Molecular self-assemblies and gels with tunable emission
The possibility to tune the emission properties of organogels derived from ?-conjugated systems was recently demonstrated. For example, a white-light-emitting organogel could be designed by the controlled self-assembly of a bischolesterol-functionalized OPV donor that allows slow energy migration and partial energy transfer in the gel state to an encapsulated acceptor.The white-light emission occurs because of the combination of blue-light emission from the OPV monomers, green-light emission from the OPV self-assembly, and red-light emission from the acceptor (Adv. Mater. 2009, 21, 2059). Subsequently it was been shown that fluorescence can be modulated by alignment of gels in liquid crystals. The aligned fibers of OPV gels showed polarized yellow emission in the direction of the long axis of fibers. New types of electro-optical and photonic systems can be visualized in the future as the polarized luminescence of these fibers is combined with the dynamic properties of the liquid crystals (Adv. Mater. 2009, 21, 4029). A facile molecular approach to generate white light emission by combining carboxylic functionalized poly(m-phenylenevinylene) polymeric architectures with lanthanide ?-diketonate complexes has been demonstrated. Investigations revealed that carboxylic functionalized polymeric material with Eu3+-?-diketonate complex exhibits unique magenta emission when excited at 310 nm. On the other hand, carboxylic functionalized polymeric material with Tb3+-?-diketonate complex shows bright sky-blue emission. Interestingly, when Eu3+ and Tb3+ were incorporated into m-PPV polymer backbone in equimolar ratio along with acetyl acetone as co-ligand, exhibited a novel white emission color with CIE 1976 color coordinates x = 0.28, y = 0.34 ( J. Phys. Chem. B, 2009, 113, 14128–14138 ).
Chemical Sciences and Technology