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Concistrè M, Mamone S, Denning M, Pileio G, Lei X, Li Y, Carravetta M, Turro NJ, Levitt MH. Anisotropic nuclear spin interactions in H₂O@C₆₀ determined by solid-state NMR. Philos Trans A Math Phys Eng Sci 2013; 371:20120102. [PMID: 23918716 DOI: 10.1098/rsta.2012.0102] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report a solid-state NMR study of the anisotropic nuclear spin interactions in H₂O@C₆₀ at room temperature. We find evidence of significant dipole-dipole interactions between the water protons, and also a proton chemical shift anisotropy (CSA) interaction. The principal axes of these interaction tensors are found to be perpendicular. The magnitude of the CSA is too large to be explained by a model in which the water molecules are partially aligned with respect to an external axis. The evidence indicates that the observed CSA is caused by a distortion of the geometry or electronic structure of the fullerene cages, in response to the presence of the endohedral water.
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Affiliation(s)
- M Concistrè
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
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Rõõm T, Peedu L, Ge M, Hüvonen D, Nagel U, Ye S, Xu M, Bačić Z, Mamone S, Levitt MH, Carravetta M, Chen JYC, Lei X, Turro NJ, Murata Y, Komatsu K. Infrared spectroscopy of small-molecule endofullerenes. Philos Trans A Math Phys Eng Sci 2013; 371:20110631. [PMID: 23918713 DOI: 10.1098/rsta.2011.0631] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Hydrogen is one of the few molecules that has been incarcerated in the molecular cage of C₆₀ to form the endohedral supramolecular complex H₂@C₆₀. In this confinement, hydrogen acquires new properties. Its translation motion, within the C₆₀ cavity, becomes quantized, is correlated with its rotation and breaks inversion symmetry that induces infrared (IR) activity of H₂. We apply IR spectroscopy to study the dynamics of hydrogen isotopologues H₂, D₂ and HD incarcerated in C₆₀. The translation and rotation modes appear as side bands to the hydrogen vibration mode in the mid-IR part of the absorption spectrum. Because of the large mass difference of hydrogen and C₆₀ and the high symmetry of C₆₀ the problem is almost identical to a vibrating rotor moving in a three-dimensional spherical potential. We derive potential, rotation, vibration and dipole moment parameters from the analysis of the IR absorption spectra. Our results were used to derive the parameters of a pairwise additive five-dimensional potential energy surface for H₂@C₆₀. The same parameters were used to predict H₂ energies inside C₇₀. We compare the predicted energies and the low-temperature IR absorption spectra of H₂@C₇₀.
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Affiliation(s)
- T Rõõm
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia.
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Horsewill AJ, Goh K, Rols S, Ollivier J, Johnson MR, Levitt MH, Carravetta M, Mamone S, Murata Y, Chen JYC, Johnson JA, Lei X, Turro NJ. Quantum rotation and translation of hydrogen molecules encapsulated inside C₆₀: temperature dependence of inelastic neutron scattering spectra. Philos Trans A Math Phys Eng Sci 2013; 371:20110627. [PMID: 23918709 DOI: 10.1098/rsta.2011.0627] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The quantum dynamics of a hydrogen molecule encapsulated inside the cage of a C60 fullerene molecule is investigated using inelastic neutron scattering (INS). The emphasis is on the temperature dependence of the INS spectra which were recorded using time-of-flight spectrometers. The hydrogen endofullerene system is highly quantum mechanical, exhibiting both translational and rotational quantization. The profound influence of the Pauli exclusion principle is revealed through nuclear spin isomerism. INS is shown to be exceptionally able to drive transitions between ortho-hydrogen and para-hydrogen which are spin-forbidden to photon spectroscopies. Spectra in the temperature range 1.6≤T≤280 K are presented, and examples are given which demonstrate how the temperature dependence of the INS peak amplitudes can provide an effective tool for assigning the transitions. It is also shown in a preliminary investigation how the temperature dependence may conceivably be used to probe crystal field effects and inter-fullerene interactions.
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Affiliation(s)
- A J Horsewill
- School of Physics and Astronomy, University of Nottingham, , Nottingham NG7 2RD, UK.
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Lei XG, Doubleday CE, Zimmt MB, Turro NJ. Photochemistry of 2-phenylcyclanones. Formation of cyclophanes and encapsulation by a ship-in-bottle and by a reptation strategy. J Am Chem Soc 2012; 108:2444-5. [PMID: 22175598 DOI: 10.1021/ja00269a051] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Ge M, Nagel U, Hüvonen D, Rõõm T, Mamone S, Levitt MH, Carravetta M, Murata Y, Komatsu K, Lei X, Turro NJ. Infrared spectroscopy of endohedral HD and D2 in C60. J Chem Phys 2012; 135:114511. [PMID: 21950875 DOI: 10.1063/1.3637948] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
We report on the dynamics of two hydrogen isotopomers, D(2) and HD, trapped in the molecular cages of a fullerene C(60) molecule. We measured the infrared spectra and analyzed them using a spherical potential for a vibrating rotor. The potential, vibration-rotation Hamiltonian, and dipole moment parameters are compared with previously studied H(2)@C(60) parameters [M. Ge, U. Nagel, D. Hüvonen, T. Rõõm, S. Mamone, M. H. Levitt, M. Carravetta, Y. Murata, K. Komatsu, J. Y.-C. Chen, and N. J. Turro, J. Chem. Phys. 134, 054507 (2011)]. The isotropic part of the potential is similar for all three isotopomers. In HD@C(60), we observe mixing of the rotational states and an interference effect of the dipole moment terms due to the displacement of the HD rotation center from the fullerene cage center.
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Affiliation(s)
- Min Ge
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
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Porel M, Jockusch S, Ottaviani MF, Turro NJ, Ramamurthy V. Interaction between encapsulated excited organic molecules and free nitroxides: communication across a molecular wall. Langmuir 2011; 27:10548-10555. [PMID: 21749113 DOI: 10.1021/la202120u] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Communication between two molecules, one confined and excited (triplet or singlet) and one free and paramagnetic, has been explored through quenching of fluorescence and/or phosphorescence by nitroxides as paramagnetic radical species. Quenching of excited states by nitroxides has been investigated in solution, and the mechanism is speculated to involve charge transfer and/or exchange processes, both of which require close orbital interaction between excited molecule and quencher. We show in this report that such a quenching, which involves electron-electron spin communication, can occur even when there is a molecular wall between the two. The excited state molecule is confined within an organic capsule made up of two molecules of a deep cavity cavitand, octa acid, that exists in the anionic form in basic aqueous solution. The nitroxide is kept free in aqueous solution. (1)H NMR and EPR experiments were carried out to ascertain the location of the two molecules. The distance between the excited molecule and the paramagnetic quencher was manipulated by the use of cationic, anionic, and neutral nitroxide and also by selectively including the cationic nitroxide within the cavity of cucurbituril. Results presented here highlight the role of the lifetime of the encounter complex in electron-electron spin communication when the direct orbital overlap between the two molecules is prevented by the intermediary wall.
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Affiliation(s)
- Mintu Porel
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124, USA
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Ge M, Nagel U, Hüvonen D, Rõõm T, Mamone S, Levitt MH, Carravetta M, Murata Y, Komatsu K, Chen JYC, Turro NJ. Interaction potential and infrared absorption of endohedral H2 in C60. J Chem Phys 2011; 134:054507. [DOI: 10.1063/1.3535598] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
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Jayaraj N, Jockusch S, Kaanumalle LS, Turro NJ, Ramamurthy V. Dynamics of capsuleplex formed between octaacid and organic guest molecules — Photophysical techniques reveal the opening and closing of capsuleplex. CAN J CHEM 2011. [DOI: 10.1139/v10-104] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This manuscript is concerned with the opening and closing of a capsuleplex made up of organic guest molecules and two cavitand molecules known as octaacid (OA). The capsuleplex is loosely held together in water through weak interactions. We have investigated the opening–closing of the OA capsuleplex by monitoring the quenching of excited singlet and (or) triplet states of nine different guest molecules encapsulated within a capsule by molecular oxygen that is dissolved in water surrounding the capsule. The rate constants for oxygen quenching of the excited guest molecules were estimated by monitoring the intensity of fluorescence/phosphorescence or lifetimes of excited states of guest molecules in the presence of different concentrations of oxygen in water. Guest molecules were chosen such that one could probe the opening–closing process during a time range of 0.05 to 922 µs. We believe that the oxygen quenching constant reflects the accessibility of oxygen to the guest enclosed within the OA capsuleplex, and this in turn depends on the capsule opening–closing rate constant. Based on the quenching studies, we conclude that guests whose lifetimes are shorter than 5 µs are inaccessible to oxygen. Results presented in this report suggest that the extent and time scale for opening depends on the guest.
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Affiliation(s)
- Nithyanandhan Jayaraj
- Department of Chemistry, University of Miami, Coral Gables, FL 33124, USA
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Steffen Jockusch
- Department of Chemistry, University of Miami, Coral Gables, FL 33124, USA
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Lakshmi S. Kaanumalle
- Department of Chemistry, University of Miami, Coral Gables, FL 33124, USA
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - N. J. Turro
- Department of Chemistry, University of Miami, Coral Gables, FL 33124, USA
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - V. Ramamurthy
- Department of Chemistry, University of Miami, Coral Gables, FL 33124, USA
- Department of Chemistry, Columbia University, New York, NY 10027, USA
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Abstract
The course of chemical reactions involving radical pairs may depend on occurrence and orientation of nuclear spins in the pairs. The influence of nuclear spins is maximized when the radical pairs are confined to a space that serves as a cage that allows a certain degree of independent diffusional and rotational motion of the partners of the pair but that also encourages reencounters of the partners within a period which allows the nuclear spins to operate on the odd electron spins of the pair. Under the proper conditions, the nuclear spins can induce intersystem crossing between triplet and singlet states of radical pairs. It is shown that this dependence of intersystem crossing on nuclear spin leads to a magnetic isotope effect on the chemistry of radical pairs which provides a means of separating isotopes on the basis of nuclear spins rather than nuclear masses and also leads to a magnetic field effect on the chemistry of radical pairs which provides a means of influencing the course of polymerization by the application of weak magnetic fields.
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Affiliation(s)
- N J Turro
- Department of Chemistry, Columbia University, New York, New York 10027
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Kulasekharan R, Jayaraj N, Porel M, Choudhury R, Sundaresan AK, Parthasarathy A, Ottaviani MF, Jockusch S, Turro NJ, Ramamurthy V. Guest rotations within a capsuleplex probed by NMR and EPR techniques. Langmuir 2010; 26:6943-6953. [PMID: 20055365 DOI: 10.1021/la904196g] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
With the help of (1)H NMR and EPR techniques, we have probed the dynamics of guest molecules included within a water-soluble deep cavity cavitand known by the trivial name octa acid. All guest molecules investigated here form 2:1 (host/guest) complexes in water, and two host molecules encapsulate the guest molecule by forming a closed capsule. We have probed the dynamics of the guest molecule within this closed container through (1)H NMR and EPR techniques. The timescales offered by these two techniques are quite different, millisecond and nanosecond, respectively. For EPR studies, paramagnetic nitroxide guest molecules and for (1)H NMR studies, a wide variety of structurally diverse neutral organic guest molecules were employed. The guest molecules freely rotate along their x axis (long molecular axis and magnetic axis) on the NMR timescale; however, their rotation is slowed with respect to that in water on the EPR timescale. Rotation along the x axis is dependent on the length of the alkyl chain attached to the nitroxide probe. Overall rotation along the y or z axis was very much dependent on the structure of the guest molecule. The guests investigated could be classified into three groups: (a) those that do not rotate along the y or z axis both at room and elevated (55 degrees C) temperatures, (b) those that rotate freely at room temperature, and (c) those that do not rotate at room temperature but do so at higher temperatures. One should note that rotation here refers to the NMR timescale and it is quite possible that all molecules may rotate at much longer timescales than the one probed here. A slight variation in structure alters the rotational mobility of the guest molecules.
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Jayaraj N, Maddipatla MVSN, Prabhakar R, Jockusch S, Turro NJ, Ramamurthy V. Closed Nanocontainer Enables Thioketones to Phosphoresce at Room Temperature in Aqueous Solution. J Phys Chem B 2010; 114:14320-8. [DOI: 10.1021/jp911698s] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nithyanandhan Jayaraj
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124, and Department of Chemistry, Columbia University, New York, New York 10027
| | - Murthy V. S. N. Maddipatla
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124, and Department of Chemistry, Columbia University, New York, New York 10027
| | - Rajeev Prabhakar
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124, and Department of Chemistry, Columbia University, New York, New York 10027
| | - Steffen Jockusch
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124, and Department of Chemistry, Columbia University, New York, New York 10027
| | - N. J. Turro
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124, and Department of Chemistry, Columbia University, New York, New York 10027
| | - V. Ramamurthy
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124, and Department of Chemistry, Columbia University, New York, New York 10027
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Isayama T, Alexeev D, Makino CL, Washington I, Nakanishi K, Turro NJ. An accessory chromophore in red vision. Nature 2006; 443:649. [PMID: 17035994 DOI: 10.1038/443649a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Accepted: 08/25/2006] [Indexed: 11/09/2022]
Abstract
In the absence of a red-sensitive visual pigment, some deep-sea fish use a chlorophyll derivative in their green-sensitive rod cells in order to see deep-red light. Here we show that living rods extracted from a salamander can also accumulate an exogenous chlorophyll derivative, chlorin e6, that renders them as sensitive to red light as they are to green. This vision enhancement by an unbleachable chlorophyll derivative might therefore be a general phenomenon in vertebrate photoreception.
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Affiliation(s)
- T Isayama
- Department of Ophthalmology, Massachusetts Eye & Ear Infirmary, Boston, Massachusetts 02114, USA
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Rao KSJ, Hegde ML, Anitha S, Musicco M, Zucca FA, Turro NJ, Zecca L. Amyloid beta and neuromelanin--toxic or protective molecules? The cellular context makes the difference. Prog Neurobiol 2006; 78:364-73. [PMID: 16682109 DOI: 10.1016/j.pneurobio.2006.03.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Revised: 03/07/2006] [Accepted: 03/13/2006] [Indexed: 12/01/2022]
Abstract
Alzheimer's disease (AD) and Parkinson's disease (PD) share several pathological mechanisms. The parallels between amyloid beta (Abeta) in AD and alpha-synuclein in PD have been discussed in several reports. However, studies of the last few years show that Abeta also shares several important characteristics with neuromelanin (NM), whose role in PD is emerging. First, both molecules accumulate with aging, the greatest risk factor for AD and PD. Second, in spite of their different structures, Abeta and NM have similar characteristics that could also lead to neuroprotection. Metals are required to catalyze their formation and they can bind large amounts of these metals, generating stable complexes and thus playing a protective role against metal toxicity. Moreover, they may be able to remove toxic species such as oligopeptides and excess cytosolic dopamine. Third, both Abeta and NM have been implicated in parallel aspects of the neuronal death that underlies AD and PD, respectively. For example, both molecules can activate microglia, inducing release of toxic factors such as tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and nitric oxide (NO). A careful analysis of these parallel effects of Abeta and NM, including their seemingly paradoxical ability to participate in both cell death and protection, may lead to an improved understanding of the roles of these molecules in neurodegeneration and also provide insights into possible parallels in the pathological mechanisms underlying AD and PD.
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Affiliation(s)
- K S J Rao
- Department of Biochemistry and Nutrition, Central Food Technological Research Institute, Mysore 570020, India
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Pan F, Wang P, Lee K, Wu A, Turro NJ, Koberstein JT. Photochemical modification and patterning of polymer surfaces by surface adsorption of photoactive block copolymers. Langmuir 2005; 21:3605-3612. [PMID: 15807608 DOI: 10.1021/la0477439] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report a simple photolithographic approach for the creation and micropatterning of chemical functionality on polymer surfaces by use of surface-active block copolymers that contain protected photoactive functional groups. The block copolymers self-assemble at the substrate-air interface to generate a surface that is initially hydrophobic with low surface tension but that can be rendered hydrophilic and functional by photodeprotection with UV radiation. The block copolymer employed, poly(styrene-b-tert butyl acrylate), segregates preferentially to the surface of a polystyrene substrate because of the low surface tension of the polyacrylate blocks. The strong adsorption of block copolymers causes a bilayer structure to form presenting a photoactive polyacrylate layer at the surface. In the example described, the tert-butyl ester groups on the polyacrylate blocks are deprotected by exposure to UV radiation in the presence of added photoacid generators to form surface carboxylic acid groups. Surface micropatterns of carboxylic acid groups are generated by UV exposure through a contact mask. The success of surface chemical modification and pattern formation is demonstrated by X-ray photoelectron spectroscopy and contact angle measurements along with imaging by optical and fluorescence microscopy methods. The resultant chemically patterned surfaces are then used to template patterns of various biomolecules by means of selective adsorption, covalent bonding and molecular recognition mechanisms. The surface modification/patterning concept can be applied to virtually any polymeric substrate because protected functional groups have intrinsically low surface tensions, rendering properly designed block copolymers surface active in almost all polymeric substrates.
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Affiliation(s)
- F Pan
- Department of Chemistry, Columbia University, 500 West 120th Street, MC4721, New York, New York 10027, USA
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Welsh KM, Dektar JL, Garcia-Garibaya MA, Hacker NP, Turro NJ. Photo-CIDNP and nanosecond laser flash photolysis studies on the photodecomposition of triarylsulfonium salts. J Org Chem 2002. [DOI: 10.1021/jo00041a023] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Arora KS, Hwang KC, Turro NJ. Photophysical investigations of the interactions of phospholipids and a pyrene-substituted poly(acrylic acid) in dilute solutions. Macromolecules 2002. [DOI: 10.1021/ma00165a025] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Fanghaenel E, Ortman W, Behrmann K, Willscher S, Turro NJ, Gould IR. Photochemical primary process of xanthene dyes. 7. Xanthene dyes as probes for the characterization of anionic micelles. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100297a048] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Rao BN, Syamala MS, Turro NJ, Ramamurthy V. Modification of photochemical reactivity by cyclodextrin complexation: a remarkable effect on the photobehavior of .alpha.-alkyldibenzyl ketones. J Org Chem 2002. [DOI: 10.1021/jo00234a004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abdel-Wahab AA, Doss SH, Duerr H, Turro NJ, Gould IR. Mechanistic investigations of the cycloaddition reactions of thioxanthenylidene S,S-dioxide. J Org Chem 2002. [DOI: 10.1021/jo00379a022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Eisenthal KB, Turro NJ, Aikawa M, Butcher JA, DuPuy C, Hefferon G, Hetherington W, Korenowski GM, McAuliffe MJ. Dynamics and energetics of the singlet-triplet interconversion of diphenylcarbene. J Am Chem Soc 2002. [DOI: 10.1021/ja00541a034] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Guillet JE, Houvenaghel-Defoort B, Kilp T, Turro NJ, Steinmetzer HC, Schuster G. "Dark" Initiation of the Photosensitized Degradation of a Styrene-Methyl Isopropenyl Ketone Copolymer by Thermally Generated Acetone Triplets. Macromolecules 2002. [DOI: 10.1021/ma60042a047] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Pyle AM, Rehmann JP, Meshoyrer R, Kumar CV, Turro NJ, Barton JK. Mixed-ligand complexes of ruthenium(II): factors governing binding to DNA. J Am Chem Soc 2002. [DOI: 10.1021/ja00190a046] [Citation(s) in RCA: 1187] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Leheny AR, Turro NJ, Drake JM. Dipole-dipole coupling between excited aromatic probe molecules and defect sites in silica gel. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100200a054] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Doss SH, Abdel-Wahab AA, Fruehof EM, Duerr HD, Gould IR, Turro NJ. Carbenadibenzocycloheptane: steady-state and time-resolved spectroscopic laser studies. J Org Chem 2002. [DOI: 10.1021/jo00379a023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Dalton JC, Dawes K, Turro NJ, Weiss DS, Barltrop JA, Coyle JD. Molecular photochemistry. XLVIII. Type I and type II photochemical reactions of some five- and six-membered cycloalkanones. J Am Chem Soc 2002. [DOI: 10.1021/ja00755a016] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Step EN, Turro NJ, Gande ME, Klemchuk PP. Mechanism of Polymer Stabilization by Hindered-Amine Light Stabilizers (HALS). Model Investigations of the Interaction of Peroxy Radicals with HALS Amines and Amino Ethers. Macromolecules 2002. [DOI: 10.1021/ma00087a022] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Step EN, Tarasov VF, Buchachenko AL, Turro NJ. Wavelength effects in the photolysis of ketones: stereoisomerization and magnetic isotope carbon-13/carbon-12 separation; a probe for adiabatic versus diabatic trajectories during bond dissociation. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100104a017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Turro NJ, Lee C, Schore N, Barltrop J, Carless HAJ. Molecular photochemistry. XLV. Structure-reactivity correlations for the quenching of acetone fluorescence by enol ethers and by conjugated unsaturated nitriles. J Am Chem Soc 2002. [DOI: 10.1021/ja00741a062] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ramamurthy V, Corbin DR, Turro NJ, Zhang Z, Garcia Garibay MA. Modification of photochemical reactivity by zeolites. A comparison between zeolite-solvent slurry and dry solid photolyses. J Org Chem 2002. [DOI: 10.1021/jo00001a048] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Kunjappu JT, Somasundaran P, Turro NJ. A luminescence quenching study on the localization problem of tris(2,2'-bipyridyl)ruthenium(2+) in micelles and hemimicelles. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100385a020] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Step EN, Buchachenko AL, Turro NJ. The cage effect in the photolysis of (S)-(+)-.alpha.-methyldeoxybenzoin: can triplet radical pairs undergo geminate recombination in nonviscous homogeneous solution? J Org Chem 2002. [DOI: 10.1021/jo00052a009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chandra AK, Turro NJ, Lyons AL, Stone P. The intramolecular external heavy atom effect in bromo-, benzo-, and naphthonorbornenes. J Am Chem Soc 2002. [DOI: 10.1021/ja00484a007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Yu CF, Youngs F, Bersohn R, Turro NJ. Photodissociation at 193 nm of cyclooctatetraene and styrene into benzene and acetylene. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100266a052] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Dalton JC, Turro NJ. Molecular photochemistry. XL. Determination of the reactivity of first excited singlet states of organic compounds toward unimolecular primary photochemical processes from molecular fluorescence characteristics. Application to intramolecular .gamma.-hydrogen abstraction reactions of alkyl ketones. J Am Chem Soc 2002. [DOI: 10.1021/ja00744a003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Eisenthal KB, Turro NJ, Dupuy CG, Hrovat DA, Langan J, Jenny TA, Sitzmann EV. State-selective photochemistry of singlet oxygen precursors: kinetics and wavelength dependence of the photodissociation of anthracene endoperoxides. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100412a055] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Tong AK, Jockusch S, Li Z, Zhu HR, Akins DL, Turro NJ, Ju J. Triple fluorescence energy transfer in covalently trichromophore-labeled DNA. J Am Chem Soc 2001; 123:12923-4. [PMID: 11749560 DOI: 10.1021/ja016904h] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- A K Tong
- Department of Chemical Engineering, Columbia Genome Center, Columbia University, New York, NY 10027, USA
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Abstract
Heterohelicene 10 is synthesized in six steps from 3,3'-bithienyl. Because the number of steps is small, because the yield is 95% in the last (the reaction of a bis-enol ether with 1,4-benzoquinone-a six-step one pot procedure that constructs the helicene skeleton), and because chromatography is not required to purify any of the products in the synthesis, significant amounts are easily prepared. To convert 10 into enantiopure 3, a helicenebisquinone surrounded by four dodecyloxy groups, requires only a precedented three-step sequence. Enantiopure helicene 3, either without solvent or in dodecane (but not in chloroform) aggregates into columnar structures whose optical properties differ markedly from those of the monomer but resemble those shown previously only by aggregates of 1. Evidence of aggregation in the pure material includes optical microscopic observation of long fibrous structures and X-ray diffraction and combined transmission electron microscopic and electron diffraction analyses showing the molecules within the fibers to be organized in columnar arrays. The circular dichroism spectra, specific rotations, and fluorescent emission spectra of the aggregated structures are all distinctive, and, as reported elsewhere, the second harmonic response is very large. The linear polarizations of the monomers' and aggregates' fluorescent emissions differ greatly. The circular polarization of the aggregates' fluorescent emission, after excitation by unpolarized light, is large.
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Affiliation(s)
- K E Phillips
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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Wada T, Shikimi M, Inoue Y, Lem G, Turro NJ. First photosensitized enantiodifferentiating isomerization by optically active sensitizer immobilized in zeolite supercages. Chem Commun (Camb) 2001:1864-5. [PMID: 12240352 DOI: 10.1039/b105381g] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Enantiodifferentiating photoisomerization of (Z)-cyclooctene sensitized by (R)- or (S)-1-methylheptyl benzoate immobilized in zeolite supercages afforded the respective enantiomer pair, (-)- and (+)-(E)-isomer (1E) in 5% enantiomeric excess, whilst racemic 1E was obtained upon homogeneous-phase photosensitization with the same antipodal sensitizer pair, thus demonstrating for the first time that chirally modified zeolites not only serve as supramolecular photosensitizing media but also enhance the original enantiodifferentiating ability of chiral photosensitizer.
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Affiliation(s)
- T Wada
- Department of Molecular Chemistry, Graduate School of Engineering, Osaka University, Yamada-oka, Suita 565-0871, Japan
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Abstract
The chemistry of radicals adsorbed on zeolites is remarkable in that the products of radical-radical reactions, which are nonselective in solution, can be made selective and can be controlled by supramolecular effects and magnetic isotope effects. The photolysis of ketones adsorbed on zeolites can be manipulated so that either primary or secondary radicals produced by photolysis can be directed to selected radical-radical reactions which are unknown in solution.
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Affiliation(s)
- N J Turro
- Department of Chemistry, Columbia University, 3000 Broadway, MC 3119, New York, New York 10027, USA
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