Quantum-Chemical Investigations on the Structure and Stability of Mixed Trimers Containing HC3N in Combination with H2C2 and/or HCN Analyzed by QTAIM, NBO and SAPT Methods

The present work deals with the computational study of HC3N (Formula presented.) HCN (Formula presented.) H2C2-, (HC3N)2 (Formula presented.) H2C2-, and HC3N (Formula presented.) (H2C2)2-mixed trimers. The different equilibrium structures of the different low-lying minima on the corresponding potential energy surface (PES) were accurately determined, and the relative stabilities were computed by extrapolation procedures to the complete basis set limit. For each mixed trimer, the non-covalent interactions ruling the structure of the most stable isomer were analyzed using the QTAIM (Quantum Theory of Atoms in Molecules) approach. Additional insights into these interactions were provided by the Natural Bond Orbital (NBO) and Symmetry-Adapted Perturbation Theory (SAPT) methods. These results can be used to assist further theoretical investigations and experimental studies on the formation of larger molecules potentially relevant in astrochemistry.