The Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division supports the project by Professor Jayawickramarajah, of the Department of Chemistry at Tulane University. Dr. Jayawickramarajah is developing an synthetic approach to make precisely controlled mutli-porphyrin arrays in water. The goal of this research is to design a system of 2-dimensional cyclic structures to form 3-dimensional cylinders that can improve light absorption and direction for electron transfer. The project uses a process called self-assembly, where the synthetic color molecules (porphyrins) spontaneously form the desired 3D architectures by mixing of carefully chosen components. Further, the project utilizes water (an abundant and non-toxic liquid) as the medium for the reaction. In addition to increasing our fundamental understanding of molecular assembly and light-collection, this project also includes an outreach component that focuses on enhancing the interest of K-12 students in chemistry and science.
The construction of defined 3D cylinders composed of multiple rungs of 2D cyclic chromophore arrays is attractive for photonic applications since such 3D architectures may provide enhanced light absorption, and directionality for excitation energy transfer (EET). The porphyrin rings can be packed densely onto functional solid substrates. The research team synthesizes the components and then studies the assembly of the cylinders in water. The strategy harnesses an array of supramolecular assembly modes, including cation-induced guanosine or isoguanosine oligonucleotide hybridization to form cylindrical quadruplexes and pentaplexes. Importantly, the researchers propose to position unique chromophores at specific sites along the cylinders to achieve directional EET. The light-harvesting porphyrins are precluded from undergoing detrimental self-stacking and thus exhibit superior photophysical properties. These properties are analyzed via steady-state and time-resolved fluorescence measurements that are conducted in collaboration with the Rubtsov and Schmehl research groups. The outreach plan includes a service-learning course pioneered by Professor Jayawickramarajah and focuses on undergraduates from Tulane conducting chemistry-centered service learning activities at inner-city New Orleans public schools.
