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Donor-substituted cyanoethynylethenes (CEEs) are planar push–pull chromophores featuring intense intramolecular charge-transfer (CT) interactions and high third-order optical nonlinearities. Their thermal stability allows for the formation of crystalline thin films by vapor-phase deposition. On the other hand, high-quality amorphous thin films are preferred for opto-electronic applications and such films can be prepared using nonplanar push–pull chromophores with a less pronounced propensity to crystallize. By taking advantage of a versatile, atom-economic 'click-chemistry'-type transformation, involving a formal [2 + 2] cycloaddition of tetracyanoethene (TCNE) to electron-rich alkynes, followed by cycloreversion, stable donor-substituted 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) are obtained in high yield and large quantities. These nonplanar push–pull chromophores also feature intense intramolecular CT and, in many cases, high third-order optical nonlinearities. Some of these compounds form high-optical-quality amorphous thin films by vapor-phase deposition, and first applications in next-generation opto-electronic devices have already been demonstrated. Chiral derivatives display high helical twisting power and are efficient dopants to translate molecular into macroscopic chirality, by switching nematic into cholesteric liquid crystalline phases.

Abstract: Structural characterization and spectroscopic study of charge transfer of two polymorphs of complex (TTF)3(TNF)2, where TTF=tetrathiafulvalene and TNF=2,4,7-trinitro-9-fluorenone. Two polymorphs, α and β, for the charge-transfer complex (TTF)3(TNF)2, with TTF=tetrathiafulvalene and TNF=2,4,7-trinitro-9-fluorenone, have been characterized by X-ray diffraction and infrared spectroscopy. A structural modification of the TNF moiety allows different packing structures. An estimation of the degree of charge transfer establishes that δβ > δα ≈0, a feature consistent with crystalline structures. To cite this article: A. Salmerón-Valverde, S. Bernès, C. R. Chimie 8 (2005). [Copyright &y& Elsevier]