Professor Anthony Harriman
Professor of Physical Chemistry
- Email: email@example.com
- Telephone: +44 (0) 191 208 8660
- Fax: +44 (0) 191 208 8660
- Personal Website: http://www.ncl.ac.uk/mpl/
- Address: Professor Anthony Harriman
Molecular Photonics Laboratory
School of Chemistry
Newcastle upon Tyne
The Molecular Photonics Laboratory is a research organisation concerned with the design, synthesis and photophysical examination of multi-component molecular systems, at both fundamental and applied levels. Our particular interest lies with the detailed investigation of molecular materials for artificial photosynthesis, including the optimisation of molecular arrays suitable as light-harvesting networks. The Laboratory is funded, in part, by EPSRC. Further details can be found at: www.ncl.ac.uk/mpl/
NB A Faraday Discussion devoted to artificial photosynthesis will be held at Edinburgh in early September. See:
Current research is concerned with the design of molecular photonic devices based on a detailed understanding of energy- and electron-transfer processes. This is an extension of earlier work aimed at the development of artificial photosynthetic systems and relies heavily on the use of photophysical studies. On-going collaborations with synthetic chemists (Raymond Ziessel at Strasbourg and Andy Benniston at Newcastle) provide the necessary materials for comprehensive examinations. Our work concerns seeking a better understanding of the fundamental principles of charge transfer in molecular systems and involves both experimental and theoretical studies. International collaborations with colleagues in Europe and the United States continue. All research work is now conducted through the Molecular Photonics Laboratory – a specialised university research centre established in 2002. Modest funding has been obtained to renovate laboratory and office space and to install safety features necessary for pulsed laser spectroscopy. Extant equipment includes a range of steady-state and time-resolved spectrometers for recording photophysical events over time scales ranging from sub-ps to minutes. Ancillary detection facilities permit the detailed examination of how the photophysical properties are influenced by application of magnetic fields, strong electrical fields, high pressure, and variable temperatures. Optical studies can be made by both emission of absorption changes. Planned equipment upgrades include the introduction of transient grating spectroscopy, extending possibilities with anisotropy work, and moving from solution phase to cover the solid state. A wide battery of quantum chemical software and hardware is available
Roles and Responsibilities
Teaching contemporary physical chemistry presents a tremendous challenge in that most students are afraid of the mathematical component. An important objective for the near future, therefore, is to introduce computer-assisted teaching - where graphical methods are used in place of numerical ones - and to teach those special mathematical skills of direct relevance to chemistry. A longer-term goal is to devise an individual electronic tutor for each student.
SRC Postdoctoral Fellow, The Royal Institution, London, U.K. 1974-75
EEC Postdoctoral Fellow, The Royal Institution, London, U.K. 1975-77
Dewar Research Fellow, The Royal Institution, London, U.K. 1977-88
Assistant Director, The Royal Institution, London, U.K. 1980-88
Visiting Scientist, National Bureau of Standards, Washington, D.C., U.S.A. 1985-86
Deputy Director, Center for Fast Kinetics Research, Austin, Texas, U.S.A. 1988-89
Director, Center for Fast Kinetics Research, Austin, Texas, U.S.A. 1989-94
Professor of Physical Chemistry, University of Texas, Austin, Texas, U.S.A. 1989-93
Professeur Invité, Université Louis Pasteur, Strasbourg, France 1993
Professeur Invité, School of Chemistry, E.H.I.C.S., Strasbourg, France 1994
Visiting Professor, Tokyo Metropolitan University, Tokyo, Japan 1995
Professeur, Université Louis Pasteur, Strasbourg, France 1995-99
Professor of Physical Chemistry, University of Newcastle, U.K. 1999-
Marseilles football supporters club
Royal Society of Chemistry
Honours and Awards
Sir James Dewar Research Fellowship 1977
Royal Society (London) Visiting Research Scholarship 1982
Corday-Morgan Medal (RSC) 1984
Le Prix Grammaticakis-Neumann en Photochimie 1985
molecular photophysics in condensed phase
quantum chemistry as applied to molecular systems
electron and energy transfer
solar energy conversion
Current research is concerned with the design of molecular-based artificial photosynthetic models using a detailed understanding of energy- and electron-transfer processes. This is an extension of earlier work aimed at the development of molecular systems aimed at solar fuels production and relies heavily on the use of photophysical studies. On-going collaborations with synthetic chemists (Dr. R. Ziessel at Strasbourg and Dr. A.C. Benniston at Newcastle) provide the necessary materials for comprehensive examinations. Our work concerns seeking a better understanding of the fundamental principles of charge and energy transfer in molecular systems and involves both experimental and theoretical studies. The main lines of investigation at present relate to (i) the fabrication of artificial light-harvesting arrays capable of efficient capture of sunlight and (ii) the design of molecular systems capable of storing multiple electrons at a catalytic site. This research relies heavily on the use of sophisticated laser spectroscopy for fast kinetic and spectroscopic studies. Additional research is aimed at improving the performance of molecular catalysts for water splitting.. We are also working with industrial companies to promote interest in solar fuels. A wide range of spectroscopic instruments has been constructed in-house, taking advantage of the School machine and electronics workshops.
(i) Photosynthetic organisms are exquisitely arranged so as to capture incident sunlight with high efficacy, and transmit the transient excitation energy to a reaction centre where chemical reactions are initiated. The energy-transfer mechanism is often described by semi-classical models that invoke ‘hopping’ of the wave-packet along discrete energy levels and over considerable distances set in 3-dimensional space. These energy levels combine to form a large peripheral light-harvesting antenna coupled to individual reaction centres. Many attempts have been made to duplicate the essential features of the natural process, ignoring elaborate events such as self-repair and quantum coherence, and great progress has been made in understanding the basic energy-transfer steps. Mostly, these bio-inspired molecular systems have been studied as standalone entities in 2-dimensions, with little consideration given to longer-range energy transfer between moieties embedded in a solid matrix. We have built and studied many molecular arrays of increasing complexity in terms of their ability to function as artificial light-harvesting networks. Rates of intramolecular energy transfer have been measured and compared to theoretical models, allowing for both through-space and through-bond interactions and utilising a multi-pole approach. The work is helping to better define the mechanism of electronic energy transfer in molecular entities. In terms of expanding the dimensionality, it should be noted that some success has been achieved with quantum dots dispersed in a polymeric film and our latest work in this area seeks to build upon this foundation by introducing an organic equivalent that has unique properties.
(ii) What are the major obstacles to the successful introduction of a viable demonstration model that unambiguously verifies the potential for a molecular-based artificial photosynthetic system? In reality there is only one such bottleneck: namely, the need to couple the inherently one-electron photochemistry with the multiple electron fuel formation without using sacrificial redox agents. We propose to solve this critical problem using a unidirectional electron-transfer cascade of the type developed recently in our group (see publication list). These arrays will be attached covalently to [FeS] clusters and the ability to store multiple electrons under illumination will be probed experimentally in the solid state. The array will be coupled to existing artificial light-harvesting panels. The intention is to illustrate, at the level of public lectures, that visible light can be used to split water in a molecular-based system under ambient conditions and that the mechanism can be followed by sophisticated spectroscopy.
construction of an artificial light-harvesting array
development of an integrated system for water splitting under visible-light illumination
All my research work is directed through the Molecular Photonics Laboratory; see the dedicated web site for further details. www.ncl.ac.uk/mpl/
Sixteen PhD students (Ben Allen; Pritesh Patel; Sarah Rostron; Sarah Mitchell; James Rostron; Eransu Llarena; Consuleo Pariani, Laura Mallon, Dorota Rewinska, Kris Elliott, Graham Copley, Beverly Stewart, Craig sams, Maryam Mehrabi, Ata Amini, Annabelle Mayeux,) have graduated since 2001. Several PDRA’s have also worked in the group (Peiyi Li, Craig Sams, Songjie Yang, Sarah Howell, Guillaume Izzet, Chunfang Yu, and Yongang Zhi) over the past few years. The main funding body has been EPSRC.
Some indicators of research commitment at a national level, restricted to last 12 months, include: oral presentations at a Dalton Discussion and Faraday Discussion, leading to being invited to organise a future Faraday Discussion on Artificial Photosynthesis; panellist for Royal Society debate on Harnessing Solar Energy; invited to edit special issue of Phys. Chem. Chem. Phys.; invited to speak at EPSRC-sponsored discussion on Adventurous Chemistry; only recipient of two awards for Adventurous Chemistry; only recipient of two awards for Physics at the Life Sciences Interface; Member of Steering Committee for Daresbury National Laboratory; member UK Computer Chemistry Working Party; primary reviewer for Atkins Physical Chemistry textbook.
Some indicators of research commitment at an international level, restricted to last 12 months, include: PhD examiner in Sweden and France (as well as in the UK); participant in several US DOE-sponsored meetings to advise on Future Energy Strategies; invited speaker at ICPP (Moscow); invited articles prepared for several science magazines and radio interviewee for energy conversion; appointed convenor for upcoming IUPAC Chemistry Congress.
Long-standing industrial collaboration with Procter & Gamble Inc., including research contracts with branches in the UK, Belgium and the United States, and with Pharmacyclics Inc (California, US), resulting in several patents. Recent collaboration started with the Bank of England to develop novel reagents. Among many other journals, regular reviewer for J. Am. Chem. Soc., J. Phys. Chem., J. Org. Chem., Inorg. Chem. and J. Chem. Phys..
• EPSRC - GR/R92615/01 - Promoting directional electron transfer via selective illumination into upper and lower excited states (£113,266)
• EPSRC - GR/R23305/01 - Controlling Through-Bond Electronic Coupling Via Orientation Effects (£266,435)
• EPSRC - GR/R79579/01 - Light Years Ahead: Photochemistry enters the public arena (£20,338)
• EPSRC - GR/N26869/01 - MTP: DESIGNING CHEMICAL SOLUTIONS (£200,861)
• EPSRC - GR/S00088/01 - Very long-range electron exchange in donor-connector-acceptor triads (£301,531)
• EPSRC - EP/C007727/1 - Chemistry at Newcastle (£60,000)
• EPSRC - EP/D001994/1 - Delayed Fluorescence as a New Form of Molecular Imaging (£85,402)
• EPSRC - EP/D032946/1 - Directed Electron Transfer (£327,903)
• EPSRC - EP/D053080/1 - Molecular self-repair (£266,735)
• EPSRC - GR/P02066/01 - Industrial case award (£121,350)
• EPSRC- EP/E014062/01 - The protein folding problem (£98,381)
• Leverhulme Trust – F/00125/J - Development of molecular-scale T-junction relays (£99,398)
• Procter & Gamble Company - Development of novel photoactive materials (£870,250)
Fluorescent tags and sensors for specific substrates (e.g., free radicals)
A total of 8 patents have been awarded, covering many areas of our applied photochemistry work.
Almost 100 PhD students and PDRA’s have been supervised directly by AH in the UK, USA and France. Of these, 27 have gone on to work in higher education, either in the UK or abroad. Several long-standing collaborations have been established with Lord George Porter, Sir John M. Thomas, Jean-Marie Lehn, Jean-Pierre Sauvage, Jonathan Sessler, Raymond Ziessel, Pedi Neta, Andrew Benniston, and Jan Verhoeven. These have resulted in the publication of joint work and the exchange of research personnel. Important collaborations have been established with colleagues in industry, most notably the Procter & Gamble Company, and have resulted in the award of eight international patents.
CHY101 ... General Chemistry : covers the basic concepts of concentrations, solutions, colligative properties, chemical equilibria, pH, buffers, hydrolysis, solubility product and rate expressions.
CHY120 … Elements of Physical Chemistry - Spectroscopy : covers the fundamentals of spectroscopy, including mass spectra, atomic spectra, UV-visible absorption and emission spectroscopy, vibrational and rotational spectroscopy, Mössbauer, NMR and EPR spectroscopy.
CHY220 … Intermediate Physical Chemistry - Quantum mechanics.
CHY320 … Advanced Physical Chemistry - Energetics and Dynamics : describes how molecules dissipate excess energy, the mechanisms of molecular diffusion and migration, activated complex theory, potential energy surfaces and molecular energy transfer.
CHY425 … Chemical Sensors - Luminescence : introduces the newly-emerging technique whereby luminescence spectroscopy, combined with advanced synthesis, provides ultrasensitive and highly specific protocols for recognition and quantitative analysis of solutes, even at the single molecule level.
The chemical sensors module is repeated at MSc level. This course is available for distance learning.
- Harriman A. 12th International Conference on Materials Chemistry Highlights of materials chemistry research. Johnson Matthey Technology Review 2016, 60(1), 55-58.
- Stachelek P, Harriman A. Electronic Communication in Closely-connected BODIPY-based Bichromophores. Journal of Physical Chemistry A 2016, (ePub ahead of Print).
- Al-Aqar R, Atahan A, Benniston AC, Perks T, Waddell PG, Harriman A. Exciton Migration and Surface Trapping for a Photonic Crystal Displaying Charge-Recombination Fluorescence. Chemistry: A European Journal 2016, Epub ahead of print.
- Karlsson JKG, Harriman A. Origin of the Red-Shifted Optical Spectra Recorded for Aza-BODIPY Dyes. Journal of Physical Chemistry A 2016, 120(16), 2537-2546.
- Thakare S, Stachelek P, Mula S, More AB, Chattopadhyay S, Ray AK, Sekar N, Ziessel R, Harriman A. Solvent-Driven Conformational Exchange for Amide-Linked Bichromophoric BODIPY Derivaties. Chemistry: A European Journal 2016, Epub ahead of print.
- Harriman A, Stachelek P, Sutter A, Ziessel R. A bifurcated molecular pentad capable of sequential electronic energy transfer and intramolecular charge transfer. Physical Chemistry Chemical Physics 2015, 17(39), 26175-26182.
- Harriman A. Artificial light-harvesting arrays for solar energy conversion. Chemical Communications 2015, 51(59), 11745-11756.
- Alamiry MAH, Harriman A, Haefele A, Ziessel R. Photochemical Bleaching of an Elaborate Artificial Light-Harvesting Antenna. ChemPhysChem 2015, 16(9), 1867-1872.
- Azizi S, Ulrich G, Guglielmino M, le Calvé S, Hagon JP, Harriman A, Ziessel R. Photoinduced Proton Transfer Promoted by Peripheral Subunits for Some Hantzsch Esters. Journal of Physical Chemistry A 2015, 119(1), 39-49.
- Harriman A, Stachelek P, Sutter A, Ziessel R. Stepwise photoconversion of an artificial light-harvesting array built from extended BODIPY units. Photochemical Photobiological Sciences 2015, 14(6), 1100-1109.
- Hedley GJ, Ruseckas A, Benniston AC, Harriman A, Samuel IDW. Ultrafast Electronic Energy Transfer Beyond the Weak Coupling Limit in a Proximal but Orthogonal Molecular Dyad. Journal of Physical Chemistry A 2015, 119(51), 12665-12671.
- Nano A, Retailleau P, Hagon J, Harriman A, Ziessel R. A hybrid bis(amino-styryl) substituted Bodipy dye and its conjugate diacid: synthesis, structure, spectroscopy and quantum chemical calculations. Physical Chemistry Chemical Physics 2014, 16(21), 10187-10198.
- Nano A, Ziessel R, Stachelek P, Alamiry MAH, Harriman A. Exciplex Emission from a Boron Dipyrromethene (Bodipy) Dye Equipped with a Dicyanovinyl Appendage. ChemPhysChem 2014, 15(1), 177-186.
- Bahaidarah E, Harriman A, Stachelek P, Rihn S, Heyer E, Ziessel R. Fluorescent molecular rotors based on the BODIPY motif: effect of remote substituents. Photochemical & Photobiological Sciences 2014, 13(10), 1397-1401.
- Barba-Bon A, Costero AM, Gil S, Harriman A, Sancenon F. Highly Selective Detection of Nerve-Agent Simulants with BODIPY Dyes. Chemistry - A European Journal 2014, 20(21), 6339-6347.
- Harriman A. Photo-Oxidation of Water under Ambient Conditions - The Search for Effective Oxygen-Evolving Catalysts. European Journal of Inorganic Chemistry 2014, (4), 573-580.
- Al-Aqar R, Avis D, Benniston AC, Harriman A. The Quest for Highly Fluorescent Chromophores: Evaluation of 1H,3H-Isochromeno[6,5,4-mna]xanthene-1,3-dione (CXD). RSC Advances 2014, 4(95), 53072-53078.
- Ziessel R, Ulrich G, Haefele A, Harriman A. An Artificial Light-Harvesting Array Constructed from Multiple Bodipy Dyes. Journal of the American Chemical Society 2013, 135(30), 11330-11344.
- Nano A, Ziessel R, Stachelek P, Harriman A. Charge-Recombination Fluorescence from Push-Pull Electronic Systems Constructed around Amino-Substituted Styryl-BODIPY Dyes. Chemistry - A European Journal 2013, 19(40), 13528-13537.
- Alamiry MAH, Bahraidah E, Harriman A, Olivier JH, Ziessel R. Influence of applied pressure on the probability of electronic energy transfer across a molecular dyad. Pure and Applied Chemistry 2013, 85(7), 1349-1365.
- Hablot D, Ziessel R, Alamiry MAH, Bahraidah E, Harriman A. Nanomechanical properties of molecular-scale bridges as visualised by intramolecular electronic energy transfer. Chemical Science 2013, 4(1), 444-453.
- Harriman A, Alamiry MAH, Hagon JP, Hablot D, Ziessel R. Through-Space Electronic Energy Transfer Across Proximal Molecular Dyads. Angewandte Chemie: International Edition 2013, 52(26), 6611-6615.
- Stewart B, Harriman A, Higham LJ. Air-stable chiral primary phosphines part (ii) predicting the air-stability of phosphines. In: Fairlamb, I.J.S., Lynam, J.M, ed. Specialist Periodical Reports: Organometallic Chemistry. London, UK: Royal Society of Chemistry, 2012, pp.36-47.
- Iehl J, Nierengarten JF, Harriman A, Bura T, Ziessel R. Artificial Light-Harvesting Arrays: Electronic Energy Migration and Trapping on a Sphere and between Spheres. Journal of the American Chemical Society 2012, 134(2), 988-998.
- Alamiry MAH, Benniston AC, Harriman A. Effect of Pressure on the Solubilization of a Fluorescent Merocyanine Dye by a Nonionic Surfactant. Journal of Physical Chemistry Part B 2012, 116(1), 253-260.
- Harriman A. Faraday Discussion 155: Artificial Photosynthesis. Platinum Metals Review 2012, 56(1), 20-24.
- Alamiry MAH, Bahaidarah E, Harriman A, Bura T, Ziessel R. Fluorescent molecular rotors under pressure: synergistic effects of an inert polymer. RSC Advances 2012, 2(26), 9851-9859.
- Alamiry MAH, Benniston AC, Copley G, Harriman A. Freezing and glass transition phenomena for 1,2-dichloroethane under high pressure as revealed by fluorescence spectroscopy. RSC Advances 2012, 2(5), 1936-1941.
- Alamiry MAH, Hagon JP, Harriman A, Bura T, Ziessel R. Resolving the contribution due to Förster-type intramolecular electronic energy transfer in closely coupled molecular dyads. Chemical Science 2012, 3(4), 1041-1048.
- Olivier JH, Barbera J, Bahaidarah E, Harriman A, Ziessel R. Self-Assembly of Charged Bodipy Dyes To Form Cassettes That Display Intracomplex Electronic Energy Transfer and Accrete into Liquid Crystals. Journal of the American Chemical Society 2012, 134(14), 6100-6103.
- Harriman A. Anthony Harriman. Chemistry World 2011, 8(2), 37.
- Hedley GJ, Ruseckas A, Harriman A, Samuel IDW. Conformational Effects on the Dynamics of Internal Conversion in Boron Dipyrromethene Dyes in Solution. Angewandte Chemie: International Edition 2011, 50(29), 6634-6637.
- Benniston AC, Harriman A, Yang S, Harrington RW. Highly-Strained Cyclophanes Bearing Both Photo- and Electro-Active Constituents. Tetrahedron Letters 2011, 52(41), 5315-5318.
- Alamiry MAH, Benniston AC, Copley G, Harriman A, Howgego D. Intramolecular Excimer Formation for Covalently Linked Boron Dipyrromethene Dyes. Journal of Physical Chemistry A 2011, 115(44), 12111-12119.
- Le Pleux L, Pellegrin Y, Blart E, Odobel F, Harriman A. Long-Lived, Charge-Shift States in Heterometallic, Porphyrin-Based Dendrimers Formed via Click Chemistry. Journal of Physical Chemistry A 2011, 115(20), 5069-5080.
- Stewart B, Harriman A, Higham LJ. Predicting the Air Stability of Phosphines. Organometallics 2011, 30(20), 5338-5343.
- Hablot D, Harriman A, Ziessel R. Using a Photoacid Generator to Switch the Direction of Electronic Energy Transfer in a Molecular Triad. Angewandte Chemie: International Edition 2011, 50(34), 7833-7836.
- Benniston AC, Harriman A, Mehrabi M, Rostran S, McCulloch IE, Sams C. Photophysical Properties of a Bis-Oxonol Dye. Journal of Photochemistry and Photobiology A: Chemistry 2004, 163(1-2), 61-67.
- Amini A, Harriman A. Computational methods for electron-transfer systems. Journal of Photochemistry and Photobiology C: Photochemistry Reviews 2003, 4(2), 155-177.
- Amini A, Harriman A. Computational methods for electron-transfer systems. Journal of Photochemistry and Photobiology C: Photochemistry Reviews 2003, 4(2), 155-177.
- Harriman A. Photophysical Processes in Condensed Phases. Photochemistry 2002, 33, 13-49.
- Harriman A. Photophysical processes in condensed phases. Photochemistry 2001, 32, 13-46.
- Harriman A, Khatyr A, Ziessel R, Benniston AC. An Unusually Shallow Distance-Dependence for Triplet-Energy Transfer. Angewandte Chemie International Edition 2000, 39(23), 4287-4290.
- Harriman A, Khatyr A, Ziessel R, Benniston AC. An unusually shallow distance-dependence for triplet-energy transfer. Angewandte Chemie - International Edition 2000, 39(23), 4287-4290.
- Dieleman CB, Matt D, Harriman A. Coordination chemistry of calix-phosphanes: Cooperativity in the assembly of a tetragold calixarene complex. European Journal of Inorganic Chemistry 2000, (5), 831-834.
- Ziessel R, Harriman A, El-ghayoury A, Douce L, Leize E, Nierengarten H, Van Dorsselaer A. First assembly of copper(I) naphthyridine-based helicates. New Journal of Chemistry 2000, 24(10), 729-732.
- El-ghayoury A, Harriman A, Ziessel R. Intercompartmental Electron Exchange in Geometrically-Constrained Ru-Os Triads built around Diethynylated Aryl Hydrocarbons. Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory 2000, 104(33), 7906-7915.
- El-ghayoury A, Harriman A, Khatyr A, Ziessel R. Intramolecular Triplet Energy Transfer in Metal Polypyridine Complexes Bearing Ethynylated Aromatic Groups. Journal of Physical Chemistry A 2000, 104(7), 1512-1523.
- Juris A, Prodi L, Harriman A, Ziessel R, Hissler M, El-ghayoury A, Wu F, Riesgo EC, Thummel RP. Mono- and dinuclear ruthenium(II) and osmium(II) polypyridine complexes built around spiro-bridged bis(phenanthroline) ligands: Synthesis, electrochemistry, and photophysics. Inorganic Chemistry 2000, 39(16), 3590-3598.
- Knight JG, Doherty S, Harriman A. Remarkable differences in catalyst activity and selectivity for the production of methyl propanoate versus CO-ethylene copolymer by a series of palladium complexes of related C4-bridged diphosphines. Organometallics 2000, 19(24), 4957-4967.
- Benniston AC, Gardner S, Farrugia LJ, Harriman A. Structure and photophysical properties of constrained donor-acceptor catenanes bearing an appended secondary donor. Journal of Chemical Research 2000, 2000(8), 360-361.
- Armspach D, Matt D, Harriman A. The first Ru(II) bipyridyl-capped cyclodextrin: Evidence of electron- transfer through the cavity. European Journal of Inorganic Chemistry 2000, 2000(6), 1147-1150.
- Harriman A, Wipff G, Ziessel R, Hissler M. Conformational control of intramolecular electron transfer in calixdiquinones and their cationic complexes. Journal of the American Chemical Society 1999, 121(1), 14-27.
- Harriman A. Electron tunneling in DNA. Angewandte Chemie-International Edition 1999, 38(7), 945-949.
- Harriman A, Ziessel R, Hissler M, Trompette O. Energy transfer in molecular dyads comprising metalloporphyrin and ruthenium(II) tris(2,2 1 -bipyridyl) terminals. Competition between internal conversion and energy transfer in the upper excited singlet state of the porphyrin. Journal of the American Chemical Society 1999, 121(11), 2516-2525.