Research
Research
Faculty Research
Jeff Nagle
Our work focuses on experimental and computational studies of the photochemistry and photophysics of luminescent platinum group molecules. Much of this effort is devoted to understanding excited state electron, energy, and atom transfer reactions, as well as exciplex (excited state complex) and excimer (excited state dimer) formation. We use optical (absorption, emission, and excitation) spectroscopies, pulsed-laser excited state lifetime measurements, and cyclic voltammetry methods to evaluate potential photocatalysts in such schemes and to test modern theories of electron transfer. Excited state reactions lie at the heart of all molecular-based solar energy conversion schemes, including photosynthesis.
An example of the type of compound we work with is provided by the Pt2(P2O4H2)44– ion (Figure 1). 
This fascinating species absorbs light in the visible region of the spectrum, resulting in an intense green luminescence in water or solids (Figures 2 and 3). It also takes part in a rich array of photochemical reactions, including interactions with DNA, and exhibits an enhanced tendency to bond to other heavy metal atoms such as silver, gold, and thallium. Such bonding interactions result in the formation of luminescent metal-metal bonded exciplexes, an area of research which my students and I have pioneered over the past several years at Bowdoin.
Such metal-metal bond formation processes involving heavy metal atoms are strongly influenced by relativistic effects. Einstein's theory of special relativity describes the behavior of particles that move at speeds approaching that of light. The electrons in platinum and related atoms provide examples of such particles, and as a consequence molecules containing these atoms experience substantial relativistic effects in their interactions with light and other atoms. We use a commercial computational program, the Amsterdam Density Functional (ADF) program to do electronic structure calculations that confirm the importance of these effects in heavy metal containing molecules.
