Accurate Thermochemistry for Organic Cations via Error Cancellation using Connectivity-Based Hierarchy

Area of Science:

• Computational chemistry
• Theoretical chemistry

Background:

• Connectivity-Based Hierarchy (CBH) is an established error-cancellation scheme for thermochemical property determination.
• The CBH method has successfully treated neutral molecules and open-shell radicals using cost-effective computational methods like density functional theory.

Purpose of the Study:

• To extend the Connectivity-Based Hierarchy (CBH) method for accurate thermochemical property calculation of organic cations.
• To address limitations in applying the standard CBH protocol to organic cations, which exhibit complex structural rearrangements and unusual structures.

Main Methods:

• An adjusted Connectivity-Based Hierarchy (CBH) protocol was developed to overcome standard method limitations for organic cations.
• The modified CBH approach was tested on a set of 25 organic cations using various density functionals.
• Computational methods, including density functional theory, were utilized.

Main Results:

• The standard CBH protocol showed significant errors for organic cations due to ineffective bond-type matching.
• The adjusted CBH protocol achieved highly effective error cancellation for organic cations.
• Modified CBH methods accurately reproduced G4 energies for the test set of organic cations within 1-2 kcal/mol.

Conclusions:

• The adjusted Connectivity-Based Hierarchy (CBH) protocol provides accurate and cost-effective thermochemical property determination for organic cations.
• This extension significantly improves the applicability of CBH to a broader range of molecular species.
• The findings enable more reliable computational predictions for organic cations in chemistry and biochemistry.