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Dr John Moore

01904 322548
Email: john.moore@york.ac.uk

Spectroscopy and Photochemistry in Solution

Our interests centre on the spectroscopy and photochemistry of molecules in solution, including the use of pulsed lasers to observe excited states and reactive intermediates in real time.

Our research has included studies of photoisomerisation, photodissociation, electron-transfer, energy-transfer, and photophysical mechanisms, and the observation of excited states, radicals, and other intermediates in organic, inorganic, and biochemical systems, as well as the development of laser techniques.

Our current interests centre on two areas:

1. Light-controlled ion switches

   Ion signalling is ubiquitous in nature. Calcium signalling, especially, is used to regulate many processes, including muscle contraction and neuron activity. We have been developing and studying "artificial" ion-signalling systems: our interests are in light-controlled ion switches which complex metal cations in solution and then release them when triggered to do so by light.

   

   Our research has included all-organic systems in which ion-switching is based on photoisomerisation, and it has extended to organometallic systems, where photoinduced electron-transfer and energy-transfer mechanisms can also be important. We use a range of steady-state spectroscopic techniques to study these molecules and their complexes with metal cations in the ground state. We then use time-resolved laser techniques to study their excited states, in some cases enabling us to observe complete ion release-and-recapture cycles in real time.

2. Photochemistry of organic dyes

   Dyes and inks need to retain their colour when they are exposed to ambient room-light and sun-light. Unfortunately, many of the dyes which give the brightest colours also fade relatively quickly, and this photofading often occurs much more quickly when the dyes are deposited onto molecular surfaces such as cellulose, as found in paper and cotton. This problem can be particularly acute for dyes used in areas of new technology, such as ink-jet printing.

   Our research focuses on two general areas, and includes studies of azo and xanthene dyes. We study how these dyes interact with molecular surfaces, such as cellulose, by applying a range of steady-state spectroscopic techniques to explore how the structures of the dyes are affected by their solvent and surface environments. We then use laser excitation and time-resolved laser techniques to study the photochemical reaction mechanisms of these dyes, both in solution and on surfaces.

   The techniques we use include UV-visible absorption and emission, IR absorption, resonance Raman, NMR, and ESR spectroscopy, allied with computational modelling and detailed data analysis. We use a wide range of lasers, including continuous-wave lasers for steady-state studies, and nanosecond and pico/femtosecond lasers for time-resolved UV-vis absorption, emission, IR, resonance Raman, and temperature-jump studies.
   

Selected Publications

• Experimental and computational studies of structure and bonding in parent and reduced forms of the azo dye Orange II.
  L C Abbott, S N Batchelor, J Oakes, B C Gilbert, A C Whitwood, J R Lindsay Smith and J N Moore, J Phys Chem A, 2005, 109, 2894-2905.
• Light-controlled ion switching: direct observation of the complete nanosecond release and microsecond recapture cycle of an azacrown-substituted [(bpy)Re(CO)3L]⁺ complex.
  J D Lewis, R N Perutz and J N Moore, J Phys Chem A, 2004, 108, 9037-9047.
  
• Semi-empirical and ab initio studies of the structure and spectroscopy of the azo dye Direct Blue 1: comparison with experiment.
  L C Abbott, S N Batchelor, J Oakes, J P Lindsay Smith and J N Moore, J Phys Chem A, 2004, 108, 10208-10218.
  
• Spectroscopic studies of the intermolecular interactions of a bis-azo dye, Direct Blue 1, on di- and trimerisation in aqueous solution and in cellulose.
  L C Abbott, S N Batchelor, J Oakes, J P Lindsay Smith and J N Moore, J Phys Chem B, 2004, 108, 13726-13735.
  
• Infrared and resonance Raman studies of metal cation sensors in which an azacrown ether is linked to (bpy)Re(CO)₃ via an alkenyl or alkynyl spacer.
  J D Lewis and J N Moore, Phys Chem Chem Phys,2004, 6, 4595-4606.
• Photoinduced Ba²⁺ release and thermal rebinding by an azacrown ether linked by a alkynyl pyridine to a (bpy)Re(CO)₃ group.
  J D Lewis and J N Moore Chem Commun, 2003, 2858-2859.
  
• Resonance Raman spectroscopy of photolabile transition metal carbonyls: controlled photoalteration with continuous wave lasers to record spectra of reactants or transient species.
  L C Abbott, C J Feilden, C L Anderton and J N Moore, Appl Spectrosc, 2003, 57, 960-969.
• Picosecond forward electron transfer and nanosecond back electron transfer in an azacrown-substituted [(bpy)Re(CO)₃(L)]⁺ complex: direct observation by time-resolved UV-visible absorption spectroscopy.
  J D Lewis, L Bussotti, P Foggi, R N Perutz and J N Moore J Phys Chem A, 2002, 106, 12202-12208.
  
• A cation-specific, light-controlled transient chromoionophore based on a benzothiazolium styryl azacrown ether dye.
  I K Lednev, R E Hester and J N Moore J Am Chem Soc, 1997, 119, 3456-3461.