Accurate pKa prediction in first-row hexaaqua transition metal complexes using the B3LYP-DBLOC method

Area of Science:

• Computational Chemistry
• Inorganic Chemistry
• Quantum Chemistry

Background:

• Predicting acid dissociation constants (pKa) for transition metal complexes is crucial for understanding their chemical behavior.
• Previous methods using density functional theory (DFT) often have significant error margins.

Purpose of the Study:

• To develop and validate a more accurate computational method for determining the pKa of first-row transition metal hexaaqua complexes.
• To assess the performance of localized orbital corrections (LOCs) in DFT calculations for inorganic species.

Main Methods:

• Density functional theory (DFT) calculations were performed using the B3LYP functional with the LACV3P** basis set.
• Results were scaled to correct for basis set effects.
• Localized orbital corrections (DBLOC) were applied without further parameter adjustment.

Main Results:

• The combined scaling and DBLOC corrections significantly improved accuracy, reducing the mean unsigned error in pKa prediction from 5.7 to 0.9 units.
• The maximum error observed was 2.2 pKa units, indicating a high degree of reliability.
• The B3LYP-DBLOC model demonstrated performance close to chemical accuracy for these transition metal systems.

Conclusions:

• The B3LYP-DBLOC model offers an accurate and robust approach for DFT calculations of transition metal species.
• This method provides a valuable tool for predicting acid dissociation constants in complex inorganic systems.
• The findings encourage further application of this model in computational inorganic chemistry.