Pentaheptafulvalene

Sesquifulvalene

Names
IUPAC name 7-Cyclopenta-2,4-dien-1-ylidenecyclohepta-1,3,5-triene
Other names Pentaheptafulvalene
Identifiers
3D model (JSmol)	Interactive image
ChemSpider	553644
PubChem CID	638082
InChI InChI=1S/C12H10/c1-2-4-8-11(7-3-1)12-9-5-6-10-12/h1-10H Key: JYRVSRMFQWYDGM-UHFFFAOYSA-N
SMILES C1=CC=CC(=C2C=CC=C2)C=C1
Properties
Chemical formula	C12H10
Molar mass	154.21 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sesquifulvalene or Pentaheptafulvalene is a hydrocarbon in the fulvalene class with chemical formula C₁₂H₁₀. It is composed of linked cyclopentadiene and cycloheptatriene rings.

In the ground state, which is a singlet state, the central double bond is polarized, with a partial positive charge on the carbon atom of heptagonal ring and a partial negative charge on the carbon atom of pentagonal ring. This shift makes each ring have closer to 4n+2 π electrons, in keeping with the Hückel's pattern of aromatic stability. However, in the lowest quintet state, the central double bond is polarized with a partial negative charge on the carbon atom of heptagonal ring and a partial positive charge on the carbon atom of pentagonal ring due to Baird's rule.