Abstract
From a dicyano-phenylenevinylene (PV) and an azobenzene (AB) skeleton, two new symmetrical salen dyes were obtained. Terminal bulky substituents able to reduce intermolecular interactions and flexible tails to guarantee solubility were added to the fluorogenic cores. Photochemical performances were investigated on the small molecules in solution, as neat crystals and as dopants in polymeric matrixes. High fluorescence quantum yield in the orange-red region was observed for the brightest emissive films (88% yield). The spectra of absorption and fluorescence were predicted by Density Functional Theory (DFT) calculations. The predicted energy levels of the frontier orbitals are in good agreement with voltammetry and molecular spectroscopy measures. Employing the two dyes as dopants of a nematic polymer led to remarkable orange or yellow luminescence, which dramatically decreases in on-off switch mode after liquid crystal (LC) order was lost. The fluorogenic cores were also embedded in organic polymers and self-assembly zinc coordination networks to transfer the emission properties to a macro-system. The final polymers emit from red to yellow both in solution and in the solid state and their photoluminescence (PL) performance are, in some cases, enhanced when compared to the fluorogenic cores.
Highlights
The development of solid state fluorescent materials, based on an organic scaffold or metal containing, is an area of research in enormous development due to the numerous applications for the study of biological [1,2,3] and photonic systems [4,5,6,7,8,9,10]
Extended π-system with donor-acceptor framework featuring a large dipole moment in the excited state are often reported as organic emitters in the solid state and as candidates for optoelectronic applications [11,12]
In two of our previous works [22,23], we reported of two liquid crystalline dyes based on a di-cyano phenylenevinylene and an azobenzene skeleton
Summary
The development of solid state fluorescent materials, based on an organic scaffold or metal containing, is an area of research in enormous development due to the numerous applications for the study of biological [1,2,3] and photonic systems [4,5,6,7,8,9,10]. The challenge to obtain solid-state photoluminescent materials translates in the easy and cost-effective assembly of macro-architectures starting from small PL active molecules [18,19,20,21]. This means dye-doped matrixes and covalently bonded emissive materials
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