To shed light on intramolecular charge-transfer phenomena in 1,2,3-triazole-linked materials, a series of 1,2,3-triazole-linked push-pull chromophores were prepared and studied experimentally and computationally. Investigated modifications include variation of donor and/or acceptor strength and linker moiety as well as regioisomers. Photophysical characterization of intramolecular charge-transfer features revealed ambipolar behavior of the triazole linker, depending on the substitution position. Furthermore, non-centrosymmetric materials were subjected to second-harmonic generation measurements, which revealed the high nonlinear optical activity of this class of materials.

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The facile preparation of three regioisomeric thienopyrrolo­[3,2,1-jk]­carbazoles applying a convenient C–H activation approach is presented. The incorporation of thiophene into the triarylamine framework significantly impacted the molecular properties in comparison to the analogous indolo­[3,2,1-jk]­carbazole scaffold. Dependent on the exact substitution pattern, the absorption onsets of the new materials are shifted toward slightly higher wavelengths compared to the analogous indolo­[3,2,1-jk]­carbazole, whereas the emission maxima of the sulfur derivatives is shifted from 375 to 410 nm. In analogy, the HOMO–LUMO energy gap of the thienopyrrolo­[3,2,1-jk]­carbazoles is reduced compared to indolo­[3,2,1-jk]­carbazole. Therefore, the developed thienopyrrolo­[3,2,1-jk]­carbazoles enrich the family of triarylamine donors and constitute a novel building block for functional organic materials.

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Three ethyne-linked push–pull materials consisting of a dimethylaniline donor and acceptors of increasing electron-withdrawing strength were prepared as nonlinear optical chromophores. Despite a high similarity of the molecular structures, all three materials featured unrelated non-centrosymmetric crystallization behavior. One of the compounds exhibits a remarkable packing with Z′ = 16 molecules in the asymmetric unit forming two interpenetrating subsystems. Inspection of the nonlinear optical activity of single crystalline powders revealed an extraordinarily efficient second harmonic generation of one of the materials with a 1200-fold increased second harmonic response compared to potassium dihydrogen phosphate. The second harmonic generation efficiency of the materials under investigation has been related to both the intrinsic molecular properties as well as the alignment of the individual chromophores within the crystal packing, highlighting the importance of a multidisciplinary approach to understand the properties of nonlinear optical materials.