Linear free energy relationship of the energy of the CTTS transition of Halide ions with the solvatochromic parameter α

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A linear free energy relationship was found between vmax, the energy of the absorption maximum of chloride, bromide, or iodide ion in various solvents, and the α solvatochromic parameter which is a measure of the hydrogen bond donor ability of the solvent. The relationships are: for chloride, vmax=6.99α+50.16 kK; for bromide, vmax=5.52α+45.20 kK; for iodide, vmax=5.02α+40.33 kK. The correlation of vmax for iodide ion with α gave a larger correlation coefficient and smaller standard deviation than a correlation with the ET(30) parameter of Dimroth. From the values of vmax for iodide ion and the solvated electron in liquid ammonia at 25°C, these correlations indicate a preliminary value of 0.00 for the α parameter of liquid ammonia. This had not been reported before and is lower than expected from a general knowledge of the physical and chemical properties of liquid ammonia but is consistent with a more detailed consideration and recent gas phase measurements of hydrogen bond donor strength. © 1989 Plenum Publishing Corporation.

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Journal of Solution Chemistry