Alkyl Chain Length‐ and Polymorph‐Dependent Photomechanochromic Fluorescence of Anthracene Photodimerization in Molecular Crystals: Role of the Lattice Stiffness

Abstract

Anthracene–pentiptycene hybrid systems 1‐Cn, where n refers to the number of carbon atoms in the linear alkyl chain, crystallize in three different polymorphs, denoted Y (yellow), G (green), and B (blue) forms in terms of the fluorescence color. While all Y‐form crystals show the same yellow‐to‐blue fluorescence color response to the photomechanical stress generated by the anthracene [4+4] photodimerization reaction, the four G forms exhibit distinct photomechanofluorochromism (PMFC): from green to blue for G‐1‐C4, to orange for G‐1‐C7, to red for G‐1‐C8, and to red then blue for G‐1‐C9, and the B forms show no photochromic activity. The intriguing RGB three‐color PMFC and abnormal topochemical reactivity of G‐1‐C9 are attributed to inherent softness of the crystal lattice.

Steric Engineering of Cyclometalated Pt(II) Complexes toward High-Contrast Monomer–Excimer-Based Mechanochromic and Vapochromic Luminescence

“…The projection overlapping ratio of the NCNPt pair is ∼45%, and the Pt–Pt distance is 5.68 Å, indicating negligible metallophilic interactions between molecules. Attention is also paid to the groups that occupy the U-shaped cavities of the pentiptycene unit, because alkyl chain threading is often observed in the crystal structures of molecules containing the Pa group. ,− However, in the case of 2b , the groups that occupy the U-cavities are the tert -butyl substituents of neighboring molecules and the DCM solvate molecules.…”

Porous Supramolecular Assembly of Pentiptycene-Containing Gold(I) Complexes: Persistent Excited-State Aurophilicity and Inclusion-Induced Emission Enhancement

“…We have recently demonstrated the utility of the bulky H-shaped pentiptycene scaffold in forming molecular solids of stimuli-responsive luminescence. − The three-dimensional pentiptycene scaffold is inherently more isotropic than a planar π-component in intermolecular nonbonded interactions. In addition, the U- and V-shaped cavities of the pentiptycene scaffold could accommodate nonspecific intermolecular π–π and C–H···π interactions.…”

Mechanochromic and vapochromic fluorescence of a bulky π‐system: Alkyl chain‐length effects, triplex emission, and differential sensing of aniline vapors

“…The latter approach relies on the fact that changing the alkyl chain length of a molecular system could tune the crystal packing mode and thus the electronic properties in the solid-state. [19][20][21][22] The results reported herein show that the combined treatments of mechanical grinding and aniline vapor fuming on PAP-Cn (n = 4, 8, 12, or 16) result in the formation of a three-component PAP-Cn/PAP-Cn/ aniline complex (triplex). In addition, mechanical grinding increases the retention time for the aniline guest in the films.…”

“…Excitation wavelength (λ ex ) is 365 nm each AF form displays dual emission ( Figure 5): that is, a residual emission of the UG state and a new emission attributable to the PAP-Cn/pMDMA complexes. While the new complex emission is much stronger than the residual UG emission for PAP-C4, -C8, and -C12, it is opposite for PAP-C16, presumably due to the long alkyl chains that occupy the pentiptycene cavities [16,22] and, therefore, slow down and reduce the aniline adsorption. The λ f of the new complex emission band is in the order PAP-C12 (λ f = 626 nm) > PAP-C4 (λ f = 615 nm)~PAP-C8 (λ f = 613 nm) > PAP-C16 (λ f = 582 nm) ( Table 2), which follows the same trend as the UG form.…”

“…Therefore, the observed d-spacing might be associated with the stacking of the molecules along with the directions of the width or the height, which is essentially determined by the pentiptycene scaffold. [25] Since the U-shaped cavities of pentiptycene are often threaded with alkyl chains in the single crystals of pentiptycene derivatives, [9,16,22,26] the n-dependent d-spacing might be associated with a different extent of the pentiptycene-alkyl chain interactions, as depicted in Figure 2c. Such interactions might create a larger overlap for the neighboring anthracene units in the case of PAP-C12, which accounts for the partial dimer fluorescence of its UG form.…”