Synthesis, Structure, and Photophysical Properties of Highly Substituted 8,8a‐Dihydrocyclopenta[a]indenes

Determining the Critical Particle Size to Induce Enhanced Emission in Aggregates of a Highly Twisted Triarylamine

“…Both the magnitude and trends with polarity for t 1 are consistent with the previous 9DAAA studies [17] in varying polarity organic solvents. Both the magnitude and trends with polarity for t 1 are consistent with the previous 9DAAA studies [17] in varying polarity organic solvents.…”

“…The UV/Vis long-wavelength absorption maximum for 50 mm 9DAAA displays a small hypsochromic shift from 443 to 437 nm as water content increases from 0 % to a fraction of 60 % v/v (Figure 2 a). Both spectra at high water content also correspond well with the neat solid-film absorption spectrum for 9DAAA (Figure S4), [17] again consistent with a dominant solid-like aggregated condition for 9DAAA in high-water-content mixtures. Also, the excitation spectrum for 9DAAA in 90 % v/v water displays a 24 nm bathochromic shift of its long-wavelength peak relative to the pure ACN result (Figure 2 b), corresponding with the absorption spectral shifts.…”

“…ICT-induced nonradiative quenching also is favored by higher polarity media in ambipolar systems like 9DAAA. The twisted ground-state conformation of 9DAAA [17] may also hinder co-facial intermolecular p overlap in an aggregate, as is seen in the known [18] 9DAAA crystal structure. [12] 9DAAA inherently favors a bisected ground-state geometry for which rotation of the dianisylamine group relative to the anthracene unit may occur in solution, but is unlikely in a highly aggregated state.…”

“…[11,12] This phenomenon has been termed aggregation-induced enhanced emission (AIEE), attributed to the suppression of non-radiative pathways for relaxation of the excited state through aggregation-assisted charge transfer, intramolecular rotations, p-p stacking or a combination of these. [12,13,17] The conditions under which AIEE onset first occurs can potentially provide fundamental insight in how solid-state particle growth affects PL, such as the effects of particle size and the surrounding environment. [13,15,16] AIEE occurring just at onset of aggregation has been associated with hypsochromic shift of the emission maximum at a slightly increased intensity, followed by a large rise in emission intensity with a stronger hypsochromic shift.…”

“…[13,15,16] AIEE occurring just at onset of aggregation has been associated with hypsochromic shift of the emission maximum at a slightly increased intensity, followed by a large rise in emission intensity with a stronger hypsochromic shift. [12,13,17] The conditions under which AIEE onset first occurs can potentially provide fundamental insight in how solid-state particle growth affects PL, such as the effects of particle size and the surrounding environment. However, close investigation of AIEE under initial onset conditions have so far received limited attention.…”