Coarse Graining Photo-Isomerization Reactions: Thermodynamic Consistency and Implications for Molecular Ratchets

TL;DR

This paper develops thermodynamically consistent coarse-graining methods for photo-isomerization reactions, showing that autonomous photo-driven molecular ratchets operate via the same information ratchet mechanism as chemically driven ones.

Contribution

It introduces a coarse-graining framework that preserves detailed balance in photo-isomerization, linking molecular ratchets to information ratchet mechanisms.

Findings

Coarse-graining preserves local detailed balance in photo-isomerization.

Photo-driven and chemically driven ratchets share the same fundamental mechanism.

Design focus should be on properties affecting information ratchet operation.

Abstract

We formulate thermodynamically consistent coarse-graining procedures for molecular systems undergoing thermally and photo-induced transitions: starting from elementary vibronic transitions, we derive effective photo-isomerization reactions interconverting ground-state species. Crucially, the local detailed balance condition, that constrains reaction kinetics to thermodynamics, remains satisfied throughout the coarse-graining procedures. It applies to the effective photo-isomerization reactions just as it does to the elementary vibronic transitions. We then demonstrate that autonomous photo-driven molecular ratchets operate via the same fundamental mechanism as chemically driven ones. Because the local detailed balance remains satisfied, autonomous photo-driven molecular ratchets, like chemically driven ones, operate exclusively through an information ratchet mechanism. This reveals that their design and optimization should prioritize molecular properties governing the information ratchet mechanism, rather than those influencing energetic bias.