The stability constants K1 and enthalpy changes ΔH1 (kJ/mol) of hydrogen, magnesium(II), calcium(II), strontium(II), and barium(II) (M2+) complexes with one molecule of 2,2′-dipyridyl (dipy) or 1,10-phenanthroline (phen) in a mixed, KCl and MCl2 aqueous solution at 25°C and the ionic strength 0.25 were derived from a thermochemical experiment. The log K1 values for 2,2′-dipyridyl complexes are
... [Show full abstract] 4.45 ± 0.03, 0.36 ± 0.02, -0.04 ± 0.01, -0.15 ± 0.02, and -0.25 ± 0.03, respectively. The respective values of ΔH1 are 16.0 ± 0.3, 6.1 ± 0.2, 17 ± 1, 15 ± 2, and 14 ± 3. For the 1,10-phenanthroline complexes of these ions, the respective values of log K1 are 5.03 ± 0.03, 1.60 ± 0.04, 1.11 ± 0.03, 0.85 ± 0.04, and 0.60 ± 0.03; the values of ΔH1 are 19.0 ± 0.5, 7.2 ± 0.7, 14 ± 1, 12± 1,and 10 ± 1, respectively.