Highly-Sensitive Dual-Mode Luminescence Manometer Based on a Novel Organic Complex Material - Eu(bpyO2)4(PF6)3

The advancement of ultra-sensitive optical manometers is crucial for exploring the behavior of materials under extreme conditions. Herein we introduce a novel rare-earth complex Eu(bpyO2)4(PF6)3 as a promising candidate for high-precision pressure sensing, addressing the gap in sensitivity of existing luminescent manometers below 1 GPa. Through comprehensive high-pressure spectroscopic and single-crystal X-ray diffraction studies, we have found a phase transition in Eu(bpyO2)4(PF6)3 at 1.25 GPa where the ambient-pressure phase α (space group Pbcn) transforms to high-pressure phase β (space group P21/n). This process reduces the contribution of intramolecular anagostic bonds complementing the coordination sphere modifying the observed emission spectra, underpinning the role of the crystal-engineering in the development of dual-mode (ratiometric and lifetime-based) luminescence manometers. The ratiometric mode, measuring the intensity ratio between two emission bands of Eu3+ ions, demonstrates a remarkable relative sensitivity, exceeding 120.7% GPa-1 around 1.6 GPa. The lifetime-based mode utilizes pressure-influenced luminescence kinetics and shows the maximal relative sensitivity of 55.1% GPa-1, classifying it as the most sensitive optical manometer operating in this mode. The unique bimodal readouts and unparalleled sensitivity of Eu(bpyO2)4(PF6)3 across both modes significantly advance pressure sensing technologies.