Diversity of coherences and origin of electronic transitions of supermolecular nanoring

TL;DR

This study investigates the complex electronic and vibrational coherences in a synthetic nanoring, revealing diverse coherence types and their roles in optical responses, with implications for understanding photochemical processes.

Contribution

It provides the first detailed analysis of electronic, vibrational, and mixed coherences in a six-porphyrin nanoring, linking spectral features to structural and vibronic factors.

Findings

Diverse electronic, vibrational, and mixed coherences identified

Clear assignment of electronic and vibronic states achieved

Estimated excitation transfer rates and decoherence times

Abstract

Quantum coherence is highly involved in photochemical functioning of complex molecular systems. Co-existence and intermixing of electronic and/or vibrational coherences, while never unambiguously identified experimentally, has been proposed to be responsible for this phenomenon. Analysis of multidimensional spectra of a synthetic belt-shaped molecular six-porphyrin nanoring with an inner template clearly shows a great diversity of separable electronic, vibrational and mixed coherences and their cooperation shaping the optical response. The results yield clear assignment of electronic and vibronic states, estimation of excitation transfer rates, and decoherence times. Theoretical considerations prove that the complexity of excitation dynamics and spectral features of the nanoring excitation spectrum is due to combined effect of cyclic symmetry, small geometrical deformations, and vibronic coupling.