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Mehata MS, Aneesha. Selectively probing ferric ions in aqueous environments using protonated and neutral forms of 7-azaindole as a multiparametric chemosensor. Photochem Photobiol Sci 2023:10.1007/s43630-023-00393-6. [PMID: 36805446 DOI: 10.1007/s43630-023-00393-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 02/05/2023] [Indexed: 02/21/2023]
Abstract
7-azaindole (7AI) dimer is a model molecule for DNA study and understanding the mutagenic behavior based on the excited-state proton transfer process in hydrogen-bonded networks. The neutral and protonated forms of 7AI monomer with significant fluorescence (FL) intensity fit the fluorescent sensor strategy to recognize selective metal ions. Out of several metal ions (Fe3+, Al3+, Fe2+, Pb2+, Ba2+, Ni2+, Zn2+, Mg2+, Ca2+, Cu2+, Hg2+ and Cd2+), the absorption, fluorescence and fluorescence lifetime of 7AI in the aqueous medium are selectively sensitive to the ferric (Fe3+) ions. The absolute value of absorption intensity increases linearly with concentration of a particular metal ions. FL intensity of both the forms of 7AI decreases gradually with Fe3+ ions and trails the linear Stern-Volmer relation. The formation of non-fluorescent complexes was confirmed with Benesi-Hildebrand and Job plots, along with FL and FL decays. The FL lifetime of the protonated form of 7AI, which is 0.83 ± 0.01 ns, is nearly constant with Fe3+ ions concentrations, confirming the static quenching mechanism. The limit of detection (LoD) of Fe3+ ions over the long range of 16-363 µM for the neutral and protonated forms of 7AI is 0.46 ± 0.02 and 0.49 ± 0.02 µM, respectively, estimated using FL spectra. Additionally, the linear plot of absorbance with Fe3+ ions of both the forms of 7AI can also act as a calibration curve with very close LoDs, as obtained by FL spectra. Thus, the multi-parameters-based probe for detecting the Fe3+ ions over long-range in real aqueous environments with operational, high sensitivity, fast response (< 5 s), and good selectivity (over 12 metal ions) is undoubtedly a superior approach over other methods.
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Affiliation(s)
- Mohan Singh Mehata
- Laser Spectroscopy Laboratory, Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi, 110042, India.
| | - Aneesha
- Laser Spectroscopy Laboratory, Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi, 110042, India
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2
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Joshi HC, Antonov L. Excited-State Intramolecular Proton Transfer: A Short Introductory Review. Molecules 2021; 26:molecules26051475. [PMID: 33803102 PMCID: PMC7963178 DOI: 10.3390/molecules26051475] [Citation(s) in RCA: 75] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 03/03/2021] [Accepted: 03/04/2021] [Indexed: 12/03/2022] Open
Abstract
In this short review, we attempt to unfold various aspects of excited-state intramolecular proton transfer (ESIPT) from the studies that are available up to date. Since Weller’s discovery of ESIPT in salicylic acid (SA) and its derivative methyl salicylate (MS), numerous studies have emerged on the topic and it has become an attractive field of research because of its manifold applications. Here, we discuss some critical aspects of ESIPT and tautomerization from the mechanistic viewpoint. We address excitation wavelength dependence, anti-Kasha ESIPT, fast and slow ESIPT, reversibility and irreversibility of ESIPT, hydrogen bonding and geometrical factors, excited-state double proton transfer (ESDPT), concerted and stepwise ESDPT.
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Affiliation(s)
- Hem C. Joshi
- Institute for Plasma Research, Bhat, Gandhinagar 382428, India;
| | - Liudmil Antonov
- Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
- Correspondence:
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3
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Mehata MS. An efficient excited-state proton transfer fluorescence quenching based probe (7-hydroxyquinoline) for sensing trivalent cations in aqueous environment. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.115379] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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4
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Dutta Choudhury S, Pal H. Supramolecular and suprabiomolecular photochemistry: a perspective overview. Phys Chem Chem Phys 2021; 22:23433-23463. [PMID: 33112299 DOI: 10.1039/d0cp03981k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In this perspective review article, we have attempted to bring out the important current trends of research in the areas of supramolecular and suprabiomolecular photochemistry. Since the spans of the subject areas are very vast, it is impossible to cover all the aspects within the limited space of this review article. Nevertheless, efforts have been made to assimilate the basic understanding of how supramolecular interactions can significantly change the photophysical and other related physiochemical properties of chromophoric dyes and drugs, which have enormous academic and practical implications. We have discussed with reference to relevant chemical systems where supramolecularly assisted modulations in the properties of chromophoric dyes and drugs can be used or have already been used in different areas like sensing, dye/drug stabilization, drug delivery, functional materials, and aqueous dye laser systems. In supramolecular assemblies, along with their conventional photophysical properties, the acid-base properties of prototropic dyes, as well as the excited state prototautomerization and related proton transfer behavior of proton donor/acceptor dye molecules, are also largely modulated due to supramolecular interactions, which are often reflected very explicitly through changes in their absorption and fluorescence characteristics, providing us many useful insights into these chemical systems and bringing out intriguing applications of such changes in different applied areas. Another interesting research area in supramolecular photochemistry is the excitation energy transfer from the donor to acceptor moieties in self-assembled systems which have immense importance in light harvesting applications, mimicking natural photosynthetic systems. In this review article, we have discussed varieties of these aspects, highlighting their academic and applied implications. We have tried to emphasize the progress made so far and thus to bring out future research perspectives in the subject areas concerned, which are anticipated to find many useful applications in areas like sensors, catalysis, electronic devices, pharmaceuticals, drug formulations, nanomedicine, light harvesting, and smart materials.
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Affiliation(s)
- Sharmistha Dutta Choudhury
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai-400085, India. and Homi Bhabha National Institute, Anushaktinagar, Trombay, Mumbai-400094, India
| | - Haridas Pal
- Homi Bhabha National Institute, Anushaktinagar, Trombay, Mumbai-400094, India and Analytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai-400085, India.
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5
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Exploring the effect of hydrogen bonding on protonation of 7,8-benzoquinoline with TFE: Water binary mixture. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2020.128119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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6
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Mehata MS, Singh AK, Sinha RK. Experimental and theoretical study of hydroxyquinolines: hydroxyl group position dependent dipole moment and charge-separation in the photoexcited state leading to fluorescence. Methods Appl Fluoresc 2016; 4:045004. [PMID: 28192284 DOI: 10.1088/2050-6120/4/4/045004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Optical absorption and fluorescence (FL) spectra of 2-, 6-, 7-, 8-hydroxyquinolines (2-,6-,7- and 8-HQs) have been measured at room temperature in the wide range of solvents of different polarities, dielectric constant and refractive index. The ground state dipole moment (µ g) and excited state dipole moment (µ e) of 2-, 6-, 7- and 8-HQs were obtained using solvatochromic shift (SS) methods and microscopic solvent polarity parameters (MSPP). Change in the dipole moment (Δµ) between the ground and photo-excited states was estimated from SS and MSPP methods. DFT and TDDFT based theoretical calculations were performed for the ground and excited states dipole moments, and for vertical transitions. A significant enhancement in the excited state dipole moment was observed following photo-excitation. The large value of Δµ clearly indicates to the charge-separation in the photo-excited states, which in turn depends on the position of the hydroxyl group in the ring.
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Affiliation(s)
- Mohan Singh Mehata
- Laser-Spectroscopy Lab, Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi 110042, India
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7
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Liu YH, Mehata MS, Lan SC. TDDFT study of the polarity controlled ion-pair separation in an excited-state proton transfer reaction. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 128:280-284. [PMID: 24681312 DOI: 10.1016/j.saa.2014.02.149] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 02/09/2014] [Accepted: 02/24/2014] [Indexed: 06/03/2023]
Abstract
6-Hydroxyquinoline (6HQ) is an ideal photoacid system for exploring excited-state proton transfer (ESPT) reactions. We have previously (Mahata et al. (2002)) shown that the ESPT reaction between 6HQ and trimethylamine (TMA) leads to an "unusual" emission in the 440-450 nm range, containing two decay components (∼5 ns and ∼12 ns). The observed results suggest the presence of a contact ion-pair and a solvent separated ion-pair. In this work, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) have been employed to study the nature of the contact ion-pair formed between 6HQ and TMA and to determine why the decay component ∼12 ns is absent in a non-polar solvent. Calculations of the hydrogen-bonded complexes formed between 6HQ and TMA and its ESPT reaction product, namely 6HQ-TMA and 6HQ-TMA-PT, respectively, have been carried out, both in the electronic ground and excited states. Moreover, by using the CPCM model, different dielectric constants have been introduced into the calculations. On increasing the dielectric constant, the hydrogen bond in 6HQ-TMA-PT becomes weaker and the hydrogen bond length becomes larger; this effectively facilitates the proton transfer reaction and formation of separated ion-pair. Thus, the separation and diffusion of the contact ion-pair can be controlled by changing the polarity of the surroundings.
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Affiliation(s)
- Yu-Hui Liu
- Department of Physics, College of Mathematics and Physics, Bohai University, Jinzhou 121013, China.
| | - Mohan Singh Mehata
- Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi 110042, India
| | - Sheng-Cheng Lan
- Department of Physics, College of Mathematics and Physics, Bohai University, Jinzhou 121013, China
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8
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Gahlaut R, Joshi HC, Joshi NK, Pandey N, Pant S. Photochemistry and excited state prototropic behaviour of 8-amino 2-naphthol. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2013; 109:164-172. [PMID: 23523759 DOI: 10.1016/j.saa.2013.01.091] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 01/04/2013] [Accepted: 01/23/2013] [Indexed: 06/02/2023]
Abstract
In the present work, photophysical behaviour of 8-amino 2-naphthol in various solvents as well as at various pH values has been investigated. Various ground and excited state species are noticed. It exhibits a completely different photo prototropic behaviour as compared to its parent molecule 2-naphthol. The spectral and transient studies indicate that at lower pH values, equilibrium between cation and neutral exists in the excited state. At neutral pH some peculiar behaviour in its spectral properties is noticed.
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Affiliation(s)
- Richa Gahlaut
- Photophysics Laboratory, Department of Physics, DSB Campus, Kumaun University, Nainital 263 002, Uttarakhand, India
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Stević MC, Ignjatović LM, Ćirić-Marjanović G, Marjanović B, Barek J, Zima J. Electrochemical oxidation of 6-hydroxyquinoline on a glassy carbon paste electrode: Voltammetric and computational study. J Electroanal Chem (Lausanne) 2012. [DOI: 10.1016/j.jelechem.2012.04.030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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10
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di Nunzio MR, Wang Y, Douhal A. Structural Spectroscopy and Dynamics of Inter- and Intramolecular H-Bonding Interactions of Topotecan, a Potent Anticancer Drug, in Organic Solvents and in Aqueous Solution. J Phys Chem B 2012; 116:7522-30. [DOI: 10.1021/jp302923a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Maria Rosaria di Nunzio
- Departamento de Química Física, Facultad
de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla−La Mancha, Avenida Carlos
III, S/N, 45071 Toledo, Spain
| | - YiLun Wang
- Departamento de Química Física, Facultad
de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla−La Mancha, Avenida Carlos
III, S/N, 45071 Toledo, Spain
| | - Abderrazzak Douhal
- Departamento de Química Física, Facultad
de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla−La Mancha, Avenida Carlos
III, S/N, 45071 Toledo, Spain
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11
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Kumpulainen T, Brouwer AM. Excited-state proton transfer and ion pair formation in a Cinchona organocatalyst. Phys Chem Chem Phys 2012; 14:13019-26. [DOI: 10.1039/c2cp41483j] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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12
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Bridhkoti J, Joshi H, Pant S. Fluorescence characteristics of 5-aminoquinoline in acetonitrile: Water. J Mol Liq 2011. [DOI: 10.1016/j.molliq.2011.09.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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13
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Bridhkoti JP, Mishra H, Joshi HC, Pant S. Photochemistry of 5-aminoquinoline in protic and aprotic solvents. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2011; 79:412-417. [PMID: 21501968 DOI: 10.1016/j.saa.2011.02.044] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 02/17/2011] [Accepted: 02/22/2011] [Indexed: 05/30/2023]
Abstract
Photophysical properties of 5-aminoquinoline (5AQ) have been investigated in various non-polar and polar (protic and aprotic) solvents using steady state and time resolved fluorescence. In aprotic solvents, the spectral maxima depend on the polarity. However, in protic solvents both the fluorescence intensity as well decay time show decrease depending on the hydrogen bonding ability of the solvent. The results suggest that photochemistry 5AQ is quite sensitive towards the polarity as well as protic character of the solvent.
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Affiliation(s)
- Jagat P Bridhkoti
- Photophysics Laboratory, Department of Physics, Kumaun University Nainital, India
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14
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Liu YH, Mehata MS, Liu JY. Excited-state proton transfer via hydrogen-bonded acetic acid (AcOH) wire for 6-hydroxyquinoline. J Phys Chem A 2010; 115:19-24. [PMID: 21141974 DOI: 10.1021/jp1101626] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Spectroscopic studies on excited-state proton transfer (ESPT) of hydroxyquinoline (6HQ) have been performed in a previous paper. And a hydrogen-bonded network formed between 6HQ and acetic acid (AcOH) in nonpolar solvents has been characterized. In this work, a time-dependent density functional theory (TDDFT) method at the def-TZVP/B3LYP level was employed to investigate the excited-state proton transfer via hydrogen-bonded AcOH wire for 6HQ. A hydrogen-bonded wire containing three AcOH molecules at least for connecting the phenolic and quinolinic -N- group in 6HQ has been confirmed. The excited-state proton transfer via a hydrogen-bonded wire could result in a keto tautomer of 6HQ and lead to a large Stokes shift in the emission spectra. According to the results of calculated potential energy (PE) curves along different coordinates, a stepwise excited-state proton transfer has been proposed with two steps: first, an anionic hydrogen-bonded wire is generated by the protonation of -N- group in 6HQ upon excitation to the S(1) state, which increases the proton-capture ability of the AcOH wire; then, the proton of the phenolic group transfers via the anionic hydrogen-bonded wire, by an overall "concerted" process. Additionally, the formation of the anionic hydrogen-bonded wire as a preliminary step has been confirmed by the hydrogen-bonded parameters analysis of the ESPT process of 6HQ in several protic solvents. Therefore, the formation of anionic hydrogen-bonded wire due to the protonation of the -N- group is essential to strengthen the hydrogen bonding acceptance ability and capture the phenolic proton in the 6HQ chromophore.
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Affiliation(s)
- Yu-Hui Liu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
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15
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Rautela R, Joshi N, Joshi H, Tewari N, Pant S. Solvatochromic study of 2-hydroxy-4-methylquinoline for the determination of dipole moments and solute–solvent interactions. J Mol Liq 2010. [DOI: 10.1016/j.molliq.2010.04.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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16
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Qian J, Brouwer AM. Excited state proton transfer in the Cinchona alkaloid cupreidine. Phys Chem Chem Phys 2010; 12:12562-9. [DOI: 10.1039/c003419c] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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17
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Mehata MS, Awasthi K, Iimori T, Ohta N. Electric field effects on state energy and molecular orientation of 2-hydroxyquinoline in solid polymer films. J Photochem Photobiol A Chem 2009. [DOI: 10.1016/j.jphotochem.2009.02.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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18
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Mehata MS. Proton Translocation and Electronic Relaxation along a Hydrogen-Bonded Molecular Wire in a 6-Hydroxyquinoline/Acetic Acid Complex. J Phys Chem B 2008; 112:8383-6. [DOI: 10.1021/jp801811e] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Mohan Singh Mehata
- Photophysics Laboratory, Department of Physics, DSB Campus, Kumaun University, Nainital 263 002, Uttarakhand, India
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Sekiya H, Sakota K. Excited-state double-proton transfer in a model DNA base pair: Resolution for stepwise and concerted mechanism controversy in the 7-azaindole dimer revealed by frequency- and time-resolved spectroscopy. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2008. [DOI: 10.1016/j.jphotochemrev.2008.04.001] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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20
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Photoinduced excited state proton rearrangement of 6-hydroxyquinoline along a hydrogen-bonded acetic acid wire. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.01.060] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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21
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Mehata MS, Iimori T, Yoshizawa T, Ohta N. Electroabsorption Spectroscopy of 6-Hydroxyquinoline Doped in Polymer Films: Stark Shifts and Orientational Effects. J Phys Chem A 2006; 110:10985-91. [PMID: 16986830 DOI: 10.1021/jp063927f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Stark absorption spectroscopy was applied to 6-hydroxyquinoline (6-HQ) doped in polymer films of poly(methyl methacrylate) (PMMA) and poly(vinyl alcohol) (PVA) at temperatures of 50-300 K. The electroabsorption (E-A) spectrum of 6-HQ markedly depends on temperature in a PMMA film. The polarization dependence as well as the temperature dependence of the E-A spectra reveals that 6-HQ is oriented along the direction of the applied electric field at room temperature in a PMMA film. As the temperature becomes lower, the field-induced orientation of 6-HQ is restricted, and only the Stark shift induced by a change in electric dipole moment and in molecular polarizability is observed. On the other hand, E-A spectra of 6-HQ doped in a PVA film are essentially independent of temperature, suggesting that 6-HQ is not oriented along the electric field even at room temperature in PVA. These results show that the molecular motion of 6-HQ in a polymer film is very sensitive to the microenvironment of the surrounding matrix.
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Affiliation(s)
- Mohan Singh Mehata
- Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan
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Kwon OH, Kim TG, Lee YS, Jang DJ. Biphasic Tautomerization Dynamics of Excited 7-Hydroxyquinoline in Reverse Micelles. J Phys Chem B 2006; 110:11997-2004. [PMID: 16800508 DOI: 10.1021/jp0573184] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The excited-state tautomerization dynamics of 7-hydroxyquinoline in the water pools of reverse micelles has been investigated by monitoring time-resolved fluorescence spectra and kinetics as well as static absorption and emission spectra with a variation of water content and isotopic fractionation. The normal and the tautomeric species are found to reside preferentially in the bound- and the free-water regions of the micelles, respectively. The excited-state tautomerization of the normal species in the bound-water layers is suggested to occur via two different channels, depending on rotamers at the moment of excitation. The cis tautomerizes via proton relay from the enol group to the imino group along a hydrogen-bonded water bridge, unusual in water but common in alcohols, whereas the trans tautomerizes via the stepwise individual acid-base reactions of two prototropic groups as found in bulk water. Proton relay can take place because water in the pools has substantially reduced polarity and disrupted hydrogen-bond networks compared with bulk water.
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Affiliation(s)
- Oh-Hoon Kwon
- School of Chemistry, Seoul National University, NS60, Seoul 151-742, Korea
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23
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Peng BH, Liu GF, Liu L, Jia DZ. Studies on solid-state proton transfer along hydrogen bond of pyrazolone-ring. Tetrahedron 2005. [DOI: 10.1016/j.tet.2005.03.096] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Solntsev KM, Clower CE, Tolbert LM, Huppert D. 6-Hydroxyquinoline-N-oxides: A New Class of “Super” Photoacids1. J Am Chem Soc 2005; 127:8534-44. [PMID: 15941289 DOI: 10.1021/ja0514545] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
N-Oxidation of hydroxyquinolines leads to a dramatic increase in their excited-state acidity. Time-resolved and steady-state emission characterization of 6-hydroxyquinoline-N-oxide and 2-methyl-6-hydroxyquinoline-N-oxide reveals a rich but less complex proton-transfer behavior than that of its parent hydroxyquinoline. The electronic effect of the oxidized heterocyclic nitrogen atom makes the excited state both less basic and more acidic than the parent and adds hydroxyquinoline N-oxides to the class of high-acidity excited-state proton donors in photochemistry and photobiology. Adiabatic photoinduced proton transfer is accompanied by the efficient nonreversible deoxygenation and 1-2 oxygen migration.
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Affiliation(s)
- Kyril M Solntsev
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA.
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Park HJ, Kwon OH, Ah CS, Jang DJ. Excited-State Tautomerization Dynamics of 7-Hydroxyquinoline in β-Cyclodextrin. J Phys Chem B 2005; 109:3938-43. [PMID: 16851447 DOI: 10.1021/jp046817m] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The excited-state tautomerization dynamics of 7-hydroxyquinoline encapsulated in beta-cyclodextrin is compared with that in pure water by measuring isotope-dependent fluorescence kinetics as well as absorption and emission spectra. The normal species tautomerizes stepwise via forming anionic intermediate species in both systems. However, the enol-deprotonation time (40 ps in water) becomes as large as 170 ps whereas the imine-protonation time of the anionic intermediate (160 ps in water) becomes as short as 85 ps in beta-cyclodextrin. The slow formation and the fast decay of the anionic species are attributed to the unstability of the charged species in hydrophobic cages. Encapsulation can be utilized to enhance fluorescence enormously and to accelerate selective reactions by retarding other processes.
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Affiliation(s)
- Han Jung Park
- School of Chemistry, Seoul National University, NS60, Seoul 151-742, Korea
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Solntsev KM, Sullivan EN, Tolbert LM, Ashkenazi S, Leiderman P, Huppert D. Excited-State Proton Transfer Reactions of 10-Hydroxycamptothecin1. J Am Chem Soc 2004; 126:12701-8. [PMID: 15453804 DOI: 10.1021/ja047821e] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Time-resolved and steady-state emission characterization of 10-hydroxycamptothecin reveals a rich but less complex proton-transfer behavior than its parent hydroxyquinoline. The electronic effect of the additional electron-withdrawing ring makes the excited-state both less basic and more acidic than the parent and adds to the class of high-acidity excited-state proton donors in photochemistry and photobiology.
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Affiliation(s)
- Kyril M Solntsev
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta 30332-0400, USA.
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Poizat O, Bardez E, Buntinx G, Alain V. Picosecond Dynamics of the Photoexcited 6-Methoxyquinoline and 6-Hydroxyquinoline Molecules in Solution. J Phys Chem A 2004. [DOI: 10.1021/jp030964n] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Olivier Poizat
- Laboratoire de Spectrochimie Infrarouge et Raman (UMR 8516 de l'Université et du CNRS), Centre d'Etudes et de Recherches Lasers et Applications (FR 2416 du CNRS), Bât. C5, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France, and Laboratoire de Chimie Générale, Conservatoire National des Arts et Métiers, 292 rue Saint-Martin, 75003 Paris, and Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires (CNRS UMR 8531), Ecole Normale Supérieure de Cachan,
| | - Elisabeth Bardez
- Laboratoire de Spectrochimie Infrarouge et Raman (UMR 8516 de l'Université et du CNRS), Centre d'Etudes et de Recherches Lasers et Applications (FR 2416 du CNRS), Bât. C5, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France, and Laboratoire de Chimie Générale, Conservatoire National des Arts et Métiers, 292 rue Saint-Martin, 75003 Paris, and Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires (CNRS UMR 8531), Ecole Normale Supérieure de Cachan,
| | - Guy Buntinx
- Laboratoire de Spectrochimie Infrarouge et Raman (UMR 8516 de l'Université et du CNRS), Centre d'Etudes et de Recherches Lasers et Applications (FR 2416 du CNRS), Bât. C5, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France, and Laboratoire de Chimie Générale, Conservatoire National des Arts et Métiers, 292 rue Saint-Martin, 75003 Paris, and Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires (CNRS UMR 8531), Ecole Normale Supérieure de Cachan,
| | - Valérie Alain
- Laboratoire de Spectrochimie Infrarouge et Raman (UMR 8516 de l'Université et du CNRS), Centre d'Etudes et de Recherches Lasers et Applications (FR 2416 du CNRS), Bât. C5, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France, and Laboratoire de Chimie Générale, Conservatoire National des Arts et Métiers, 292 rue Saint-Martin, 75003 Paris, and Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires (CNRS UMR 8531), Ecole Normale Supérieure de Cachan,
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Mehata MS, Joshi HC, Tripathi HB. Fluorescence characteristics of protonated form of 6-hydroxyquinoline in Nafion film. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2003; 59:559-567. [PMID: 12524126 DOI: 10.1016/s1386-1425(02)00206-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Fluorescence characteristics of 6-hydroxyquinoline (6-HQ) have been studied at room temperature in Nafion(R) film by steady state and nano-second time-resolved fluorescence spectroscopy. The fluorescence spectrum exhibits single emission band corresponding to the protonated form of 6-HQ in this matrix. However, the decay fits with two or three exponential functions depending on the emission wavelength monitored. At blue edge of the emission, the decay fits to three-exponential function, whereas at longer wavelengths, the decay fits to bi-exponential function. Two tentative mechanisms have been proposed to explain the experimental data, viz. a closely lying charge transfer state (CT) or an excited state proton transfer (ESPT) process. The photophysical parameters appear to be sensitive to the change in microstructure due to swelling of the membrane by the solvents.
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Affiliation(s)
- M S Mehata
- Photophysics Laboratory, Department of Physics, DSB Campus, Kumaon University, Nainital 263 002, India.
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Mehata M, Joshi H, Tripathi H. Complexation of 6-hydroxyquinoline with trimethylamine in polar and non-polar solvents. Chem Phys Lett 2002. [DOI: 10.1016/s0009-2614(02)01579-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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