Metal-Arylisocyanide Chromophores for Photoredox Chemistry and Imaging

California Institute Of Technology, Pasadena CA

Investigators

Abstract

In this project, funded by the Chemical Structure, Dynamics and Mechanisms B Program of the NSF Chemistry Division, Professors Harry B. Gray and Jay R. Winkler of the Division of Chemistry and Chemical Engineering at the California Institute of Technology (Caltech) are developing a class of luminescent transition metal complexes with exceptional properties for applications in organic synthesis and biological imaging. Both organic synthesis and biological imaging are important in developing cures for diseases. A strong STEM outreach program, the solar energy activity labs, was developed under prior NSF support. In this grant period, Professors Gray and Winkler, their postdoctoral scholars, graduate students, and undergraduates will continue their participation in this effort to translate and transfer the essence of Caltech research for the purpose of increasing public awareness and understanding of basic science and engineering principles. Preliminary research has revealed that homoleptic tungsten arylisocyanide complexes display remarkable spectroscopic and photophysical properties. These molecules have high 1-photon absorption extinction coefficients (ten to the power of 5), luminesce with quantum efficiencies as high as 25%, and have excited-state lifetimes longer than 1 microsecond. Of particular note are their two-photon absorption cross sections at 811 nm, a property of great importance in biological imaging. These cross sections are 10-100 times greater than many commercial 2-photon dyes. Several new groups of transition metal arylisocyanides are designed to enhance the spectroscopic and photophysical properties of this class of luminescent molecules. Four types of fused-ring arylisocyanide ligands will be prepared based on naphthyl-, phenanthryl-, biphenylene and triphenylene ring systems. The new arylisocyanide ligands will be coordinated to transition metals from groups 6, 7 and 8. New molecules will be structurally characterized by X-ray crystallography whenever feasible. The 1- and 2-photon absorption properties of the molecules will be evaluated and the excited-state lifetimes and quantum yields of all luminescent molecules will be determined. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.