Sulflower

Sulflower (a portmanteau of sulfur and sunflower) is a stable heterocyclic octacirculene based on thiophene. Sulflower does not contain any hydrogen. With molecular formula (C₂S)₈ the compound is considered a type of carbon sulfide. The molecule is flat and together with the 9-membered homolog is at a local strain energy minimum.^[1]

Crystal structure

Stacking of sulflower molecules in the crystal structure	Packing of sulflower molecules in the crystal structure

Sulflower

Ball-and-stick model Space-filling model
Names
Preferred IUPAC name 1,12:3,4:6,7:9,10-Tetrasulfanocycloocta[1,2-c:3,4-c′:5,6-c′′:7,8-c′′′]tetrathiophene
Other names Octathio[8]circulene
Identifiers
CAS Number	921210-36-8
3D model (JSmol)	Interactive image
ChemSpider	21267678
PubChem CID	101427667
CompTox Dashboard (EPA)	DTXSID00891950
InChI InChI=1S/C16S8/c17-9-1-2-4-6-8-7-5-3(1)11(18-9)20-13(5)22-15(7)24-16(8)23-14(6)21-12(4)19-10(2)17 Key: SNTHAZVSUIFTDO-UHFFFAOYSA-N
SMILES c12c3c4c5c6c7c8c1c9sc2sc3sc4sc5sc6sc7sc8s9
Properties
Chemical formula	C16S8
Molar mass	448.66 g·mol−1
Appearance	Dark red powder
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Its synthesis (a variation of the Ferrario reaction) is based on deprotonation of a tetrathiophene with lithium diisopropylamide followed by reaction with elemental sulfur to a sulfur-substituted intermediate followed by vacuum pyrolysis.

Sulflower synthesis

The sulflower molecule has a planar structure with D_8h symmetry, i.e., all eight sulfur atoms as well as the two faces of the molecule are undistinguishable. Because of its planar structure, it is predicted to be able to store many hydrogen molecules between the stacks. The conformation of the H₂ molecule is calculated to be "standing up" over the five membered rings. Detailed DFT calculations have been performed on these molecules.^[2]