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 pi-pi stacking. Hydrogen bonding is the main character. In addition, the interaction energies range from -20.98 kJ center dot mol(-1) to -63.14 kJ center dot 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 center dot center dot center dot H-N, which exist in geometries 3, 4, 5, and 14, are interacting between the closed-shell and shared-shell. N-H horizontal ellipsis N is almost linear, which is more conducive to the study of the role of hydrogen bonds in the system.