The s-tetrazine-water (T-W) interactions have been investigated by examining the van der Waals clusters TW_n (n＝2, 3 and 4) using the density functional theory B3LYP method and the 6-31＋＋G** basis, obtaining 6, 9 and 12 minima of the ground state for the TW₂, TW₃ and TW₄ clusters respectively. The fully optimized ge-ometries and binding energies DE² were reported, including corrections of the basis set superposition error and zero point energies for the various stationary points. The global minima of the TW₂, TW₃ and TW₄ clusters have a hydrogen bond N…H—O and a chain of water molecules, terminated by a hydrogen bond O…H—C. The corresponding binding energies are 41.35, 70.9 and 94.61 kJ/mol, respectively, after the basis set superposition error and zero-point corrections. The H—O symmetric stretching modes of water in complex is red-shifted relative to that of the monomer water. In ad-dition, the shorter the bond length of N…H, the angle of N…H—O is closer to 180°, the stronger the hydro-gen bond interaction. The first singlet (n, p*) vertical excitation energy 2.227 eV of the monomer s-tetrazine and the T-W_n clusters have been investigated by time-dependent density functional theory.

Key words: s-tetrazine, intermolecular interaction, hydrogen bonding complex, density functional theory