Abstract
When a solution containing the complex ion, [PtCl6]=, and NH4+ ions is irradiated, a photochemical change occurs in which the chloride ions of the ligand are sequentially replaced by 1, 2, or 3 ammonia molecules. The total charge on the complex ion decreases by 1 negative charge for each replacement. These changes can be followed by changes occurring in absorption spectra or in ionophoretic patterns. Each charged species of the complex has a unique effect on the bacteriological growth of Escherichia coli. The doubly negative species is a bacteriocide. The singly negative species appears to have little effect on either growth or cell division processes. The neutral species has little effect on growth, but markedly inhibits cell division processes, forcing filamentous growth. The cis and trans forms of the diamino complex, [PtCl4(NH3)2]0, have been synthesized. The absorption spectra of both have a λmax at 207 mµ. The electrophoretic patterns indicate predominantly neutral species in both cases. The trans form is relatively inefficient in inhibiting cell division, whereas the cis form is fully as efficient as the neutral species in inhibiting cell division. We identify the neutral species as the cis form of the complex.
Highlights
When a solution containing the complex ion, [PM&,]‘, and NH4+ ions is irradiated, a photochemical change occurs in which the chloride ions of the ligand are sequentially replaced by 1, 2, or 3 ammonia molecules
In a previous paper (1) we reported the discovery that platinum complexes present in nutrient medium in low concentrations can inhibit cell division in Escher&&a coli and cause the development of long filaments
If a fresh solution of (NHa)s(PtCla) was prepared and added to the medium, filaments appeared only at concentrations well above this value and, generally, an inhibition of growth occurred instead. It was soon noticed’ that solutions of (NHI)2[PtC16] which had remained standing in the laboratory for a few days were far more efficacious at lower concentrations in producing filaments
Summary
When a solution containing the complex ion, [PM&,]‘, and NH4+ ions is irradiated, a photochemical change occurs in which the chloride ions of the ligand are sequentially replaced by 1, 2, or 3 ammonia molecules. If a fresh solution of (NHa)s(PtCla) was prepared and added to the medium, filaments appeared only at concentrations well above this value and, generally, an inhibition of growth occurred instead It was soon noticed’ that solutions of (NHI)2[PtC16] which had remained standing in the laboratory for a few days were far more efficacious at lower concentrations in producing filaments. The fresh solutions were a light yellow in color, while the aged solutions were almost colorless All this implied that a photochemical change of the platinum complex was occurring, and that the products were the agents more active in inhibiting division. A fresh solution of (NH,)z[PtC16] forms the doubly negative ion, [PtCl$, in solution This ion, when present in the nutrient medium in low concentrations (1 to 5 ppm) acts to inhibit growth of the bacteria, and is a bacteriocide (2). It is the cis form of the doubly substituted complex, [PtCla(NH3)#
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