Unusual Electronic Structure of the Donor–Acceptor Cocrystal Formed by Dithieno[3,2-a:2′,3′-c]phenazine and 7,7,8,8-Tetracyanoquinodimethane

Abstract

Mixed cocrystals derived from electron-rich donor (D) and electron-deficient acceptor (A) molecules showcase electronic, optical, and magnetic properties of interest for a wide range of applications. We explore the structural and electronic properties of a cocrystal synthesized from dithieno[3,2-a:2',3'-c]phenazine (DTPhz) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), which has a mixed-stack packing arrangement of the (π-electronic) face-to-face stacks in a 2:1 D:A stoichiometry. Density functional theory investigations reveal that the primary electronic characteristics of the cocrystal are not determined by electronic interactions along the face-to-face stacks, but rather they are characterized by stronger electronic interactions orthogonal to these stacks that follow the edge-to-edge donor-donor or acceptor-acceptor contacts. These distinctive electronic characteristics portend semiconducting properties that are unusual for semiconducting mixed cocrystals and suggest further potential to design organic semiconductors with orthogonal transport characteristics for different charge carriers.

Structure‐Packing‐Property Correlation of Self‐Sorted Versus Interdigitated Assembly in TTF⋅TCNQ‐Based Charge‐Transport Materials

“…F12⋅Q of Class 3a possesses an E g value of 0.001 eV, which is lower than that of F⋅Q. Recently, a computational investigation by Risko and co‐workers on the electronic structures of mixed D‐A co‐crystals proved that the primary electronic properties of mixed systems are determined by the edge‐to‐edge D‐D or A‐A interactions rather than face‐to‐face interactions (Figure ) . F12⋅Q exhibits a packing with effective edge‐to‐edge electronic interactions, which may lead to the lower E g .…”

“…Recently,acomputational investigation by Risko and co-workers on the electronic structures of mixed D-A co-crystals proved that the primary electronic properties of mixed systems are determined by the edge-to-edge D-D or A-A interactions rather than face-to-face interactions ( Figure 6). [90] F12·Q exhibits ap acking with effective edge-to-edge electronic interactions, which may lead to the lower E g .B and-structure and DOS calculations on F14·Q of Class 3b show ah igher E g of 0.228 eV.I nF 14·Q, edge-to-edge D-D and A-A molecules are displaced, leadingt ot he less effective deterministic electronic interactions. The less effectual edge-to-edge D-Da nd A-A interactions in F14·Q may lead to the larger E g in F14·Q.…”

Carrier Charge Polarity in Mixed-Stack Charge-Transfer Crystals Containing Dithienobenzodithiophene

“…Donor–acceptor (D–A) polymers composed of electron-donating and electron-accepting components have been investigated extensively owing to their excellent properties in organic field-effect transistors and photovoltaics. − In this connection, cocrystals of organic donor and acceptor molecules have attracted a great deal of attention because of their potential electronic and photonic applications. − These charge-transfer complexes potentially enable both hole and electron transport, but they usually achieve unipolar transport. Accordingly, their conducting mechanism is a focus of increasing interest. − …”

Organic Cocrystals: Recent Advances and Perspectives for Electronic and Magnetic Applications

“…Considering that the electrical properties of cocrystals highly rely on the molecular structures ( Zhu et al, 2014 ; Ai et al, 2017 ), selecting D-A molecules with matching structures as constituents is another strategy to achieve the ambipolar properties. For example, DTTCNQ [DTTCNQ, 4,8-bis(dicyanomethylene)-4,8-dihydrobenzo(1,2-b:4,5-b')-dithiophene] with the extended π-conjugated system may better match the donor molecule than TCNQ.…”