Luminogens Based on Cyano‐Substituted Anthracene Isomers: Different Molecular Packing and Distinct Piezochromic Properties

Abstract

Pure organic materials with piezochromic property have been intensively studied in recent years. Many examples describe response to both mechanical grinding and hydrostatic pressure, but the examples in realizing high color contrast as well as high sensitivity, especially under high external pressure, are very rare which hampers their practical applications as pressure sensors. Herein, two anthracene‐based structural isomers, NDHA‐p and NDHA‐m, are developed applying 9,10‐bis(diphenylmethylene)‐9,10‐dihydroanthracene (DHA) as the basic skeleton and substituted by four cyano groups on para‐ or meta‐positions of the periphery benzene rings, respectively. In high‐pressure experiment, as compared to the NDHA‐m which shows a color contrast of 60 nm and a sensitivity of 7.87 nm·GPa‐1, NDHA‐p exhibits a dramatically larger color contrast of 138 nm and higher sensitivity of 13.20 nm·GPa‐1, whose performance is among the best pure organic piezochromic materials so far. The systematical experimental and theoretical analyses indicate that NDHA‐p possesses a lower crystal density, relatively looser molecular packing mode, and higher degree of electronic communications than NDHA‐m, which are responsible for the excellent piezochromic performance. This design method will open a new avenue for controlling the molecular packing configuration of luminescent materials via structural isomerization, and further extending their applications.

NIR-II semiconducting polymers forin vivohigh-resolution imaging and theranostics

“…[32][33][34] Aside from the conjugated backbone alteration, subtle modification of the substituted groups may also impact the photophysical properties. [35][36][37][38] Although SPs could have very small bandgaps and strong NIR absorption, the development of high-brightness candidates is still less than satisfactory because the strong intermolecular interaction such as π-π stacking and interchain entanglement may cause serious fluorescence quenching in the aggregate state. [39][40][41][42] Most SPs possess a conjugated backbone structure and hydrophobic nature, so they have to be fabricated into nanoparticles (NPs) to provide good water solubility and biocompatibility.…”

Precise peripheral design enables propeller-like squaraine dye with highly sensitive and wide-range piezochromism

“…[1][2][3][4][5] Since the seminal work of 1957, 6 the eld of PCF materials has signicantly ourished by exploiting purely organic luminophores. [7][8][9][10][11][12] During this process, molecular packing rearrangements, [13][14][15] molecular conformational changes, 16,17 and bond breaking 18,19 have been well assigned to cause their piezochromic behavior. 20 Nevertheless, due to small-shied luminescence spectra upon mechanical stimuli, most PCF materials exhibit inconspicuous color switching.…”

Dimeric tetrabromo-p-quinodimethanes: synthesis and structural/electronic properties

“…14 The steric hindrance of the anthracene peri hydrogens allows conceiving molecules with switchable geometry, which makes TBQs ideal platforms for synthetising materials with aggregation-induced emission (AIE) and photochromism properties. [15][16][17] If the core of the TBQ is a pentacene, then the substitution with phenyl derivatives yields a structure that is prone to undergo a cyclodehydrogenation reaction to provide hexabenzocoronenes, which have potential as semiconducting materials for eldeffect transistor applications. 18 Another example of their potential in materials science is found in molecules with selfassembly capabilities.…”