Dramatically Enhanced and Red‐shifted Photoluminescence Achieved by Introducing an Electron‐withdrawing Group into a Non‐traditional Luminescent Small Organic Compound

Abstract

Small organic compounds without any traditional fluorescent chromophores are generally non‐emissive, and only very few are reported to emit weak blue fluorescence. Here we synthesized a non‐traditional luminescent small organic compound N‐(2,2,2‐trifluoroethyl)acrylamide (TFAM) with dramatically enhanced and red‐shifted photoluminescence by introducing a strong electron‐withdrawing group into acrylamide (AM). Very impressively, TFAM emits cyan (472 nm) and yellow‐green (560 nm) fluorescence in solutions and solid state, respectively. TFAM also shows aggregation‐induced emission enhancement (AIEE) and excitation‐dependent fluorescence (EDF) characteristics, as well as temperature and metal cations‐responsive fluorescence. Theoretical calculations show that the introduction of electron‐withdrawing group leads to a lower energy gap between the HOMO–LUMO energy levels in TFAM than in AM. And strong cooperative hydrogen bonds are formed in TFAM molecules, resulting in rigidification of molecular conformations. The study provides a strategy for preparing non‐traditional luminescent compounds with enhanced and red‐shifted photoluminescence.

Mechanosynthesis of Polyureas and Studies of Their Responses to Anions

“…Based on all the above-mentioned results, one can see that among the PUs 4-9 only ortho-substituted PUs, such as PU 4 and PU 7, exhibited a selective fluorescence "turn-on" response towards TBAF, while other PUs exhibited no selectivity to F − , and all the PUs exhibited a visually detected response to OH − . To the best of our knowledge, the herein reported case is the very first example of a selective response to the fluoride anion among the biphenyl-based thioureas [82,83]. The importance of fluoride selective detection is based on its wide presence in dental products, food, drinking water, and tap water [84], and, on the other hand, existing risk health problems caused by the excessive consumption of fluoride, as well as the presence of fluoride in warfare agents [85].…”

Ultra‐Thin 2D Ionic Salt Supported with Strong Hydrogen‐Bonding Assisted Ionic Interaction

“…The fluorescence spectroscopy reveals that crystal 1 has a strong emission at 499 nm and a small peak at 620 nm, while crystal 2 has a strong emission at 642 nm and a slightly weaker peak at 487 nm, when excited at 370 nm (Figure 1e). The redshifts of the absorption [ 17 ] and emission [ 18 ] are attributed to a strong H‐bonding‐assisted ionic interaction in crystal 2, which will be further discussed by density functional theory (DFT) calculation and natural bond orbital (NBO) analysis.…”

Effects of nonaromatic through‐bond conjugation and through‐space conjugation on the photoluminescence of nontraditional luminogens

“…[37] On the contrary, most reported natural and synthetic NTLs contain two or more continuous unsaturated bonds and/or atoms with n electrons, which can form π-π, p-π or multiple conjugations. For example, C═O and O (or N) atoms in carboxyl group [38] and amide group [39] can form π-p conjugation, and C═C, C═O and N atoms in acrylamide [40] can form π-π-p conjugation. The reported NTLs with high QYs and red-shifted emissions are generally with TBC effect.…”