6-(Arylvinylene)-3-bromopyridine derivatives as lego building blocks for liquid crystal, nonlinear optical, and blue light emitting chromophores

A novel general synthetic strategy, based on a convergent approach, allowed us to prepare a series of conjugated 6,6′-distyryl-3,3′-bipyridine derivatives via the Suzuki reaction. First, the key electron-donor and electron-acceptor 6-(arylvinylene)-3-bromopyridine building blocks were synthesized by Knoevenagel-or Siegrist-type reactions. Second, some of them were transformed to the corresponding pyridylboronic esters. Finally, for the first time, we successfully demonstrated that such blocks can be homo- and cross-coupled in high yields and multigram scales, leading to noncentrosymmetic or symmetric chromophores. Their mesogenic, electrochemical, and optical properties have been investigated depending on the electronic structure. In this series, push-pull compounds are liquid crystals and promising for NLO applications. Whatever the structure, all of these compounds exhibit a high electron affinity and are strongly fluorescent. As an application, lasing properties of one push-pull and one symmetrical compound are reported. In addition, a blue-emitting LED was fabricated whose performances at 10 mA/cm ² are a luminous efficiency of 3.9 cd/A, a power efficiency of 1.4 lmAV, and an external quantum efficiency of 2.9%. Thus, this versatile synthetic route is of particular interest due to the potential applications of the chromophores in several optoelectronic fields.