Dispersion-corrected DFT calculations on C(60)-porphyrin complexes

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Density functional theory (DFT) is a widely used method for electronic structure calculations.
• Accurate modeling of non-covalent interactions, such as dispersion forces, is crucial for supramolecular chemistry.
• Empirical dispersion corrections (DFT + E(disp)) have been developed to improve DFT's description of these interactions.

Purpose of the Study:

• To evaluate the performance of empirical dispersion corrections in DFT for fullerene-porphyrin supramolecular complexes.
• To investigate the influence of different DFT functionals, damping functions, and basis sets on the accuracy of dispersion-corrected calculations.
• To compare the results with those obtained for simple aromatic dimers.

Main Methods:

• Calculations were performed using three density functionals, two damping functions, and two basis sets (DZP and TZP).
• The study focused on supramolecular complexes of fullerene (C(60)) with free-base and metal porphyrins (Por).
• Benzene, naphthalene, and anthracene dimers were included for comparative analysis.

Main Results:

• Dispersion energies in fullerene-porphyrin systems are significant, ranging from 0.5 to 1 eV.
• DFT + E(disp) methods perform well for complexes with large intermolecular distances (e.g., C(60).H(2)TPP, C(60).ZnTPP, C(60).ZnP), but require large basis sets (TZP).
• For complexes with short intermolecular distances (e.g., C(60).FeP), DFT + E(disp) results are sensitive to the damping function and DFT method, impacting spin state energies.

Conclusions:

• Empirical dispersion corrections can be reliable for fullerene-porphyrin complexes with large intermolecular distances, provided large basis sets are used.
• For systems with short intermolecular distances, like C(60).FeP, the accuracy of DFT + E(disp) is questionable without experimental validation.
• Pure DFT calculations with smaller basis sets (DZP) can yield accurate results for some systems due to error cancellation.