XCN molecules (X = F, Cl, Br, I) are linear pseudohalogen species containing a reactive and toxic cyanide group. Their high electrophilicity and toxicity limit experimental studies. Therefore, this work employs ab initio theoretical methods to investigate their interactions with COSe. Our calculations reveal that the interaction between XCN and COSe leads to the formation of three distinct linear complexes, stabilized via halogen bonding (O⋯X), tetrel bonding (N⋯C), and chalcogen bonding (N⋯Se), denoted as SA, SB, and SC, respectively. Among these, the SC-structure complexes exhibit the highest stability, followed by SA and SB. The interaction energies (ΔE0) range from 0.48 to 2.50 kcal⋅mol 1, following the stability order SC ( 2.05 to 2.50) > SA ( 0.48 to 2.30) > SB ( 1.13 to 1.37). Energy decomposition analysis (EDA) reveals that electrostatic interactions dominate in the SA and SC complexes (≈48–57 %), whereas dispersion contributions prevail in the SB complexes (≈49 %), highlighting distinct bonding mechanisms for each type. These energetic and electronic characteristics, further supported by NBO (Natural Bond Orbital), QTAIM (Quantum Theory of Atoms in Molecules), and NCI (Noncovalent Interaction Index) analyses, confirm the critical role of σ-hole and π-hole features in stabilizing the noncovalent assemblies.
