Multimodal luminescence manometers based on a novel organic complex material – Eu(bpyO2)4(PF6)3

Abstract

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 luminescence 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 the 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 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 at approximately 1.6 GPa. The lifetime-based mode utilizes pressure-influenced luminescence kinetics and shows a 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 represent a significant advancement in pressure sensing technologies.