Regulation of π‐Stacked Anthracene Arrangement for Fluorescence Modulation of Organic Solid from Monomer to Excited Oligomer Emission

Abstract

The construction and precise control of the face-to-face π-stacked arrangements of anthracene fluorophores in the crystalline state led to a remarkable red shift in the fluorescence spectrum due to unprecedented excited oligomer formation. The arrangements were regulated by using organic salts including anthracene-1,5-disulfonic acid (1,5-ADS) and a variety of aliphatic amines. Because of the smaller number of hydrogen atoms at the edge positions and the steric effect of the sulfonate groups, 1,5-ADS should prefer face-to-face π-stacked arrangements over the usual edge-to-face herringbone arrangement. Indeed, as the alkyl substituents were lengthened, the organic salts altered their anthracene arrangement to give two-dimensional (2D) edge-to-face and end-to-face herringbone arrangements, one-dimensional (1D) face-to-face zigzag and slipped stacking arrangements, a lateral 1D face-to-face arrangement like part of a brick wall, and a discrete monomer arrangement. The monomer arrangement behaved as a dilute solution even in the close-packed solid state to emit deep blue light. The 1D face-to-face zigzag and slipped stacking of the anthracene fluorophores caused a red shift of 30-40 nm in the fluorescence emission with respect to the discrete arrangement, probably owing to ground-state associations. On the other hand, the 2D end-to-face stacking induced a larger red shift of 60 nm, which is attributed to the excimer fluorescence. Surprisingly, the brick-like lateral face-to-face arrangement afforded a remarkable red shift of 150 nm to give yellow fluorescence. This anomalous red shift is probably due to excited oligomer formation in such a lateral 1D arrangement according to the long fluorescence lifetime and little shift in the excitation spectrum. The regulation of the π-stacked arrangement of anthracene fluorophores enabled the wide modulation of the fluorescence and a detailed investigation of the relationships between the photophysical properties and the arrangements.

Anthracene-Based Lanthanide Metal-Organic Frameworks: Synthesis, Structure, Photoluminescence, and Radioluminescence Properties

“…For Structure 2 (Tb), lifetimes τ1 = 0.2 ns and τ2 = 0.5 ns and weighted average lifetime τo = 0.3 ns are much shorter than the 4.9 ns, 16 ns, and 9.5 ns, respectively, we determined for H2ADC (ESI Table S2). These lifetimes are also shorter than the average lifetime value of τo = 2.0 ns reported elsewhere for anthracene in monomeric isolated arrangements [39] and shorter than τo = 5 ns reported for Zn-PCN-14 [2]. As discussed earlier, changes in the excited state geometry of bulk ligand molecules due to the rotation of its -COOH groups to near coplanar conformation with the anthracene moiety and reorganization towards end-to-face herringbone arrangement, which can facilitate excimer formation and strong interchromophore interactions, are quite likely.…”

“…For Structure 2 (Tb), lifetimes τ 1 = 0.2 ns and τ 2 = 0.5 ns and weighted average lifetime τ o = 0.3 ns are much shorter than the 4.9 ns, 16 ns, and 9.5 ns, respectively, we determined for H 2 ADC (ESI Table S2). These lifetimes are also shorter than the average lifetime value of τ o = 2.0 ns reported elsewhere for anthracene in monomeric isolated arrangements [39] and shorter than τ o = 5 ns reported for Zn-PCN-14 [2]. which corresponds to two different photo emissive rates, where I is the intensity, τ is the time, τ1 and τ2 are their corresponding excited state decay lifetimes, and α is the pre-exponential factor.…”

Anion-controlled dimer distance induced unique solid-state fluorescence of cyano substituted styrene pyridinium

“…The cationic fluorogens are usually designed with complex and flexible structures to against the strong dipole-dipole interactions, which open the non-radiation decay channels and thus quench the solid-state luminescence. The changes of the anions would also greatly influence the emission in aggregation of organic salts because the strength of electrostatic attraction between cationic and anionic species and steric hindrance may deeply affect the molecular packing in aggregation4445464748495051. Bhattacharya, et al .…”

A novel ratiometric fluorescent probe through aggregation-induced emission and analyte-induced excimer dissociation

“…Anthracene molecules easily form intermolecular excimers (emission at 516 nm) due to aggregation, and the excimer could return to the monomer state via excimer dissociation [37][38][39][40][41]. This particular property has been employed to design some luminescent materials [42][43][44][45][46][47].…”