Hybridization of a Flexible Cyclooctatetraene Core and Rigid Aceneimide Wings for Multiluminescent Flapping π Systems

Abstract

The hybridization of flexible and rigid π-conjugated frameworks is a potent concept for producing new functional materials. In this article, a series of multifluorescent flapping π systems that combine a flexible cyclooctatetraene (COT) core and rigid aceneimide wings with various π-conjugation lengths has been designed and synthesized, and their structure/properties relationships have been investigated. Whereas these molecules have a V-shaped bent conformation in the ground state, the bent structure changes to a planar conformation in the lowest excited singlet (S1 ) state irrespective of the lengths of the aceneimide wings. However, the fluorescence behavior in solution is distinct between the naphthaleneimide system and the anthraceneimide system. The former has a nonemissive S1 state owing to the significant contribution of the antiaromatic character of the planar COT frontier molecular orbitals, thereby resulting in complete fluorescence quenching in solution. In contrast, the latter anthraceneimide system shows an intense emission, which is ascribed to the planar but distorted S1 state that shows the allowed transition between the π-molecular orbitals delocalized over the COT core and the acene wings. The other characteristic of these π systems is the significantly redshifted fluorescence in the crystalline state relative to their monomer fluorescence. The relationship between the packing structures and the fluorescence properties was investigated by preparing a series of hybrid π systems with different sizes of substituents on the imide moieties, which revealed the effect of the twofold π-stacked structure of the V-shaped molecules on the large bathochromic shift in emission.

Exploring Potential Energy Surfaces for Aggregation‐Induced Emission—From Solution to Crystal

“…The role of CIs involving ar ing puckering coordinate also seemst ob ei mportant in the radiationless decay of three similar acenimides with different luminescent behavior.T hese are three conjugateds ystems consisting of aC OT core and diphenylene, dinaphthalene, and dianthraceneimide wings (DPCOT, DNCOT,a nd DACOT,s ee Figure 2). [67,68] Their PES hasb een studied with SF-TD-DFT calculations combined with the global reactionroute mapping (GRRM) [69,70] strategy. [43] DNCOT has AIE behavior and is V-shaped in the ground state because of the boat-like COT structure (Figure 10, left panel), with the wings attached to the two raised sides of the cycle.…”

Molecular dynamics in computational materials sciences: From the study of nanostructure formation to the design of fluorescent dyes

“…In the second case, we used straight-forward TD-DFT PES mapping to simulate conformational changes of a cyclooctatetraenebased dye in the presence of different environmental surroundings, using the PBE0 functional. We have designed and synthesized a π-conjugated system that consists of a flexible and nonplanarπjoint and two emissive rigid and planar wings (see Figure 4) [13,14]. This molecular system exhibits respectively red, green, and blue (RGB) emission from a single-component luminophore in different environments, namely in polymer matrix, in solution, and in crystals.…”

Starphenes and Phenes: Structures and Properties

“…There are no conventional synthetic accesses for such tetrabenzocyclooctatetraene scaffolds, although Yamaguchi et al combined a flexible cyclooctatetraene core with two aceneimide wings. 58 Our shotgun approach is a superb exploratory tool but, unfortunately, it does not allow the isolation of single products in larger amounts. Figure 10 displays photographs and UV-vis spectra of solutions of the air-stable benzannulated phenes T 2 B and P 2 B.…”