In this project funded by the Chemical Structure, Dynamics and Mechanism (CSDM-B) Program of the Chemistry Division, Marcin Ptaszek from the University of Maryland, Baltimore County will synthesize and study electronic, optical, and photochemical properties of strongly conjugated bacteriochlorin arrays. Bacteriochlorins, which are tetrapyrrolic macrocycles, exhibit strong absorption and emission in the near-infrared spectral window (700-800 nm) and a high yield of singlet oxygen photosensitization; hence they are attractive for a variety of imaging and therapeutic applications. Assembling of bacteriochlorins into strongly conjugated dyads with linkers, which allow extensive electronic communications between bacteriochlorin subunits, results in pronounced alteration of their electronic, optical, and photochemical properties. The goals of the proposed research are to develop an understanding of structure-photophysics relationships in conjugated bacteriochlorin arrays, and to establish their feasibility for ultimately developing long-wavelength fluorophores and activatable singlet oxygen photosensitizers with potential in vivo imaging and therapeutic utility. The influence of the arrays' structure on the absorption and emission wavelengths, quantum yields of fluorescence and intersystem crossing, and intramolecular charge transfer will be studied in detail. Subsequently, activation of fluorescence and singlet oxygen photosensitization by the conversion of strongly into weakly conjugated bacteriochlorin arrays, induced by well-defined chemical transformation, will be studied. The proposed research will provide much deeper understanding of the basic photochemical properties of bacteriochlorin arrays, and greatly expand their potential as diagnostic and therapeutic agents.
The proposed research will advance our understanding of fundamental physicochemical properties of novel molecular architectures, strongly absorbing light in the near-infrared region. This basic research will ultimately lead to the development of novel, light-activated diagnostic and therapeutic agents, which diagnostic and therapeutic functions will be activated only in the target cells. The broader impact of proposed research also includes engagement of graduate, undergraduate, and high school students in highly interdisciplinary research, spanning molecular design, organic synthesis, spectroscopy, photochemistry, and biochemistry. A workshop presenting a fundamental role of photosynthetic pigments in nature, and their diverse applications, ranging from energy-related science to medicine, will be developed and offered for high school students.
