Heteroleptic ruthenium(II) complexes based on 6,6′-disubstituted 4,4′-bipyrimidines: New room temperature red-emitting species

Red-Emitting [Ru(bpy)2(N-N)]2+ Photosensitizers: Emission from a Ruthenium(II) to 2,2′-Bipyridine 3MLCT State in the Presence of Neutral Ancillary “Super Donor” Ligands

“…The judicious choice of the ligands bonded to Ru(II) can tune the energy of the excited state, − the excited-state lifetime, ,, and the absorption energy of the complex, − while overcoming the limitation imposed by the energy gap law , on the excited-state lifetime at the same time. Several strategies have been adopted by various groups to red-shift the absorption and emission of Ru(II)-heteroleptic complexes and to prolong their excited-state lifetimes; for example, (a) introduction of coplanar electron-withdrawing aromatic moiety containing bidiazine ligands bearing two-ring N heteroatoms, − thereby stabilizing the 3 MLCT state, (b) functionalization of bpy with various substituents in order to lower the LUMO, , (c) introduction of an organic chromophore to establish an equilibrium between the 3 MLCT and the organic chromophore triplet 3 LC states, (d) introduction of fused polyaromatic systems (benzoeilatin, 952 nm; isoeilatin, 994 nm; dipyridophenazine, 790 nm), and (e) the formation of oligonuclear complexes with additional electron-withdrawing metal ions. , In general, the two principal approaches toward red-emitting Ru(II) complexes are (i) the incorporation of a better acceptor ligand, , in place of one bpy in Ru(bpy) 3 2+ , thereby decreasing the energy of the LUMO of the new Ru(bpy) 2 (acceptor) 2+ species, and (ii) introduction of a better donor ligand that functions by raising the energy of the HOMO in the new Ru(bpy) 2 (donor) 2+ species …”

Substituted pyridazines as ligands in homoleptic (fac and mer) and heteroleptic Ru(ii) complexes

“…27 The second and third highly consistent reductions are assigned to the bpy ligands, though there are pyrimidyl complexes known where the second reduction is thought to occur preferentially on the non-bpy ligand. 28 The values of the oxidation potentials indicate the effect of the pyridazine-centre on the electrochemistry of the complexes; its lower pK a (an indicator of lower s-bonding strength) relative to pyridine results in higher Ru(II/III) oxidation potentials. The final column in values can have error values of up to ± 20 mV, the results were found to be highly reproducible.…”

One‐Step Synthesis of 4,4′‐Dicyano‐2,2′‐bipyridine and Its Bis(4,4′‐di‐tert‐butyl‐2,2′‐bipyridine)ruthenium(II) Complex

“…Ruthenium complexes emitting in the red are known in the literature. [13,14] Most of these compounds are difficult to synthesise because large π-systems are used to generate the red emission which makes it a complicated and often multistep preparation. The presented dnbpy-containing ruthenium complex is emissive in the red at room temperature and in fluids without further substituents and can be obtained easily.…”