Dinuclear Triple-Stranded Helicates Composed of Tetradentate Ligands with Aluminum(III) Chromophores: Optical Resolution and Multi-color Circularly Polarized Luminescence Properties.

New chiroptical chromophores, dinuclear triple-stranded helicates, composed of tetradentate ligands with aluminum(III) ions, are described. These are synthesized in two steps using inexpensive pyrrole derivatives, hydrazine, and aluminum chloride. These molecular architectures (ALPHY) show multi-color (cyan, yellow, and orange) photoluminescence in solution and in the solid-state, which depends on the substituents of the ligands. The photoluminescence quantum yields of helicates were up to 54 %. The right-handed (P) and left-handed (M) helicates are so stable that they do not undergo racemization in some solvents and are mirror images according to circular dichroism and circularly polarized luminescence (CPL) with an absolute luminescence dissymmetry factor (glum ) of up to the 10-3 order. Mixing the different helicates produces white-light emission with CPL characters. This study offers a glimpse into the potential applications of chromophores with diverse photophysical properties.

Switching of Monomer Fluorescence, Charge-Transfer Fluorescence, and Room-Temperature Phosphorescence Induced by Aromatic Guest Inclusion in a Supramolecular Host.

Crystal engineering of three-component crystals with guest-dependent photoluminescence switching, including (i) crystallization-induced emission enhancement, (ii) intermolecular charge-transfer emission, and (iii) room-temperature phosphorescence under ultraviolet irradiation, was demonstrated. This strategy was based on the confinement of aromatic guests in a supramolecular host (denoted as EBPDI-TPFB) composed of 5,5'-(ethyne-1,2-diyl)bis(2-pyridin-3-yl-isoindoline-1,3-dione (EBPDI) with two tris(pentafluorophenyl)borane (TPFB) molecules linked by B-N dative bonds that acted as Lewis pairs. The single-crystal X-ray structures of complexes with eight different guests were collected, revealing that the size and/or shape of the supramolecular host EBPDI-TPFB was modulated by the included guest molecules. The excellent guest inclusion ability of EBPDI-TPFB allowed systematic photoluminescence regulation of the complexes, which exhibited multicolor emissions in the crystalline state. Photoluminescence switching characteristics of the complexes were observed upon removing the guests or mechanical grinding of the crystals. These results indicated that using the host-guest chemistry of multicomponent crystals not only facilitates crystallization, but also can reveal hidden optical functions by combining molecules of interest, which should contribute to the fields of physical chemistry and materials science.