Spectroscopic Studies and Structures of trans-Ruthenium(II) and Ruthenium(III) Bis(cyanide) Complexes Supported by a Tetradentate Macrocyclic Tertiary Amine Ligand

Department of Chemistry and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
Inorganic Chemistry (Impact Factor: 4.76). 10/2008; 47(22):10308-16. DOI: 10.1021/ic800743a
Source: PubMed


trans-[Ru(16-TMC)(C[triple bond]N)2] (1; 16-TMC = 1,5,9,13-tetramethyl-1,5,9,13-tetraazacyclohexadecane) was prepared by the reaction of trans-[Ru(16-TMC)Cl2]Cl with KCN in the presence of zinc powder. The oxidation of 1 with bromine gave trans-[Ru(16-TMC)(CN)2]+ isolated as PF6 salt (2.PF6). The Ru-C/C-N distances are 2.061(4)/1.130(5) and 2.069(5)/1.140(7) A for 1 and 2, respectively. Both complexes show a Ru(III/II) couple at 0.10 V versus FeCp2+/0. The UV-vis absorption spectrum of 1 is dominated by an intense high-energy absorption at lambda(max) = 230 nm, which is mainly originated from dpi(RuII) --> pi*(N[triple bond]C-Ru-C[triple bond]N) charge-transfer transition. Complex 2 shows intense absorption bands at lambda(max) <or= 228 nm and weaker vibronically structured absorption bands with peak maxima at 315-441 nm (epsilon(max) approximately (5-8) x 10(2) dm3 mol-1 cm-1), which are assigned to dpi(RuIII) --> pi*(N[triple bond]C-Ru-C[triple bond]N) and sigma(-CN) --> d(RuIII) charge-transfer transition, respectively. Density functional theory and time-dependent density-functional theory calculations have been performed on trans-[(NH3)4Ru(C[triple bond]N)2] (1') and trans-[(NH3)4Ru(C[triple bond]N)2]+ (2') to examine the Ru-cyanide interaction and the nature of associated electronic transition(s). The 230 nm band of 1 has been probed by resonance Raman spectroscopy. Simulations of the absorption band and the resonance Raman intensities show that the nominal nuC[triple bond]N stretch mode accounts for ca. 66% of the total vibrational reorganization energy. A change of nominal bond order for the cyanide ligand from 3 to 2.5 is estimated upon the electronic excitation.

9 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: This chapter reviews the literature published during 2008 on macrocyclic coordination chemistry. Porphyrin ligands and supramolecular chemistry are not covered in this review which primarily focuses on complexes formed with transition metals and lanthanide ions, although a few examples of s-block, p-block and actinide metals are included. In general, the focus is on the coordination properties and reactivity of the compounds, although some applications will also be discussed, particularly in a brief section at the end of the chapter. Representations of X-ray structures have been included to show interesting coordination geometries, ion encapsulation or ligand orientation.
    No preview · Article · Jun 2009 · Annual Reports Section A"" (Inorganic Chemistry)"""
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: By reacting metal cyanide complexes with NaBPh(4) in the presence of acid at room temperature, a new class of neutral isocyanotriphenylborate-containing complexes trans-Ru(L)(4)(CNBPh(3))(2) (L = pyridine, 1; 4-methylpyridine, 2; 4-tert-butylpyridine, 3), cis-Ru(bipy)(2)(CNBPh(3))(2) (4, bipy = 2,2'-bipyridine) and cis-M(phen)(2)(CNBPh(3))(2) (M = Ru, 5; M = Fe, 6; phen = 1,10-phenanthroline) have been synthesized. These new complexes are characterized by IR, UV spectroscopy and single-crystal X-ray diffractions. The electron withdrawing triphenylborate group on the isocyanide ligands has a pronounced effect on the photophysical properties of complexes 1-6 in comparison with other ruthenium(II) and iron(II) isocyanide complexes. The excitation energies corresponding to metal-to-ligand charge transfer (MLCT) shift to higher energies while the (3)MLCT emissions are quenched at room temperature.
    Full-text · Article · Dec 2009 · Dalton Transactions
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ruthenium(II)−chloride, −cyanide, and −phenylacetylide complexes bearing aromatic diimine (2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (Me2bpy), or dipyrido-[3,2-f:2′,3′-h]-quinoxaline (dpq)) and cyclic tridentate thioether 1,4,7-trithiacyclononane ([9]aneS3) have been prepared. The crystal structures of [Ru([9]aneS3)(bpy)(C≡N)](PF6) and [Ru([9]aneS3)(diimine)(C≡CPh)](PF6) (diimine = bpy and Me2bpy) reveal Ru−C distances of 2.024(4) and 2.030(3)−2.038(2) Å, respectively. The oxidation waves for the complexes are attributed to the removal of an electron from a [dπ(Ru) + L] hybrid orbital (L = −Cl, −C≡N, and −C≡CPh), whereas the reduction waves are assigned as reduction of the aromatic diimine. The lowest-energy dipole-allowed absorptions for the complexes (λmax = 403−475 nm, εmax = (3−5) × 103 dm3 mol−1 cm−1) are assigned as [dπ(RuII) + L] → π*(diimine) charge transfer transitions. All the acetylide complexes weakly emit at λmax = 663−680 nm in CH3CN at 298 K with quantum yield = (5−8) × 10−4 (λex = 450 nm), and these emissions are described as [dπ(Ru) + L] → π*(diimine) triplet charge transfer in nature. Density functional theory (DFT) and time-dependent-DFT (TD-DFT) calculations have been employed to examine the composition of the frontier molecular orbitals and the nature of the electronic transitions associated with the complexes.
    No preview · Article · Nov 2010 · Organometallics
Show more