Gas-Phase Molecular Structure of Decachlorocorannulene, C20Cl10. An Electron-Diffraction Study Augmented by ab Initio, DFT, and Normal Coordinate Calculations

The molecular structure of decachlorocorannulene has been investigated by gas-phase electron diffraction with help from quantum chemical calculations at the HF and B3LYP level with several basis sets and from normal coordinate analysis. The structure is in excellent agreement with the prediction from the B3LYP/ 6-311G* calculation. The molecule of C 5 v symmetry is bowl-shaped with five six-membered rings fused to the central five-membered ring and to each other. The bowl is flatter than the similar corannulene molecule and is consistent with the lower inversion barrier predicted from calculations. The bond lengths (r g/Å) with uncertainties of 2σ for the four different types of C−C bonds are C1−C2 (in the C5 ring, or “hub”) = 1.421(17), C1−C6 (spokes from the hub) = 1.383(23), C6−C7 (flanking bonds from ends of spokes) =1.472(18), and C7−C8 (the rim bonds) = 1.410(27). The C−Cl bond length is 1.732(5) Å.