Three new stilbenyl‐azopyrroles 3 a–c were synthesized through a Mizoroki‐Heck C−C‐type coupling reaction between the 2‐(4′‐iodophenyl‐azo)‐N‐methyl pyrrole (1), and three different para‐substituted styrene derivatives. Inclusion of additional NO2 and NMe2 groups at the para‐position of the stilbenyl section resulted in significant changes of their linear and non‐linear optical properties. The photoisomerization behavior was studied through ultrafast laser techniques for single‐ and two‐photon excitation. The time‐resolved studies indicate that, despite the drastic changes in conjugation, the typical path for photoisomerization is maintained in these systems for both single and biphotonic excitation. In particular, the NO2 substituted molecule showed improved two‐photon absorption capacities, together with a significant trans−cis isomerization channel, implying that the photoswitching process can be controlled with high spatial precision through non‐linear optical excitation.
New push–pull biphenyl-azopyrrole photoswitches are efficiently obtained via a Suzuki cross-coupling reaction, give rise to J-type aggregates in binary MeOH : H2O solvents and undergo a water-assisted cis-to-trans isomerization at room temperature.
We report the synthesis of two [N,N]-donor ligands (5 a-b) containing a 2-chalcogenazoline as the structural motif. These compounds were synthesized from a common intermediate Fischer type aminocarbene complex (3). The palladium-complexes of these [N,N]-donor ligands were successfully used as catalytic precursors in the Mizoroki-Heck coupling reaction between aryl halides and methyl acrylate, styrene and ethylene. For methyl acrylates, high yields with TOF values between 0.6 and 5.5 × 10 5 h À 1 were obtained. In the case of ethylene, we reached high regioselectivities to obtain a diversity of styrene derivatives under soft pressure conditions, with good values of TON and TOF.
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