Sensing Ability of Hybrid Cyclic Nanopeptides Based on Thiourea Cryptands for Different Ions, A Joint DFT-D3/MD Study

Theoretical studies, including quantum chemistry (QM) calculations and 25 ns molecular dynamic (MD) simulations, were performed on two types of hybrid cyclic nanopeptides (HCNPs) that are constructed of tren-capped cryptand (HCNP1) and 1,3,5-triethylbenzene-capped cryptand (HCNP2) for selective complex formation with OAC^-, NO₃^-, HSO₄^-, F^-, Br^-, and Cl^- ions in the gas phase and DMSO. Obtained data by M05-2X, M05-2X-D3, B3LYP, and B3LYP-D3 functionals indicated that HCNPs form a stable complex with F^- in comparison to other ions. DFT-D3 results and quantum theory of atoms in molecules (QTAIM) analysis indicated that dispersion and electrostatic interactions are the most important driving forces in HCNP-ion complex formation, respectively. Moreover, HOMO-LUMO analysis reveals that the reactivity of HCNP2, due to a lower band gap, is more than HCNP1. High sensing ability of the studied HCNPs for different ions was confirmed by Fermi level shifting of HNCPs to higher values during the complex formation. Finally, MD simulation results in DMSO are in good agreement with QM calculations and indicate that F^- forms the most stable complexes with HCNPs because of stronger electrostatic interactions.