Modulating Triplet States in Light‐Harvesting Antennas: Multicolor (Including White) Emission from Molecular Europium Complex Siblings

Monochromatic red or single-component white light-emissive mononuclear complexes have a massive international demand for various applications. In this report, two siblings molecular Eu-complexes are synthesized by integrating with the sibling's organic antenna. The ligands are designed with a phenanthroimidazole-based core substituted with 1-Naphthyl and 2-Naphthyl groups at the C1 position. This study leads to the design of a slight change in the structure of the ancillary ligand that could modulate the complex emission. Pure white light emission was obtained from 1-Naphthyl functionalized complex in solution. In contrast, the 2-Naphthyl functionalized complex showed red emission. The experimental investigation reveals that the ligand emission cooperates with the narrowband red emission of the Eu(III) ion and can generate white light. In contrast, such behavior is not seen in the 2-Naphthyl-based Eu(III) complex. A single-component hybrid white light-emitting diode (LED) was fabricated, and the LED showed appreciable optical performance [CRI (82%), CIE (0.32, 0.31), and CCT (5152 K)]. Due to the dual emissive characteristics of the investigated Eu-complex, the molecular thermometer behavior is explored with a sensitivity of 2.01 K^-1. The complexes are vital for vapoluminescence sensing because of the intense collaboration of ligand and Eu(III) ions. "On-off-on" luminescence-based visual detection of acid-base vapors was explored using these complexes, which can be used for anticounterfeiting applications.