Steric Engineering of Cyclometalated Pt(II) Complexes toward High-Contrast Monomer-Excimer-Based Mechanochromic and Vapochromic Luminescence.

Ligands play a crucial role in the supramolecular photoluminescence properties of Pt(II) square-planar complexes. To improve the luminescence color responses of N∧C∧N cyclometalated Pt(II) complexes to external stimuli such as mechanical stress and chemical vapors, we have conducted a steric engineering of the previous systems - [ , 56, 4978-4989] by introducing two -butyl groups to the tridentate ligand to form complexes -. Unlike the "too low" or "too high" steric hindrance of the NCNPt core in -, the combined steric effects of the -butyl groups at one side and the pentiptycene group at the other side of the NCNPt core in are "just right" for generating as-prepared powders with pure monomer (green) emission or pure excimer (red) emission, depending on the rate of precipitation from solutions.

Spongelike Porous Silica Nanosheets: From "Soft" Molecular Trapping to DNA Delivery.

Spongelike porous silica nanosheets, with nanometer thicknesses and pores whose diameters are on the hundreds-of-nanometers scale, have been used as a novel carrier for molecular immobilization of different guests. Enhanced properties of encapsulation were shown for drug molecules of different dimensions due to "softness" caused by the specific nanometric features of the porous structure. The encapsulating effect of the structure results in sustained and stimuli-responsive release behavior of immobilized guest molecules.