Tailoring the optical and dynamic properties of iminothioindoxyl photoswitches through acidochromism

Multi-responsive functional molecules are key for obtaining user-defined control of the properties and functions of chemical and biological systems. In this respect, pH-responsive photochromes, whose switching can be directed with light and acid-base equilibria, have emerged as highly attractive molecular units. The challenge in their design comes from the need to accommodate application-defined boundary conditions for both light- and protonation-responsivity. Here we combine time-resolved spectroscopic studies, on time scales ranging from femtoseconds to seconds, with density functional theory (DFT) calculations to elucidate and apply the acidochromism of a recently designed iminothioindoxyl (ITI) photoswitch. We show that protonation of the thermally stable Z isomer leads to a strong batochromically-shifted absorption band, allowing for fast isomerization to the metastable E isomer with light in the 500-600 nm region. Theoretical studies of the reaction mechanism reveal the crucial role of the acid-base equilibrium which controls the populations of the protonated and neutral forms of the E isomer. Since the former is thermally stable, while the latter re-isomerizes on a millisecond time scale, we are able to modulate the half-life of ITIs over three orders of magnitude by shifting this equilibrium. Finally, stable bidirectional switching of protonated ITI with green and red light is demonstrated with a half-life in the range of tens of seconds. Altogether, we designed a new type of multi-responsive molecular switch in which protonation red-shifts the activation wavelength by over 100 nm and enables efficient tuning of the half-life in the millisecond-second range.</p

Dataset Collagen Self Assembly in H2O and D2O.

This zip file contains data, and analysis for the paper "Elucidating the role of water in collagen self-assembly by isotopically modulating collagen hydration".Please feel free to contact us in case of questions or details

The challenge and the beauty of molecular complexity

Molecular complexity increases according to various coordinates such as (1) the size of the molecule, (2) the frequency of excitation and (3) the spectral resolution. Facing molecular complexity is relevant in itself but also in many fields, for example (1) to monitor volatile organic compounds, (2) to rationalize the mechanisms governing the energy level structure in highly vibrational excited states and/or to challenge always more and more quantum physics and chemistry. In this talk, I will review results obtained in my group and through collaborations on the development of experimental tools and related spectral analysis to go beyond the state of the art following these three coordinates. I will discuss the excitation of van der Waals molecular complexes far beyond the dissociation limit and our attempt to achieve the same success on ionic complexes. For this part of the talk, I will highlight the possible importance of such studies in atmospheric chemistry and how the combinations of those studies could shed new light on fundamental questions. I will also discuss how the study of the spectral signature of a molecule as small as methanol in the first overtone OH stretching range can represent a significant challenge. Finally, I will present the development of different spectrometers and light sources in order to be able to record the spectral signature of any molecular species from the MW to the UV