1
|
Ju CW, Shen Y, French EJ, Yi J, Bi H, Tian A, Lin Z. Accurate Electronic and Optical Properties of Organic Doublet Radicals Using Machine Learned Range-Separated Functionals. J Phys Chem A 2024. [PMID: 38382058 DOI: 10.1021/acs.jpca.3c07437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Luminescent organic semiconducting doublet-spin radicals are unique and emergent optical materials because their fluorescent quantum yields (Φfl) are not compromised by the spin-flipping intersystem crossing (ISC) into a dark high-spin state. The multiconfigurational nature of these radicals challenges their electronic structure calculations in the framework of single-reference density functional theory (DFT) and introduces room for method improvement. In the present study, we extended our earlier development of ML-ωPBE [J. Phys. Chem. Lett., 2021, 12, 9516-9524], a range-separated hybrid (RSH) exchange-correlation (XC) functional constructed using the stacked ensemble machine learning (SEML) algorithm, from closed-shell organic semiconducting molecules to doublet-spin organic semiconducting radicals. We assessed its performance for a new test set of 64 doublet-spin radicals from five categories while placing all previously compiled 3926 closed-shell molecules in the new training set. Interestingly, ML-ωPBE agrees with the nonempirical OT-ωPBE functional regarding the prediction of the molecule-dependent range-separation parameter (ω), with a small mean absolute error (MAE) of 0.0197 a0-1, but saves the computational cost by 2.46 orders of magnitude. This result demonstrates an outstanding domain adaptation capacity of ML-ωPBE for diverse organic semiconducting species. To further assess the predictive power of ML-ωPBE in experimental observables, we also applied it to evaluate absorption and fluorescence energies (Eabs and Efl) using linear-response time-dependent DFT (TDDFT), and we compared its behavior with nine popular XC functionals. For most radicals, ML-ωPBE reproduces experimental measurements of Eabs and Efl with small MAEs of 0.299 and 0.254 eV, only marginally different from those of OT-ωPBE. Our work illustrates a successful extension of the SEML framework from closed-shell molecules to doublet-spin radicals and will open the venue for calculating optical properties for organic semiconductors using single-reference TDDFT.
Collapse
Affiliation(s)
- Cheng-Wei Ju
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
| | - Yili Shen
- Manning College of Information and Computer Sciences, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Ethan J French
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, United States
| | - Jun Yi
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109, United States
| | - Hongshan Bi
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Aaron Tian
- Manning College of Information and Computer Sciences, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Zhou Lin
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| |
Collapse
|
2
|
Salim MM, Radwan AS, Hadad GM, Belal F, Elkhoudary MM. Green fluorometric strategy for simultaneous determination of the antihypertensive drug telmisartan (A tentative therapeutic for COVID-19) with Nebivolol in human plasma. Sci Rep 2023; 13:3576. [PMID: 36864220 PMCID: PMC9980868 DOI: 10.1038/s41598-023-30400-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 02/22/2023] [Indexed: 03/04/2023] Open
Abstract
Telmisartan (TEL) and Nebivolol (NEB) are frequently co-formulated in a single dosage form that is frequently prescribed for the treatment of hypertension, moreover, telmisartan is currently proposed to be used to treat COVID19-induced lung inflammation. Green rapid, simple, and sensitive synchronous spectrofluorimetric techniques for simultaneous estimation of TEL and NEB in their co-formulated pharmaceutical preparations and human plasma were developed and validated. Synchronous fluorescence intensity at 335 nm was used for TEL determination (Method I). For the mixture, the first derivative synchronous peak amplitudes (D1) at 296.3 and 320.5 nm were used for simultaneous estimation of NEB and TEL, respectively (Method II). The calibration plots were rectilinear over the concentration ranges of 30-550 ng/mL, and 50-800 ng/mL for NEB and TEL, respectively. The high sensitivity of the developed methods allowed for their analysis in human plasma samples. NEB`s Quantum yield was estimated by applying the single-point method. The greenness of the proposed approaches was evaluated using the Eco-scale, National Environmental Method Index (NEMI), and Green Analytical Procedure Index (GAPI) methods.
Collapse
Affiliation(s)
- Mohamed M Salim
- Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura, Egypt.
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Horus University- Egypt, New Damietta, Egypt.
| | - Aya Saad Radwan
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Horus University- Egypt, New Damietta, Egypt
- Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Suez Canal University, Ismailia, Egypt
| | - Ghada M Hadad
- Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Suez Canal University, Ismailia, Egypt
| | - Fathalla Belal
- Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura, Egypt
| | - Mahmoud M Elkhoudary
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Horus University- Egypt, New Damietta, Egypt
| |
Collapse
|
3
|
Radwan AS, Elkhoudary MM, Hadad GM, Belal F, Salim MM. A highly sensitive spectrofluorimetric method for the determination of bilastine in its pharmaceutical preparations and biological fluids. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 276:121246. [PMID: 35429867 DOI: 10.1016/j.saa.2022.121246] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 03/24/2022] [Accepted: 04/05/2022] [Indexed: 06/14/2023]
Abstract
Allergic rhinitis and urticaria are extremely prevalent among all age groups. From the clinical experience, usually, an essential second-generation non-sedating H1-antihistaminic drug, such as bilastine is given to relieve allergic symptoms. Bilastine is preferred to be used instead of oral corticosteroids and first -generation sedating H1-antihistaminics to avoid their side effects. A highly sensitive and simple spectrofluorometric method was developed and validated for the determination of bilastine in its dosage forms and biological fluids. The quantum yield was calculated and was found to be as high as 0.48. Aqueous water solution of bilastine gives high native fluorescence emission at 298 nm after excitation at 272 nm. A rectilinear calibration plot was obtained over the concentration range of 1.0-50.0 ng mL-1. The limits of quantitation and detection were 1.0 and 0.33 ng mL-1, respectively. The parameters influencing its spectrofluorimetric behavior, viz, type of solvent, pH and organized media were studied. The proposed method was successfully applied for the determination of the drug in pharmaceutical dosage form and the results obtained were in good agreement with those of given by reported method. The high sensitivity of the proposed method enabled the estimation of the drug in biological matrices, including human plasma and urine samples after simple protein precipitation, and the results obtained were satisfactory.
Collapse
Affiliation(s)
- Aya Saad Radwan
- Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Suez Canal University, Ismailia, Egypt; Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Horus University- Egypt, New Damietta, Egypt.
| | - Mahmoud M Elkhoudary
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Horus University- Egypt, New Damietta, Egypt
| | - Ghada M Hadad
- Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Suez Canal University, Ismailia, Egypt
| | - Fathalla Belal
- Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt
| | - Mohamed M Salim
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Horus University- Egypt, New Damietta, Egypt; Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt
| |
Collapse
|
4
|
Taniguchi M, Lindsey JS. Database of Absorption and Fluorescence Spectra of >300 Common Compounds for use in Photochem
CAD. Photochem Photobiol 2018; 94:290-327. [DOI: 10.1111/php.12860] [Citation(s) in RCA: 236] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 10/22/2017] [Indexed: 12/11/2022]
|
5
|
Salomatova V, Pozdnyakov I, Sherin P, Grivin V, Plyusnin V. Photochemistry of bisphenol F in aqueous solutions: A mechanistic study. J Photochem Photobiol A Chem 2015. [DOI: 10.1016/j.jphotochem.2015.03.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|
6
|
Abstract
The use of standards for the measurement of photoluminescence quantum yields (QYs) in dilute solutions is reviewed. Only three standards can be considered well established. Another group of six standards has been investigated by several independent researchers. A large group of standards is frequently used in recent literature, but the validity of these is less certain. The needs for future development comprise: (i) confirmation of the validity of the QY values of many commonly used standard materials, preferably in the form of SI traceable standards; (ii) extension of the set of standard materials to the UV and near-IR spectral ranges; and (iii) good standards or robust protocols for the measurements of low QYs.
Collapse
|
7
|
Zhang Y, Yousef YA, Li H, Melø TB, Naqvi KR. Comparison of the photochemical behaviors of α-tocopherol and its acetate in organic and aqueous micellar solutions. J Phys Chem A 2011; 115:8242-7. [PMID: 21675787 DOI: 10.1021/jp202805k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photoionization is known to take place when α-tocopherol (TOH) is excited to the S(1) state in a polar medium. It has been previously suggested that TO(•) is formed only as a result of proton release by TOH(•+), a process that is expected to occur, in a protic solvent, on the subnanosecond time scale. Recent redeterminations of the molar absorption coefficients of e(aq)(–) (Hare J. Phys. Chem. A 2010, 114, 1766) and of TOH(•+) and TO(•) (Naqvi J. Phys. Chem. A 2010, 114, 10795) have paved the way for testing the above suggestion, even if subnanosecond time resolution is not available, since it implies the equality of [e(aq)(–)](0) and [TO(•)](0), where [···](0) denotes the concentration of the enclosed species immediately after a nanosecond laser pulse. Nanosecond pump-probe spectroscopy of TOH in aqueous micellar solution (AMS) and two organic solvents with similar polarities (acetonitrile and methanol) has revealed that prompt formation of TO(•) through dissociation (TOH + hν → TO(•) + H(•)) is not negligible even in AMS. In acetonitrile, TOH(•+) and TO(•) are formed with comparable yields, and the former converts quantitatively into TO(•) within 15 μs. In methanol, TO(•) was observed, but no evidence was found for electron ejection from TOH. Only one photoproduct, namely TO(•), could be detected when α-tocopherol acetate (TOAc) was excited to the S(1) state in several polar and nonpolar solvents; TOAc has been found to be a more efficient energy degrader than TOH.
Collapse
Affiliation(s)
- Ye Zhang
- Department of Physics, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
| | | | | | | | | |
Collapse
|
8
|
Oueslati I, Coleman AW, de Castro B, Berberan-Santos MN. A Fluorescent and Phosphorescent Nanoporous Solid: Crystalline Calix[4]arene. J Fluoresc 2008; 18:1123-9. [DOI: 10.1007/s10895-008-0362-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 03/10/2008] [Indexed: 11/30/2022]
|
9
|
Enhanced solid-state fluorescence in the oxadiazole-based excited-state intramolecular proton-transfer (ESIPT) material: Synthesis, optical property, and crystal structure. J Photochem Photobiol A Chem 2007. [DOI: 10.1016/j.jphotochem.2007.04.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
10
|
Lin MF, Dyakov YA, Lee YT, Lin SH, Mebel AM, Ni CK. Photodissociation of S atom containing amino acid chromophores. J Chem Phys 2007; 127:064308. [PMID: 17705597 DOI: 10.1063/1.2761916] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photodissociation of 3-(methylthio)propylamine and cysteamine, the chromophores of S atom containing amino acid methionine and cysteine, respectively, was studied separately in a molecular beam at 193 nm using multimass ion imaging techniques. Four dissociation channels were observed for 3-(methylthio)propylamine, including (1) CH(3)SCH(2)CH(2)CH(2)NH(2)-->CH(3)SCH(2)CH(2)CH(2)NH+H, (2) CH(3)SCH(2)CH(2)CH(2)NH(2)-->CH(3)+SCH(2)CH(2)CH(2)NH(2), (3) CH(3)SCH(2)CH(2)CH(2)NH(2)-->CH(3)S+CH(2)CH(2)CH(2)NH(2), and (4) CH(3)SCH(2)CH(2)CH(2)NH(2)-->CH(3)SCH(2)+CH(2)CH(2)NH(2). Two dissociation channels were observed from cysteamine, including (5) HSCH(2)CH(2)NH(2)-->HS+CH(2)CH(2)NH(2) and (6) HSCH(2)CH(2)NH(2)-->HSCH(2)+CH(2)NH(2). The photofragment translational energy distributions suggest that reaction (1) and parts of the reactions (2), (3), (5) occur on the repulsive excited states. However, reaction (4), (6) occur only after the internal conversion to the electronic ground state. Since the dissociation from an excited state with a repulsive potential energy surface is very fast, it would not be quenched completely even in the condensed phase. Our results indicate that reactions following dissociation may play an important role in the UV photochemistry of S atom containing amino acid chromophores in the condensed phase. A comparison with the potential energy surface from ab initio calculations and branching ratios from RRKM calculations was made.
Collapse
Affiliation(s)
- Ming-Fu Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617, Taiwan
| | | | | | | | | | | |
Collapse
|
11
|
Joshi R, Kapoor S, Mukherjee T. Triplet state and phenoxyl radical formation of 3, 4-methylenedioxy phenol: a combined laser flash photolysis and pulse radiolysis study. J PHYS ORG CHEM 2007. [DOI: 10.1002/poc.1172] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
12
|
Abstract
Vitamin E offers protection against oxidative stress and is an efficient quencher of singlet oxygen. A recent report suggests that photo-excitation of vitamin E results in the formation of a triplet state (Naqvi et al. Photochem Photobiol Sci 2, 381 (2003)). This leads to the possibility of the triplet state of vitamin E being able to sensitize singlet oxygen and if this is the case it would be counter productive in terms of the biological protective function of vitamin E. We report the production of singlet oxygen, detected by 1270 nm luminescence, from pulsed laser excitation (308 nm) of vitamin E and an analogue, 2,2,5,7,8-pentamethyl-6-hydroxy-chroman (PMHC), with quantum yields between ~0.1 and 0.2. The luminescence was identified as singlet oxygen from self-quenching by vitamin E with solvent-dependent rate constants similar to published values. Whilst the beneficial antioxidant aspects of vitamin E are well established, these results indicate that vitamin E when directly excited can sensitize singlet oxygen formation and may, therefore, be capable of inducing biochemical and biological damage. The results are discussed in relation to recent reports on the deleterious effects of vitamin E dietary supplementation and pro-oxidant effects of vitamin E.
Collapse
Affiliation(s)
- Shakeela Dad
- Biosciences Research Institute, University of Salford, Salford M5 4WT, UK
| | - Roger H Bisby
- Biosciences Research Institute, University of Salford, Salford M5 4WT, UK
| | - Ian P Clark
- Lasers for Science Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
| | - Anthony W Parker
- Lasers for Science Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
| |
Collapse
|
13
|
Oueslati I, Sa Ferreira RA, Carlos LD, Baleizão C, Berberan-Santos MN, de Castro B, Vicens J, Pischel U. Calix[4]azacrowns as Novel Molecular Scaffolds for the Generation of Visible and Near-Infrared Lanthanide Luminescence. Inorg Chem 2006; 45:2652-60. [PMID: 16529488 DOI: 10.1021/ic051159l] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two calix[4]azacrowns, capped with two aminopolyamide bridges, were used as ligands for the complexation of lanthanide ions [Eu(III), Tb(III), Nd(III), Er(III), La(III)]. The formation of 1:2 and 1:1 complexes was observed, and stability constants, determined by UV absorption and fluorescence spectroscopy, were found to be generally on the order of log beta(11) approximately 5-6 and log beta(12) approximately 10. The structural changes of the ligands upon La(III) complexation were probed by 1H NMR spectroscopy. The two ligands were observed to have opposite fluorescence behaviors, namely, fluorescence enhancement (via blocking of photoinduced electron transfer from amine groups) or quenching (via lanthanide-chromophore interactions) upon metal ion complexation. Long-lived lanthanide luminescence was sensitized by excitation in the pi,pi band of the aromatic moieties of the ligands. The direct involvement of the antenna triplet state was demonstrated via quenching of the ligand phosphorescence by Tb(III). Generally, Eu(III) luminescence was weak (Phi(lum) </= 0.01%) and much shorter lived (tau(lum) = 0.36 ms) than the Tb(III) emission. The latter, on the other hand, reached lifetimes of up to 2.60 ms and quantum yields as high as 12% for one of the ligands. Water/deuterium oxide exchange experiments showed the presence of only one solvent molecule in the coordination sphere of the lanthanides. However, Eu(III) luminescence was efficiently quenched by NH oscillators and the presence of a ligand-to-metal charge transfer state. Near-infrared luminescence of Nd(III) was also generated by energy-transfer sensitization.
Collapse
Affiliation(s)
- Issam Oueslati
- REQUIMTE/Departamento de Química, Universidade do Porto, Rua Campo Alegre, 4169-007 Porto, Portugal.
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Manet I, Monti S, Bortolus P, Fagnoni M, Albini A. The Photochemistry of 4-Chlorophenol in Water Revisited: The Effect of Cyclodextrins on Cation and Carbene Reactions. Chemistry 2005; 11:4274-82. [PMID: 15861376 DOI: 10.1002/chem.200401227] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The photochemistry of 4-chlorophenol (1) in water and in the presence of cyclodextrins has been studied by means of steady-state and time-resolved experiments. These have shown that 1 undergoes photoheterolysis of the C--Cl bond in the triplet state to yield the 4-hydroxyphenyl cation (3)2 in equilibrium with 4-oxocyclohexa-2,5-dienylidene, (3)3. These triplet intermediates scarcely react with a n nucleophile, such as water, nor abstract hydrogen from this solvent, thus they are long-lived (approximately 1 micros). Specific trapping of both intermediates has been achieved. The cation adds to 2-propenol, k(add) approximately 1.3 x 10(8) m(-1) s(-1), to form the long-lived phenonium ion 11 (with lambda(max) = 290 nm), which then converts to 3-(4-hydroxyphenyl)propane-1,2-diol (10). Carbene (3)3 is trapped by oxygen to give benzoquinone and is reduced by D-glucose (k(q) = 8.5 x 10(6) m(-1) s(-1)) to give the phenoxyl radical (8) and phenol (9). Cyclodextrins have been found to trap the intermediates much more efficiently (k(q) = 9.4 x 10(8) m(-1) s(-1) with beta-CD), which indicates that inclusion is involved. Ground state 1 forms inclusion complexes with 1:1 stoichiometry and association constants of 140 and 300 M(-1) with alpha- and beta-CD, respectively. Complexation does not change the efficiency or the mode of photofragmentation of 1; however, it does influence the course of the reaction because the major portion of the intermediates are reduced to phenol within the cavity (k'(red)> or = 5 x 10(7) s(-1)) either via a radical 8 or via a radical cation 9(+)(.). Under these conditions, neither 2-propenol nor oxygen trap the intermediates to a significant extent.
Collapse
Affiliation(s)
- Ilse Manet
- Istituto per la Sintesi Organica e la Fotoreattività (ISOF), Consiglio Nazionale delle Ricerche (CNR), Bologna, Italy
| | | | | | | | | |
Collapse
|
15
|
Dad S, Bisby R, Clark I, Parker A. Identification and reactivity of the triplet excited state of 5-hydroxytryptophan. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2005; 78:245-51. [PMID: 15708522 PMCID: PMC1890304 DOI: 10.1016/j.jphotobiol.2004.11.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2004] [Revised: 11/22/2004] [Accepted: 11/22/2004] [Indexed: 11/28/2022]
Abstract
Both the neurotransmitter serotonin and the unnatural amino acid 5-hydroxytryptophan (5HT), contain the 5-hydroxyindole chromophore. The photochemistry of 5HT is being investigated in relation to the multiphoton excitation of this chromophore to produce a characteristic photoproduct with green fluorescence ('hyperluminescence'). Laser flash photolysis (308 nm) of 5HT in aqueous solution at neutral pH produces both the neutral 5-indoloxyl radical (lambda(max) 400-420 nm) and another transient absorption with lambda(max) 480 nm and lifetime of 2 micros in deaerated solutions. Based on quenching by oxygen and beta-carotene, the species at 480 nm is identified as the triplet excited state of 5HT. In acidic solution a new oxygen-insensitive intermediate with lambda(max) 460 is assigned to the radical cation of 5HT. Time-resolved measurements of luminescence at 1270 nm have shown that the triplet state of 5HT is able to react with oxygen to form singlet excited oxygen (1O2*) with a quantum yield of approximately 0.1. However, 5HT has also been found to be an effective quencher of singlet oxygen with a second order rate constant of 1.3 x 10(8) dm3 mol(-1) s(-1). The results are discussed in the light of recent observations on the multiphoton-excited photochemistry of serotonin.
Collapse
Affiliation(s)
- S. Dad
- Biosciences Research Institute, University of Salford, Salford M5 4WT, UK
| | - R.H. Bisby
- Biosciences Research Institute, University of Salford, Salford M5 4WT, UK
| | - I.P. Clark
- Lasers for Science Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
| | - A.W. Parker
- Lasers for Science Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
| |
Collapse
|
16
|
Yoshihara T, Druzhinin SI, Demeter A, Kocher N, Stalke D, Zachariasse KA. Kinetics of Intramolecular Charge Transfer with N-Phenylpyrrole in Alkyl Cyanides. J Phys Chem A 2005; 109:1497-509. [PMID: 16833471 DOI: 10.1021/jp046586j] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
For the electron acceptor/donor molecule N-phenylpyrrole (PP), the fast intramolecular charge transfer (ICT) reaction accompanied by dual fluorescence from a locally excited (LE) and an ICT state is investigated in alkyl cyanide solvents as a function of temperature. After a comparison of the X-ray crystal structure of PP with calculations from the literature, absorption and fluorescence spectra of PP in a series of solvents over a wide polarity range are discussed. ICT with PP strongly depends on solvent polarity and starts to appear in solvents more polar than diethyl ether. From an analysis of the ICT/LE fluorescence quantum yield ratio Phi'(ICT)/Phi(LE), approximate data for the change in enthalpy -DeltaH of the ICT reaction of PP are obtained, ranging from 9 kJ/mol in acetonitrile (MeCN) to 4 kJ/mol in n-butyl cyanide (BuCN). From ICT and LE fluorescence decays of PP measured as a function of temperature, the forward (Ea = 9 kJ/mol in ethyl cyanide (EtCN) and 6 kJ/mol in MeCN) and backward (Ed = 16 kJ/mol in EtCN and MeCN) ICT reaction barriers are determined. From these data, -Delta H (7 kJ/mol (EtCN); 10 kJ/mol (MeCN)) is calculated, in good agreement with the results coming from Phi'(ICT)/Phi(LE). The data for Ea show that the forward ICT barrier becomes smaller with increasing solvent polarity, whereas the absence of change for Ed comes from the compensating increase of -DeltaH. Both observations are indicative of a late transition state for the LE --> ICT reaction. For PP in EtCN and MeCN, the ICT radiative rate constant k'(f)(ICT) increases with temperature. This is caused by the ICT low transition dipole moment and hence does not contain information on the molecular structure (twisted or planar) of the ICT state. The fast ICT observed with PP supports our previous conclusion, based on a comparison of PP with its planarized derivative fluorazene, that the pyrrole and phenyl moieties in the ICT state of PP are coplanar and possess substantial electronic coupling.
Collapse
Affiliation(s)
- Toshitada Yoshihara
- Max-Planck-Institut für biophysikalische Chemie, Spektroskopie und Photochemische Kinetik, 37070 Göttingen, Germany
| | | | | | | | | | | |
Collapse
|
17
|
Manet I, Monti S, Fagnoni M, Protti S, Albini A. Aryl Cation and Carbene Intermediates in the Photodehalogenation of Chlorophenols. Chemistry 2005; 11:140-51. [PMID: 15540240 DOI: 10.1002/chem.200400681] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The photochemistry of 2,6-dimethyl-4-chlorophenol (6) has been studied in methanol and trifluoroethanol (TFE) through product studies and transient absorption spectroscopy. Chloride loss from triplet 6 gave triplet hydroxyphenyl cation 14, which equilibrated with triplet oxocyclohexadienylydene 15 within a few tens of nanoseconds; the cation can, however, be selectively trapped by allyltrimethylsilane (k(ad) = 10(8)-10(9) m(-1) s(-1)) to give a phenonium ion and the allylated phenol. In neat alcohols, 14 and 15 are reduced through different mechanisms, namely by hydrogen transfer through radical cation 17 and via phenoxyl radical 16, respectively. The mechanistic rationalization has been substantiated by the parallel study of an O-silylated derivative. The work shows that the chemistry of the highly (but selectively) reactive phenyl cation 14 can not only be discriminated from that of the likewise highly reactive carbene 15, but also exploited for synthetically useful reactions, as in this case with alkenes. Photolysis of electron-donating substituted halobenzenes may be the method of choice for the mild generation of some classes of phenyl cations.
Collapse
Affiliation(s)
- Ilse Manet
- Istituto ISOF-CNR, Area della Ricerca, Via Piero Gobetti 101, 40129 Bologna, Italy
| | | | | | | | | |
Collapse
|
18
|
|
19
|
Tero-Kubota S, Tachikawa T, Ito F, Matsui M, Konishi K. Photoinduced phenoxyl radical formation from ligno-p-cresol as studied by steady-state and time-resolved EPR spectroscopy. Chem Phys Lett 2003. [DOI: 10.1016/j.cplett.2003.09.097] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
20
|
Naqvi KR, Melø TB, Sliwka HR, Mohamad SBB, Partali V. Photochemical and photophysical behaviour of vitamin E: interaction of its long-lived transient photoproducts with carotenoids. Photochem Photobiol Sci 2003; 2:381-5. [PMID: 12760534 DOI: 10.1039/b210972g] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Multi-channel, flash kinetic spectroscopy with microsecond time resolution has been used for investigating the interactions between carotenoids and the following photoproducts of alpha-tocopherol (EH) in hexane, methanol, acetonitrile, and dimethyl sulfoxide: (a) the lowest triplet, (b) the tocopherol radical cation, which could be seen only in the polar aprotic solvents acetonitrile and dimethyl sulfoxide, and (c) the neutral tocopheroxyl radical. The first two species reconvert to EH by transferring triplet excitation and positive charge (respectively) to the carotenoid; the third is unreactive. The relevance of these observations to photoprotection and the photoionisation of sterically hindered phenols is pointed out.
Collapse
Affiliation(s)
- K Razi Naqvi
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway.
| | | | | | | | | |
Collapse
|
21
|
Brede O, Naumov S, Hermann R. Sterically hindered phenols are extremely efficient light quenchers. Chem Phys Lett 2002. [DOI: 10.1016/s0009-2614(01)01451-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
22
|
Hermann R, Mahalaxmi GR, Jochum T, Naumov S, Brede O. Balance of the Deactivation Channels of the First Excited Singlet State of Phenols: Effect of Alkyl Substitution, Sterical Hindrance, and Solvent Polarity. J Phys Chem A 2002. [DOI: 10.1021/jp013976m] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- R. Hermann
- University of Leipzig, Interdisciplinary Group Time-Resolved Spectroscopy, Permoserstrasse 15, D-04303 Leipzig, Germany
| | - G. R. Mahalaxmi
- University of Leipzig, Interdisciplinary Group Time-Resolved Spectroscopy, Permoserstrasse 15, D-04303 Leipzig, Germany
| | - T. Jochum
- University of Leipzig, Interdisciplinary Group Time-Resolved Spectroscopy, Permoserstrasse 15, D-04303 Leipzig, Germany
| | - S. Naumov
- University of Leipzig, Interdisciplinary Group Time-Resolved Spectroscopy, Permoserstrasse 15, D-04303 Leipzig, Germany
| | - O. Brede
- University of Leipzig, Interdisciplinary Group Time-Resolved Spectroscopy, Permoserstrasse 15, D-04303 Leipzig, Germany
| |
Collapse
|
23
|
Bussandri A, van Willigen H. Photoionization of Phenolates and Scavenging of Hydrated Electrons by No3-: A Study of the Reaction Mechanism by FT-EPR. J Phys Chem A 2001. [DOI: 10.1021/jp0036590] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alejandro Bussandri
- Department of Chemistry, University of Massachusetts at Boston, Boston, Massachusetts 02125
| | - Hans van Willigen
- Department of Chemistry, University of Massachusetts at Boston, Boston, Massachusetts 02125
| |
Collapse
|
24
|
Sortino S, De Guidi G, Giuffrida S, Belvedere A, Condorelli G. Photochemistry of Diflunisal in Nonionic (Brij-35) Micelles: Influence of the Microenvironment on Photoionization, Electron Trapping, and Persistent Radical Effect. J Phys Chem A 2000. [DOI: 10.1021/jp0024322] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
25
|
Electron transfer from phenolic compounds to parent n -butyl chloride radical cations—a quantum chemical study of product transient formation and stability. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0166-1280(00)00513-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
26
|
Perfect switching of photoreactivity by acid: photochemical decarboxylation versus transesterification of mesityl cyclohexanecarboxylate. Org Lett 2000; 2:3401-4. [PMID: 11029221 DOI: 10.1021/ol0065266] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mesityl cyclohexanecarboxylate has been photodecarboxylated upon excitation at 254 nm to form cyclohexylmesitylene in good yield in neutral acetonitrile solutions. In the presence of a catalytic amount of the acid and ethanol as a nucleophile, however, the same compound undergoes facile transesterification upon irradiation, affording its ethyl ester in almost quantitative yield.
Collapse
|
27
|
|
28
|
|
29
|
Grabner G, Monti S, Marconi G, Mayer B, Klein C, Köhler G. Spectroscopic and Photochemical Study of Inclusion Complexes of Dimethoxybenzenes with Cyclodextrins. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp962231r] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gottfried Grabner
- Institut für Theoretische Chemie und Strahlenchemie, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria, and Istituto di Fotochimica e Radiazioni d'Alta Energia, CNR-Area della Ricerca, Via Piero Gobetti 101, I-40129 Bologna, Italy
| | - Sandra Monti
- Institut für Theoretische Chemie und Strahlenchemie, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria, and Istituto di Fotochimica e Radiazioni d'Alta Energia, CNR-Area della Ricerca, Via Piero Gobetti 101, I-40129 Bologna, Italy
| | - Giancarlo Marconi
- Institut für Theoretische Chemie und Strahlenchemie, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria, and Istituto di Fotochimica e Radiazioni d'Alta Energia, CNR-Area della Ricerca, Via Piero Gobetti 101, I-40129 Bologna, Italy
| | - Bernd Mayer
- Institut für Theoretische Chemie und Strahlenchemie, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria, and Istituto di Fotochimica e Radiazioni d'Alta Energia, CNR-Area della Ricerca, Via Piero Gobetti 101, I-40129 Bologna, Italy
| | - Christian Klein
- Institut für Theoretische Chemie und Strahlenchemie, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria, and Istituto di Fotochimica e Radiazioni d'Alta Energia, CNR-Area della Ricerca, Via Piero Gobetti 101, I-40129 Bologna, Italy
| | - Gottfried Köhler
- Institut für Theoretische Chemie und Strahlenchemie, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria, and Istituto di Fotochimica e Radiazioni d'Alta Energia, CNR-Area della Ricerca, Via Piero Gobetti 101, I-40129 Bologna, Italy
| |
Collapse
|
30
|
Brede O, Orthner H, Zubarev V, Hermann R. Radical Cations of Sterically Hindered Phenols as Intermediates in Radiation-Induced Electron Transfer Processes. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp953526s] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ortwin Brede
- Max Planck Society, Research Unit Time-Resolved Spectroscopy at the University of Leipzig, Permoserstrasse 15, D-04303 Leipzig, Germany
| | - Hans Orthner
- Max Planck Society, Research Unit Time-Resolved Spectroscopy at the University of Leipzig, Permoserstrasse 15, D-04303 Leipzig, Germany
| | - Valentin Zubarev
- Max Planck Society, Research Unit Time-Resolved Spectroscopy at the University of Leipzig, Permoserstrasse 15, D-04303 Leipzig, Germany
| | - Ralf Hermann
- Max Planck Society, Research Unit Time-Resolved Spectroscopy at the University of Leipzig, Permoserstrasse 15, D-04303 Leipzig, Germany
| |
Collapse
|
31
|
|
32
|
Phenol-assisted photolytic and radiolytic radical cation formation of a sterically hindered tertiary amine. Chem Phys Lett 1994. [DOI: 10.1016/0009-2614(94)01076-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
33
|
Nakagawa K, Tero-Kubota S, Ikegami Y, Tsuchihashi N. EPR and TREPR spectroscopic studies of antioxidant sesamolyl and related phenoxyl radicals. Photochem Photobiol 1994; 60:199-204. [PMID: 7972369 DOI: 10.1111/j.1751-1097.1994.tb05091.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Sesamolyl and related phenoxyl radicals were studied by conventional and time-resolved electron paramagnetic resonance (EPR) spectroscopic techniques. Continuous UV irradiation of sesamol in benzene produces two types of radicals. Based on the hyperfine coupling values obtained we determined that one is the neutral sesamolyl radical and the others are the dimer radicals. Comparison was made with related compounds, especially 3,4-dimethoxyphenol. We found that the 3,4-dimethoxyphenoxyl radical had a shorter lifetime than the neutral sesamolyl radical. The EPR results obtained suggest that a near perpendicular orientation of the oxygen p-orbitals with respect to the benzene ring of sesamol makes the radical more stable. This stability may be important for the antioxidant properties.
Collapse
Affiliation(s)
- K Nakagawa
- RI Laboratory, Fukushima Medical College, Japan
| | | | | | | |
Collapse
|
34
|
Vágó J, Biczók L, Grabner G, Köhler G, Quint RM, Getoff N. On the photochemical decomposition of aromatic α-azohydroperoxides. J Photochem Photobiol A Chem 1993. [DOI: 10.1016/1010-6030(93)80175-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
35
|
Köhler G, Grabner G, Rotkiewicz K. Nonradiative deactivation and triplet states in donor-aryl-acceptor compounds (dialkylaminobenzonitriles). Chem Phys 1993. [DOI: 10.1016/0301-0104(93)80145-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
36
|
Chloride-catalyzed oxidation of phenol in pulsed-laser irradiation titanium dioxide sols. J CHEM SCI 1991. [DOI: 10.1007/bf02842113] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
37
|
Adsorption processes on semiconductor colloids studied by pulsed-laser-induced electron-transfer reactions. J CHEM SCI 1991. [DOI: 10.1007/bf02842114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|