Engineering the vibrational coherence of vision into a synthetic molecular device

Abstract

The light-induced double-bond isomerization of the visual pigment rhodopsin operates a molecular-level optomechanical energy transduction, which triggers a crucial protein structure change. In fact, rhodopsin isomerization occurs according to a unique, ultrafast mechanism that preserves mode-specific vibrational coherence all the way from the reactant excited state to the primary photoproduct ground state. The engineering of such an energy-funnelling function in synthetic compounds would pave the way towards biomimetic molecular machines capable of achieving optimum light-to-mechanical energy conversion. Here we use resonance and off-resonance vibrational coherence spectroscopy to demonstrate that a rhodopsin-like isomerization operates in a biomimetic molecular switch in solution. Furthermore, by using quantum chemical simulations, we show why the observed coherent nuclear motion critically depends on minor chemical modifications capable to induce specific geometric and electronic effects. This finding provides a strategy for engineering vibrationally coherent motions in other synthetic systems.

Anabaena Sensory Rhodopsin: Effect of point mutations on PSBR photo-isomerization speed

“…For AT W76F, the central 180±20cm -1 mode is the dominant excited state mode. Additionally, a similar data treatment for the PA band (not shown) reveals a dominant 80cm -1 mode attributed to ground oscillations induced by the ultrafast S1 decay, analogous to those reported for rhodopsin-mimicking molecular photo-switches [7].…”

A molecular movie of ultrafast singlet fission

“…These are slightly shifted (<10 cm −1 ) and exhibit markedly different intensity profile, especially in the high-frequency region. Based on these subtle differences, we tentatively assign this spectrum to the excited S 1 state, albeit with underlying ground-state contributions preventing unambiguous assignment (see Supplementary Discussion, section 2) 68 .…”

“…3c, right). Fourier transformation of the detected coherent oscillations over the absorption spectrum of DP-Mes allows us to independently measure a time-domain Raman spectrum which is directly comparable to resonant impulsive Raman spectra when probed in the same wavelength region 64,66,68,82 .…”

Photophysical Investigation of Iron(II) Complexes Bearing Bidentate Annulated Isomeric Pyridine-NHC Ligands

“…where a large excited state excess energy (> 1eV) is almost impulsively released into the ground state, leading to a non-equilibrated ground state population, which decays within several picoseconds. 49,50 This is the most plausible interpretation, but not a definitive proof the nature of S0 + . Scheme 3 summarises this alternative purely sequential scheme.…”