Water-soluble multifunctional red luminescent materials constructed by macrocycle–ligand–lanthanide synergetic assembly strategy

Abstract

The high-efficiency red luminescent materials in water are attractive in the field of luminescent materials. In particular, those red luminescent materials with multifunctional intelligent responsiveness and good stability are very challenging and important. In this work, a purplish red emission is achieved by a synergetic supramolecular amphiphilic assembly strategy based on the water-soluble macrocyclic calixpyridinium, the bidentate ligand bathophenanthrolinedisulfonic acid disodium salt (BPhDS) and the lanthanide Eu3+. BPhDS and Eu3+ could only form a simple complex emitting a purplish blue fluorescence. Calixpyridinium and BPhDS could construct a spherical assembly. Benefitting from its pH-responsive fluorescence emission, by precise fine-tuning of its pH, a perfect white light emission was obtained and applied in a fluorescent ink. White light is an ideal light source because it has a perfect color reproducibility and stability. More excitingly, a purplish red emission is achieved by calixpyridinium-assisted amphiphilic assembly of non-red emissive BPhDS−Eu3+ complex in water. It paves a new way to construct the high-efficiency red luminescent material based on a lanthanide complex in water and exhibits many advantages: (1) all the assembly components are easy-to-get and the synergetic assembly process is very simple; (2) the supramolecular amphiphilic assembly has a synergetic effect on the luminescence of lanthanide complex in water: the natural hydrophobic inner of the assembly can expel the water molecules around lanthanide complexes and reduce the number of coordination water; the binding of the ligand by macrocycle can limit its rotation, increase its rigidity and reduce its energy loss; the synergetic assembly can shorten the distance of donor–acceptor complexes and enhance their energy transfer efficiency; (3) although the luminescent material does not contain any responsive site, the multiple weak and therefore reversible non-covalent interactions endow it with many intelligent responsiveness in various applications, such as temperature-controlled switch, anti-counterfeit material, and confidential material.