On-Demand Vitrification of Multicomponent Lanthanide Complexes for Magnetism and Up-Conversion Emission

Molecule-based glassy systems and their solid solutions emerge as advanced optical materials that circumvent the inherent limitations of inorganic and polymer glasses such as energy-intensive synthesis and stringent processing requirements. This work presents rationally designed discrete lanthanide complexes [Ln(dbm)₃(C₄PO)] (dbm= dibenzoylmethane, C₄PO = tri-<i>n</i>-butylphosphine oxide) demonstrating an unprecedented reversible "crystal (<b>1-Ln</b>) → liquid → glass (<b>1-Ln-Q</b>) → glass-ceramic (<b>1-Ln-H</b>) → crystal" phase transition cycle, featuring the melting points of around 130 °C alongside the glass transition temperatures of approximately 20 °C. Our molecular engineering strategy provides an opportunity to achieve dual functional breakthroughs in magnetism and up-conversion (UC) emission while reducing the thermal budget. By integrating the glass transition into single-molecule magnets, we enable mild thermal processing that converts crystalline <b>1-Dy</b> architectures into deformable glassy <b>1-Dy-Q</b> phases. Subsequent structural evolution realizes a 96.9% reversible recovery of dynamic magnetism in reconstructed <b>1-Dy-H</b>. Solid solution engineering through controlled eutectic/glass transitions produces composition-tunable materials <b>1-Yb</b>/<b>1-Eu</b>, <b>1-Yb</b>/<b>1-Sm</b>, and <b>1-Y</b>/<b>1-Yb</b>/<b>1-Pr</b>, and <b>1-Yb</b>/<b>1-Eu</b> achieves a quantum yield of UC emission values up to 3.07 × 10^-5% under 980 nm irradiation comparable to conventional solution-processed benchmarks. This study establishes a paradigm for developing molecule-based solid solutions in lanthanide photonics, synergistically preserving intrinsic optical merits while enabling phase-programmable functionality and sustainable device fabrication.