Assembly-enhanced triplet-triplet annihilation upconversion in the aggregation formed by Schiff-base Pt(II) complex grafting-permethyl-β-CD and 9, 10-diphenylanthracence dimer

Water-soluble triplet sensitizer with permethyl-β-cyclodextrin (PMCD) grafting on a Schiff-base Pt(II) complex (Pt-2), in which PMCD unit serves as a host for binding the acceptors and the Schiff-base Pt(II) complex serves as a triplet sensitizer, was synthesized to investigate the effect of supramolecular complexation and assembly on the triplet-triplet annihilation upconversion emission in water. 9, 10-Diphenylanthracence (DPA) carboxylate (A-1) and its dimer (A-2) in which two DPA carboxylate were covalently linked with an alkyl chain were synthesized as triplet acceptors which also play a role of guest molecules for PMCD. A-1 and A-2 showed high affinity with PMCD, and A-2 can readily aggregate in water and form micron sized assemblies due to the hydrophobic effect and π-π stacking of anthracene core in A-2. The efficiency of TTA-UC was demonstrated to be enhanced by a synergistic effect of host-guest complexation of Pt-2 with A-2 and the self-aggregation of the acceptor A-2, which facilitated the energy transfer and energy fusion among donor and acceptor.