 because 
 of their unique electronic properties , cyclic molecular 
 structures ranging from benzene to natural light - harvesting complexes 
 have received much attention . 
 rigid -conjugated templated porphyrin 
 nanorings serve as excellent model systems here because they possess 
 well - defined structures that can readily be controlled and because 
 they support highly delocalized excitations . in this study , we have 
 deliberately modified a series of six - porphyrin nanorings to examine 
 the impact of lowering the rotational symmetry on their photophysical 
 properties . 
 we reveal that as symmetry distortions increase in severity 
 along the series of structures , spectral changes and an enhancement 
 of radiative emission strength occur , which derive from a transfer 
 of oscillator strength into the lowest ( k = 0 ) state . 
 
 we find that concomitantly , the degeneracy of the dipole - allowed first 
 excited ( k = 1 ) state is lifted , leading to 
 an ultrafast polarization switching effect in the emission from strongly 
 symmetry - broken nanorings . 
Supplementary Material