Association Constants of Ferrocene with Cyclodextrins in Aqueous Medium Determined by Solubility Measurements of Ferrocene

摘要

The association constants of ferrocene with cyclodextrins (CyD's) in an aqueous medium at 25 ℃ have been determined by solubility measurements of ferrocene in both the absence and presence of CyD. The solubility of ferrocene in pure water was found to be (4.25 ± 0.02) * 10~(-5) mol dm~(-3) at 25.0 ± 0.1 ℃. The β-and γ-CyD's form only 1:1 complexes with ferrocene. The 1:1 association constants were determined to be (1.39 ± 0.21) * 10~(-2) (α), (1.65 ± 0.04) * 10~(-4) (β), and (9.04 ± 0.11) * 10~(-2) dm~3 mol~(-1) (γ). The 2:1 (CyD: ferrocene) association constant was (2.36 ± 0.06) * 10~(-3) dm~3 mol~(-1) (α). Ferrocene-included CyD precipitates were also prepared in water, and their stability upon drying in air was studied. The sublimation enthalpy of ferrocene in the temperature range of 290.65 to 298.15 K was estimated to be 74.2 ± 1.5 kJ mol~(-1).