- Main-group catalysis
- Synthetic methodology
- New sensitizers for photodynamic therapy
- Dendrimer catalysts
- Ph.D., The Ohio State University 1977 (Organic Chemistry)
Main-group Catalysis, Synthetic Methodology, New sensitizers for photodynamic therapy, Dendrimer Catalysts
A. Synthesis and Properties of Infrared-Absorbing Dyes
The group has several projects related to the synthesis of novel dye chromophores, exploration of chemical and photophysical properties of these chromophores, and application of these dyes to "solving" chemical problems. One such problem is Photodynamic Therapy (PDT), a fairly new approach to the treatment of cancer in which a tumor-specific dye is irradiated to produce a cytotoxic reagent (singlet oxygen, superoxide, radical species) or reaction (cross-linking) in or around the cancer cell. Human tissue is most transparent to wavelengths of light between 700 nm (beyond hemoglobin) and 1100 nm (infrared harmonics of water). New dyes for PDT must balance absorption, singlet-oxygen production, solubility, and hydrolytic stability to produce a clinically attractive drug.
A second project involves the design of infrared-absorbing chromophores for the production of heat. Typical applications of dyes include emission (fluorescence or luminescence), bleaching, photoinduced electron-transfer, triplet production, and the generation of heat. We are interested in the optimization of each of these processes in the design of chromophores. Many graphic arts applications require laser-induced generation of heat. We are designing chromophores to give efficient generation of heat at wavelengths compatible with 830-nm, 900-nm, 1064-nm, and 1100-nm lasers. Representative absorption spectra for several near infrared-absorbing dyes can be found on this web page.
B. Synthetic Enzymes and Redox Catalysts
Diorganoselenides and tellurides undergo reversible two-electron redox processes based on oxidative-addition and reductive-elimination catalysts. These cycles are the basis for the construction of synthetic enzymes which mimic horseradish peroxidase or the haloperoxidases for the activation of hydrogen peroxide, templates for chiral halogenations, and templates for the kinetic resolution of enantiomeric mixtures of vicinal dihalides through dehalogenation reactions. Other dihydrochalcogenopyranyl substrates mimic NADH and related hydride transfer reagents. We are currently developing chiral derivatives for chiral reductions.
C. Dyes with "Switchable" Photophysical Properties
The pyrylium and xanthylium dyes have been shown to bind to a variety of biopolymers including DNA, RNA, and proteins. Upon binding, the fluorescence quantum yields increase for these two classes of compounds because binding reduces the rate of internal conversion. We are interested in the synthesis of thio-, seleno-, and telluro-analogues of these dye classes. Not only fluorescence, but also intersystem crossing to the triplet should be more competitive following binding to a biopolymer. Such “switchable” dyes offer new opportunities for biosensing, diagnostic, and phototreatment platforms.
D. New Registration Systems for Biosensing Applications
The ultimate purpose for this research is to develop a new generation of biosensing/registration platforms for real-world sensing applications in a collaborative effort between our group and Prof. Frank Bright's group in the Department of Chemistry at SUNY Buffalo. There have been numerous biosensing/bioassay platforms developed over the years to detect and quantify analytes in complex samples. Unfortunately, all current systems are limited because they are not universal, suffer from background signals that bias the measurements, and/or they are somewhat difficult to manufacture. We propose an entirely new approach to circumvent the aforementioned problems and aim to develop a new generation of biosensing/registration platforms that exploit the tailored recognition/switching dye chemistry pioneered by the Detty group and the Bright group's expertise in sol-gel-derived composite materials, analytical biosensing, protein biophysics, and optical spectroscopy.
Selected Recent Publications