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Your search keyword '"Cupellini, Lorenzo"' showing total 39 results
Start Over Author "Cupellini, Lorenzo" Publisher american chemical society (acs)
39 results on '"Cupellini, Lorenzo"'

14. Ultrafast Transient Infrared Spectroscopy of Photoreceptors with Polarizable QM/MM Dynamics

Author

Macaluso, Veronica, Hashem, Shaima, Nottoli, Michele, Lipparini, Filippo, Cupellini, Lorenzo, and Mennucci, Benedetta

Subjects
Spectrophotometry, Infrared, Infrared, Infrared spectroscopy, Flavin group, 010402 general chemistry, 01 natural sciences, Molecular physics, Article, QM/MM, symbols.namesake, Molecular dynamics, Bacterial Proteins, Stokes shift, 0103 physical sciences, Materials Chemistry, Physical and Theoretical Chemistry, Spectroscopy, Physics, Flavoproteins, 010304 chemical physics, Chromophore, Protein Structure, Tertiary, 0104 chemical sciences, Surfaces, Coatings and Films, Flavin-Adenine Dinucleotide, symbols
Abstract

Ultrafast transient infrared (TRIR) spectroscopy is widely used to measure the excitation-induced structural changes of protein-bound chromophores. Here, we design a novel and general strategy to compute TRIR spectra of photoreceptors by combining μs-long MM molecular dynamics with ps-long QM/AMOEBA Born–Oppenheimer molecular dynamics (BOMD) trajectories for both ground and excited electronic states. As a proof of concept, the strategy is here applied to AppA, a blue-light-utilizing flavin (BLUF) protein, found in bacteria. We first analyzed the short-time evolution of the embedded flavin upon excitation revealing that its dynamic Stokes shift is ultrafast and mainly driven by the internal reorganization of the chromophore. A different normal-mode representation was needed to describe ground- and excited-state IR spectra. In this way, we could assign all of the bands observed in the measured transient spectrum. In particular, we could characterize the flavin isoalloxazine-ring region of the spectrum, for which a full and clear description was missing.

Published
2021

19. Absorption and Circular Dichroism Spectra of Molecular Aggregates With the Full Cumulant Expansion

Author

Massachusetts Institute of Technology. Department of Chemistry, Cupellini, Lorenzo, Lipparini, Filippo, Cao, Jianshu, Massachusetts Institute of Technology. Department of Chemistry, Cupellini, Lorenzo, Lipparini, Filippo, and Cao, Jianshu

Abstract

Copyright © 2020 American Chemical Society. The exciton Hamiltonian of multichromophoric aggregates can be probed by spectroscopic techniques such as linear absorption and circular dichroism. To compare calculated Hamiltonians to experiments, a lineshape theory is needed, which takes into account the coupling of the excitons with inter- and intramolecular vibrations. This coupling is normally introduced in a perturbative way through the cumulant expansion formalism and further approximated by assuming a Markovian exciton dynamics, for example with the modified Redfield theory. Here, we present the implementation of the full cumulant expansion (FCE) formalism (J. Chem. Phys. 142, 2015, 094106) to efficiently compute absorption and circular dichroism spectra of molecular aggregates beyond the Markov approximation, without restrictions on the form of exciton-phonon coupling. By employing the LH2 system of purple bacteria as a challenging test case, we compare the FCE lineshapes with the Markovian lineshapes obtained with the modified Redfield theory, showing that the latter presents a less satisfying agreement with experiments. The FCE approach instead accurately describes the lineshapes, especially in the vibronic sideband of the B800 peak. We envision that the FCE approach will become a valuable tool for accurately comparing model exciton Hamiltonians with optical spectroscopy experiments.

Published
2022

36. Efficient Photoinduced Charge Separation in a BODIPY–C60 Dyad

Author

Iagatti, Alessandro, primary, Cupellini, Lorenzo, additional, Biagiotti, Giacomo, additional, Caprasecca, Stefano, additional, Fedeli, Stefano, additional, Lapini, Andrea, additional, Ussano, Eleonora, additional, Cicchi, Stefano, additional, Foggi, Paolo, additional, Marcaccio, Massimo, additional, Mennucci, Benedetta, additional, and Di Donato, Mariangela, additional

Published
2016
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39. Efficient Photoinduced Charge Separation in a BODIPY–C60 Dyad

Author

Alessandro Iagatti, Stefano Cicchi, Stefano Caprasecca, Eleonora Ussano, Massimo Marcaccio, Lorenzo Cupellini, Stefano Fedeli, Giacomo Biagiotti, Benedetta Mennucci, Andrea Lapini, Mariangela Di Donato, Paolo Foggi, Iagatti, Alessandro, Cupellini, Lorenzo, Biagiotti, Giacomo, Caprasecca, Stefano, Fedeli, Stefano, Lapini, Andrea, Ussano, Eleonora, Cicchi, Stefano, Foggi, Paolo, Marcaccio, Massimo, Mennucci, Benedetta, and Di Donato, Mariangela

Subjects
Fullerene, ULTRAFAST ENERGY-TRANSFER, 02 engineering and technology, DONOR, 010402 general chemistry, Photochemistry, Electronic, Optical and Magnetic Materials, Energy (all), Physical and Theoretical Chemistry, Surfaces, Coatings and Films, Surfaces, Energy (all), 01 natural sciences, Coatings and Films, MOLECULES, Electron transfer, chemistry.chemical_compound, REACTION CENTER MIMICRY, Ultrafast laser spectroscopy, Electronic, Moiety, ELECTRON-TRANSFER, Optical and Magnetic Materials, Chromophore, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Surfaces, LIGHT, General Energy, STATES, chemistry, Photoinduced charge separation, Absorption band, BODIPY, C-60, 0210 nano-technology, FULLERENE, DYES
Abstract

A donor acceptor dyad composed of a BF2-chelated dipyrromethene (BODIPY) and a C-60 fullerene has been newly synthesized and characterized. The two moieties are linked by direct addition of an azido substituted BODIPY on the C-60, producing an imino fullerene BODIPY adduct. The photoinduced charge transfer process in this system was studied by ultrafast transient absorption spectroscopy. Electron transfer toward the fullerene was found to occur selectively exciting both the BODIPY chromophore at 475 nm and the C-60 unit at 266 nm on a time scale of a few picoseconds, but the dynamics of charge separation was different in the two cases. Eletrochemical studies provided information on the redox potentials of the involved species and spectroelectrochemical measurements allowed to unambiguously assign the absorption band of the oxidized BODIPY moiety, which helped in the interpretation of the transient absorption spectra. The experimental studies were complemented by a theoretical analysis based on DFT computations of the excited state energies of the two components and their electronic couplings, which allowed identification of the charge transfer mechanism and rationalization of the different kinetic behavior observed by changing the excitation conditions.

Published
2016

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