Uncovering the Intramolecular Emission and Tuning the Nonlinear Optical Properties of Organic Materials by Cocrystallization

Abstract

The spectroscopic and photophysical properties of organic materials in the solid-state are widely accepted as a result of their molecular packing structure and intermolecular interactions, such as J- and H-aggregation, charge-transfer (CT), excimer and exciplex. However, in this work, we show that Spe-F DIB cocrystals (SFCs) surprisingly retain the energy levels of photoluminescence (PL) states of Spe crystals, despite a significantly altered molecular packing structure after cocrystallization. In comparison, Npe-F DIB cocrystals (NFCs) with new spectroscopic states display different spectra and photophysical behaviors as compared with those of individual component crystals. These may be related to the molecular configuration in crystals, and we propose Spe as an "intramolecular emissive" material, thus providing a new viewpoint on light-emitting species of organic chromophores. Moreover, the nonlinear optical (NLO) properties of Npe and Spe are firstly demonstrated and modulated by cocrystallization. The established "molecule-packing-property" relationship helps to rationally control the optical properties of organic materials through cocrystallization.

Insights into the Control of Optoelectronic Properties in Mixed‐Stacking Charge‐Transfer Complexes

“…Both X‐ray photoelectron spectroscopy (XPS) and energy‐dispersive X‐ray spectroscopy (EDS) element mapping (Figures S1–S3 in the Supporting Information) proved co‐assembly of the two components with coexistence of N, O, and F (or Cl) elements in the final product. Differential scanning calorimetry (DSC) traces with smooth baseline and sharp melting peak (Figure S4 in the Supporting Information) confirmed crystal structures without included solvent molecules, and the different melting points compared with those of the single components further indicate significantly changed intermolecular interactions after cocrystallization and formation of a new lattice structure. Moreover, the typical powder XRD profiles of cocrystals (TMFA and TMCA) exhibit different peaks from single components.…”

Organic Cocrystals: Beyond Electrical Conductivities and Field‐Effect Transistors (FETs)

“…In addition to those mentioned above,t here are many other properties that have been reported for organic cocrystals,s uch as nonlinear optical (NLO) properties of Spe(4styryl-pyridine)-F4DIB,N pe-F4DIB,a nd Spe-TCNB cocrystals (Figure 9a,b), [89,114] energetic-energetic cocrystals based on 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and 2,4,6-trinitrotoluene (TNT) [115] as well as diacetone diperoxide and trihalotrinitrobenzene explosives, [116] elastic and bendable cocrystals formed by caffeine and 4chloro-3-nitrobenzoic acid, [117] mechanical properties of cocrystals consist of resorcinol or 4,6-diX-res (X = Cl, Br, I) and Bpe, [118] near-infrared photothermal conversion and imaging of DBTTF-TCNB cocrystal (Figure 9c). [39] …”

“…[85][86][87][88][89][90][91][92][93] Compared with 1D organic crystals,2 Dc rystals can transfer photons along different directions,m aking them much more suitable for applications in optical planar diodes, [85a,b] awhispering-gallery-mode (WGM) resonator including controlling directional waveguides [86] and organic crystal lasing. [85][86][87][88][89][90][91][92][93] Compared with 1D organic crystals,2 Dc rystals can transfer photons along different directions,m aking them much more suitable for applications in optical planar diodes, [85a,b] awhispering-gallery-mode (WGM) resonator including controlling directional waveguides [86] and organic crystal lasing.…”

“…[87] However,v ery few organic molecules present 2D self-assembly behaviors for asingle component material, greatly impeding the development of 2D organic photonics and electronics. [1,[89][90][91][92] As mentioned in the Introduction, the cocrystals can also exhibit versatile optoelectronic properties that cannot be obtained in single component. [1,[89][90][91][92] As mentioned in the Introduction, the cocrystals can also exhibit versatile optoelectronic properties that cannot be obtained in single component.…”

Achieving Balanced Energetics through Cocrystallization

“…ADN has failed to see wide‐spread implementation due to issues with processing, hygroscopicity, and thermal stability . As cocrystallization has proved effective at modulating bulk materials properties in various fields including drug delivery, non‐linear optics, organic electronics, and EMs this presents a promising route to balanced EMs while concomitantly redressing ADNs undesirable properties. However, whereas cocrystallization is now widely studied, cocrystallization between neutral and ionic coformers has yet to significantly impact areas outside of pharmaceuticals .…”