-[Rh(4-n-propylpyridine)4Cl2]Cl . H2O does not cause the loss of intracellular manganese ions from the gram-negative bacteria, Escherichia coli JS-1. In this case, a concentration of at least 63 ppm of this rhodium compound is required to prevent the growth of this organism in M9TUH medium at 35 degrees C. On the basis of these results, it is suggested that gross membrane disruption effects caused by the surfactants trans-[Rh(L)4Cl2A1Cl . nH2O are not directly responsible for their observed antibacterial action.