Unveiling excited-state chirality of Binaphthols by sub-picosecond circular dichroism and quantum-chemical calculations

Time-resolved circular dichroism (TR-CD) is a powerful tool for probing the conformational dynamics of molecules over large time-scales. By using Binaphthol and two bridged derivatives (PL1 and PL2) as chiral prototypes, we present the first comprehensive study of this type in the middle UV, combining femtosecond TR-CD and quantum mechanical calculations (TD-DFT). We show that excitation of the three compounds induces large variations of their transient CD signals, in sharp contrast to those of their achiral transient absorption, which arise both from the alteration of the electronic distribution and the change of the dihedral angle in the excited state.