Luminescent Cyanoruthenate(II)Diimine and Cyanoruthenium(II)Diimine Complexes

Abstract

To improve the emission and excited-state properties of luminescent cyanometalates, new classes of highly solvatochromic luminescent cyanoruthenium(II) and cyanoruthenate(II) complexes of the general formulae [Ru(PR3)2(CN)2(NN)] and K[Ru(PR3)(CN)3(NN)], respectively, were developed. These complexes could be readily synthesized through the ligand-substitution reaction of K2[Ru(CN)4(PR3)2] with a diimine ligand. The geometrical isomerism of these complexes was characterized by using various spectroscopic techniques. Their photophysical properties, solvatochromism, and electrochemistry have also been investigated. Our detailed study showed that many of these complexes exhibited extremely environmentally sensitive emissions and significantly improved emission quantum efficiencies and lifetimes compared with the well-studied tetracyanoruthenate systems.

Acid–Base Behaviour in the Absorption and Emission Spectra of Ruthenium(II) Complexes with Hydroxy‐Substituted Bipyridine and Phenanthroline Ligands

“…The cis ‐N–Ru–N chelate angles are in the range 78.4–79.1°, that is, less than 90°. This is due to the steric requirements of the chelating ligands and such angles are commonly found in related diimine transition‐metal complexes . The Ru–N bond lengths in these structures are within the range 2.04–2.10 Å, which is consistent with other Ru II tris(bipyridyl) complexes .…”

“…Thus, the lowest‐energy absorption band has tentatively been ascribed to the MLCT transition from dπ(Ru) to the π* orbital of the unsubstituted bpy. Compared with the MLCT absorption of [Ru II (bpy) 3 ] 2+ ( λ abs = 422 nm),, the lowest‐lying MLCT transitions of these complexes are considerably redshifted ( λ abs = 461–488 nm). This has been attributed to the greater destabilization of the π(Ru) orbitals in these complexes due to the presence of the more electron‐rich and weaker π‐accepting hydroxy‐substituted diimine ligands.…”

The Tunable Luminescence of Ruthenium(II) Complexes Containing Different Tetrazolate Ligands

“…The two cis ‐N–Ru–N chelate angles in bpy ligands are 78.2 and 79.1°, respectively that are less than 90°, due to the steric requirements of the chelating ligand. These angles are commonly found in related bpy transition‐metal complexes, it is noteworthy that these two chelate angles are slightly larger than the corresponding bond angle in L 3 with a value of 77.6°. The Ru–N(py) bond lengths are nearly identical with an average value of 2.07 Å, which is consistent with other Ru II tris(bipyridyl) complexes .…”

“…Thus, it is reasonable to assign the lowest‐energy absorption as the 1 MLCT transition from dπ(Ru) to the π* orbital of the unsubstituted bpy. Compared with the 1 MLCT absorption of [Ru II (bpy) 3 ] 2+ ( λ abs = 422 nm),, the lowest‐lying MLCT transitions of these complexes ( λ abs = 469–476 nm) are considerably red‐shifted. This is possibly attributed to the greater destabilization of the dπ(Ru) orbitals in these complexes due to the presence of the negatively charged tz ligands.…”

“…In order to further tune their luminescence and enhance their potential applications, our research attention is extended on utilizing various tetrazole (tz)‐containing ligands, not only because these N‐rich tz ligands could be readily prepared via well‐developed [3 + 2] dipolar cycloaddition reactions of various nitrile and azide in mild conditions, but also because they could exhibit abundant coordination modes . However, it is noteworthy that although tz‐containing ligands have been widely used in synthesis of metal‐organic frameworks with various interesting properties and luminescent compounds of iridium and rhenium , its applications in luminescent Ru II complexes were still scarcely considered and investigated. It is anticipated that the electron configuration of these luminescent compounds could be readily influenced by their abundant N‐donors and rich coordination modes.…”