Synthesis and electrochemical properties of bis(bipyridine)ruthenium(II) complexes bearing pyridinyl- and pyridinylidene ligands induced by cyclometalation of N′-methylated bipyridinium analogs

Koizumi, Toru; Tomon, Takashi; Tanaka, Koji

doi:10.1016/j.jorganchem.2004.11.032

Cited by 23 publications

(20 citation statements)

References 53 publications

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“…93,110 Inherent in the association of a larger 13 C chemical shift with more "carbene character" is the assumption that metalto-carbene π-back-donation does not effect the same amount of carbon shielding to the donor C atom as participation in π-bond formation within the heterocyclic ring. In the outstanding work of Tanaka and co-workers, 106,108,109 such conclusions are corroborated by significant shifts of the metal oxidation potentials, as a consequence of the expected difference in charge transfer. The sensitivity of the chemical shift of the C donor atom toward the effect exercised by ancillary ligands is probably most dramatically illustrated by the work of Rourke's group.…”

Section: Carbenes or Zwitterionic Ligands?mentioning

confidence: 91%

“…Reaction of 150 with the in situ formed metal precursor [Ru(bpy) 2 (EtOH) 2 ](PF 6 ) 2 has led to the remote isomer 151 exclusively (see Scheme 50). 106 Based on the discussion in the previous section, this reaction outcome may be understood by considering a synergistic interplay between the electronic preference for pyridinium C4 metallation and the steric protection of the pyridinium ortho positions by the methyl group (F-strain 83 ). The pyridine-assisted cyclometallation protocol has been further extended to prepare Ru complexes that contain terpyridinium-derived N,C,N-and N,N,C-chelating pyridylidenes.…”

Section: Scheme 49mentioning

confidence: 99%

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Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

et al. 2009

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theme are found via the replacement or displacement of one N atom, thus providing carbenes derived from pyrazolium, isothiazolium, and even quinolinium salts that contain a stabilizing heteroatom in a remote position (G-J in Figure 1). Recently, carbenes such as K, which are comprised of only one heteroatom and lack delocalization through the heterocycle, have been discovered as versatile ligands, thus constituting another important class of carbenes with low heteroatom stabilization. Both the synthesis of the organometallic complexes of these ligands as well as the (catalytic) properties of the coordinated metal centers generally show distinct differences, compared to the more classical NHC complexes, such as C2-metallated imidazolylidenes. This review intends to describe such differences and highlights the chemical peculiarities of these types of N-heterocyclic carbene complexes. It introduces, in a qualitative manner, the synthetic routes that have been established for the preparation of such complexes, covering the literature from the very beginning of activities in this area up to 2008. While specialized reviews on some aspects of the present topic have recently appeared, 7 a comprehensive overview of the subject has not been available thus far. Rather than just being descriptive, the present account is mainly directed toward the impact of these still unusual metal-carbene bonding modes on the electronic properties and on the new catalytic applications that have been realized by employing such new carbene complexes. As a consequence of our focus on complexes with less-stabilized heterocyclic ligands, systems comprising acyclic carbenes have not been included, and the interested reader is, instead, referred to the pioneering and

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Section: Carbenes or Zwitterionic Ligands?mentioning

confidence: 91%

Section: Scheme 49mentioning

confidence: 99%

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

et al. 2009

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“…This redshift was due to a destabilization of the HOMO by the carbanionic ligand through an increase in the crystal field strength 39,189,219. Exceptions included complexes 125 and 127 reported by Tanaka et al, where the double bond character of Ru–C para to a N ‐methylpyridinium group annihilated the cyclometallation redshift effect 191,221…”

Section: Physicochemical Propertiesmentioning

confidence: 98%

Cycloruthenated Compounds – Synthesis and Applications

et al. 2009

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The syntheses of cycloruthenated compounds by several methods, and especially by the C-H activation pathway, have been reviewed. Many ruthenium-containing starting materials lead to these interesting organometallic compounds, which have found various applications in different fields of chemistry. Their reactivity highlights both the variety of reactions that were found to occur at the Ru-C bonds as well as the inertness of the organometallic moiety when these species are exposed to strongly oxidizing molecules or to reactive halogenation reagents. Their use as catalyst precursors showed them to be particularly efficient for hydrogenation reactions, either by H 2 or by hydride transfer.

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“…45 The only previous account of structurally related species concerns catalytic studies with hydride complexes that are unsuitable for luminescence. 46 A number of reports of cyclometalated complexes of N-methylbipyridinium species with Pd/Pt 47 or Ru 48 have appeared. The bright blue or blue-green emission and aqueous solubility of our Ir III 3,2′-C^N species 45 suggests potential uses in highly efficient OLEDs and/or bio-sensing/imaging.…”

Section: Introductionmentioning

confidence: 99%

Cyclometalated Ir(iii) complexes of deprotonated N-methylbipyridinium ligands: effects of quaternised N centre position on luminescence

et al. 2015

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Six new tricationic Ir(III) complexes of cyclometalating ligands derived from 1-methyl-2-(2'-pyridyl)pyridinium or 1-methyl-4-(2'-pyridyl)pyridinium are described. These complexes of the form [Ir(III)(C^N)2(N^N)](3+) (C^N = cyclometalating ligand; N^N = α-diimine) have been isolated and characterised as their PF6(-) and Cl(-) salts. Four of the PF6(-) salts have been studied by X-ray crystallography, and structures have been obtained also for two complex salts containing MeCN and Cl(-) or two Cl(-) ligands instead of N^N. The influence of the position of the quaternised N atom in C^N and the substituents on N^N on the electronic/optical properties are compared with those of the analogous complexes where C^N derives from 1-methyl-3-(2'-pyridyl)pyridinium (B. J. Coe, et al., Dalton Trans., 2015, 44, 15420). Voltammetric studies reveal one irreversible oxidation and multiple reduction processes which are mostly reversible. The new complexes show intramolecular charge-transfer absorptions between 350 and 450 nm, and exhibit bright green luminescence, with λmax values in the range 508-530 nm in both aqueous and acetonitrile solutions. In order to gain insights into the factors that govern the emission properties, density functional theory (DFT) and time-dependent DFT calculations have been carried out. The results confirm that the emission arises largely from triplet excited states of the C^N ligand ((3)LC), with some triplet metal-to-ligand charge-transfer ((3)MLCT) contributions.

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Synthesis and electrochemical properties of bis(bipyridine)ruthenium(II) complexes bearing pyridinyl- and pyridinylidene ligands induced by cyclometalation of N′-methylated bipyridinium analogs

Cited by 23 publications

References 53 publications

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

Cycloruthenated Compounds – Synthesis and Applications

Cyclometalated Ir(iii) complexes of deprotonated N-methylbipyridinium ligands: effects of quaternised N centre position on luminescence

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