the pKa by
\[\mathrm{pK_a}=\mathrm{pK_a^{ref}} + \frac{\Delta G^\circ}{RT\ln (10)} + (N_C - 1)\]
where \(\Delta G^\circ\) denotes the change in standard free energy for the reaction
\[\mathrm{ BH^+ + B_{ref} \rightleftharpoons B + B_{ref}H^+ }\]
and is approximated as the sum of the electronic and solvation free energy. \(N_C\) - 1 is an empirical correction accounting for