1
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Jaiswal AK, Saha P, Jiang J, Suzuki K, Jasny A, Schmidt BM, Maeda S, Hecht S, Huang CYD. Accessing a Diverse Set of Functional Red-Light Photoswitches by Selective Copper-Catalyzed Indigo N-Arylation. J Am Chem Soc 2024; 146:21367-21376. [PMID: 39058407 DOI: 10.1021/jacs.4c03543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2024]
Abstract
The ability to correlate the structure of a molecule with its properties is the key to the rational and accelerated design of new functional compounds and materials. Taking photoswitches as an example, the thermal stability of the metastable state is a crucial property that dictates their application in molecular systems. Indigos have recently emerged as an attractive motif for designing photoswitchable molecules due to their red-light addressability, which can be advantageous in biomedical and material applications. The lack of synthetic techniques to derivatize the abundant parent dye and a thorough understanding of the impact of structural factors on the photochemical and thermal properties hinder broad applications of this emerging photoswitch class. Herein, we report an efficient copper-catalyzed indigo N-arylation that enables the installation of a wide variety of aryl moieties carrying useful functional groups. The exclusive selectivity for monoarylation likely originates from a bimetallic cooperative mechanism through a binuclear copper-indigo intermediate. Functional N-aryl-N'-alkylindigos were prepared and shown to photoisomerize efficiently under red light. Moreover, this design allows for the modulation of thermal half-lives through N-aryl substituents, while the N'-alkyl groups enable the independent attachment of functional moieties without affecting the photochromic properties. A strong correlation between the structure of the N-aryl moiety and the thermal stability of the photogenerated Z-isomers was achieved by multivariate linear regression models obtained through a data-science workflow. This work thus builds an avenue leading to versatile red-light photoswitches and a general method for structure-property correlation that is expected to be broadly applicable to the design of photoresponsive molecules.
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Affiliation(s)
- Amit K Jaiswal
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
| | - Priya Saha
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
| | - Julong Jiang
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-8628, Japan
| | - Kimichi Suzuki
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
| | - Anna Jasny
- DWI-Leibniz Institute for Interactive Materials, Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Aachen 52074, Germany
| | - Bernd M Schmidt
- Institute for Organic Chemistry and Macromolecular Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstraße 1, Düsseldorf 40225, Germany
| | - Satoshi Maeda
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-8628, Japan
| | - Stefan Hecht
- Department of Chemistry, IRIS Adlershof and Center for the Science of Materials Berlin, Humboldt-Universität zu Berlin, Berlin 12489, Germany
| | - Chung-Yang Dennis Huang
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
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2
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Kuntze K, Isokuortti J, van der Wal JJ, Laaksonen T, Crespi S, Durandin NA, Priimagi A. Detour to success: photoswitching via indirect excitation. Chem Sci 2024; 15:11684-11698. [PMID: 39092110 PMCID: PMC11290455 DOI: 10.1039/d4sc02538e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Accepted: 07/02/2024] [Indexed: 08/04/2024] Open
Abstract
Photoswitchable molecules that undergo nanoscopic changes upon photoisomerisation can be harnessed to control macroscopic properties such as colour, solubility, shape, and motion of the systems they are incorporated into. These molecules find applications in various fields of chemistry, physics, biology, and materials science. Until recently, research efforts have focused on the design of efficient photoswitches responsive to low-energy (red or near-infrared) irradiation, which however may compromise other molecular properties such as thermal stability and robustness. Indirect isomerisation methods enable photoisomerisation with low-energy photons without altering the photoswitch core, and also open up new avenues in controlling the thermal switching mechanism. In this perspective, we present the state of the art of five indirect excitation methods: two-photon excitation, triplet sensitisation, photon upconversion, photoinduced electron transfer, and indirect thermal methods. Each impacts our understanding of the fundamental physicochemical properties of photochemical switches, and offers unique application prospects in biomedical technologies and beyond.
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Affiliation(s)
- Kim Kuntze
- Faculty of Engineering and Natural Sciences, Tampere University Tampere Finland
| | - Jussi Isokuortti
- Department of Chemistry, University of Texas at Austin Austin TX USA
| | - Jacob J van der Wal
- Department of Chemistry, Ångström Laboratory, Uppsala University Uppsala Sweden
| | - Timo Laaksonen
- Faculty of Engineering and Natural Sciences, Tampere University Tampere Finland
- Faculty of Pharmacy, University of Helsinki Helsinki Finland
| | - Stefano Crespi
- Department of Chemistry, Ångström Laboratory, Uppsala University Uppsala Sweden
| | - Nikita A Durandin
- Faculty of Engineering and Natural Sciences, Tampere University Tampere Finland
| | - Arri Priimagi
- Faculty of Engineering and Natural Sciences, Tampere University Tampere Finland
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3
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Simms CH, Nielsen VRM, Sørensen TJ, Faulkner S, Langton MJ. Photoswitchable luminescent lanthanide complexes controlled and interrogated by four orthogonal wavelengths of light. Phys Chem Chem Phys 2024; 26:18683-18691. [PMID: 38922672 DOI: 10.1039/d4cp02243b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
Optical information storage requires careful control of excitation and emission wavelengths in a reversible and orthogonal manner to enable efficient reading, writing, and erasing of information. Photochromic systems, in which a photoswitch is typcially coupled to an emissive organic fluorophore, have much promise in this regard. However, these suffer from considerable spectral overlap between the switch and fluorophore, such that their emissive and photoswitchable properties are not orthogonal. Here, we overcome this limitation by coupling visible/NIR emissive lanthanide complexes with molecular photoswitches, enabling reversible and orthogonal photoswitching with visible light. Crucially, photoswitching does not lead to sensitised emission from the lanthanide, while excitation of the lanthanide does not induce photoswitching, enabling the state of the system to be probed without perturbation of the switch. This opens up the possibility of developing multi-colour read-write methods for information storage using emissive photoswitches.
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Affiliation(s)
- Charlie H Simms
- Department of Chemistry, University of Oxford Chemistry Research Laboratory, Mansfield road, Oxford, OX1 3TA, UK.
| | - Villads R M Nielsen
- Nano-Science Centre and Department of Chemistry University of Copenhagen Universitetsparken 5, 2100 København Ø, Denmark
| | - Thomas Just Sørensen
- Nano-Science Centre and Department of Chemistry University of Copenhagen Universitetsparken 5, 2100 København Ø, Denmark
| | - Stephen Faulkner
- Department of Chemistry, University of Oxford Chemistry Research Laboratory, Mansfield road, Oxford, OX1 3TA, UK.
| | - Matthew J Langton
- Department of Chemistry, University of Oxford Chemistry Research Laboratory, Mansfield road, Oxford, OX1 3TA, UK.
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4
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Bandyopadhyay S. Tuning properties of functionalized azobenzene photoswitches through variation of substitution and their position. Photochem Photobiol 2024; 100:1151-1153. [PMID: 38664875 DOI: 10.1111/php.13954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2024] [Accepted: 04/14/2024] [Indexed: 07/30/2024]
Abstract
This perspective article features the recent work published in this journal on functionalized azobenzene photoswitches, studied by Venkataramani and coworkers [Grewal, S. et al (2024) Photochem. Photobiol., 1-16]. Azobenzene-based photochromic molecules undergo reversible trans-to-cis isomerization under exposure to light. The reverse cis-to-trans isomerization also takes place under thermal conditions in the dark. The study explores how different functional groups at various positions affect the responses of these compounds to light, their thermal stabilities, the isomeric ratios in the photostationary states, and their supramolecular behavior. Results show varied thermal half-lives, influenced by the terminal groups and their positions. Aggregation studies reveal the formation of supramolecular architectures, from microcrystals to gels with these systems. Despite complexities with the large volume of work with 30 different compounds, the research provides insights into designing efficient photochromic supramolecular motifs.
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Affiliation(s)
- Subhajit Bandyopadhyay
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, Nadia, West Bengal, India
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5
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Golovina GV, Egorov AE, Khodot EN, Kostyukov AA, Timokhina EN, Astakhova TY, Nekipelova TD. The effect of substituent position and solvent on thermal Z‒E isomerization of dihydroquinolylazotetrazole dyes: kinetic, thermodynamic, and spectral approaches. Photochem Photobiol Sci 2024; 23:177-187. [PMID: 38071235 DOI: 10.1007/s43630-023-00511-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 11/12/2023] [Indexed: 02/02/2024]
Abstract
Kinetic and thermodynamic parameters have been investigated for the thermal Z‒E isomerization of dihydroquinolylazotetrazole dyes with alkyl substituents (Me, t-Bu, and Adm) at positions 1 (dyes 2) and 2 (dyes 3) of the tetrazole moiety in two solvents of different polarity, acetonitrile (MeCN) and toluene. The experimental results show crucial dependence of these parameters on a substituent position in the tetrazole moiety and on a solvent. For dyes 2, Eact and ΔH‡ are lower in MeCN than in toluene that results in a high increase in the lifetimes of the Z isomers: from milliseconds in MeCN to minutes in toluene. For dyes 3, the difference in Eact and ΔH‡ in the two solvents is opposite: Eact and ΔH‡ are by more than 20 kJ mol-1 higher in MeCN, nevertheless, the rate constants for 3 in toluene are comparable with those in MeCN at the ambient temperature and the difference in the behavior is determined by the value of negative entropy of activation. Quantum-chemical calculations of the thermal Z‒E isomerization show the possibility of the process to occur via crossing from the S0 to the thermally induced T1 state. The contribution of this path is highest for 3 in toluene. The analysis of the absorption spectra demonstrates that for the E isomers, the n‒π* and π‒π* transitions are within the long-wavelength absorption band and their positions relative each other are opposite in the solvents: the n‒π* transition is blue-shifted relative to the π‒π* transition in MeCN and is red-shifted in toluene.
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Affiliation(s)
- Galina V Golovina
- Emanuel Institute of Biochemical Physics RAS, Kosygin Str. 4, Moscow, 119334, Russia
| | - Anton E Egorov
- Emanuel Institute of Biochemical Physics RAS, Kosygin Str. 4, Moscow, 119334, Russia
| | - Evgenii N Khodot
- Zelinsky Institute of Organic Chemistry RAS, Leninskii Pr. 47, Moscow, 119991, Russia
| | - Alexey A Kostyukov
- Emanuel Institute of Biochemical Physics RAS, Kosygin Str. 4, Moscow, 119334, Russia
| | - Elena N Timokhina
- Emanuel Institute of Biochemical Physics RAS, Kosygin Str. 4, Moscow, 119334, Russia
| | - Tatiana Yu Astakhova
- Emanuel Institute of Biochemical Physics RAS, Kosygin Str. 4, Moscow, 119334, Russia
| | - Tatiana D Nekipelova
- Emanuel Institute of Biochemical Physics RAS, Kosygin Str. 4, Moscow, 119334, Russia.
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6
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Li CH, Tabor DP. Generative organic electronic molecular design informed by quantum chemistry. Chem Sci 2023; 14:11045-11055. [PMID: 37860647 PMCID: PMC10583709 DOI: 10.1039/d3sc03781a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Accepted: 09/11/2023] [Indexed: 10/21/2023] Open
Abstract
Generative molecular design strategies have emerged as promising alternatives to trial-and-error approaches for exploring and optimizing within large chemical spaces. To date, generative models with reinforcement learning approaches have frequently used low-cost methods to evaluate the quality of the generated molecules, enabling many loops through the generative model. However, for functional molecular materials tasks, such low-cost methods are either not available or would require the generation of large amounts of training data to train surrogate machine learning models. In this work, we develop a framework that connects the REINVENT reinforcement learning framework with excited state quantum chemistry calculations to discover molecules with specified molecular excited state energy levels, specifically molecules with excited state landscapes that would serve as promising singlet fission or triplet-triplet annihilation materials. We employ a two-step curriculum strategy to first find a set of diverse promising molecules, then demonstrate the framework's ability to exploit a more focused chemical space with anthracene derivatives. Under this protocol, we show that the framework can find desired molecules and improve Pareto fronts for targeted properties versus synthesizability. Moreover, we are able to find several different design principles used by chemists for the design of singlet fission and triplet-triplet annihilation molecules.
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Affiliation(s)
- Cheng-Han Li
- Department of Chemistry, Texas A&M University College Station TX 77842 USA
| | - Daniel P Tabor
- Department of Chemistry, Texas A&M University College Station TX 77842 USA
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7
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Singer N, Schlögl K, Zobel JP, Mihovilovic MD, González L. Singlet and Triplet Pathways Determine the Thermal Z/ E Isomerization of an Arylazopyrazole-Based Photoswitch. J Phys Chem Lett 2023; 14:8956-8961. [PMID: 37772734 PMCID: PMC10577781 DOI: 10.1021/acs.jpclett.3c01785] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 09/21/2023] [Indexed: 09/30/2023]
Abstract
Understanding the thermal isomerization mechanism of azobenzene derivatives is essential to designing photoswitches with tunable half-lives. Herein, we employ quantum chemical calculations, nonadiabatic transition state theory, and photosensitized experiments to unravel the thermal Z/E isomerization of a heteroaromatic azoswitch, the phenylazo-1,3,5-trimethylpyrazole. In contrast to the parent azobenzene, we predict two pathways to be operative at room temperature. One is a conventional ground-state reaction occurring via inversion of the aryl group, and the other is a nonadiabatic process involving intersystem crossing to the lowest-lying triplet state and back to the ground state, accompanied by a torsional motion around the azo bond. Our results illustrate that the fastest reaction rate is not controlled by the mechanism involving the lowest activation energy, but the size of the spin-orbit couplings at the crossing between the singlet and the triplet potential energy surfaces is also determinant. It is therefore mandatory to consider all of the multiple reaction pathways in azoswitches in order to predict experimental half-lives.
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Affiliation(s)
- Nadja
K. Singer
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, 1090 Vienna, Austria
- Vienna
Doctoral School in Chemistry (DoSChem), University of Vienna, Währinger Str. 42, 1090 Vienna, Austria
| | - Katharina Schlögl
- Institute
of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria
| | - J. Patrick Zobel
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, 1090 Vienna, Austria
| | - Marko D. Mihovilovic
- Institute
of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria
| | - Leticia González
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, 1090 Vienna, Austria
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8
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Bakhtiiari A, Costa GJ, Liang R. On the Simulation of Thermal Isomerization of Molecular Photoswitches in Biological Systems. J Chem Theory Comput 2023; 19:6484-6499. [PMID: 37607344 DOI: 10.1021/acs.jctc.3c00451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Molecular photoswitches offer precise, reversible photocontrol over biomolecular functions and are promising light-regulated drug candidates with minimal side effects. Quantifying thermal isomerization rates of photoswitches in their target biomolecules is essential for fine-tuning their light-controlled drug activity. However, the effects of protein binding on isomerization kinetics remain poorly understood, and simulations are crucial for filling this gap. Challenges in the simulation include describing multireference electronic structures near transition states, disentangling competing reaction pathways, and sampling protein-ligand interactions. To overcome these challenges, we used multiscale simulations to characterize the thermal isomerization of photostatins (PSTs), which are light-regulated microtubule inhibitors for potential cancer phototherapy. We employed a new ab initio multireference electronic structure method in a quantum mechanics/molecular mechanics setting and combined it with enhanced sampling techniques to characterize the cis to trans free-energy profiles of three PSTs in a vacuum, aqueous solution, and tubulin dimer. The significant advantage of our novel approach is the efficient treatment of the multireference character in PSTs' electronic wavefunction throughout the conformational sampling of protein-ligand interactions along their isomerization pathways. We also benchmarked our calculations using high-level ab initio multireference electronic structure methods and explored the competing isomerization pathways. Notably, calculations in a vacuum and implicit solvent models cannot predict the order of the PSTs' thermal half-lives in the aqueous solution observed in the experiment. Only by explicitly treating the solvent molecules can the correct order of isomerization kinetics be reproduced. Protein binding perturbs free-energy barriers due to hydrogen bonding between PSTs and nearby polar residues. Our work generates comprehensive, high-quality benchmark data and offers guidance for selecting computational methods to study the thermal isomerization of photoswitches. Ab initio multireference free-energy calculations in explicit molecular environments are crucial for predicting the effects of substituents on the thermal half-lives of photoswitches in biological systems.
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Affiliation(s)
- Amirhossein Bakhtiiari
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
| | - Gustavo J Costa
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
| | - Ruibin Liang
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
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9
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Axelrod S, Shakhnovich E, Gómez-Bombarelli R. Mapping the Space of Photoswitchable Ligands and Photodruggable Proteins with Computational Modeling. J Chem Inf Model 2023; 63:5794-5802. [PMID: 37671878 DOI: 10.1021/acs.jcim.3c00484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
Light-activated drugs are a promising way to localize biological activity and minimize side effects. However, their development is complicated by the numerous photophysical and biological properties that must be simultaneously optimized. To accelerate the design of photoactive drugs, we describe a procedure that combines ligand-protein docking with chemical property prediction based on machine learning (ML). We apply this procedure to 58 proteins and 9000 photo-drug candidates based on azobenzene cis-trans isomerism. We find that most proteins display a preference for trans isomers over cis and that the binding affinities of nominally active/inactive pairs are in fact highly correlated. These findings have significant value for photopharmacology research, and reinforce the need for virtual screening to identify compounds with rare desirable properties. Further, we combine our procedure with quantum chemical validation to identify promising candidates for the photoactive inhibition of PARP1, an enzyme that is over-expressed in cancer cells. The top compounds are predicted to have long-lived active forms, differential bioactivity, and absorption in the near-infrared therapeutic window.
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Affiliation(s)
- Simon Axelrod
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Eugene Shakhnovich
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Rafael Gómez-Bombarelli
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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10
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Zhang B, Lin J, Du L, Zhang L. Harnessing Data Augmentation and Normalization Preprocessing to Improve the Performance of Chemical Reaction Predictions of Data-Driven Model. Polymers (Basel) 2023; 15:polym15092224. [PMID: 37177370 PMCID: PMC10180765 DOI: 10.3390/polym15092224] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/03/2023] [Accepted: 05/03/2023] [Indexed: 05/15/2023] Open
Abstract
As a template-free, data-driven methodology, the molecular transformer model provides an alternative by which to predict the outcome of chemical reactions and design the route of the retrosynthetic plane in the field of organic synthesis and polymer chemistry. However, in consideration of the small datasets of chemical reactions, the data-driven model suffers from the difficulty of low accuracy in the prediction tasks of chemical reactions. In this contribution, we integrate the molecular transformer model with the strategies of data augmentation and normalization preprocessing to accomplish the three tasks of chemical reactions, including the forward predictions of chemical reactions, and single-step retrosynthetic predictions with and without the reaction classes. It is clearly demonstrated that the prediction accuracy of the molecular transformer model can be significantly raised by the use of proposed strategies for the three tasks of chemical reactions. Notably, after the introduction of the 40-level data augmentation and normalization preprocessing, the top-1 accuracy of the forward prediction increases markedly from 71.6% to 84.2% and the top-1 accuracy of the single-step retrosynthetic prediction with additional reaction class increases from 53.2% to 63.4%. Furthermore, it is found that the superior performance of the data-driven model originates from the correction of the grammatical errors of the SMILES strings, especially for the case of the reaction classes with small datasets.
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Affiliation(s)
- Boyu Zhang
- Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Jiaping Lin
- Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Lei Du
- Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Liangshun Zhang
- Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
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11
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Reimann M, Teichmann E, Hecht S, Kaupp M. Solving the Azobenzene Entropy Puzzle: Direct Evidence for Multi-State Reactivity. J Phys Chem Lett 2022; 13:10882-10888. [PMID: 36394331 DOI: 10.1021/acs.jpclett.2c02838] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A solution to the azobenzene "entropy puzzle" [ J. Phys.: Condens. Matter, 2017, 29, 314002] is provided. Previous computational studies of the thermal Z → E (back-)isomerization of azobenzene could not describe the experimentally observed large negative activation entropies. Here it is shown that the experimental results are only compatible with a more complicated multistate rotation mechanism that involves a triplet excited state. Using nonadiabatic transition state theory, close to perfect agreement is achieved between all calculated and experimental Eyring parameters. We also provide new experiments that indicate the presence of a noticeable external heavy-atom effect, which is a direct result of spin-orbit coupling effects being important in the proposed mechanism. These results suggest a reexamination of the mechanisms of related thermal double bond isomerizations in other systems in cases when an excited state of triplet (or other) multiplicity becomes thermally accessible during a rotation process.
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Affiliation(s)
- Marc Reimann
- Theoretische Chemie/Quantenchemie, Institut für Chemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, 10623, Berlin, Germany
| | - Ellen Teichmann
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489, Berlin, Germany
| | - Stefan Hecht
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489, Berlin, Germany
- DWI-Leibniz Institute for Interactive Materials, Forckenbeckstraße 50, 52074, Aachen, Germany
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringer Weg 2, 52074, Aachen, Germany
| | - Martin Kaupp
- Theoretische Chemie/Quantenchemie, Institut für Chemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, 10623, Berlin, Germany
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