Luminescence behavior of protonated N-heterocycles : toward white light emission
Keywords: diazines, photoluminescence, white light emitters.
White light-emitting diodes (WOLEDs) are an efficient alternative to conventional lighting sources. Nevertheless, approaches to obtain WOLEDs still require complex processes that lead to high costs. In this sense, the use of a single emitting material that can take two forms of complementary emitting colors has emerged as a new strategy for the fabrication of WOLEDs. Our approach is to study the luminescent behavior upon protonation of a series of D-π-A push-pull molecules based on a diazine acceptor unit. Protonation of some blue-emitting pyrimidine derivatives that exhibited white photoluminescence by controlled protonation both in solution and the solid state has been designed .
Design of push-pull organometallics chromophores for second-order nonlinear optics
Keywords : dialkynyl Ru and Pt complexes; pyranylidene push-pull chromophores, second order non linear optics (NLO); ICT
Transition-metal complexes with second-order Non-Linear Optical (NLO) properties are important as molecular building block materials for the growing field of molecular photonics. Over the past few years, our research has dealt with synthesizing and studying the properties of asymmetrical push-pull dialkynyl ruthenium- and platinum-based complexes with D–π–M–π–A arrangements. All complexes incorporate pro-aromatic donor groups (D), such as pyranylidene ligands whose electron-donating ability is based on the formation of an aromatic pyrylium fragment upon an ICT process, and various electron attracting groups (A), such as methyl pyrimidinium, separated by a metal center and π-conjugated linkers.
While we have synthesized asymmetrical Ru(II) and Pt(II) complexes through conventional cross-coupling reactions, we have developed an original one-pot approach for the synthesis of targeted ruthenium-diacetylide complexes.
Second-order Non-Linear Optical (NLO) properties of the synthesized complexes and their entirely organic analogues were determined by the Electric Field-Induced Second Harmonic (EFISH) generation method. All compounds (organic and organometallic) exhibited positive µβ values, which dramatically increased upon methylation of the pyrimidine acceptor fragment. With the same donor-acceptor combination, the strongest NLO response was obtained with the ruthenium complexes placing them among the more efficient NLO alkynyl metal complexes reported so far.