Supramolecular architectures featuring Se N secondary-bonding interactions in crystals of selenium-rich molecules: a comparison with their congeners

• Published in: CrystEngComm 2022-12, Vol.25 (1), p.9-39
• Main Author: Tiekink, Edward R. T
• Format: Article
• Language: English
• Subjects: Agglomeration; Chalcogen bonds; Congeners; Contact potentials; Crystals; Equivalence; Selenium; Selenium compounds
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/d2ce01414a

Supramolecular aggregates featuring Se N contacts have been identified in 88 crystals containing two, three or four selenium atoms, corresponding to 9% of crystals where Se N contacts have the potential to form. Molecules with two selenium atoms make up the majority of examples (58) followed by molecules with three (12) and four (18) selenium atoms. A wide range of supramolecular aggregation patterns has been identified in the 88 crystals featuring Se N contacts with one- (42%) and two- (31%) dimensional aggregation forming the majority compared with zero- (17%) and three- (10%) dimensional aggregation making up the rest. The overwhelming majority of Se N contacts correspond to chalcogen-bonding interactions based on σ-hole interactions. Correlations in intermolecular separations were evident for isostructural crystals which showed that a comparable Te N interaction was stronger than the equivalent Se N interaction, and the Se N interaction was always stronger than the equivalent S N interaction. When compared to crystals of mono-nuclear selenium compounds, a very similar adoption rate was observed in their crystals but with a bias towards smaller aggregation patterns, i.e. 50, 44, 5 and 1% for zero-, one-, two- and three- dimensional, respectively. This observation is clearly consistent with the greater opportunity for multi-nuclear selenium molecules to form more interactions. However, as exemplified by the 18 tetra-nuclear molecules, not all selenium atoms participated in a Se N contact as two, 10, two and four selenium atoms, out of a possible four, formed a Se N contact in their crystals. The importance of Se N chalcogen-bonding in supramolecular assembly is demonstrated.