Anisotropic molecular rotation in solution: the interpretation of carbon-13 T₁ data for triptycene and 9H-fluorene

Abstract

Rotational correlation times for triptycene and 9H-fluorene in chloroform-d₁ were deduced from carbon-13 relaxation data, using bond lengths predicted from infra-red stretching frequencies. In each case the situation is over-determined in the sense that there are more measurable T ₁'s than independent correlation times. Deduced correlation times are shown to be sensitive to the variability of C-H bond lengths. The results for 9H-fluorene are discussed in terms of the slipping boundary hydrodynamic model.