Multiple aggregates from multiple polymorphs: structural and mechanistic insight into organic dye aggregates

Abstract

This case study provides evidence for the appearance of multiple aggregation forms of a single organic dye, arising from its packing polymorphs in the solid state. Each aggregate can be...

Molecular and Aggregate Synergistic Engineering of Aggregation-Induced Emission Luminogens to Manipulate Optical/Electronic Properties for Efficient and Diversified Functions

“…Interestingly, it was during the cultivation processes of single crystal for ACIK in various solvents that another kind of platelet-like red single crystals, namely, ACIK-N, was obtained by the slow evaporation from a propanol/chloroform mixture solution (Figure B). ACIK-N displayed NIR emission centered at 687 nm (Φ f = 7.6%), which was spectroscopically matched to the aggregates formed in an acetone/water mixture solution ( f w = 90%) probably owing to their similar aggregation form (Figure C) . The difference of emission maxima between ACIK-Y and ACIK-N was 102 nm, which was relatively large considering they were all constructed from the identical molecule.…”

“…ACIK-N displayed NIR emission centered at 687 nm (Φ f = 7.6%), which was spectroscopically matched to the aggregates formed in an acetone/water mixture solution (f w = 90%) probably owing to their similar aggregation form (Figure 2C). 42 The difference of emission maxima between ACIK-Y and ACIK-N was 102 nm, which was relatively large considering they were all constructed from the identical molecule. Impressively, the emission of ACIK-Y was even 20 nm-blue-shifted with respect to that of CIK (λ em = 605 nm), indicating a great potential of aggregation engineering in regulating the optical properties of solid fluorescent materials.…”

“…Moreover, the comparable emission of ACIK dots and ACIK-N (683 nm versus 687 nm) manifested their similar aggregation form in terms of relatively planar molecular conformation and infinite π−π stacking, where the strong push−pull dipolar character as well as the extended π-conjugation were expected to endow ACIK dots with interesting two-photon absorption (2PA) properties. 5,42 For the two-photon excitation process, a fluorophore simultaneously absorbed two photons and was pumped to the excited state, which further underwent a radiative decay pathway to release a photon (Figure 8D). Upon the excitation of a 1040 nm fs laser, the fluorescence spectrum of ACIK dots was recorded in Figure 8E.…”