Stability constant (log K) calculation
Stability constant (log K) is an equilibrium constant for the formation of a complex in solution.
It is a measure of the strength of the interaction between the reactants that come together to form the complex.
Here, it refers to the interaction of a metal ion with a ligand.
Log K provides the information required to calculate the concentration(s) of the complex(es) in solution (speciation).
It can be measured by titrations combined with different measurements, such as absorbance spectra, fluorescence spectra, and NMR spectra.
However, due to the practical reasons, experimental measurements of log K are not always possible.
Therefore, theoretical calculations with quantum mechanics (QM) methods provide a feasible option to evaluate it.
This module aims to design an user-friendly interface for researchers to perform the calculation with QM methods.
Theoretical model
QM calculation of log K based on stepwise reactions. For example, given reaction
M2+ + 2 L- ----> ML2 β
The stepwise reactions are:M2+ + L- ----> ML+ K1 = [ML+]/[M2+][L-]
ML+ + L- ----> ML2 K2 = [ML2]/[ML+][L-]
Once the log K1 and log K2 are calculated, then the log β can be obtained by,log β = log K1 + log K2
Therefore, the user should perform QM calculation twice. For each step, the structures of reactants and products are required.