RUI: CAS: Alkynyl Complexes of Titanium(IV) and Platinum(II): Phosphors, Photocatalysts, and Fundamental Photophysics

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In this RUI project, funded by the Chemical Structure, Dynamics & Mechanism B Program of the Chemistry Division, Professor Paul Wagenknecht of the Department of Chemistry at Furman University is developing new transition-metal alkynyl complexes for use as photocatalysts and as phosphors. Transition-metal photocatalysts are crucial components in organic synthesis and in systems for the conversion of solar energy into electricity and/or chemical fuels. Professor Wagenknecht aims to use complexes of earth-abundant elements to replace precious metal photocatalysts. Transition-metal phosphors are essential components of organic light-emitting diodes (OLEDs). The development of phosphors for OLEDs in Professor Wagenknecht’s group involves a set of complexes designed to enhance blue emission, which remains a technical challenge. These complexes also show promise for the development of single-component white OLEDs (WOLEDs). Students involved in the proposed activities will be trained in methods directly related to device chemistry and the conversion of solar energy to stored chemical energy. This will result in the development of a STEM workforce prepared to solve problems of serious social significance. Students in the Professor Wagenknecht’s laboratory are also active in after-hours tutoring programs and/or providing chemistry demonstrations to local elementary and middle schools. They are also active in outreach to high school students and high school teachers. Recent reports demonstrate that complexes of earth-abundant metals with ligand-to-metal charge transfer excited states represent a new class of possible photocatalysts. Titanocenes previously developed in Professor Wagenknecht’s laboratory have proven to be a synthetically accessible class of compounds with excited-state redox potentials appropriate for use as photocatalysts and as dyes for dye-sensitized solar cells (DSSCs). New alkynyl-titanocenes with rigid structures and/or with Cu(I) coordinated between the alkynes are proposed to have higher stability and longer excited-state lifetimes and will be compared to those without such modification. This could lead to a stronger understanding of the photophysical principles necessary to design first-row transition-metal sensitizers. Professor Wagenknecht’s group has developed a titanocene precursor with carboxylate anchoring groups so that a range of titanocenes can be prepared and appended to titanium dioxide to investigate their possible use as sensitizers in DSSCs and investigate principles of charge injection. The Pt-alkynyl complexes proposed are being prepared to mechanistically investigate the role of the trifluoropropynyl ligand in blue-shifting emission while maintaining high phosphorescence quantum yields. Furthermore, the interplay between the blue monomer emission and the orange excimer emission will be investigated for possible applications in WOLED devices. These activities are supported by a robust computational component.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.