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New Studies of Photoisomerization
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New Studies of Photoisomerization

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 23645

Special Issue Editor

Prof. Dr. Martial Boggio-Pasqua

E-Mail Website
Guest Editor
Universite de Toulouse, Toulouse, France
Interests: theoretical chemistry; excited states; dynamics; photochemistry; photochromism

Special Issue Information

Dear Colleagues,

Photoisomerization, which is the photochemical process resulting in a change of isomer, is a very common response upon light irradiation of photoactive molecular systems. It can involve different types of molecular reorganization such as bond rotation, skeletal rearrangements or atom- or group-transfer. Typical examples are cis-trans photoisomerizations, photoinduced cycloadditions, electrocyclic reactions and tautomerizations. Photoisomerization is the primary photochemical reaction of chromophores in several biological photoreceptors. The most prominent example is the cis-trans photoisomerization of the retinal chromophore in rhodopsin which is the primary photochemical event involved in vision. Photoisomerization is often associated with changes in physical and chemical properties of the molecular system: Along with the geometrical rearrangement, it may be accompanied by spectral changes, change of refractive index, dielectric constant, dipole moment, oxidation/reduction potential. This light-activated process is in most cases completely reversible, and the molecules can be switched back and forth between two or more isomeric forms, providing what is commonly known as photoswitches. Photoisomerizable molecules have entered the new generation of innovative functional materials with high added value. Applications are already widespread in nanosciences, biology, and photonic or optoelectronic devices. For example, they have been exploited to develop various technological devices such as sensors, actuators, information storage and processing and high-resolution imaging techniques.

A variety of synthetic photoswitches, that can undergo a reversible change in their structure upon irradiation with light, have been designed. The vast majority of these compounds rely on organic molecules. Among the main groups of compounds that have found numerous applications as switching molecules, one can cite azobenzenes, stilbenes, dihydroazulenes, diarylethenes, spiropyrans and spirooxazines, naphthopyrans, fulgides, fulgimides, and related compounds. Transition metal complexes have also been designed to display photoisomerizable capabilities. These systems are often based on linkage isomerizations between the metal center, and various ambidentate ligands (e.g., sulfoxide, sulfur dioxide, nitrosyl). The advantage of using such inorganic systems lies in the large flexibility available to tune the photoisomerizable properties with the use of different ligands.

This forthcoming Special Issue of Molecules entitled “New Studies of Photoisomerization” will be devoted to photoisomerizable compounds, collecting original contributions both from experimental and theoretical studies.

Prof. Martial Boggio-Pasqua
Guest Editor

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Keywords

  • photoswitches
  • photochromism
  • synthesis
  • molecular design
  • optical properties
  • time-resolved spectroscopy
  • computational photochemistry
  • photodynamics

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Published Papers (7 papers)

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Research

20 pages, 5178 KiB  
Article
Effect of a =X-NH-Fragment, (X = C, N), on Z/E Isomerization and ON/OFF Functionality of Isatin Arylhydrazones, ((Arylamino)Methylene)Indolin-2-Ones and Their Anions
by Pavol Tisovský, Klaudia Csicsai, Jana Donovalová, Róbert Šandrik, Róbert Sokolík and Anton Gáplovský
Molecules 2020, 25(13), 3082; https://doi.org/10.3390/molecules25133082 - 6 Jul 2020
Cited by 8 | Viewed by 2794
Abstract
The subject of this work was the study of thermally and photochemically stimulated Z ↔ E isomerization and hydrazo ↔ azo tautomerism of Z- and E-isomers of isatin arylhydrazones and ((arylamino)methylene)indolin-2-ones and their anions. Using NMR, UV-Vis spectroscopy, kinetic measurements, and [...] Read more.
The subject of this work was the study of thermally and photochemically stimulated Z ↔ E isomerization and hydrazo ↔ azo tautomerism of Z- and E-isomers of isatin arylhydrazones and ((arylamino)methylene)indolin-2-ones and their anions. Using NMR, UV-Vis spectroscopy, kinetic measurements, and HPLC, we studied the relationship of structure, (Z- and E-isomers), of these compounds and hydrazo=azo tautomerism. The ON/OFF functionality of these compounds and their anions using light to stimulate switching between ON and OFF states was investigated. We pointed out the characterization of the effect of =N- and =CH- structural fragments and aryl structure on ON and OFF states of isatin arylhydrazones and ((arylamino)methylene)indolin-2-ones. Full article
(This article belongs to the Special Issue New Studies of Photoisomerization)
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16 pages, 4570 KiB  
Article
Computational and Crystallographic Examination of Naphthoquinone Based Diarylethene Photochromes
by Dinesh G. Patel, Martial Boggio-Pasqua, Travis B. Mitchell, Ian M. Walton, William R. Quigley and Frank A. Novak
Molecules 2020, 25(11), 2630; https://doi.org/10.3390/molecules25112630 - 5 Jun 2020
Cited by 4 | Viewed by 3488
Abstract
Photochromic compounds have a lengthy history of study and a profusion of applications that stand to gain from these studies. Among the classes of photochromic compounds, diarylethenes show desirable properties including high fatigue resistance and thermal stability, thus meeting some of the most [...] Read more.
Photochromic compounds have a lengthy history of study and a profusion of applications that stand to gain from these studies. Among the classes of photochromic compounds, diarylethenes show desirable properties including high fatigue resistance and thermal stability, thus meeting some of the most important criteria necessary to enter the realm of practical applications. Recently, photochromic diarylethenes containing quinone functionalities have demonstrated interesting optical and solid-state properties. When properly interfaced with suitable electron withdrawing groups on the aryl component, both the ring-opening and ring-closing reactions can be achieved with visible light; this is in contrast to most other diarylethenes where UV light is required for ring closure. Unfortunately, quantitative conversion from open to closed forms is not possible. In this work, we examine the relative energies of conformations of solid-state structures observed by X-ray crystallography and evaluate their thermal stabilities based on density functional theory (DFT) calculations. Time-dependent DFT (TD–DFT) is used to model the UV-vis absorption spectra of these quinone diarylethenes. We show that spectral overlap between open and closed forms is a major hindrance to full photoconversion. Full article
(This article belongs to the Special Issue New Studies of Photoisomerization)
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11 pages, 2286 KiB  
Article
CASPT2 Potential Energy Curves for NO Dissociation in a Ruthenium Nitrosyl Complex
by Francesco Talotta, Leticia González and Martial Boggio-Pasqua
Molecules 2020, 25(11), 2613; https://doi.org/10.3390/molecules25112613 - 4 Jun 2020
Cited by 19 | Viewed by 3515
Abstract
Ruthenium nitrosyl complexes are fascinating photoactive compounds showing complex photoreactivity, such as N→O linkage photoisomerism and NO photorelease. This dual photochemical behavior has been the subject of many experimental studies in order to optimize these systems for applications as photoswitches or therapeutic agents [...] Read more.
Ruthenium nitrosyl complexes are fascinating photoactive compounds showing complex photoreactivity, such as N→O linkage photoisomerism and NO photorelease. This dual photochemical behavior has been the subject of many experimental studies in order to optimize these systems for applications as photoswitches or therapeutic agents for NO delivery. However, despite recent experimental and computational studies along this line, the underlying photochemical mechanisms still need to be elucidated for a more efficient design of these systems. Here, we present a theoretical contribution based on the calculations of excited-state potential energy profiles for NO dissociation in the prototype trans-[RuCl(NO)(py)4]2+ complex at the complete active space second-order perturbation theory (CASPT2). The results point to a sequential two-step photon absorption photorelease mechanism coupled to partial photoisomerization to a side-on intermediate, in agreement with previous density functional theory calculations. Full article
(This article belongs to the Special Issue New Studies of Photoisomerization)
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15 pages, 1758 KiB  
Article
Photorelaxation Pathways of 4-(N,N-Dimethylamino)-4′-nitrostilbene Upon S1 Excitation Revealed by Conical Intersection and Intersystem Crossing Networks
by Ziyue He, Ruidi Xue, Yibo Lei, Le Yu and Chaoyuan Zhu
Molecules 2020, 25(9), 2230; https://doi.org/10.3390/molecules25092230 - 9 May 2020
Cited by 2 | Viewed by 3186
Abstract
Multi-state n-electron valence state second order perturbation theory (MS-NEVPT2) was utilized to reveal the photorelaxation pathways of 4-(N,N-dimethylamino)-4′-nitrostilbene (DANS) upon S1 excitation. Within the interwoven networks of five S1/S0 and three T2/T1 conical [...] Read more.
Multi-state n-electron valence state second order perturbation theory (MS-NEVPT2) was utilized to reveal the photorelaxation pathways of 4-(N,N-dimethylamino)-4′-nitrostilbene (DANS) upon S1 excitation. Within the interwoven networks of five S1/S0 and three T2/T1 conical intersections (CIs), and three S1/T2, one S1/T1 and one S0/T1 intersystem crossings (ISCs), those competing nonadiabatic decay pathways play different roles in trans-to-cis and cis-to-trans processes, respectively. After being excited to the Franck–Condon (FC) region of the S1 state, trans-S1-FC firstly encounters an ultrafast conversion to quinoid form. Subsequently, the relaxation mainly proceeds along the triplet pathway, trans-S1-FC → ISC-S1/T2-trans → CI-T2/T1-trans → ISC-S0/T1-twist → trans- or cis-S0. The singlet relaxation pathway mediated by CI-S1/S0-twist-c is hindered by the prominent energy barrier on S1 surface and by the reason that CI-S1/S0-trans and CI-S1/S0-twist-t are both not energetically accessible upon S1 excitation. On the other hand, the cis-S1-FC lies at the top of steeply decreasing potential energy surfaces (PESs) towards the CI-S1/S0-twist-c and CI-S1/S0-DHP regions; therefore, the initial twisting directions of DN and DAP moieties determine the branching ratio between αC=C twisting (cis-S1-FC → CI-S1/S0-twist-c → trans- or cis-S0) and DHP formation relaxation pathways (cis-S1-FC → CI-S1/S0-DHP → DHP-S0) on the S1 surface. Moreover, the DHP formation could also take place via the triplet relaxation pathway, cis-S1-FC → ISC-S1/T1-cis → DHP-T1 → DHP-S0, however, which may be hindered by insufficient spin-orbit coupling (SOC) strength. The other triplet pathways for cis-S1-FC mediated by ISC-S1/T2-cis are negligible due to the energy or geometry incompatibility of possible consecutive stepwise S1 → T2 → T1 or S1 → T2 → S1 processes. The present study reveals photoisomerization dynamic pathways via conical intersection and intersystem crossing networks and provides nice physical insight into experimental investigation of DANS. Full article
(This article belongs to the Special Issue New Studies of Photoisomerization)
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19 pages, 2186 KiB  
Article
Multistep Photochemical Reactions of Polypyridine-Based Ruthenium Nitrosyl Complexes in Dimethylsulfoxide
by Nataliia Marchenko, Pascal G. Lacroix, Valerii Bukhanko, Marine Tassé, Carine Duhayon, Martial Boggio-Pasqua and Isabelle Malfant
Molecules 2020, 25(9), 2205; https://doi.org/10.3390/molecules25092205 - 8 May 2020
Cited by 15 | Viewed by 2863
Abstract
The photorelease of nitric oxide (NO·) has been investigated in dimethylsulfoxide (DMSO) on two compounds of formula [Ru(R-tpy)(bpy)(NO)](PF6)3, in which bpy stands for 2,2′-bipyridine and R-tpy for the 4′-R-2,2′:6′,2″-terpyridine with R = H and MeOPh. It is [...] Read more.
The photorelease of nitric oxide (NO·) has been investigated in dimethylsulfoxide (DMSO) on two compounds of formula [Ru(R-tpy)(bpy)(NO)](PF6)3, in which bpy stands for 2,2′-bipyridine and R-tpy for the 4′-R-2,2′:6′,2″-terpyridine with R = H and MeOPh. It is observed that both complexes are extremely sensitive to traces of water, leading to an equilibrium between [Ru(NO)] and [Ru(NO2)]. The photoproducts of formula [Ru(R-tpy)(bpy)(DMSO)](PF6)2 are further subjected to a photoreaction leading to a reversible linkage isomerization between the stable Ru-DMSO(S) (sulfur linked) and the metastable Ru-DMSO(O) (oxygen linked) species. A set of 4 [Ru(R-tpy)(bpy)(DMSO)]2+ complexes (R = H, MeOPh, BrPh, NO2Ph) is investigated to characterize the ratio and mechanism of the isomerization which is tentatively related to the difference in absorbance between the Ru-DMSO(S) and Ru-DMSO(O) forms. In addition, the X-ray crystal structures of [Ru(tpy)(bpy)(NO)](PF6)3 and [Ru(MeOPh-tpy)(bpy)(DMSO(S))](PF6)2 are presented. Full article
(This article belongs to the Special Issue New Studies of Photoisomerization)
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13 pages, 2014 KiB  
Article
Ultrafast Backbone Protonation in Channelrhodopsin-1 Captured by Polarization Resolved Fs Vis-pump—IR-Probe Spectroscopy and Computational Methods
by Till Stensitzki, Suliman Adam, Ramona Schlesinger, Igor Schapiro and Karsten Heyne
Molecules 2020, 25(4), 848; https://doi.org/10.3390/molecules25040848 - 14 Feb 2020
Cited by 7 | Viewed by 3487
Abstract
Channelrhodopsins (ChR) are light-gated ion-channels heavily used in optogenetics. Upon light excitation an ultrafast all-trans to 13-cis isomerization of the retinal chromophore takes place. It is still uncertain by what means this reaction leads to further protein changes and channel conductivity. [...] Read more.
Channelrhodopsins (ChR) are light-gated ion-channels heavily used in optogenetics. Upon light excitation an ultrafast all-trans to 13-cis isomerization of the retinal chromophore takes place. It is still uncertain by what means this reaction leads to further protein changes and channel conductivity. Channelrhodopsin-1 in Chlamydomonas augustae exhibits a 100 fs photoisomerization and a protonated counterion complex. By polarization resolved ultrafast spectroscopy in the mid-IR we show that the initial reaction of the retinal is accompanied by changes in the protein backbone and ultrafast protonation changes at the counterion complex comprising Asp299 and Glu169. In combination with homology modelling and quantum mechanics/molecular mechanics (QM/MM) geometry optimization we assign the protonation dynamics to ultrafast deprotonation of Glu169, and transient protonation of the Glu169 backbone, followed by a proton transfer from the backbone to the carboxylate group of Asp299 on a timescale of tens of picoseconds. The second proton transfer is not related to retinal dynamics and reflects pure protein changes in the first photoproduct. We assume these protein dynamics to be the first steps in a cascade of protein-wide changes resulting in channel conductivity. Full article
(This article belongs to the Special Issue New Studies of Photoisomerization)
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13 pages, 3275 KiB  
Article
Mechanosynthesis of Photochromic Oligophenyleneimines: Optical, Electrochemical and Theoretical Studies
by Miguel Angel Amado-Briseño, Luis Ángel Zárate-Hernández, Karina Alemán-Ayala, Oscar Coreño Alonso, Julián Cruz-Borbolla, José Manuel Vásquez-Pérez, Víctor Esteban Reyes-Cruz, María Aurora Veloz-Rodríguez, Esteban Rueda-Soriano, Thangarasu Pandiyan and Rosa Angeles Vázquez-García
Molecules 2019, 24(5), 849; https://doi.org/10.3390/molecules24050849 - 28 Feb 2019
Cited by 11 | Viewed by 3183
Abstract
In this work, two oligophenyleneimines type pentamers with terminal aldehydes, designated as DAFCHO (4,4′-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis(azanyl ylidene))bis(9H-fluorene-7,2-diyl))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) and FDACHO (4,4′-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis (azanylylidene))bis(4,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) were synthesized by mechanochemistry method using 2,5-bis(octyloxy) terephtal aldehyde and 2,7-diaminofluorene or 1,4-phenylenediamine. All compounds were spectroscopically characterized using 1H and [...] Read more.
In this work, two oligophenyleneimines type pentamers with terminal aldehydes, designated as DAFCHO (4,4′-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis(azanyl ylidene))bis(9H-fluorene-7,2-diyl))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) and FDACHO (4,4′-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis (azanylylidene))bis(4,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) were synthesized by mechanochemistry method using 2,5-bis(octyloxy) terephtal aldehyde and 2,7-diaminofluorene or 1,4-phenylenediamine. All compounds were spectroscopically characterized using 1H and 13C-NMR, FT-IR and mass spectrometry MALDITOF. The optical properties of the compounds were analyzed by UV-vis spectroscopy using different solvents. We observed that DAFCHO and FDACHO exhibit interesting photochromic properties when they are dissolved in chloroform and exposed to sunlight for 3, 5 and 10 min. The value of the energy band gap was calculated from the absorption spectra without irradiation Egap(optical). It was 2.50 eV for DAFCHO in chloroform solution, and it decreased to 2.34 eV when it is in films. For FDACHO, it was 2.41 eV in solution and 2.27 eV in film. HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital) and Egap(electrochemical) values were obtained by electrochemical studies. The results indicate that the compounds can be considered as organic semiconductors since their values are 2.35 eV for DAFCHO and 2.06 eV for FDACHO. The structural and electronic properties of the compounds were corroborated with a DFT (Density Functional Theory) study. Full article
(This article belongs to the Special Issue New Studies of Photoisomerization)
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