Crystal Engineering, Electron Conduction, Molecular Recognition and Reactivity by Chalcogen Bonds in Tetracyanoquinodimethanes Fused with [1,2,5]Chalcogenadiazoles

Abstract

AbstractStudies on a series of tetracyanoquinodimethanes (TCNQs) fused with [1,2,5]chalcogenadiazole rings reveals that chalcogen bonds (ChBs), through E•••N≡C (E = S or Se) contacts, are a decisive factor in determining their crystal structures, with the formation of one- or two-dimensional networks in a lateral direction. For anion-radical salts generated by one-electron reduction, electron conduction occurs in the direction of the network due to intermolecular electronic interactions involving ChBs. Based on the reliable synthon E•••N≡C for crystal engineering, molecular recognition occurs so that solid-state molecular complexes are selectively formed with certain donors, such as xylenes, among their isomers by charge-transfer-type clathrate formation. The inclusion cavity of the clathrate might provide a reaction environment for photoinduced electron transfer in the solid state. The accommodation of multiple conformers of overcrowded ethylene exhibiting thermo/mechanochromism is another example of a novel function that can be realized by ChBs through E•••N≡C contacts. Therefore, these chalcogenadiazolo-TCNQs endowed with the ability to form ChBs are promising materials for the development of novel solid-state functions.1 Introduction2 Bis[1,2,5]thiadiazolo-TCNQ (BTDA)2.1 Chalcogen Bonds in Crystal Structures of BTDA and its Se Analogues2.2 Electronic Effects of Chalcogen Bonds in Organic Conductors Consisting of BTDA2.3 Molecular Recognition by Chalcogen Bonds in Molecular Complexes of BTDA2.4 Single-Crystalline-State Photoreactions of Molecular Complexes of BTDA2.5 Overcrowded Ethylene Composed of a BTDA Substructure3 TCNQ Analogues Fused with a [1,2,5]Chalcogenadiazole3.1 Crystal Structures of Chalcogenadiazolo-TCNQs3.2 Crystal Structures of Chalcogenadiazolo-TCNNQs: An E•••N≡C Chalcogen Bond versus a Weak C–H•••N≡C Hydrogen Bond3.3 Molecular Recognition by Chalcogen Bonds in TCNNQ Derivatives4 Outlook