Raman modes, dipole moment and chirality in periodically positioned Au₈ clusters

This study reports the solution-based assembly of hexagonal + 1 shaped Au₈ clusters surrounded by six ligands into a local periodic structure (LPS) of periodicity 1.47 nm, which was confirmed by experimental and theoretical Raman scattering analyses as well as transmission electron microscopy, X-ray diffraction and small angle X-ray scattering measurements. The enhancement of the net electric dipole moment to 21.17 Debye is due to the rearrangement of the charge distribution in the electronic states of the LPS. This results in exciton-exciton coupling through dipole interactions, which was evidenced by the splitting of the excitonic states in the circular dichroism (CD) spectra. The strong negativity of the CD index at the longer wavelength confirms the negative chirality of the LPS-Au₈.