Molecular systems containing donor-bridge-acceptor sites or molecular antennas constitute promising candidates for organic photovoltaic device implementation. Photo-induced electron transfer in multi-chromophore molecular systems is defined by a subtle interaction between the donor and the molecular bridge, and by the system-solvent coupling. Here, we address the computation of quantum properties such as population inversion and electron transfer in molecular photo-systems composed of fulleroisoxazoline, fulleropyrrolidine, BODIPY and Zn-porphyrin, as well as their system-solvent ultrafast dynamics. The molecular complexes are modelled as two- and three-site systems, and we use the density functional theory (DFT) for obtaining the site energies required in the construction of the open system diabatic Hamiltonians relevant to the computation of the electron transfer. The site energies and electronic couplings are calculated by using a continuous polarizable model that allow for the analysis of different solvent environments, and the site-to-site couplings are computed by means of the generalized Mulliken Hush method at the DFT level. We find that the stabilization energy of the charge transfer states exhibit a significant variation for a compound embedded in different polar environments, and thus the effect due to the solvent has been analyzed for the specific cases of Methanol, THF and Toluene. We show that the incorporation of a molecular bridge generates the creation of an intermediate state that plays a crucial role in the charge transfer process by defining $Λ$ or cascaded-type energy schemes; this affects the asymptotic value of the transfer rate and favors the cascaded-type configuration.
Solvent Effects on Triplet Yields in BODIPY-Based Photosensitizers
University of California, Berkeley（加州大学伯克利分校）；University of California, Los Angeles（加州大学洛杉矶分校）；Kavli Energy NanoScience Institute（卡弗里能源纳米科学研究所）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
Aqueous proton transport plays a key role in acid-base neutralization, and energy transport through biological membranes and hydrogen fuel cells. Extensive experimental and theoretical studies have resulted in a highly detailed elucidation of one of the underlying microscopic mechanisms for aqueous excess proton transport, known as the von Grotthuss mechanism, involving different hydrated proton configurations with associated high fluxional structural dynamics. Hydroxide transport, with approximately two-fold lower bulk diffusion rates than those of excess protons, has received much less atten…
The transition between the gas-, supercritical-, and liquid-phase behaviour is a fascinating topic which still lacks molecular-level understanding. Recent ultrafast two-dimensional infrared spectroscopy experiments suggested that the vibrational spectroscopy of N$_2$O embedded in xenon and SF$_6$ as solvents provides an avenue to characterize the transitions between different phases as the concentration (or density) of the solvent increases. The present work demonstrates that classical molecular dynamics simulations together with accurate interaction potentials allows to (semi-)quantitatively …
Graphene oxide (GO) membranes continue to attract intense interest due to their unique molecular sieving properties combined with fast permeation rates. However, the membranes' use has been limited mostly to aqueous solutions because GO membranes appear to be impermeable to organic solvents, a phenomenon not fully understood yet. Here, we report efficient and fast filtration of organic solutions through GO laminates containing smooth two-dimensional (2D) capillaries made from flakes with large sizes of ~ 10-20 micron. Without sacrificing their sieving characteristics, such membranes can be mad…
Interactions between proteins and their solvent environment can be studied in a bottom-up approach using hydrogen-bonded chromophore-solvent clusters. The ultrafast dynamics following UV-light-induced electronic excitation of the chromophores, potential radiation damage, and their dependence on solvation are important open questions. The microsolvation effect is challenging to study due to the inherent mix of the produced gas-phase aggregates. We use the electrostatic deflector to spatially separate different molecular species in combination with pump-probe velocity-map-imaging experiments. We…
X-ray photoelectron spectroscopy (XPS) and KLL Auger spectra of aqueous KCl solution were measured for the K$^+$ and Cl$^-$ edges. While the XPS spectra of potassium and chloride have similar structures, both exhibiting only weak satellite structures near the main line, the Auger spectra of these isoelectronic ions differ dramatically. A very strong satellite peak was found in the K$^+$ KLL Auger spectrum at the low kinetic energy side of the $^1$D state. Using equivalent core models and ab initio calculations this spectral structure was assigned to electron transfer processes from solvent wat…
Real-Time Emergence of Charge-Transfer-to-Solvent States from Core Excitation
Institute of Advanced Computational Science, Stony Brook University（石溪大学先进计算科学研究所）；Department of Chemistry, Michigan State University（密歇根州立大学化学系）；Department of Chemistry, Stony Brook University（石溪大学化学系）；Department of Physical Chemistry, University of Chemistry and Technology, Prague（布拉格化工大学物理化学系）；NVidia（英伟达）
Understanding electron transfer in organic molecules is of great interest in quantum materials for light harvesting, energy conversion, and integration of molecules into solar cells. This, however, poses the challenge of designing specific optimal molecular structure for which the processes of ultrafast quantum coherence and electron transport are not so well understood. In this work, we investigate subpicosecond time scale quantum dynamics and electron transfer in an efficient electron acceptor Rhodanine chromophoric complex. We consider an open quantum system approach to model the complex-so…
Charge-transfer-to-solvent (CTTS) reactions of hydroxide induced by 200 nm monophotonic or 337 nm and 389 nm biphotonic excitation of this anion in aqueous solution have been studied by means of pump-probe ultrafast laser spectroscopy. Transient absorption kinetics of the hydrated electron, eaq-, have been observed, from a few hundred femtoseconds out to 600 ps, and studied as function of hydroxide concentration and temperature. The geminate decay kinetics are bimodal, with a fast exponential component (ca. 13 ps) and a slower power "tail" due to the diffusional escape of the electrons. For th…
Picosecond geminate recombination kinetics for electrons generated by multiphoton ionization of liquid water become power dependent when the radiance of the excitation light is greater than 0.3-0.5 TW/cm^2 (the terawatt regime). To elucidate the mechanism of this power dependence, tri- 400 nm photon ionization of water has been studied using pump-probe laser spectroscopy on the pico- and femtosecond time scales. We suggest that the observed kinetic transformations are caused by a rapid temperature jump in the sample. Such a jump is inherent to multiphoton ionization in the terawatt regime, whe…
