Weak Interactions between Epinephrine and Thymine

The weak interactions between epinephrine and thymine were investigated by combining the 6-311+G(d,p) basis set with the M06-2X method based on density functional theory. Results suggest that epinephrine and thymine form 22 steady geometries through weak interactions, which primarily contain hydrogen bonds and π–π stacking. Hydrogen bonding is the main character. In addition, the interaction energies range from −20.98 kJ·mol⁻¹ to −63.14 kJ·mol⁻¹, with the basis set superposition error correction, which are in line with the energy range of the hydrogen bond. Geometrical parameters, frequency analysis, natural bond orbital (NBO) analysis, atoms-in-molecules (AIM) analysis, and reduced density gradient (RDG) analysis were also used to analyze and verify hydrogen bond formation. Most of the hydrogen bonds in optimized structures of the epinephrine–thymine complex are closed-shell interaction and electrostatic dominant, whereas N···H–N, which exist in geometries 3, 4, 5, and 14, are interacting between the closed-shell and shared-shell. N-H…N is almost linear, which is more conducive to the study of the role of hydrogen bonds in the system.