Rapid rotation of energy in the excited state of a circular hexa-carbazole array

Hexacarbazolylbenzene, a symmetrical propeller array of six carbazole units, has been synthesised. The relaxed S1 excited state has transient broken symmetry and a dipole moment of 8 debye caused by an excimer-like interaction between neighbouring carbazole units. The excimeric distortion undergoes rapid rotary diffusion within the array resulting in more than 1000 `round-tripsʹ during the course of the ca. 5 ns lifetime of the photoexcitation, thus mimicking the `storage-ringʹ function of the chlorophyllic arrays in light-harvesting bacteria.