ALAN B. BROWN

A.B., Middlebury College, 1979
Ph.D., University of Wisconsin-Madison, 1986
NIH Fellow, Columbia University, 1986-1988

Email:abrown@fit.edu
Phone: (321) 674-7433

Office: 322 Olin Physical Sciences Building

RESEARCH INTERESTS

Structural organic chemistry: the interplay of macroscopic properties and molecular structure.

The development of molecular sensors is the focus of great interest world-wide.  Our program in this area is a collaboration with Clayton Baum's group, and shows how fundamental science can broaden into applied work.  Carbazoles fluoresce; the fluorescence is quenched by several hydrogen-bond acceptors including pyridine.  To test whether the carbazole-pyridine hydrogen bond is directly involved in quenching, or acts simply as a "hook", we prepared 1 and 2. 

Each contains one carbazole grouping and one pyridine, in proximity; 1 can form an intramolecular hydrogen bond, but 2 cannot.  As expected, the fluorescence of 1 is quenched; however, 2 retains fluorescence (we think: 2 is hard to purify!).  Further, excess ammonia (or a hydrazine) restores the fluorescence of 1, by disrupting the hydrogen bond.  Two conclusions follow: (1) the hydrogen bond is directly involved in quenching; (2) calibration of fluorescence intensity versus analyte concentration lets 1

Second-generation sensors might involve quenching by acridine (3), whose energy levels differ from those of pyridine; tuning of hydrogen-bond strength via substitution on the pyridine ring (4); or a larger cavity (5).  The same principles can extend to sensors for other hydrogen-bonding analytes. 

There are some similarities, but there are more differences, between the chemistries of phosphorus and carbon. However, vinylphosphine oxides (C=C-P=O) resemble α,β-enones: e.g., both groupings undergo conjugate addition. In collaboration with György Keglevich (Budapest University of Technology and Economics), we are probing the extent of this resemblance, by exploring the photochemistry of vinylphosphine oxides. Since cyclopentenone photodimerizes, our first study is of the potential dimerization of a phosphorus analogue, 6. (Many dimers are possible; only one is shown.) Future studies will include possible [2+2] cycloadditions of 6 with alkenes, and more highly "conjugated" phosphorus compounds such as 7.

Other research in progress includes extensive theoretical studies of annulation effects, particularly on valence isomerism of aromatics, in collaboration with Paul Kiprof (University of Minnesota - Duluth), and improvements on various organic synthetic methodologies.  I am also interested in unconventional applications of NMR spectroscopy, e.g. to whole-animal studies of live fish.

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