DFT-based computational screening of the ability of C₆₀-based nanostructures to adsorb the diethylcyclidine drug

Dieticyclidine (DTC) is a psychoactive compound for which efficient capture and identification remain analytically relevant. In this study, density functional theory calculations were used to comparatively screen pristine C₆₀ and the substitutionally doped BC₅₉ and SiC₅₉ nanocages as candidate platforms for DTC adsorption. Gas-phase calculations were performed at the B97-D/6-31G(d) level, whereas aqueous-phase behavior was examined using M06-2X/LANL2DZ with a polarizable continuum model. Optimized geometries, molecular electrostatic potentials, frontier orbitals, density-of-states profiles, dipole moments, BSSE-corrected adsorption energies, recovery times, electronic-response descriptors, natural bond orbital interactions, and ELF/LOL maps were analyzed. Doping generated localized interaction sites and shortened the adsorbate-nanocage contacts relative to pristine C₆₀. The calculated adsorption energies were -2.98, -19.35, and -29.87 kcal mol^-1 in the gas phase and -4.93, -24.57, and -41.31 kcal mol^-1 in water for C₆₀@DTC, BC₅₉@DTC, and SiC₅₉@DTC, respectively. Adsorption also reduced the HOMO-LUMO gaps and produced positive DTC-fragment charges, suggesting electron-density transfer from DTC to the nanocages. NBO and real-space localization analyses further indicated that B and Si substitution strengthens lone-pair-assisted, polarized donor-acceptor interactions with possible partial bonding character, while not providing definitive evidence for conventional covalent B-N or Si-N bond formation. Overall, the Eads-based recovery descriptor qualitatively indicated lower relative retention for C60@DTC, intermediate retention for BC59@DTC, and the highest relative retention for SiC59@DTC. These values were used only for comparative screening and were not interpreted as quantitative desorption times. These findings constitute a pre-synthesis screening framework and require experimental validation under realistic conditions.