1
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Paul I, Konieczny KA, Chavez R, Garcia-Garibay MA. Reaction amplification with a gain: Triplet exciton-mediated quantum chain using mixed crystals with a tailor-made triplet sensitizer. Proc Natl Acad Sci U S A 2024; 121:e2401982121. [PMID: 38536753 PMCID: PMC10998555 DOI: 10.1073/pnas.2401982121] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 02/26/2024] [Indexed: 04/08/2024] Open
Abstract
Photochemical valence bond isomerization of a crystalline Dewar benzene (DB) diacid monoanion salt with an acetophenone-linked piperazinium cation that serves as an intramolecular triplet energy sensitizer (DB-AcPh-Pz) exhibits a quantum chain reaction with as many as 450 product molecules per photon absorbed (Φ ≈ 450). By contrast, isomorphous crystals of the DB diacid monosalt of an ethylbenzene-linked piperazinium (DB-EtPh-Pz) lacking a triplet sensitizer showed a less impressive quantum yield of ca. Φ ≈ 22. To establish the critical importance of a triplet excited state carrier in the adiabatic photochemical reaction we prepared mixed crystals with DB-AcPh-Pz as a dilute triplet sensitizer guest in crystals of DB-EtPh-Pz. As expected from their high structural similarities, solid solutions were easily formed with the triplet sensitizer salt in the range of 0.1 to 10%. Experiments carried out under conditions where light is absorbed by the triplet sensitizer-linked DB-AcPh-Pz can be used to initiate a triplet state adiabatic reaction from 3DB-AcPh-Pz to 3HB*-AcPh-Pz, which can serve as a chain carrier and transfer energy to an unreacted DB-EtPh-Pz where exciton delocalization in the crystalline solid solution can help carry out an efficient energy transfer and enable a quantum chain employing the photoproduct as a triplet chain carrier. Excitation of mixed crystals with as little as 0.1% triplet sensitizer resulted in an extraordinarily high quantum yield Φ ≈ 517.
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Affiliation(s)
- Indrajit Paul
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA90024-1569
| | - Krzysztof A. Konieczny
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA90024-1569
| | - Roberto Chavez
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA90024-1569
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2
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Ahmed N, Kavikarage JPK, Judkins DF, Mendis WD, Merugu R, Krause JA, Ault BS, Gudmundsdottir AD. Unraveling the Solid-State Photoreactivity of Carbonylbis(4,1-Phenylene)dicarbonazidate with Laser Flash Photolysis. J Phys Chem A 2023; 127:9705-9716. [PMID: 37939705 DOI: 10.1021/acs.jpca.3c04867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Solid-state photoreactions are generally controlled by the rigid and ordered nature of crystals. Herein, the solution and solid-state photoreactivities of carbonylbis(4,1-phenylene)dicarbonazidate (1) were investigated to elucidate the solid-state reaction mechanism. Irradiation of 1 in methanol yielded primarily the corresponding amine, whereas irradiation in the solid state gave a mixture of photoproducts. Laser flash photolysis in methanol showed the formation of the triplet ketone (TK) of 1 (τ ∼ 99 ns), which decayed to triplet nitrene 31N (τ ∼ 464 ns), as assigned by comparison to its calculated spectrum. Laser flash photolysis of a nanocrystalline suspension and diffuse reflectance laser flash photolysis also revealed the formation of TK of 1 (τ ∼ 106 ns) and 31N (τ ∼ 806 ns). Electron spin resonance spectroscopy and phosphorescence measurements further verified the formation of 31N and the TK of 1, respectively. In methanol, 31N decays by H atom abstraction. However, in the solid state, 31N is sufficiently long lived to thermally populate its singlet configuration (11N). Insertion of 11N into the phenyl ring to produce oxazolone competes with 31N cleavage to form a radical pair. Notably, 1 did not exhibit photodynamic behavior, likely because the photoreaction occurs only on the crystal surfaces.
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Affiliation(s)
- Noha Ahmed
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - Janaka P K Kavikarage
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - DeAnte F Judkins
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - W Dinindu Mendis
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - Rajkumar Merugu
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - Jeanette A Krause
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - Bruce S Ault
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - Anna D Gudmundsdottir
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
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3
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King J, Garcia-Garibay MA. Kinetics of Photoreactive 4,4'-Dimethylbenzophenone Nanocrystals: Relative Contributions to Triplet Decay from Intermolecular H-Atom Transfer and Reductive Charge Transfer Quenching. J Phys Chem A 2023; 127:7216-7220. [PMID: 37606353 DOI: 10.1021/acs.jpca.3c03828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
Crystals of 4,4'-dimethylbenzophenone (DMBP) are known to react by intermolecular H atom transfer, followed by radical pair recombination. To determine the contribution of the H atom transfer reaction to the deactivation of the triplet ketone, transient absorption spectra and kinetics were obtained using aqueous nanocrystalline suspensions. Single-exponential lifetimes of ca. 1185 ns with no deuterium isotope effect and inefficient product formation suggest that the reaction does not contribute significantly to the kinetics of triplet decay. By contrast, the observed lifetime is consistent with previous observations with p,p'-disubstituted benzophenones that undergo an efficient self-quenching process by a reductive charge transfer mechanism.
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Affiliation(s)
- Jared King
- The Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569 United States
| | - Miguel A Garcia-Garibay
- The Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569 United States
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4
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Hipwell VM, Meyer AR, Garcia-Garibay MA. Exceptionally Long Lifetimes of Strongly Entangled Acyl-Trityl Radical Pairs Photochemically Generated in Crystalline Trityl Ketones. J Am Chem Soc 2023; 145:1342-1348. [PMID: 36598840 DOI: 10.1021/jacs.2c11787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Triplet acyl-alkyl radical pairs generated by pulsed laser excitation within the constraints of their nanocrystalline ketone precursors were recently introduced as a potential platform for the robust and repeated instantiation of spin qubit pairs for applications in quantum information science. Here, we report the transient spectroscopy of a series of nanocrystalline trityl-alkyl and trityl-aryl ketones capable of generating correlated triplet radical pairs with persistent triphenylmethyl radicals forced to remain within bonding distances of highly reactive acyl radicals. Whereas triplet trityl-acyl radical pairs decay by competing product-forming decarbonylation and intersystem crossing, triplet trityl-benzoyl radical pairs have lifetimes of up to ca. 4 ms and exclusively regenerate the starting ketone. We propose that these long lifetimes are the result of the short inter-radical distances and the colinear orientation of the two singly occupied orbitals, which are expected to result in large singlet-triplet energy gaps, large zero-field splitting parameters, and a poor geometry for spin-obit coupling. Ketones generating trityl-benzoyl radical pairs demonstrate promising performance along multiple dimensions that are crucial for quantum information science.
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Affiliation(s)
- Vince M Hipwell
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
| | - Alana Rose Meyer
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
| | - Miguel A Garcia-Garibay
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
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5
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Park JH, Hipwell VM, Rivera EA, Garcia-Garibay MA. Strongly Entangled Triplet Acyl-Alkyl Radical Pairs in Crystals of Photostable Diphenylmethyl Adamantyl Ketones. J Am Chem Soc 2021; 143:8886-8892. [PMID: 34081867 DOI: 10.1021/jacs.1c03026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Radical pairs generated in crystalline solids by bond cleavage reactions of triplet ketones offer the unique opportunity to explore a frontier of spin dynamics where rigid radicals are highly entangled as the result of short inter-radical distances, large singlet-triplet energy gaps (ΔEST), and limited spin-lattice relaxation mechanisms. Here we report the pulsed laser generation and detection of strongly entangled triplet acyl-alkyl radical pairs generated in nanocrystalline suspensions of 1,1-diphenylmethyl 2-ketones with various 3-admantyl substituents. The sought-after triplet acyl-alkyl radical pairs could be studied for the first time in the solid state by taking advantage of the efficient triplet excited state α-cleavage reactions of 1,1-diphenylmethyl ketones and the slow rate of CO loss from the acyl radicals, which would have to generate highly unstable phenyl and primary alkyl radicals or relatively unstable secondary and tertiary alkyl radicals. With the loss of CO prevented, the lifetime of the triplet acyl-alkyl radical pair intermediates is determined by intersystem crossing to the singlet radical pair state, which is followed by immediate bond formation to the ground state starting ketone. Experimental results revealed biexponential kinetics with long-lived components that account for ca. 87-92% of the transient population and lifetimes that extend to the range of 53-63 μs, the longest reported so far for this type of radical pair. Structural information inferred from the starting ketone will make it possible to analyze the affects of proximity and orientation of the singly occupied orbitals and potentially help set a path for the use of triplet radical pairs as qubits in quantum information technologies.
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Affiliation(s)
- Jin H Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
| | - Vince M Hipwell
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
| | - Edris A Rivera
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
| | - Miguel A Garcia-Garibay
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
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6
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Vittardi SB, Thapa Magar R, Breen DJ, Rack JJ. A Future Perspective on Phototriggered Isomerizations of Transition Metal Sulfoxides and Related Complexes. J Am Chem Soc 2021; 143:526-537. [PMID: 33400512 DOI: 10.1021/jacs.0c08820] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Photochromic molecules are examples of light-activated bistable molecules. We highlight the design criteria for a class of ruthenium and osmium sulfoxide complexes that undergo phototriggered isomerization of the bound sulfoxide. The mode of action in these complexes is an excited-state isomerization of the sulfoxide from S-bonded to O-bonded. We discuss the basic mechanism for this transformation and highlight specific examples that demonstrate the effectiveness and efficiency of the isomerization. We subsequently discuss future research directions within the field of phototriggered sulfoxide isomerizations on transition metal polypyridine complexes. These efforts involve new synthetic directions, including the choice of metal as well as new ambidentate ligands for isomerization.
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Affiliation(s)
- Sebastian B Vittardi
- Department of Chemistry and Chemical Biology, 300 Terrace Street NE, University of New Mexico, Albuquerque, New Mexico 87131-001 United States
| | - Rajani Thapa Magar
- Department of Chemistry and Chemical Biology, 300 Terrace Street NE, University of New Mexico, Albuquerque, New Mexico 87131-001 United States
| | - Douglas J Breen
- Department of Chemistry and Chemical Biology, 300 Terrace Street NE, University of New Mexico, Albuquerque, New Mexico 87131-001 United States
| | - Jeffrey J Rack
- Department of Chemistry and Chemical Biology, 300 Terrace Street NE, University of New Mexico, Albuquerque, New Mexico 87131-001 United States
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7
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Pang J, Deng Z, Sun S, Huang G, Zhang G, Islam A, Dang L, Phillips DL, Li MD. Unprecedentedly Ultrafast Dynamics of Excited States of C═C Photoswitching Molecules in Nanocrystals and Microcrystals. J Phys Chem Lett 2021; 12:41-48. [PMID: 33296591 DOI: 10.1021/acs.jpclett.0c03232] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The C═C photoswitching molecules [1,2-di(4-pyridyl)ethylene (DPE), 4-styrylpyridine (SP), and trans-1,2-stilbene (TS)] show favorable photoisomerization characteristics. Although the solid states of photoswitching molecules are usually used in optical devices, their excited state's evolution has been little explored. Here, the excited state's relaxation of DPE, SP, and TS in nanocrystal/microcrystal suspensions as well as in solution phase was studied to uncover the early events of their excited states. The dynamics of nanocrystal/microcrystal suspensions was tremendously accelerated in comparison to the kinetics obtained in the solution for these molecules under excitation. DPE exhibits the slowest decay rate, while SP shows the fastest decay rate in nanocrystal suspensions or solution, suggesting SP may be the best candidate for the photoswitching device. The intermolecular interactions and space restriction of the crystal lead to the acceleration of the excited state's evolution for DPE, SP, and TS. This provides new insight into the design of optical materials.
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Affiliation(s)
- Junhong Pang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Ziqi Deng
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Shanshan Sun
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Guanheng Huang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Guohui Zhang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Amjad Islam
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Li Dang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - David Lee Phillips
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Ming-De Li
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, China
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8
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Deng Z, Sun S, Zhou M, Huang G, Pang J, Dang L, Li MD. Revealing Ultrafast Energy Dissipation Pathway of Nanocrystalline Sunscreens Oxybenzone and Dioxybenzone. J Phys Chem Lett 2019; 10:6499-6503. [PMID: 31589456 DOI: 10.1021/acs.jpclett.9b02592] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Two widely used ultraviolet filters, oxybenzone and dioxybenzone, are applied in a variety of areas, particularly in sunscreen cosmetics. Ultrafast femtosecond transient absorption is utilized to trace the excited states and transient states of the nanocrystalline suspension and solution phase of these two molecules. The analysis reveals the intriguing discovery that the transient species of the oxybenzone nanocrystalline suspension have shorter lifetimes than that in solution. The energy dissipation mechanism of these molecules is simulated by density functional theory calculations, and the potential energy surface calculations and the single-crystal structure can well explain the fast decay dynamics of the nanocrystalline transient states of these two molecules.
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Affiliation(s)
- Ziqi Deng
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence , Shantou University , Shantou 515063 , China
| | - Shanshan Sun
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence , Shantou University , Shantou 515063 , China
| | - Miaomiao Zhou
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence , Shantou University , Shantou 515063 , China
| | - Guanheng Huang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence , Shantou University , Shantou 515063 , China
| | - Junhong Pang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence , Shantou University , Shantou 515063 , China
| | - Li Dang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence , Shantou University , Shantou 515063 , China
| | - Ming-De Li
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence , Shantou University , Shantou 515063 , China
- Chemistry and Chemical Engineering Guangdong Laboratory , Shantou 515031 , China
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9
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Hipwell VM, Garcia-Garibay MA. Mechanistic Studies of Adamantylacetophenones with Competing Reaction Pathways in Solution and in the Crystalline Solid State. J Org Chem 2019; 84:11103-11113. [PMID: 31412205 DOI: 10.1021/acs.joc.9b01720] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photochemical reactions in crystals occur under conditions of highly restricted molecular mobility such that only one product is generally obtained, even when there are many others that can be observed in the gas phase or in solution. A series of 2-(1-adamantyl)-o-alkyl-acetophenones with γ-hydrogen atoms on both the adamantyl and ortho aromatic groups was selected to determine whether one can engineer and observe competing Norrish type II reaction pathways in the crystalline state. It was shown that excited state competition for hydrogen abstraction between secondary adamantyl and benzylic hydrogens is affected not only by the relative bond dissociation energies but also by the molecular conformation in the crystal. The subsequent fate of the resulting biradical species is determined by competition between radical recombination to form the photoproduct and reverse hydrogen atom transfer to regenerate the starting ketone. Crystallographic information, photoproduct distributions in solution and in the solid state, and the results of multiple mechanistic experiments, including transient absorption spectroscopy in acetonitrile and with nanocrystals suspended in water, are reported. The results demonstrate that it is possible to engineer competing reactions in crystals and that consideration of all of the aforementioned factors is necessary to account for the observed photoproduct selectivity.
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Affiliation(s)
- Vince M Hipwell
- Department of Chemistry and Biochemistry , University of California , Los Angeles , California 90095-1569 , United States
| | - Miguel A Garcia-Garibay
- Department of Chemistry and Biochemistry , University of California , Los Angeles , California 90095-1569 , United States
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10
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Dotson JJ, Perez-Estrada S, Garcia-Garibay MA. Taming Radical Pairs in Nanocrystalline Ketones: Photochemical Synthesis of Compounds with Vicinal Stereogenic All-Carbon Quaternary Centers. J Am Chem Soc 2018; 140:8359-8371. [PMID: 29842773 DOI: 10.1021/jacs.8b03988] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Here we describe the use of crystalline ketones to control the fate of the radical pair intermediates generated in the Norrish type I photodecarbonylation reaction to render it a powerful tool in the challenging synthesis of sterically congested carbon-carbon bonds. This methodology makes the synthetically more accessible hexasubstituted ketones ideal synthons for the construction of adjacent, all-carbon substituted, stereogenic quaternary stereocenters. We describe here the structural and thermochemical parameters required of the starting ketone in order to react in the solid state. Finally, the scope and scalability of the reaction and its application in the total synthesis of two natural products is described.
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Affiliation(s)
- Jordan J Dotson
- Department of Chemistry and Biochemistry , University of California , Los Angeles , California 90095 , United States
| | - Salvador Perez-Estrada
- Department of Chemistry and Biochemistry , University of California , Los Angeles , California 90095 , United States
| | - Miguel A Garcia-Garibay
- Department of Chemistry and Biochemistry , University of California , Los Angeles , California 90095 , United States
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11
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Breslin VM, Barbour NA, Dang DK, Lopez SA, Garcia-Garibay MA. Nanosecond laser flash photolysis of a 6-nitroindolinospiropyran in solution and in nanocrystalline suspension under single excitation conditions. Photochem Photobiol Sci 2018; 17:741-749. [PMID: 29796517 DOI: 10.1039/c8pp00095f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nanosecond transient absorption spectroscopy was used to study the photochemical ring-opening reaction for a 6-nitroindolinospiropyran (SP1) in solution and in nanocrystalline (NC) suspension at 298 K. We measured the kinetics in argon purged and air saturated acetonitrile and found that the presence of oxygen affected two out of the three components of the kinetic decay at 440 nm. These are assigned to the triplet excited states of the Z- and E-merocyanines (3Z-MC* and 3E-MC*). In contrast, a long-lived growth component at 550 nm and the decay of a band centered at 590 nm showed no dependence on oxygen and are assigned, respectively, to the ground state Z- and E-merocyanines (Z-MC0 and E-MC0). Laser flash photolysis studies performed in NC suspensions initially showed a very broad, featureless absorption spectrum that decayed uniformly for ca. 70 ns before revealing a more defined spectrum that persisted for greater than 4 ms and is consistent with a mixture of the more stable Z- and E-MC0 structures. We performed quantum mechanical calculations on the interconversion of E- and Z-MCs on the S0 and S1 potential energy surfaces. The computed UV-vis spectra for a scan along the Z → E interconversion reaction coordinate show substantial absorptivity from 300-600 nm, which suggests that the broad, featureless transient absorption spectrum results from the contribution of the transition structure and other high-energy species during the Z to E isomerization.
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Affiliation(s)
- Vanessa M Breslin
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
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12
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Zvereva E, Segarra-Martí J, Marazzi M, Brazard J, Nenov A, Weingart O, Léonard J, Garavelli M, Rivalta I, Dumont E, Assfeld X, Haacke S, Monari A. The effect of solvent relaxation in the ultrafast time-resolved spectroscopy of solvated benzophenone. Photochem Photobiol Sci 2018; 17:323-331. [DOI: 10.1039/c7pp00439g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Modeling time-resolved spectra to unravel ultra fast solvent reorganization.
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13
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Chung TS, Park JH, Garcia-Garibay MA. Triplet Sensitized Photodenitrogenation of Δ 2-1,2,3-Triazolines To Form Aziridines in Solution and in the Crystalline State: Observation of the Triplet 1,3-Alkyl-aminyl Biradical. J Org Chem 2017; 82:12128-12133. [PMID: 29052987 DOI: 10.1021/acs.joc.7b01924] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Taking advantage of an operationally simple technique to perform transmission pump-probe spectroscopy in crystalline solids, based on the use nanocrystalline suspensions in water, we analyzed the intermediates in the photodenitrogenation of a Δ2-1,2,3-triazoline bearing a benzophenone group that served as an internal triplet sensitizer. Measurements carried out in acetonitrile solution revealed the formation of a transient with a λmax= 570 nm with a lifetime of 70 ns. Measurements in the solid state displayed an analogous blue-shifted transient with a λmax= 510 nm that first grows and then decays with time constants of 63 and 270 ns, respectively. Based on the comparison of the observed transient spectra with the one obtained from an independently generated aminyl radical, we assign it to the corresponding 1,3,-alkyl-aminyl biradical. We conclude that triplet state denitrogenation and the subsequent intersystem crossing-limited product formation are slower in the solid state than in solution.
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Affiliation(s)
- Tim S Chung
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
| | - Jin H Park
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
| | - Miguel A Garcia-Garibay
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
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14
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Chung TS, Ayitou AJL, Park JH, Breslin VM, Garcia-Garibay MA. Photochemistry and Transmission Pump-Probe Spectroscopy of 2-Azidobiphenyls in Aqueous Nanocrystalline Suspensions: Simplified Kinetics in Crystalline Solids. J Phys Chem Lett 2017; 8:1845-1850. [PMID: 28383895 DOI: 10.1021/acs.jpclett.7b00499] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Aqueous nanocrystalline suspensions provide a simple and efficient medium for performing transmission spectroscopy measurements in the solid state. In this Letter we describe the use of laser flash photolysis methods to analyze the photochemistry of 2-azidobiphenyl and several aryl-substituted derivatives. We show that all the crystalline compounds analyzed in this study transform quantitatively into carbazole products via a crystal-to-crystal reconstructive phase transition. While the initial steps of the reaction cannot be followed within the time resolution of our instrument (ca. 8 ns), we detected the primary isocarbazole photoproducts and analyzed the kinetics of their formal 1,5-H shift reactions, which take place in time scales that range from a few nanoseconds to several microseconds. It is worth noting that the high reaction selectivity observed in the crystalline state translates into a clean and simple kinetic process compared to that in solution.
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Affiliation(s)
- Tim S Chung
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
| | - Anoklase J-L Ayitou
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
| | - Jin H Park
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
| | - Vanessa M Breslin
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
| | - Miguel A Garcia-Garibay
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
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15
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Matsumoto A, Tsuchiya S, Hagiwara Y, Ishikawa K, Koshima H, Asahi T, Soai K. Absolute Structure Determination of Chiral Crystals Consisting of Achiral Benzophenone with Single-crystal X-ray Diffraction and Its Correlation with Solid-state Circular Dichroism. CHEM LETT 2016. [DOI: 10.1246/cl.160114] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
| | - Sumeru Tsuchiya
- Department of Applied Chemistry, Tokyo University of Science
| | - Yuki Hagiwara
- Graduate Schools of Advanced Science and Engineering, Waseda University
| | - Kazuhiko Ishikawa
- Graduate Schools of Advanced Science and Engineering, Waseda University
| | - Hideko Koshima
- Research Organizations for Nano and Life Innovation, Waseda University
| | - Toru Asahi
- Graduate Schools of Advanced Science and Engineering, Waseda University
- Research Organizations for Nano and Life Innovation, Waseda University
| | - Kenso Soai
- Department of Applied Chemistry, Tokyo University of Science
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16
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Ayitou AJL, Flynn K, Jockusch S, Khan SI, Garcia-Garibay MA. Structure–Kinetics Correlations in Isostructural Crystals of α-(ortho-Tolyl)-acetophenones: Pinning Down Electronic Effects Using Laser-Flash Photolysis in the Solid State. J Am Chem Soc 2016; 138:2644-8. [DOI: 10.1021/jacs.5b11657] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anoklase J.-L. Ayitou
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, Los
Angeles, California 90095, United States
| | - Kristen Flynn
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, Los
Angeles, California 90095, United States
| | - Steffen Jockusch
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Saeed I. Khan
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, Los
Angeles, California 90095, United States
| | - Miguel A. Garcia-Garibay
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, Los
Angeles, California 90095, United States
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17
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Cai Y, Guo Z, Chen J, Li W, Zhong L, Gao Y, Jiang L, Chi L, Tian H, Zhu WH. Enabling Light Work in Helical Self-Assembly for Dynamic Amplification of Chirality with Photoreversibility. J Am Chem Soc 2016; 138:2219-24. [PMID: 26709946 DOI: 10.1021/jacs.5b11580] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Light-driven transcription and replication are always subordinate to a delicate chirality transfer. Enabling light work in construction of the helical self-assembly with reversible chiral transformation becomes attractive. Herein we demonstrate that a helical hydrogen-bonded self-assembly is reversibly photoswitched between photochromic open and closed forms upon irradiation with alternative UV and visible light, in which molecular chirality is amplified with the formation of helixes at supramolecular level. The characteristics in these superhelixes such as left-handed or right-handed twist and helical length, height, and pitch are revealed by SEM and AFM. The helical photoswitchable nanostructure provides an easily accessible route to an unprecedented photoreversible modulation in morphology, fluorescence, and helicity, with precise assembly/disassembly architectures similar to biological systems such as protein and DNA.
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Affiliation(s)
- Yunsong Cai
- Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology , Shanghai 200237, P. R. China
| | - Zhiqian Guo
- Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology , Shanghai 200237, P. R. China
| | - Jianmei Chen
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, P. R. China
| | - Wenlong Li
- Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology , Shanghai 200237, P. R. China
| | - Liubiao Zhong
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, P. R. China
| | - Ya Gao
- College of Fundamental Studies, Shanghai University of Engineering Science , Shanghai 201620, P. R. China
| | - Lin Jiang
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, P. R. China
| | - Lifeng Chi
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, P. R. China.,Physikalisches Institut and Center for Nanotechnology (CeNTech), Universität Münster , Münster 48149, Germany
| | - He Tian
- Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology , Shanghai 200237, P. R. China
| | - Wei-Hong Zhu
- Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology , Shanghai 200237, P. R. China
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18
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Pensack RD, Tilley AJ, Parkin SR, Lee TS, Payne MM, Gao D, Jahnke AA, Oblinsky DG, Li PF, Anthony JE, Seferos DS, Scholes GD. Exciton Delocalization Drives Rapid Singlet Fission in Nanoparticles of Acene Derivatives. J Am Chem Soc 2015; 137:6790-803. [DOI: 10.1021/ja512668r] [Citation(s) in RCA: 171] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Ryan D. Pensack
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Andrew J. Tilley
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Sean R. Parkin
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Tia S. Lee
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Marcia M. Payne
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Dong Gao
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Ashlee A. Jahnke
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Daniel G. Oblinsky
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Peng-Fei Li
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - John E. Anthony
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Dwight S. Seferos
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Gregory D. Scholes
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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19
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Hernández-Linares MG, Guerrero-Luna G, Pérez-Estrada S, Ellison M, Ortin MM, Garcia-Garibay MA. Large-Scale Green Chemical Synthesis of Adjacent Quaternary Chiral Centers by Continuous Flow Photodecarbonylation of Aqueous Suspensions of Nanocrystalline Ketones. J Am Chem Soc 2015; 137:1679-84. [DOI: 10.1021/ja512524j] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
| | - Gabriel Guerrero-Luna
- Department of Chemistry
and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Salvador Pérez-Estrada
- Department of Chemistry
and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Martha Ellison
- Department of Chemistry
and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Maria-Mar Ortin
- Department of Chemistry
and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Miguel A. Garcia-Garibay
- Department of Chemistry
and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
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20
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Sergentu DC, Maurice R, Havenith RWA, Broer R, Roca-Sanjuán D. Computational determination of the dominant triplet population mechanism in photoexcited benzophenone. Phys Chem Chem Phys 2014; 16:25393-403. [DOI: 10.1039/c4cp03277b] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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21
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Commins P, Garcia-Garibay MA. Photochromic molecular gyroscope with solid state rotational states determined by an azobenzene bridge. J Org Chem 2014; 79:1611-9. [PMID: 24428572 DOI: 10.1021/jo402516n] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We describe the synthesis, characterization, photochemical isomerization, and rotational dynamics of a crystalline molecular gyroscope containing an azobenzene bridge (trans-2) that spans from one end of the stator to other, with the intention of exploring its function as a molecular brake. While single crystal X-ray diffraction analysis of a photochemically inactive dichloromethane solvate was used to confirm the molecular and packing structures of trans-2, a nanocrystalline pseudopolymorph was shown to be photoactive, and it was analyzed by powder X-ray diffraction (PXRD), scanning electron microscopy, and variable temperature solid state (2)H NMR before and after photoisomerization. It was shown that the nanocrystalline suspension irradiated with λ = 340 nm reaches a photostationary state with 34% of cis-isomer, as compared to that observed in solution where the corresponding value is 74%. Line shape analysis of solid state (2)H NMR spectra of a phenylene-d4 isotopologue, obtained as a function of temperature, indicated that rotation in crystals of the trans-2 isomer, with a mean activation energy of 4.6 ± 0.6 kcal/mol and a pre-exponential factor exp(29.4 ± 1.7), is ten times faster than that of samples containing the cis-2 isomer, which has a higher mean activation energy of 5.1 ± 0.6 kcal/mol and a lower pre-exponential factor of exp(27.9 ± 1.3).
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Affiliation(s)
- Patrick Commins
- Contribution from the Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States
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22
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Abstract
The photophysical behavior of organic semiconductors is governed by their excitonic states. In this review, I classify the three different exciton types (Frenkel singlet, Frenkel triplet, and charge transfer) typically encountered in organic semiconductors. Experimental challenges that arise in the study of solid-state organic systems are discussed. The steady-state spectroscopy of intermolecular delocalized Frenkel excitons is described, using crystalline tetracene as an example. I consider the problem of a localized exciton diffusing in a disordered matrix in detail, and experimental results on conjugated polymers and model systems suggest that energetic disorder leads to subdiffusive motion. Multiexciton processes such as singlet fission and triplet fusion are described, emphasizing the role of spin state coherence and magnetic fields in studying singlet ↔ triplet pair interconversion. Singlet fission provides an example of how all three types of excitons (triplet, singlet, and charge transfer) may interact to produce useful phenomena for applications such as solar energy conversion.
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23
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Yan D, Bučar DK, Delori A, Patel B, Lloyd GO, Jones W, Duan X. Ultrasound-Assisted Construction of Halogen-Bonded Nanosized Cocrystals That Exhibit Thermosensitive Luminescence. Chemistry 2013; 19:8213-9. [DOI: 10.1002/chem.201203810] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 03/09/2013] [Indexed: 11/11/2022]
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24
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Kuzmanich G, Vogelsberg CS, Maverick EF, Netto-Ferreira JC, Scaiano JC, Garcia-Garibay MA. Reaction Mechanism in Crystalline Solids: Kinetics and Conformational Dynamics of the Norrish Type II Biradicals from α-Adamantyl-p-Methoxyacetophenone. J Am Chem Soc 2011; 134:1115-23. [DOI: 10.1021/ja2090004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gregory Kuzmanich
- Department of Chemistry and
Biochemistry, University of California,
Los Angeles, California 90095-1559, United States
| | - Cortnie S. Vogelsberg
- Department of Chemistry and
Biochemistry, University of California,
Los Angeles, California 90095-1559, United States
| | - Emily F. Maverick
- Department of Chemistry and
Biochemistry, University of California,
Los Angeles, California 90095-1559, United States
| | - José Carlos Netto-Ferreira
- Department of Chemistry and
Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - J. C. Scaiano
- Department of Chemistry and
Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Miguel A. Garcia-Garibay
- Department of Chemistry and
Biochemistry, University of California,
Los Angeles, California 90095-1559, United States
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25
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Kuzmanich G, Simoncelli S, Gard MN, Spänig F, Henderson BL, Guldi DM, Garcia-Garibay MA. Excited State Kinetics in Crystalline Solids: Self-Quenching in Nanocrystals of 4,4′-Disubstituted Benzophenone Triplets Occurs by a Reductive Quenching Mechanism. J Am Chem Soc 2011; 133:17296-306. [DOI: 10.1021/ja204927s] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gregory Kuzmanich
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
| | - Sabrina Simoncelli
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, 1428 Buenos Aires, Argentina
| | - Matthew N. Gard
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
| | - Fabian Spänig
- Department of Chemistry and Pharmacy & Interdisciplinary Center of Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91054 Erlangen, Germany
| | - Bryana L. Henderson
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
| | - Dirk M. Guldi
- Department of Chemistry and Pharmacy & Interdisciplinary Center of Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91054 Erlangen, Germany
| | - Miguel A. Garcia-Garibay
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569, United States
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26
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Kuzmanich G, Xue J, Netto-Ferreira JC, Scaiano JC, Platz M, Garcia-Garibay MA. Steady state and transient kinetics in crystalline solids: the photochemistry of nanocrystalline 1,1,3-triphenyl-3-hydroxy-2-indanone. Chem Sci 2011. [DOI: 10.1039/c1sc00184a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
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27
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García-Garibay MA. The entropic enlightenment of organic photochemistry: strategic modifications of intrinsic decay pathways using an information-based approach. Photochem Photobiol Sci 2010; 9:1574-88. [PMID: 21060939 DOI: 10.1039/c0pp00248h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Early photochemistry flourished with sunlight plus the experimental and intellectual infrastructure provided by the chemistry of organic compounds. Through the pioneering work of Giacomo Ciamician and Emanuele Paternò, it was shown that photochemical reactions give rise to products that are not accessible by thermal methods, and the green chemistry potential of organic photoreactions was already recognized at the time. Over the last century, the photochemical behavior of many chromophores and functional groups has been well documented in solution. From those studies, it has become clear that applications in organic synthesis suffer from complications arising from competing decay pathways that are intrinsic to those excited states. While there are few opportunities to control the outcome of excited molecules in solution, the potential of organic photochemistry under the influence of highly ordered structures can be appreciated with examples from photobiology. Knowing that nature can synthesize triglycerides with light, CO(2), H(2)O and a few thermal reactions, organic photochemistry should have a great potential and aim high. With that in mind, after exploring the modes of action used by living organisms to take advantage of sunlight, one can identify an approach that relies on entropic factors that result from changes in the information content of the reactant. Analogies with information theory suggest a strategy that may be used to manage chemical information to modify the intrinsic properties of chromophores. Extrapolating from recent examples, it is suggested that an information-based approach to organic photochemistry may result in important advances not only in chemical synthesis and green chemistry, but also in many other applications.
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Affiliation(s)
- Miguel A García-Garibay
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
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28
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Castiglioni E, Biscarini P, Abbate S. Experimental aspects of solid state circular dichroism. Chirality 2010; 21 Suppl 1:E28-36. [PMID: 19722271 DOI: 10.1002/chir.20770] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The interest of circular dichroism in the solid state is stimulated by several needs, such as the desire to get solvent free spectra, the insolubility of the sample or the intrinsic process in which the sample itself is prepared or manipulated. We approach the argument on the basis of the sampling technique, since each different case calls for specific care in getting proper results.
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29
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Pescitelli G, Kurtán T, Flörke U, Krohn K. Absolute structural elucidation of natural products--a focus on quantum-mechanical calculations of solid-state CD spectra. Chirality 2010; 21 Suppl 1:E181-201. [PMID: 19902530 DOI: 10.1002/chir.20795] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In this review article we examine state-of-the-art techniques for the structural elucidation of organic compounds isolated from natural sources. In particular, we focus on the determination of absolute configuration (AC), perhaps the most challenging but inevitable step in the whole process, especially when newly isolated compounds are screened for biological activity. Among the many methods employed for AC assignment that we review, special attention is paid to electronic circular dichroism (CD) and to the modern tools available for quantum-mechanics CD predictions, including TDDFT. In this context, we stress that conformational flexibility often poses a limit to practical CD calculations of solution CD spectra. Many crystalline natural products suitable for X-ray analysis do not contain heavy atoms for a confidential AC assignment by resonant scattering. However, their CD spectra can be recorded in the solid state, for example with the KCl pellet technique, and analyzed possibly by nonempirical means to provide stereochemical information. In particular, solid-state CD spectra can be compared with those calculated with TDDFT or other high-level methods, using the X-ray geometry as input. The solid-state CD/TDDFT approach, described in detail, represents a quick and reliable tool for AC assignment of natural products.
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Affiliation(s)
- Gennaro Pescitelli
- Dipartimento di Chimica e Chimica Industriale, University of Pisa, Pisa, Italy.
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30
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Simoncelli S, Kuzmanich G, Gard MN, Garcia-Garibay MA. Photochemical reaction mechanisms and kinetics with molecular nanocrystals: surface quenching of triplet benzophenone nanocrystals. J PHYS ORG CHEM 2010. [DOI: 10.1002/poc.1659] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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31
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Lebedeva NV, Tarasov VF, Resendiz MJE, Garcia-Garibay MA, White RC, Forbes MDE. The Missing Link Between Molecular Triplets and Spin-Polarized Free Radicals: Room Temperature Triplet States of Nanocrystalline Radical Pairs. J Am Chem Soc 2009; 132:82-4. [DOI: 10.1021/ja909521u] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Natalia V. Lebedeva
- Caudill Laboratories, Department of Chemistry, CB #3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290, Semenov Institute of Chemical Physics, Kosygin St. 4, Moscow 119991, Russia, and Department of Chemistry, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095
| | - Valery F. Tarasov
- Caudill Laboratories, Department of Chemistry, CB #3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290, Semenov Institute of Chemical Physics, Kosygin St. 4, Moscow 119991, Russia, and Department of Chemistry, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095
| | - Marino J. E. Resendiz
- Caudill Laboratories, Department of Chemistry, CB #3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290, Semenov Institute of Chemical Physics, Kosygin St. 4, Moscow 119991, Russia, and Department of Chemistry, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095
| | - Miguel A. Garcia-Garibay
- Caudill Laboratories, Department of Chemistry, CB #3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290, Semenov Institute of Chemical Physics, Kosygin St. 4, Moscow 119991, Russia, and Department of Chemistry, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095
| | - Ryan C. White
- Caudill Laboratories, Department of Chemistry, CB #3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290, Semenov Institute of Chemical Physics, Kosygin St. 4, Moscow 119991, Russia, and Department of Chemistry, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095
| | - Malcolm D. E. Forbes
- Caudill Laboratories, Department of Chemistry, CB #3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290, Semenov Institute of Chemical Physics, Kosygin St. 4, Moscow 119991, Russia, and Department of Chemistry, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095
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32
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Kuzmanich G, Gard MN, Garcia-Garibay MA. Photonic Amplification by a Singlet-State Quantum Chain Reaction in the Photodecarbonylation of Crystalline Diarylcyclopropenones. J Am Chem Soc 2009; 131:11606-14. [DOI: 10.1021/ja9043449] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gregory Kuzmanich
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569
| | - Matthew N. Gard
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569
| | - Miguel A. Garcia-Garibay
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569
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