Symposium: Applications of Inorganic Photochemistry
Symposium: Applications of Inorganic Photochemistry
Applications of Inorganic Photochemistry in the Chemical and Biological Sciences—Contemporary Developments
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Kirk S. Schanze Department of Chemistry, University of Florida, Gainesville, FL 32611-7200 Russell H. Schmehl Department of Chemistry, Tulane University, New Orleans, LA 70118-5698 In the early 1980s this photochemistry narrowed as hybrid inorganic systems were Journal published a series of developed. One example is the class of nanocrystalline semi“State of The Art” issues, in conductors, specifically prepared clusters having on the orwhich pedagogical articles der of a few hundred atoms that exhibit photophysical bediscussing basic principles havior between that of bulk semiconductors and discrete and recent advances in a vamolecular species. Hybrid materials have also been preriety of chemical subdiscipared by covalently linking transition metal complexes to plines were gathered. One of make clusters that exhibit behavior reflecting extended inthese dealt with advances in termetallic interactions. Traditional transition metal cominorganic photochemistry (1). plexes having well characterized photophysical and photoThe issue was based upon a chemical behavior began to be used in a variety of applicasymposium organized by tions such as luminescence sensors, photoreactive polymers, Morton Hoffman of Boston and semiconductor sensitizers. These changes reflect the University and held at the fact that the study of photochemical and photophysical Seattle meeting of the Ameriproperties of inorganic substances has matured to the point can Chemical Society in 1983. The articles published in the that fundamental principles can be exploited in the develJournal provide an excellent introduction to the basic prinopment of more complex chemical systems and in very parciples of spectroscopy and photophysics of inorganic molticular applications. ecules as well as a discussion of the photochemistry of parBecause of these changes we were motivated to conduct ticular molecular systems being actively investigated at the a second symposium, which brought together individuals time. The collection of articles remains to this day an excelfrom a broad range of interdisciplinary areas that make use lent resource to introduce students to the concepts of inorof inorganic photochemistry. The articles collected herein ganic photochemistry. stem from a symposium sponsored jointly by the Division In his introduction to the series in 1983, Hoffman deof Chemical Education and the Division of Inorganic Chemfined inorganic photochemistry as relating to “the interacistry at the American Chemical Society meeting held in Ortion of photons with substances regarded as ‘inorganic’ ”. He lando, Florida, in August 1996. The two-day symposium fothen proceeded to provide a narcused on applications of rower description that would fit the inorganic photochemistry focus of the symposium: “ …the into three general areas: teraction of visible and ultraviolet biological chemistry, lulight with metal complexes and orminescence sensors, and ganometallic compounds, largely advanced materials. In but not exclusively in solution and the first two areas, classilargely but not exclusively at room cal coordination comtemperature”. Since the 1983 symplexes have been utilized posium, research in inorganic phocreatively in a variety of tochemistry has continued at a applications ranging from brisk pace and new and exciting arunderstanding electron eas have evolved. From the undertransfer reactions in biostanding of the photophysics and logical macromolecules to photochemistry of monometallic evaluating aerodynamic transition metal complex chroflow over aircraft wings. Electron transfer reactions in mophores sprang the evolution of Inorganic chemists with a proteins (Durham et al. p 636) what are known as supramolecular variety of specializations, photochemical systems, discrete including organometalmolecular ensembles of two or more chromophores designed lics, solid-state chemistry, and classical transition metal to perform a function unique to the system (2). In addition, chemistry have contributed to the development of new highthe gap between solid-state photophysics and molecular technology materials.
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Symposium: Applications of Inorganic Photochemistry
Luminescence sensors (Sullivan et al. p 685)
Inorganic photochemistry and nucleic acids (Thorp et al. p 641)
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Applications of inorganic photochemistry to chemical sensing (Ellis p 680)
Only one of the authors contributing to this collection wrote an article for the 1983 “State of the Art” issue. However, most of the authors of the articles presented here were either graduate students or postdoctoral associates of one of the earlier contributors. This collection begins with a discussion of particular applications to biological sciences. The article by Bill Durham and co-workers focuses on the use of Ru(II) diimine complexes as sensitizers for triggering electron transfer reactions in proteins. This is followed by an introduction to the use of bimetallic Pt(II) complexes in the cleavage and footprinting of DNA, as presented by Holden Thorp. An area of intense current interest is photoinduced electron transfer reactions of chromophores that intercalate into DNA. Thomas Netzel’s article outlines the
general arguments and presents a summary of some current results in this area. The focus then switches to applications related to the development of new materials. In his article on light-to-electricalenergy conversion, Gerald Meyer illustrates how various transition metal complex chromophores can be used as sensitizers for charge injection into nanocrystalline semiconductors in photoelectrochemical cells. This is followed by a discussion by Joseph Hupp of fundamental aspects of the charge injection process into nanocrystalline semiconductors. Next, Andrew Bocarsly discusses inorganic approaches to the development of new materials for photolithography and pattern generation at interfaces using complexes of Pt(II) Electron transfer reactions and Fe(II). The focus switches in DNA (Netzel p 646) to applications of organometallic complexes and is described here by David Tyler; he illustrates novel approaches to generating polymers that photodegrade to yield environmentally benign products. The final article of this section, by Raymond Ziessel, illustrates fundamental work directed toward the use of supramolecular transition metal complexes in the development of stillunrealized nanoscale electronic devices. The final section of this discussion of developments in inorganic photochemistry involves applications of luminescent inorganic materials and complexes to chemical sensing. The use of luminescent semiconductors in the detection of various organic vapors is discussed by Arthur Ellis, whose group is largely responsible for defining this chemistry. The final three articles discuss applications of luminescent transition metal complexes of Ru(II) and Re(I) in chemical sensing. In his article, Patrick Sullivan illustrates how ion intercalation into crown ethers covalently linked to luminescent Re(I) complexes can provide a basis for analyzing levels of specific metal ions in solution. James Demas then
Luminescence of pressure sensitive paint for wind tunnel research (Gouterman p 697)
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Journal of Chemical Education • Vol. 74 No. 6 June 1997
Symposium: Applications of Inorganic Photochemistry
Oxygen sensing by luminescence quenching (Demas et al. p 696)
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Photo-induced energy or electron transfer in supramolecular systems (Ziessel p 673)
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Generating photodegradable polymers (Tyler p 668)
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demonstrates applications of particular Ru(II) diimine complexes in pH and pO2 measurement. Demas also includes an experiment that illustrates the utility of luminescence quenching by molecular oxygen in sensor development. Finally, Martin Gouterman shows how the oxygen-sensing ability of luminescent Ru(II) complexes is exploited in aircraft design! Overall, the collected works presented here are meant to provide readers with a general picture of the types of applications that have evolved from the fundamental knowledge base of inorganic photochemistry, and no effort has been made to comprehensively cover this research area. Since applications are generally interdisciplinary extensions of the basic science, the range of existing and potential applications of inorganic photochemistry extends far beyond the domains selected as focus points in this collection. We hope that this series of articles will serve to illustrate that as basic science in a particular area matures, it gives rise to applications that could not have been envisioned before the research area was developed.
Charge injection process (Hupp et al. p 657)
Photolithography and pattern generation (Bocarsly et al. p 663)
Acknowledgment Finally, we would like to acknowledge those who have supported this endeavor. First are the authors. The persons contributing to this collection took the time, made the effort, and, for the most part, bore the expense of participating in the symposium and preparing thoughtful, well organized manuscripts. We would also like to thank Morton Hoffman, who provided us with guidance in the initial stages of planning. In addition, we were fortunate to receive financial support for the symposium from the Petroleum Research Fund of the American Chemical Society, the Division of Chemical Education, and UVTech Associates. Finally, we would like to express our special thanks to Glenn Crosby of Washington State University for providing an insightful review of the entire symposium in print. Literature Cited 1. Inorganic Photochemistry: State of the Art; Hoffman, M. Z., Ed. J. Chem. Educ. 1983, 60, 784–887. Also available as a reprint book from Journal of Chemical Education Subscription and Book Order Department, P. O. Box 606, Vineland, NJ 08360; Order No. IN1. 2. Balzani, V.; Scandola, F. Supramolecular Photochemistry; Ellis Horwood: New York, 1991.
Efficient light-to electrical energy conversion: nanocrystalline TiO 2 films modified with inorganic sensitizers (Meyer p 652)
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