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Cantón-Díaz AM, Muñoz-Flores BM, Macías-Gamboa LF, Moggio I, Arias E, Turlakov G, Dias HVR, Colombo G, Brenna S, Jiménez-Pérez VM. Temperature-dependent photoluminescence down to 77 K of organotin molecular rotors: eco-friendly synthesis, photophysical characterization, X-ray structures, and DFT studies. Dalton Trans 2024. [PMID: 39155846 DOI: 10.1039/d4dt01518e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/20/2024]
Abstract
Fluorescent organotin compounds are useful in sensing, optoelectronic devices, and in vitro bioimaging. Although in vitro fluorescence bioimaging shows low resolution at room temperature, a better resolution is possible at cryotemperatures. Therefore, the search for new cryoluminescent materials with potential application in high-resolution fluorescence bioimaging remains a great challenge. Herein, we report the cryoluminescence properties of two fluorescent bis-organotin compounds, namely, BisNTHySnBu2 (5) and BisNTHySnPh2 (6), synthesized via microwave irradiation. All compounds were fully characterized using 1H, 13C, and 119Sn NMR spectroscopy, Raman spectroscopy, IR spectroscopy, and HR-MS. The 119Sn δ and 3J(1H,119Sn) of 5 and 6 indicate that two Sn-ligands are chemically and electronically equivalent, as confirmed by cyclic voltammetry. The crystal structure of 6 showed pentacoordinate tin atoms with skeleton ligands. The study of self-assembled monolayers of both Sn-complexes via STM microscopy revealed a similar supramolecular packing in lamella-like patterns, adopting a face-on arrangement, where molecules stay flat lying on HOPG in accordance with the height profile of closely packed monolayers on graphite of about 0.33 nm thickness. However, only the Sn complex 6, which bears phenyls, covers large surface areas. The photophysical properties of bis-organotin compounds were also investigated in solution (room and low temperatures) and in the solid state. Good luminescence properties in solutions with fluorescence quantum yields (Φ) of approximately 35% and 50% were found. Despite this, Φ is quenched in the solid state because of aggregation, as supported by solvent/non solvent fluorescence studies, which is in agreement with STM and AFM investigation.
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Affiliation(s)
- Arelly M Cantón-Díaz
- Universidad Autónoma de Nuevo León, Facultad de Ciencias Químicas, Ciudad Universitaria, Av. Universidad s/n. C. P. 66451, Nuevo León, Mexico.
| | - Blanca M Muñoz-Flores
- Universidad Autónoma de Nuevo León, Facultad de Ciencias Químicas, Ciudad Universitaria, Av. Universidad s/n. C. P. 66451, Nuevo León, Mexico.
| | - Luis F Macías-Gamboa
- Universidad Autónoma de Nuevo León, Facultad de Ciencias Químicas, Ciudad Universitaria, Av. Universidad s/n. C. P. 66451, Nuevo León, Mexico.
| | - Ivana Moggio
- Centro de Investigación en Química Aplicada, Boulevard Enrique Reyna 140, 25294 Saltillo, Coahuila, Mexico
| | - Eduardo Arias
- Centro de Investigación en Química Aplicada, Boulevard Enrique Reyna 140, 25294 Saltillo, Coahuila, Mexico
| | - Gleb Turlakov
- Centro de Investigación en Química Aplicada, Boulevard Enrique Reyna 140, 25294 Saltillo, Coahuila, Mexico
| | - H V Rasika Dias
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas, 76019-0065, USA
| | - Gioele Colombo
- Dipartimento di Scienza e Alta Tecnologia, Università degli Studi dell'Insubria and CIRCC, Via Valleggio, 9, 22100, Como, Italy
| | - Stefano Brenna
- Dipartimento di Scienza e Alta Tecnologia, Università degli Studi dell'Insubria and CIRCC, Via Valleggio, 9, 22100, Como, Italy
| | - Víctor M Jiménez-Pérez
- Universidad Autónoma de Nuevo León, Facultad de Ciencias Químicas, Ciudad Universitaria, Av. Universidad s/n. C. P. 66451, Nuevo León, Mexico.
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Usui K, Amano A, Murayama K, Sasaya M, Kusumoto R, Umeno T, Murase S, Iizuka N, Matsumoto S, Fuchi Y, Takahashi K, Kawahata M, Kobori Y, Karasawa S. Photoisomerization of "Partially Embedded Dihydropyridazine" with a Helical Structure. Chemistry 2023; 29:e202302413. [PMID: 37612241 DOI: 10.1002/chem.202302413] [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: 07/26/2023] [Revised: 08/21/2023] [Accepted: 08/23/2023] [Indexed: 08/25/2023]
Abstract
Herein, we report the synthesis of two "partially embedded fused-dihydropyridazine N-aryl aza[5]helicene derivatives" (PDHs) and the demonstration of their intrinsic photo-triggered multi-functional properties based on a Kekulé biradical structure. Introducing bulky electron-withdrawing trifluoromethyl or pentafluoroethyl groups into the aza[5]helicene framework (PDH-CF3 and -C2 F5 ) gives PDH axial chirality based on the helicity of the P and M forms, even at room temperature. Upon photo-irradiation of PDH-CF3 in a frozen solution, an ESR signal from the triplet biradical with zero-field splitting values, generated by N-N bond dissociation, was observed. However, when the irradiation was turned off, the ESR signal became silent, thus indicating the existence of two equilibria: between the biradical and quinoidal forms based on the Kekulé structure, and between N-N bond cleavage and recombination. The observed photo- and thermally induced behaviors indicate that T-type photochromic molecules are involved in the photoisomerization mechanism involving the two equilibria. Inspired by the photoisomerization, chirality control of PDH by photoracemization was achieved. Multiple functionalities, such as T-type photochromism, photo-excitation-mediated triplet biradical formation, and photoracemization, which are attributed to the "partially embedded dihydropyridazine" structure, are demonstrated.
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Affiliation(s)
- Kazuteru Usui
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Ami Amano
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Kasumi Murayama
- Department of Chemistry, Graduate School of Science Kobe University, Kobe, Hyogo, 657-8501, Japan
| | - Miho Sasaya
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Ryota Kusumoto
- Department of Chemistry, Graduate School of Science Kobe University, Kobe, Hyogo, 657-8501, Japan
| | - Tomohiro Umeno
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Satsuki Murase
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Naoko Iizuka
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Shota Matsumoto
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Yasufumi Fuchi
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Kazuyuki Takahashi
- Department of Chemistry, Graduate School of Science Kobe University, Kobe, Hyogo, 657-8501, Japan
| | - Masatoshi Kawahata
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
| | - Yasuhiro Kobori
- Department of Chemistry, Graduate School of Science Kobe University, Kobe, Hyogo, 657-8501, Japan
- Molecular Photoscience Research Center, Graduate School of Science Kobe University, Kobe, Hyogo, 657-8501, Japan
| | - Satoru Karasawa
- Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3512-1 Higashi-tamagawagakuen, Machida, Tokyo, 194-8543, Japan
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3
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da Rocha VN, Köhler MH, Nagata K, Piquini PC. Theoretical study of C 6F 5-corrole molecules functionalized with aromatic groups for Photodynamic Therapy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 293:122500. [PMID: 36827812 DOI: 10.1016/j.saa.2023.122500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 02/07/2023] [Accepted: 02/12/2023] [Indexed: 06/18/2023]
Abstract
The singlet oxygen generation by electronically excited molecules in photodynamic therapy (PDT) requires light absorption within a specific wavelength window, and a subsequent intersystem crossing transition to a triplet excited state that is, at least, 0.98 eV higher in energy than the singlet ground state. Tetrapyrrolic macrocycles, such as porphyrin and corrole, have been widely used in oxygen singlet generation for PDT. Suitable functionalization can potentialize these macrocycles as photosensitizers. In this contribution, we use Density Functional Theory (DFT) calculations to determine the structural, electronic and spectroscopic properties of corrole macrocycles bound to different polycyclic aromatic groups in the gas phase, dichloromethane, and water. We also calculate the spin-orbit coupling (SOC) matrix elements of the intersystem crossing channels involving the first excited singlet states and excited triplet states. The results for optical absorption show that the threshold wavelength for optical absorption increases with the polarity of the environment and the number of aromatic rings of the ligands, whereas the oscillator strengths increase with the polarity of the environment but decrease with the number of aromatic rings. It is verified that the triplet excited states involved in the intersystem crossing transitions satisfy the energy requirement for the oxygen singlet generation. The magnitude of spin-orbit coupling (SOC) matrix elements associated with the intersystem crossing are also seen to be dependent on the environment involving the corrole molecules, and on the number of aromatic rings of the ligands connected to the corrole. Further, the binding of the functionalized corrole molecules with biomolecules as the calf thymus DNA and human serum albumin is studied and characterized through molecular docking. These results show that the corrole macrocycles, suitably functionalized with polycyclic aromatic groups, fulfill several criteria to be considered as good PDT photosensitizers.
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Affiliation(s)
- Vinícius N da Rocha
- Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil.
| | - Mateus H Köhler
- Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil.
| | - Khayth Nagata
- Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil; Instituto de Ciências e Tecnologia das Águas, Universidade Federal do Oeste do Pará, 68040-470, Santarém, PA, Brazil.
| | - Paulo C Piquini
- Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil.
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Usui K, Narita N, Eto R, Suzuki S, Yokoo A, Yamamoto K, Igawa K, Iizuka N, Mimura Y, Umeno T, Matsumoto S, Hasegawa M, Tomooka K, Imai Y, Karasawa S. Oxidation of an Internal‐Edge‐Substituted [5]Helicene‐Derived Phosphine Synchronously Enhances Circularly Polarized Luminescence. Chemistry 2022; 28:e202202922. [DOI: 10.1002/chem.202202922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Indexed: 11/23/2022]
Affiliation(s)
- Kazuteru Usui
- Faculty of Pharmaceutical Sciences Showa Pharmaceutical University Higashi-Tamagawagakuen, Machida Tokyo 194-8543 Japan
- Graduate School of Pharmaceutical Sciences Kyushu University Maidashi Higashi-ku Fukuoka 812-8582 Japan
| | - Nozomi Narita
- Faculty of Pharmaceutical Sciences Showa Pharmaceutical University Higashi-Tamagawagakuen, Machida Tokyo 194-8543 Japan
| | - Ryosuke Eto
- Faculty of Pharmaceutical Sciences Showa Pharmaceutical University Higashi-Tamagawagakuen, Machida Tokyo 194-8543 Japan
| | - Seika Suzuki
- Department of Applied Chemistry, Faculty of Science and Engineering Kindai University Higashi-Osaka Osaka 577-8502 Japan
| | - Atsushi Yokoo
- Graduate School of Pharmaceutical Sciences Kyushu University Maidashi Higashi-ku Fukuoka 812-8582 Japan
| | - Kosuke Yamamoto
- Graduate School of Pharmaceutical Sciences Kyushu University Maidashi Higashi-ku Fukuoka 812-8582 Japan
| | - Kazunobu Igawa
- Department of Chemistry, Faculty of Advanced Science and Technology Kumamoto University Kurokami 2–39-1 Kumamoto 860-8555 Japan
| | - Naoko Iizuka
- Faculty of Pharmaceutical Sciences Showa Pharmaceutical University Higashi-Tamagawagakuen, Machida Tokyo 194-8543 Japan
| | - Yuki Mimura
- Department of Applied Chemistry, Faculty of Science and Engineering Kindai University Higashi-Osaka Osaka 577-8502 Japan
| | - Tomohiro Umeno
- Faculty of Pharmaceutical Sciences Showa Pharmaceutical University Higashi-Tamagawagakuen, Machida Tokyo 194-8543 Japan
| | - Shota Matsumoto
- Faculty of Pharmaceutical Sciences Showa Pharmaceutical University Higashi-Tamagawagakuen, Machida Tokyo 194-8543 Japan
| | - Masashi Hasegawa
- Graduate School of Science Kitasato University Sagamihara Kanagawa 252-0373 Japan
| | - Katsuhiko Tomooka
- Institute for Materials Chemistry and Engineering Kyushu University Kasuga Fukuoka 816-8580 Japan
| | - Yoshitane Imai
- Department of Applied Chemistry, Faculty of Science and Engineering Kindai University Higashi-Osaka Osaka 577-8502 Japan
| | - Satoru Karasawa
- Faculty of Pharmaceutical Sciences Showa Pharmaceutical University Higashi-Tamagawagakuen, Machida Tokyo 194-8543 Japan
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Alberto ME, Pirillo J, Russo N, Adamo C. Theoretical Exploration of Type I/Type II Dual Photoreactivity of Promising Ru(II) Dyads for PDT Approach. Inorg Chem 2016; 55:11185-11192. [DOI: 10.1021/acs.inorgchem.6b01782] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Marta Erminia Alberto
- Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris (IRCP), F-75005 Paris, France
| | - Jenny Pirillo
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Via P. Bucci, 87036 Rende, Italy
| | - Nino Russo
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Via P. Bucci, 87036 Rende, Italy
| | - Carlo Adamo
- Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris (IRCP), F-75005 Paris, France
- Institut Universitaire de France, 103 Boulevard
Saint Michel, F-75005 Paris, France
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6
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Mazzone G, Alberto ME, De Simone BC, Marino T, Russo N. Can Expanded Bacteriochlorins Act as Photosensitizers in Photodynamic Therapy? Good News from Density Functional Theory Computations. Molecules 2016; 21:288. [PMID: 26938516 PMCID: PMC6273748 DOI: 10.3390/molecules21030288] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 02/19/2016] [Accepted: 02/24/2016] [Indexed: 01/10/2023] Open
Abstract
The main photophysical properties of a series of expanded bacteriochlorins, recently synthetized, have been investigated by means of DFT and TD-DFT methods. Absorption spectra computed with different exchange-correlation functionals, B3LYP, M06 and ωB97XD, have been compared with the experimental ones. In good agreement, all the considered systems show a maximum absorption wavelength that falls in the therapeutic window (600-800 nm). The obtained singlet-triplet energy gaps are large enough to ensure the production of cytotoxic singlet molecular oxygen. The computed spin-orbit matrix elements suggest a good probability of intersystem spin-crossing between singlet and triplet excited states, since they result to be higher than those computed for 5,10,15,20-tetrakis-(m-hydroxyphenyl)chlorin (Foscan©) already used in the photodynamic therapy (PDT) protocol. Because of the investigated properties, these expanded bacteriochlorins can be proposed as PDT agents.
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Affiliation(s)
- Gloria Mazzone
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, I-87036 Arcavacata di Rende, Italy.
| | - Marta E Alberto
- Chimie ParisTech, CNRS, Institut de Recherche de Chimie Paris (IRCP), PSL Research University, F-75005 Paris, France.
| | - Bruna C De Simone
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, I-87036 Arcavacata di Rende, Italy.
| | - Tiziana Marino
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, I-87036 Arcavacata di Rende, Italy.
| | - Nino Russo
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, I-87036 Arcavacata di Rende, Italy.
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Ji S, Ge J, Escudero D, Wang Z, Zhao J, Jacquemin D. Molecular Structure-Intersystem Crossing Relationship of Heavy-Atom-Free BODIPY Triplet Photosensitizers. J Org Chem 2015; 80:5958-63. [PMID: 25942069 DOI: 10.1021/acs.joc.5b00691] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A thiophene-fused BODIPY chromophore displays a large triplet-state quantum yield (ΦT = 63.7%). In contrast, when the two thienyl moieties are not fused into the BODIPY core, intersystem crossing (ISC) becomes inefficient and ΦT remains low (ΦT = 6.1%). First-principles calculations including spin-orbit coupling (SOC) were performed to quantify the ISC. We found larger SOC and smaller singlet-triplet energy gaps for the thiophene-fused BODIPY derivative. Our results are useful for studies of the photochemistry of organic chromophores.
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Affiliation(s)
- Shaomin Ji
- ‡State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian 116024, P. R. China
| | - Jie Ge
- ‡State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian 116024, P. R. China
| | - Daniel Escudero
- §CEISAM UMR CNRS 6230, Université de Nantes, 2 rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France
| | - Zhijia Wang
- ‡State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian 116024, P. R. China
| | - Jianzhang Zhao
- ‡State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian 116024, P. R. China
| | - Denis Jacquemin
- §CEISAM UMR CNRS 6230, Université de Nantes, 2 rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.,∥Institut Universitaire de France, 103 boulevard St Michel, 75005 Paris Cedex 5, France
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8
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Nogueira JJ, Oppel M, González L. Enhancing Intersystem Crossing in Phenotiazinium Dyes by Intercalation into DNA. Angew Chem Int Ed Engl 2015; 54:4375-8. [DOI: 10.1002/anie.201411456] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Indexed: 11/06/2022]
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Nogueira JJ, Oppel M, González L. Steigerung der Interkombinationseffizienz in Phenothiazinfarbstoffen durch Einlagerung in DNA. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201411456] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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10
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Photostability and Photoreactivity in Biomolecules: Quantum Chemistry of Nucleic Acid Base Monomers and Dimers. CHALLENGES AND ADVANCES IN COMPUTATIONAL CHEMISTRY AND PHYSICS 2008. [DOI: 10.1007/978-1-4020-8184-2_16] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Serrano-Pérez JJ, González-Luque R, Merchán M, Serrano-Andrés L. On the Intrinsic Population of the Lowest Triplet State of Thymine. J Phys Chem B 2007; 111:11880-3. [DOI: 10.1021/jp0765446] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Juan José Serrano-Pérez
- Instituto de Ciencia Molecular, Universitat de València, Apartado 22085, ES-46071 Valencia, Spain
| | - Remedios González-Luque
- Instituto de Ciencia Molecular, Universitat de València, Apartado 22085, ES-46071 Valencia, Spain
| | - Manuela Merchán
- Instituto de Ciencia Molecular, Universitat de València, Apartado 22085, ES-46071 Valencia, Spain
| | - Luis Serrano-Andrés
- Instituto de Ciencia Molecular, Universitat de València, Apartado 22085, ES-46071 Valencia, Spain
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12
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Braga D, Chen S, Filson H, Maini L, Netherton MR, Patrick BO, Scheffer JR, Scott C, Xia W. 1,4-Hydroxybiradical Behavior Revealed through Crystal Structure−Solid-State Reactivity Correlations. J Am Chem Soc 2004; 126:3511-20. [PMID: 15025478 DOI: 10.1021/ja039076w] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structure-reactivity correlations for triplet 1,4-hydroxybiradicals in solution are made difficult by the presence of multiple reactive conformers and the possibility of conformation-dependent intersystem crossing. These problems can be overcome by working in the crystalline state, where the conformations of the 1,4-hydroxybiradicals are fixed and determinable by X-ray crystallography of the parent ketones, assuming that hydrogen atom abstraction occurs with little or no change in conformation. This approach is applied to 15 bi- and tricyclic ketones designed to have slightly different biradical conformations, so that the effect of small and incremental changes in geometry on biradical behavior can be tested. The results indicate that, while geometry does have a strong influence on 1,4-hydroxybiradical partitioning between cyclization, cleavage, and reverse hydrogen transfer, a full understanding of the results requires that the strain involved in forming the cyclization products be taken into account.
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Affiliation(s)
- Dario Braga
- Department of Chemistry, University of British Columbia, Vancouver, Canada V6T 1Z1
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