Chiral Discrimination of Amino Acids by Using a Twisted Carbon Nanobelt: A DFT Study

Beyond the confines of chemistry, molecular chirality and related ideas like symmetry, asymmetry, handedness, symmetry breaking, and chiral recognition have a growing influence in science. In the current study, a twisted carbon nanobelt (TCNB) is used for the chiral discrimination of amino acids (AA) using density functional theory study. The values of interaction energy (E_int) range from −28.55 to −34.45 kcal mol^–1. Two distinct trends of E_int are identified, with the TCNB demonstrating selectivity for R-enantiomers of proline and S-enantiomers of histidine. Similarly, for threonine, the TCNB is selective toward SR-threonine. Chiral discrimination energy is most pronounced for threonine@TCNB (SR and RS) enantiomeric complexes, i.e., 6.90 kcal mol^–1. Quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) analyses reveal that the S enantiomer in each case has maximum interactions compared to the R enantiomer. Electron density difference (EDD) and natural bond orbital (NBO) analyses indicate charge transfer from amino acids toward the belt, with RS-thre@TCNB having a maximum charge transfer, i.e., 2.260 (e^–). Frontier molecular orbital (FMO) analysis reveals a decline in energy gap upon complexations. The highest decrease in energy gap is seen for R-pro@TCNB (3.42 eV from 3.59 eV), which displays high selectivity of the TCNB toward proline. The current study highlights the selectivity of the TCNB toward chiral molecules, showing a significant chiral discrimination ability for S and R enantiomers of amino acids. This work contributes valuable insights into the molecular interactions and chiral recognition involving twisted carbon nanobelts.