Green‐, Red‐, and Infrared‐Emitting Polymorphs of Sterically Hindered Push–Pull Substituted Stilbenes

Abstract

The synthesis, XRD single‐crystal structure, powder XRD, and solid‐state fluorescence of two new DPA‐DPS‐EWG derivatives (DPA=diphenylamino, DPS=2,5‐diphenyl‐stilbene, EWG=electron‐withdrawing group, that is, carbaldehyde or dicyanovinylene, DCV) are described. Absorption and fluorescence maxima in solvents of various polarity show bathochromic shifts with respect to the parent DPA‐stilbene‐EWGs. The electronic coupling in dimers and potential twist elasticity of monomers were studied by density functional theory. Both polymorphs of the CHO derivative emit green fluorescence (527 and 550 nm) of moderate intensity (10 % and 5 %) in polycrystalline powder form. Moderate (5 %) red (672 nm) monomer‐like emission was also observed for the first polymorph of the DCV derivative, whereas more intense (32 %) infrared (733 nm) emission of the second polymorph was ascribed to the excimer fluorescence.

Colour-tuneable solid-state fluorescence of crystalline powders formed from push–pull substituted 2,5-diphenyl-stilbenes

“…The key intermolecular interactions that form the columns are of the edge-to-face C-H/p type. Contrary to DPA-DPS-CHO, where y-shaped C-H/p interactions connected the side-phenyls of adjacent molecules, 34 in DPA-DPS-DMV, these interactions are of a Tshape 43 and form a network with multiple contacts either between the side-phenyls and the phenyls of a DPA group, or between the phenyls of triphenylamine groups mutually.…”

“…Such a decisive role of side-phenyls was also observed in DPA-DPS-DCV, in which case the side-phenyls were coupled by parallel offset face-to-face stacks. 34 The geometry of both alternating dimers 1 and 2 of DPA-DPS-CMV (Fig. 3) was recomputed from crystal structures by DFT (uB97X-D/6-31G(d,p)) 40 and compared with the experimental data.…”

“…32,33 We have recently observed that one of the polymorphs of DPA-DPS-DCV (Chart 1) forms a crystal arrangement with such alternating dimers and consequent intense infrared excimer-type emission was observed. 34 Research on solid-state emitters has paid special attention to the series of derivatives based on the same building block with SSF maxima tuned by a variation of simple substituents. [35][36][37] An impressive interval of SSF maxima from 383 to 631 nm, i.e.…”

Complete Set of Diketopyrrolopyrrole Centrosymmetrical Cofacial Stacked Pairs

“…4 and S4) forms an almost perfect stack with respect to lateral shifts. [33] Infinite columns of dimer 3 (file LAHCIJ [34a] ) or ChemPhysChem dimer 4 (file QUIHIC [34b] ) stacks were also found among N,N'di(n-alkyl) derivatives of PhDPP.…”

Less is More: Tunable Polymorphs with Packing-Dependent Deep-Red to Near-Infrared Emission Based on a Geometrically Simple Molecule

“…However, most of the reported polymorphic systems involves two common problems: (1) The polymorphism often accompanied by simultaneously different molecular conformation and packing modes, it is difficult to figure out which factor dominants the photophysical properties; − (2) Polymorphism with deep-red (DR) and near-infrared (NIR) emission is rarely reported due to the inherent difficulty of crystallization arising from their complex structures. − Therefore, from both fundamental and application viewpoints, designing simple molecules with NIR polymorphic emission and establishing unambiguous structure–property relationship is challenging yet highly desirable.…”