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Your search keyword '"Frampton, Michael J."' showing total 26 results
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26 results on '"Frampton, Michael J."'

1. Probing the efficiency of electron transfer through porphyrin-based molecular wires

Author

Winters, Mikael U., Dahlstedt, Emma, Blades, Holly E., Wilson, Craig J., Frampton, Michael J., Anderson, Harry L., and Albinsson, Bo

Subjects
Electron transport -- Research, Porphyrins -- Structure, Porphyrins -- Electric properties, Butadiene -- Structure, Butadiene -- Electric properties, Chemistry
Abstract

Numerous studies and researches are conducted to analyze several molecular systems, like the butadiyne-linked porphyrin oligomers and molecular wires, which can efficiently mediate electrons in a controlled manner over nanometer distances. The analysis reveals that such oligomers exhibit extremely fast rates of long-range charge recombination and very weak distance dependence and hence can be widely used as molecular wires.

Published
2007

2. Synthesis and Near-Infrared Luminescence of a Deuterated Conjugated Porphyrin Dimer for Probing the Mechanism of Non-Radiative Deactivation (Postprint)

Author

AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE, Rogers, Joy E., Fleitz, Paul A., Frampton, Michael J., Anderson, Harry L., Accorsi, Gianluca, Armaroli, Nicola, McEwan, Kenneth J., AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE, Rogers, Joy E., Fleitz, Paul A., Frampton, Michael J., Anderson, Harry L., Accorsi, Gianluca, Armaroli, Nicola, and McEwan, Kenneth J.

Abstract

Beta-meso-beta-Fused porphyrin oligomers have many attractive photophysical features such as strong absorption in the near-IR at wavelengths greater than 1000 nm, and high two-photon cross sections. However their ultrafast S(sub-1)-S(sub-0) deactivation limits potential applications. We have synthesised a deuterated fused porphyrin dimer to test whether deuteration influences the rate of non-radiative deactivation. An efficient synthetic strategy was developed, starting with deuteration of dipyrromethane. Deuteration of the zinc porphyrin dimer does not affect its fluorescence quantum yield in CD2Cl2. This implies that the ultrafast non-radiative deactivation is not simply a consequence of the small S(sub-1)-S(sub-0) energy gaps to the beta-meso-beta-fused porphyrin oligomers but with slower rates of S(sub-1)-S(sub-0) decay., Published in Organic & Biomolecular Chemistry, p1056-1061, 2007. Prepared in collaboration with University of Oxford, United Kingdom; Istituto per la Sintesi Organica e la Fotoreattivit'a, Bologna, Italy; and Defence Science and Technology Laboratory, Malvern, U.K. The original document contains color images. All DTIC reproductions will be in black and white.

Published
2007

3. White Electroluminescence by Supramolecular Control of Energy Transfer in Blends of Organic-Soluble Encapsulated Polyfluorenes

Author

Brovelli, Sergio, primary, Meinardi, Francesco, additional, Winroth, Gustaf, additional, Fenwick, Oliver, additional, Sforazzini, Giuseppe, additional, Frampton, Michael J., additional, Zalewski, Leszek, additional, Levitt, James A., additional, Marinello, Francesco, additional, Schiavuta, Piero, additional, Suhling, Klaus, additional, Anderson, Harry L., additional, and Cacialli, Franco, additional

Published
2010
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5. Laser action from a sugar-threaded polyrotaxane

Author

Mróz, Marta M., primary, Perissinotto, Stefano, additional, Virgili, Tersilla, additional, Gigli, Giuseppe, additional, Salerno, Marco, additional, Frampton, Michael J., additional, Sforazzini, Giuseppe, additional, Anderson, Harry L., additional, and Lanzani, Guglielmo, additional

Published
2009
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7. Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents

Author

Frampton, Michael J., primary, Sforazzini, Giuseppe, additional, Brovelli, Sergio, additional, Latini, Gianluca, additional, Townsend, Emily, additional, Williams, Charlotte C., additional, Charas, Ana, additional, Zalewski, Leszek, additional, Kaka, Naeem S., additional, Sirish, Mallena, additional, Parrott, Lisa J., additional, Wilson, Joanne S., additional, Cacialli, Franco, additional, and Anderson, Harry L., additional

Published
2008
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11. Stabilisation of a heptamethine cyanine dye by rotaxane encapsulation

Author

Yau, C. M. Simon, primary, Pascu, Sofia I., additional, Odom, Susan A., additional, Warren, John E., additional, Klotz, Eric J. F., additional, Frampton, Michael J., additional, Williams, Charlotte C., additional, Coropceanu, Veaceslav, additional, Kuimova, Marina K., additional, Phillips, David, additional, Barlow, Stephen, additional, Brédas, Jean-Luc, additional, Marder, Seth R., additional, Millar, Val, additional, and Anderson, Harry L., additional

Published
2008
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23. The effect of intermolecular interactions on the electro-optical properties of porphyrin dendrimers with conjugated dendrons

Author

Frampton, Michael J., Magennis, Steven W., Pillow, Jonathan N. G., Burn, Paul L., and Samuel, Ifor D. W.

Abstract

We have synthesised a new family of dendrimers with stilbene dendrons attached to a porphyrin core via a stilbene unit and compared their properties with a family of dendrimers with the same core and dendrons but with the dendrons attached via a phenyl unit. The oxidation and reduction half potentials of the two dendrimer families were found to be the same and independent of generation indicating that the dendrons were not creating a micro-environment for the core. However, the rate of heterogeneous electron transfer was found to be strongly dependent on link type and generation. The photoluminescence quantum yield (PLQY) of the dendrimers was also found to be strongly dependent on the method of attachment of the core. In solution the dendrimers with the stilbene link between core and dendrons had PLQYs 1.5 times higher than their phenyl counterparts but in the solid state the trend was reversed with the phenyl linked dendrimers generally having a higher PLQY. The difference in properties has been assigned to the comparative openness of the dendrimer architectures and the effect of the dendrons on the shape of the porphyrin core.

Published
2003

24. Insulated molecular wires.

Author

Frampton MJ and Anderson HL

Abstract

An astonishing assortment of structures have been described as "insulated molecular wires" (IMWs), thus illustrating the diversity of approaches to molecular-scale insulation. These systems demonstrate the scope of encapsulation in the molecular engineering of optoelectronic materials and organic semiconductors. This Review surveys the synthesis and structural characterization of IMWs, and highlights emerging structure-property relationships to determine how insulation can enhance the behavior of a molecular wire. We focus mainly on three IMW architectures: polyrotaxanes, polymer-wrapped pi systems, and dendronized polymers, and compare the properties of these systems with those of conjugated polymers threaded through mesoporous frameworks and zeolites. Encapsulation of molecular wires can enhance properties as diverse as luminescence, electrical transport, and chemical stability, which points to applications in electroluminescent displays, sensors, and the photochemical generation of hydrogen.

Published
2007
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25. Control of electron transfer in a conjugated porphyrin dimer by selective excitation of planar and perpendicular conformers.

Author

Winters MU, Kärnbratt J, Blades HE, Wilson CJ, Frampton MJ, Anderson HL, and Albinsson B

Abstract

A donor-acceptor system is presented in which the electron-transfer rates can be sensitively controlled by means of excitation wavelength and temperature. The electron donor is a butadiyne-linked zinc porphyrin dimer that is connected to a C(60) electron acceptor. The broad distribution of conformations allowed by the butadiyne linker makes it possible to selectively excite perpendicular or planar donor conformers and thereby prepare separate initial states with driving forces for electron transfer that differ by almost 0.2 eV. This, as well as significant differences in electronic coupling, leads to distinctly different rate constants for electron transfer, which in consequence can be controlled by changing excitation wavelength. By extending the system with a secondary donor (ferrocene), a second, long-range charge-separated state can be formed. This system has been used to test the influence of conformational heterogeneity on electron transfer mediated by the porphyrin dimer in the ground state. It was found that if the dimer is forced to a planar conformation by means of a bidentate ligand, the charge recombination rate increased by an order of magnitude relative to the unconstrained system. This illustrates how control of conformation of a molecular wire can affect its behaviour.

Published
2007
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26. Synthesis, crystal structure, and nonlinear optical behavior of beta-unsubstituted meso-meso E-vinylene-linked porphyrin dimers.

Author

Frampton MJ, Akdas H, Cowley AR, Rogers JE, Slagle JE, Fleitz PA, Drobizhev M, Rebane A, and Anderson HL

Abstract

[structure: see text] A vinylene-linked porphyrin dimer, with no substituents at the beta-positions, has been synthesized by CuI/CsF promoted Stille coupling. In the crystal structure of this dimer, the C(2)H(2) bridge is twisted by 45 degrees relative to the plane of the porphyrins. The absorption, emission spectra, and electrochemistry reveal substantial porphyrin-porphyrin pi-conjugation. The triplet excited-state absorption spectrum of this dimer makes it suitable for reverse saturable absorption at 710-900 nm.

Published
2005
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