Nanotube formation favored by chalcogen-chalcogen interactions

Close contacts between sulfur, selenium, and tellurium centers are used to construct nanotubes in the solid state which are able to host other molecules.

Cyclic tetraselenadiynes: rigid cycles with long-range van der Waals forces between chalcogen centers

The synthesis of cyclic tetraselenadiynes could be achieved by a stepwise approach. Key steps were the reaction of the lithium salt of trimethylsilylacetylene (1) with alpha,omega-diselenocyanatoalkanes 2(m) (m = 2-5). By treating the bis-lithium salt of the resulting alpha,omega-diselenaalkadiynes 4(m) (m = 2-5) again with 2(n) (n = 2-5) the cyclic tetraselenadiynes 5(m.n) resulted, with methylene chains of length m and n between the SeC triple bond CSe units. The structures of seven ring systems could be investigated in the solid state. These investigations reveal that the molecular structures are determined by the rigid SeC triple bond CSe units, which try to adopt torsion angles of the CH(2)-Se sigma-bonds between 60 degrees and 90 degrees. In the solid state, the systems 5(3.3) and 5(5.5) show columnar structures that can be traced back to close contacts between Se atoms of neighboring rings.

Self-organization of chalcogen-containing cyclic alkynes and alkenes to yield columnar structures

Close contacts between chalcogen atoms in cyclic dienes and diynes are used to create columnar structures in the solid state. Rigid and fairly planar cycles with chalcogen centers are the preconditions for forming those columnar structures.

Tethered dithiacyclopropenones. syntheses and structural properties of tetrathiacyclopropenonophanes

The reaction of the cyclic tetrathiadiynes 4(m.n) (where m and n indicate the number of methylene groups between the dithiaacetylene units) with sodium trichloroacetate and subsequent hydrolysis of the gem-dichlorocyclopropenes afforded the mono- and biscyclopropenone derivatives 5(m.n) and 6(m.n) in moderate yields. Investigation of the X-ray crystal structures revealed small torsion angles between the CH(2)-S bond and the C-C double bond, indicating conjugation between the sulfur 3p lone pair and the cyclopropenone ring. The maintenance of the conjugation determines the secondary structure of both (5, 6) ring systems.