Cocrystals Strategy towards Materials for Near‐Infrared Photothermal Conversion and Imaging

Abstract

A cocrystal strategy with a simple preparation process is developed to prepare novel materials for near-infrared photothermal (PT) conversion and imaging. DBTTF and TCNB are selected as electron donor (D) and electron acceptor (A) to self-assemble into new cocrystals through non-covalent interactions. The strong D-A interaction leads to a narrow band gap with NIR absorption and that both the ground state and lowest-lying excited state are charge transfer states. Under the NIR laser illumination, the temperature of the cocrystal sharply increases in a short time with high PT conversion efficiency (η=18.8 %), which is due to the active non-radiative pathways and inhibition of radiative transition process, as revealed by femtosecond transient absorption spectroscopy. This is the first PT conversion cocrystal, which not only provides insights for the development of novel PT materials, but also paves the way of designing functional materials with appealing applications.

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

“…Reprinted (adapted) with permission from Refs. [114], [89], [39]. Copyright 2017, 2016, 2018 Wiley-VCH,r espectively.…”

“…Actually,c harge-transfer interactions (Figure 1d), in which the charge-transfer from the highest occupied molecular orbital (HOMO) of the electron-rich donor to the lowest unoccupied molecular orbital (LUMO) of the electrondeficient acceptor, [38a] exist in most organic cocrystals and act as the main driving force for the formation of cocrystals when astrong acceptor assembles with an suitable donor, such as TCNQ-perylene,T CNQ-TTF,a nd tetracyanobenzene-(TCNB)-dibenzotetrathiafulvalene (DBTTF). [15,16,39] The strength of charge-transfer interaction depends on the electron affinity energy of the acceptors,t he ionization potential of the donor and the electrostatic Coulomb forces between the D-A pairs, [38a] which can be characterized by IR and Raman spectroscopy. [40] Another important driving force is hydrogen bond formation ( Figure 1b).…”

“…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]…”

Diphenylene‐Tetracyanoquinodimethane Cocrystals as Stable Organic Rectifiers

“…Combined with the single crystal structure of STC cocrystal, we can judge that these two new peaks are (020) and (040) faces of STC. By this token, the (0k0) lattice plane is parallel to the substrate . The calculated energy diagrams (Figure d) imply that the highest occupied molecular orbital (HOMO) of STC cocrystal is −6.027 eV, which is closer to the HOMO (−5.505 eV) of STB, meanwhile, the lowest unoccupied molecular orbital (LUMO) of cocrystal (−4.279 eV) is near to the LUMO (−4.819 eV) of TCNQ.…”

Thermally Activated Delayed Fluorescence in an Organic Cocrystal: Narrowing the Singlet–Triplet Energy Gap via Charge Transfer

“…[20] TCNB usually acts as the acceptor in CT cocrystals. [21,22] We synthesized the TSB-TCNB cocrystal (TTC) with yellow color from the supramolecular assembly of TSB and TCNB molecules ( Figure 1b and Supporting Information, Figure S2a). Further experimental and theoretical analysis confirm that the ICT in the rigid crystalline state of TTC is responsible for efficient RISC.…”