MOF-Inspired Porphyrinic Single Sites as Promising Platforms for Stable Immobilization of 2-Thiouracil: A DFT Study

The potential of MOF-inspired porphyrinic Fe–N ₄ and Mg–N ₄ single sites as platforms for the stable immobilization of 2-thiouracil (2TU) is examined using density functional theory (DFT) and time-dependent DFT. Counterpoise-corrected adsorption energies reveal strong chemisorption through both O- and S-anchoring groups, with Fe–N4 sites exhibiting considerably higher affinity than Mg–N ₄ . AIM and NBO analyses indicate partially covalent Fe–O/S interactions, while Mg–O/S contacts remain predominantly electrostatic, and additional H···N hydrogen bonding with the nanocone matrix further stabilizes the complexes. Electronic-structure descriptors and TD-DFT spectra show only minor perturbations upon adsorption, suggesting limited sensing capability. These findings identify porphyrinic Fe–N ₄ single sites as promising candidates for robust and orientation-specific immobilization of 2-thiouracil within functional nanocarrier architectures.