A Coordinating Small Organic Molecule with Tunable Lower Critical Solution Temperature for Efficient Management of...

Structurally well-defined small molecules with lower critical solution temperature (LCST) behavior offer enormous prospects for fine-tuning their phase transition properties to be "on-demand" applied in the specific scene but are still underexplored. Herein, a novel amphiphilic small LCST molecule is rationally designed and synthesized. The molecule, namely TG, features a conjugation of multiple short ethylene glycol (EG) chains with the functional coordinating terpyridine (Tpy) moiety. The molecule TG demonstrates excellent LCST behavior down to 0.05 × 10^-3 m in a water solution. And a cloud point T_cp = 30.9 °C with a very short thermal hysteresis ΔT = 0.2 °C and good reversibility can be achieved when c = 0.1 × 10^-3 m. The excellent LCST properties of TG have enabled its successful performance as the smart window for solar radiation management with the ∆T_lum, ∆T_IR, and ∆T_sol being 83.6%, 49.1%, and 67.2%, respectively. Moreover, the presence of Tpy moiety in TG enables its coordination with Ru³⁺ and the resulting complex also exhibits modulated LCST behavior with different concentration-dependent T_cp. These studies would provide novel small-molecule-based scaffolds for constructing better solar radiation management systems as well as other thermal-responsive smart materials.