pH- and Saccharide-Responsive Cyclometalated Iridium(III) Complexes with Boronic Acid Moieties Displaying a Wide Range of Phosphorescence Colors.

Single compounds displaying a wide range of luminescent colors are attractive optical materials for sensor applications. In this study, we present the beneficial combination of a cyclometalated iridium(III) complex scaffold and boronic acid units for designing stimuli-responsive luminescent materials with various emission colors. Five iridium(III) complexes bearing a diboronic acid ligand (bpyB2) were synthesized: Ir(C^N)bpyB2 (C^N = 2-phenylpyridine (1), 2-(2,4-difluorophenyl)pyridine (2), 2-(4-methoxyphenyl)pyridine (3), benzo[h]quinoline (4), 1-phenylisoquinoline (5)).

Stability of a double twisted structure in spherical cholesteric droplets.

We found for the first time the stabilization of a double twisted structure in cholesteric liquid crystals confined to small spherical droplets under weak anchoring conditions. The direct observation of the droplets using a polarized microscope revealed the physical properties of the structure. The experimental results showed that the stability of the double twisted structure is determined by the relationship between the helical pitch length and the droplet size.