Calorimetric investigation of copper(II) and lead(II) complexes with lactate and 3-hydroxypropionate

Role of Solution Chemistry in Determining the Morphology and Photoconductivity of Electrodeposited Cuprous Oxide Films

“…Therefore, we attribute the increasing absorption peak to the endothermic nature of the dominant complex formed under these conditions (CuLac 2 ). 21 For the basic solution (starting pH = 10 at 25 °C), the increasing peak absorption intensity and red-shift of the peak wavelength position with increasing temperature (decreasing pH) seen in Figure 5b mirror the observed behavior upon changing pH alone (Figure 4). As such, the thermochemistry of forming the dominant complex present under highly basic conditions cannot be determined by these measurements alone.…”

“…Equilibrium concentrations of all species present in the copper-lactate aqueous system under acidic pH conditions (pH = 5.27) were calculated using the Hydra-Medusa multitasking software . Although most studies suggest the existence of two primary copper lactate complexes (CuLac + and CuLac 2 ), the formation thermochemistry of the different complexes is still unclear, as several contradictory trends have been suggested. − For this work, the stability constants for the copper-lactate complexes were adopted from reference : .25ex2ex Cu 2 + + Lac − = CuLac + log nobreak0em.25em⁡ italicK = 2.66 Cu 2 + + 2 Lac − = CuLac 2 log nobreak0em.25em⁡ italicK = 4.28 All other species association constants were taken from the software database (critically reviewed values)…”

“…(a) Calculated equilibrium distribution of copper species in solution as a function of lactate/copper ratio at pH = 5.27, 25 °C, 0.02 M CuSO 4 (dotted lines indicates speciation at 60 °C calculated using data from ref ). (b) Linear sweep voltammograms measured for copper-lactate solutions of various Lac/Cu 2+ molar ratios at pH = 5.27.…”

“…While acetate does not form a stable copper complex in alkaline media, copper-lactate complexes can be stable over a wide pH range. Two complexes are believed to dominate within acidic copper/lactate systems, CuLac + and CuLac 2 . , It has also been suggested that the chelation process is affected by the hydrogen ion concentration . In the high pH regime commonly used to electrodeposit Cu 2 O, the existence of alkaline copper-lactate complexes has been proposed, but not experimentally confirmed .…”

Critical evaluation of stability constants for alpha-hydroxycarboxylic acid complexes with protons and metal ions and the accompanying enthalpy changes. Part II. Aliphatic 2-hydroxycarboxylic acids (IUPAC Technical Report)

“…The reported value is rejected as the authors admit that the uncertainty in the experimental data is rather large and that the reliability of the obtained protonation enthalpy is rather low [78FB]. The remaining values are to be considered as provisional.…”