Contrasting Solid-State Fluorescence of Diynes with Small and Large Aryl Substituents: Crystal Packing Dependence and Stimuli-Responsive Fluorescence Switching

Abstract

There has been a significant current interest in solid state luminescence of organic molecules and their stimuli responsive fluorescence switching behavior. Although small organic derivatives with olefinic, acetylenic, phenylenevinylenic, phenyleneethynylenic spacers are widely documented as solid state emitters in the literature, the solid state photophysics of organic derivatives with "butadiyne" spacer still remains unexplored. We provide detailed investigation on the solid state fluorescence properties of a series of butadiynyl fluorophores. Replacement of a phenyl ring, which is at periphery of the butadiyne bridge, with a large moiety such as pyrenyl group furnishes contrasting emissions in the solid state. While the butadiyne bridged phenyl derivatives show a blue shift of emission maxima in the solid powder with respect to monomer spectra in solution state, the butadiyne bridged pyrenyl derivatives exhibit a red shift in the solid state. The blue shift of the emission maxima of the butadiyne bridged phenyl derivatives in the solid powder is attributed to allowed excitonic transition in aggregates with nearly parallel transition dipoles. On the other hand, formation of pyrenyl excimer accounts for the red shift of the butadiyne bridged pyrenyl derivatives in the solid powder. In addition to that, the solid state fluorescence of the pyrenyl analogues is reversibly switched between two aggregate forms through external heating and rubbing stimuli.

Photophysical Impact of Diacetylenic Conjugation on Classical Donor–Acceptor Electronic Energy Pair

“…The spectral shift is consistent with our earlier observation on diacetylenic pyrene−phenyl hybrid fluorophores in mixed-aqueous media. 27,28 In addition to the dominant aggregate emission, a weak LE emission band appeared at around 400−450 nm (Figure 5f), which is consistent with the LE band observed in nonaqueous solvents (Figure 2f). Further, to evaluate how the excited-state lifetime of the redshifted emissive species differs from the LE state, we carried out time-resolved fluorescence decay experiments.…”

NCN‐Coordinating Ligands based on Pyrene Structure with Potential Application in Organic Electronics

“…Compared with the solution‐phase emission spectra, a significant bathochromic shift is visible in the order P4 > P1 > P5 . Therefore, it is highly probable that the emission is associated with J‐aggregate formation of compounds in their solid form . Interestingly, the emission lifetimes presented in Table for P1 , P4 , and P5 in the solid state increased relative to those in solution, indicating emission from the aggregates rather than from the monomers.…”

Emissive Single-Crystalline Boroxine-Linked Colloidal Covalent Organic Frameworks

“…This behavior is consistent with the understanding that intersheet diphenylbutadiyne chromophores undergo aggregation-induced fluorescence. [45][46] During the polymerization of DBD-COF, molecular chromophores are brought into close proximity, similar to their aggregation-induced assembly in previous reports, which restricts their molecular motion and enhances their fluorescence quantum yield.…”