Carbon-13 chemical-shift tensors in polycyclic aromatic compounds. 9. Biphenylene

The principal values of the C-13 chemical-Shift tensors of natural abundanc e biphenylene were measured at room temperature with the FIREMAT experiment . Of 18 crystallographically distinct positions (three sets of six congruen t carbons each), the three primary bands have been resolved into seven sing le peaks and four degenerate peaks (two double, one triple, and one quadrup le). Hence, eleven different chemical-shift tensors are reported. An interp retation of the data is made by comparison to carbon chemical-shift tensors in other molecules with similar chemical environments. Experimental and th eoretical values based on a model of the asymmetric unit of the crystal uni t cell are in good agreement.