Session: COMP Poster Session:

Europium(III)-based luminescent complexes promise extensive potential applications in immunoassay technology, high throughput drug screening, organic light emitting diodes, and biomedical imaging. Europium metal-ligand complexes exhibit unique luminescent properties including monochromatic emission with a well-defined emission maximum at 614nm, long luminescent lifetimes enabling time-resolved measurements, minimal photobleaching, and large Stokes shifts. Ligand design for enhancing the luminescence of europium complexes is currently active. Electronic structure calculations can support the molecular design of europium complexes with improved optical properties. Here, we report the structural and spectroscopic properties of a series of europium(III) complexes containing fluorobenzoic acid derivatives using density functional theory calculations. The absorption maximum wavelength shows a blue shift upon increasing the ligand fluorination. Excited state energy gaps of the complexes were found to be sensitive to the identity and the position of the ligand substituents. A nitro substitution results in a decrement of the vertical excited states, significantly reducing the luminescent quantum yield. The inter-system crossing energy gap is strongly regulated by the position of the ligand substituent. It is significantly reduced by having substituents closer to the metal coordination site. The optimum energy gaps resulting enhanced luminescent quantum yields were identified. The correlation among the calculated electronic energy levels and the experimental luminescent quantum yields will be discussed in order to provide insight into designing highly luminescent europium complexes.

Matteo Fratarcangeli

Western Carolina University

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