II ) And Ir Research Articles

TD-DFT Benchmark on Inorganic Pt(II) and Ir(III) Complexes

We report in the present paper a comprehensive investigation of representative Pt(II) and Ir(III) complexes with special reference to their one-photon absorption spectra employing methods rooted in density functional theory and its time dependent extension. We have compared nine different functionals ranging from generalized gradient approximation (GGA) to global or range-separated hybrids, and two different basis sets, including pseudopotentials for 4 iridium and 7 platinum complexes. It turns out that hybrid functionals with the same exchange part give comparable results irrespective of the specific correlation functional (i.e., B3LYP is very close to B3PW91 and PBE0 is very close to MPW1PW91). More recent functionals, such as CAM-B3LYP and M06-2X, overestimate excitation energies, whereas local functionals (BP86 -GGA-, M06-L -Meta GGA-) strongly underestimate transition energies with respect to experimental results. As expected, basis set effects are weak, and the use of a triple-ζ polarized (def2-TZVP) basis set does not significantly improve the computed excitation energies with respect to a classical double-ζ basis set (LANL2DZ) augmented by polarization functions, but it significantly raises the computational effort.

Ru(II), Os(II), and Ir(III) complexes with chelating pyridyl-mesoionic carbene ligands: structural characterization and applications in transfer hydrogenation catalysis.

Chelating ligands with one pyridine donor and one mesoionic carbene donor are fast establishing themselves as privileged ligands in homogeneous catalysis. The synthesis of several new Ir(III)-Cp*- and Os(II)-Cym complexes (Cp* = pentamethylcyclopentadienyl, Cym = p-cymene=4-isopropyl-toluene) derived from chelating pyridyltriazolylidenes where the additional pyridine donor was incorporated via the azide part of the triazole is presented. Furthermore, different 4-substituted phenylacetylene building blocks have been used to introduce electronic fine-tuning in the ligands. The ligands thus can be generally described as 4-(4-R-phenyl)-3-methyl-1-(pyridin-2-yl)-1H-1,2,3-triazol-5-ylidene (with R being H (L(1)), Me (L(2)), OMe (L(3)), CN (L(4)), CF3 (L(5)), Br (L(6)) or NO2 (L(7))). The corresponding complexes (Ir-1 to Ir-7 and Os-1 to Os-7) were characterized by standard spectroscopic methods, and the expected three-legged, piano-stool type coordination was unambiguously confirmed by X-ray diffraction analysis of selected compounds. Together with Ru(II) analogues previously reported by us, a total of 21 complexes were tested as (pre)catalysts for the transfer hydrogenation of carbonyl groups, showing a remarkable reactivity even at very low catalyst loadings. The electronic effects of the ligands as well as different substrates were investigated. Some mechanistic elucidations are also presented.

Synthesis and characterization of Ru(II) and Ir(III) complexes that bear camphoric 1,3-diamine ligands

Two rigid N-monosulfonylated 1,3-diamine ligands have been prepared starting from commercially available d-camphor through three steps. Their reactions with [Ru(η6-arene)(μ-Cl)Cl]2 (arene = p-cymene or C6H5CO2Et) or [Ir(η5-C5Me5)(μ-Cl)Cl]2 afforded five new complexes. The structures of one monosulfonamide 1,3-diamine ligand and three organometallic complexes were confirmed by X-ray crystallography.

Stabilization of cucurbituril/guest assemblies via long-range Coulombic and CH···O interactions.

Cucurbit[n]urils (CB[n], n = 6-8) interact strongly with metal-bound 4'-substituted terpyridine ligands (M = Fe(II) and Ir(III)) via CH···O hydrogen bonding, despite significant separation between the positive metallic cation and the carbonylated rim of CB[n], and the location of the latter in the second coordination sphere of the metal ion. While water has been shown to mediate interactions between cations and CB[n]s in some assemblies, mediation by organic ligands is unprecedented. The recognition process is driven by the contrasted combination of extremely favorable binding enthalpies (up to 20.2 kcal/mol) and very unfavorable entropic components (as low as -10.2 kcal/mol). Dynamic oligomers were prepared in the presence of CB[8], which acts as a "soft", noncovalent linker between metal/terpyridine complexes, and interconnects two 4'-substituents inside its cavity. Social self-sorting between CB[8] and metal/terpyridine complexes bearing 4'-(2-naphthyl) and 4'-(2,3,5,6-tetrafluorophenyl) substituents was also observed, and could afford well-organized oligomers with alternating Fe(II) and Ir(III) cations.

A facile and versatile methodology for cysteine specific labeling of proteins with octahedral polypyridyl d6 metal complexes

We have synthesized and characterized four octahedral polypyridyl d6 metal complexes bearing the 5,6-epoxy-5,6-dihydro-[1,10]phenanthroline ligand (L1) as cysteine specific labeling reagents. The proposed synthetic pathways allow the preparation of the metal complexes containing Re(I), Ru(II), Os(II) and Ir(III) while preserving the epoxide functionality. The complexes were characterized by 1H and 13C NMR, mass spectrometry, UV–visible and luminescence spectroscopies as well as cyclic voltammetry. As proof of concept, a set of non-native single cysteine P450 BM3 heme domain mutants previously developed in our laboratory was used to study the labeling reaction. We demonstrate that the proposed labels can selectively react, often in high yield, with cysteine residues of the protein via the nucleophilic thiol ring opening of the epoxide moiety. In addition, under basic conditions, subsequent loss of a water molecule led to the aromatization of the phenanthroline ring on the protein-bound label compounds, as observed by mass spectrometry and luminescence measurements.

Effect of metal centres and substituents on the structure and optoelectronic properties of diarylethene compounds: A theoretical study

Diarylethene derivatives are a class of fascinating photochromic materials because of their open and closed isomers with different absorption spectra and many other characteristics. To reveal the detailed structure and optoelectronic properties as well as the effect of metal centres and substituents on them, a systematic study on a series of diarylethene derivatives and their Re(I), Pt(II), and Ir(III) complexes was performed via theoretical calculation. The optimized geometries, electronic properties, frontier molecular orbitals, ionization potentials, electron affinities, reorganization energies, and absorption spectra for both of their open- and closed-isomers have been calculated and analyzed. Metal-coordination and substituents exhibit great influence on the photophysical, charge-injection and -transporting characteristics. In addition, the binding of F− with the boron atom of dimesitylboryl group through Lewis acid/base interactions also induces great changes of structural, photophysical and electronic properties for these diarylethene derivatives, and consequently the compound with the substituent of dimesitylboryl group can be used as selective near-infrared phosphorescent F− probe.

Spin-Orbit Coupling and Outer-Core Correlation Effects in Ir- and Pt-Catalyzed C-H Activation.

The transition metal-dependent spin-orbit coupling (SOC) and outer-core (5s5p) correlation effects in Ir- and Pt-catalyzed C-H activation processes are studied here using high level ab initio computations. The catalysts involve complexes with oxidation states: Ir(I), Ir(III), Pt(0), and Pt(II). It is demonstrated that for these heavy 5d transition metal-containing systems, the SOC effect and outer-core correlation effect on C-H activation are up to the order of ∼1 kcal/mol, and should be included if chemical accuracy is aimed. The interesting trends in our studied systems are: (1) the SOC effect consistently increases the C-H activation barriers and is apparently larger in higher oxidation states (Pt(II) and Ir(III)) than in low-oxidation states (Pt(0) and Ir(I)); and (2) the magnitude of outer-core (5s5p) correlation effects is larger in less coordinate-saturated system. The effect of basis set on the outer-core correlation correction is significant; larger basis sets tend to increase the C-H activation barriers.

Transition metal complexes with strong absorption of visible light and long-lived triplet excited states: from molecular design to applications

Transition metal complexes of Ru(II), Pt(II) and Ir(III) with strong absorption of visible light and long-lived T1 excited states were summarized. A design rationale of these complexes, i.e. direct metalation of organic chromophore, was proposed. Alternatively an organic chromophore can be dangled on the peripheral moiety of the coordination center. In both cases the long-lived intraligand triplet excited state (3IL) can be accessed. However, the 3IL excited state is usually emissive for the former case and it is very often non-emissive for the latter case. Two methods used for study of the long-lived triplet excited state, i.e. the time-resolved transient difference absorption spectroscopy and the spin density analysis, are briefly introduced. Preliminary applications of the complexes in luminescent O2 sensing and triplet–triplet annihilation (TTA) upconversions were discussed.

Designing organometallic compounds for catalysis and therapy

Bioorganometallic chemistry is a rapidly developing area of research. In recent years organometallic compounds have provided a rich platform for the design of effective catalysts, e.g. for olefin metathesis and transfer hydrogenation. Electronic and steric effects are used to control both the thermodynamics and kinetics of ligand substitution and redox reactions of metal ions, especially Ru(II). Can similar features be incorporated into the design of targeted organometallic drugs? Such complexes offer potential for novel mechanisms of drug action through incorporation of outer-sphere recognition of targets and controlled activation features based on ligand substitution as well as metal- and ligand-based redox processes. We focus here on η(6)-arene, η(5)-cyclopentadienyl sandwich and half-sandwich complexes of Fe(II), Ru(II), Os(II) and Ir(III) with promising activity towards cancer, malaria, and other conditions.

ChemInform Abstract: Organometallic Pt(II) and Ir(III) Triplet Emitters for OLED Applications and the Role of Spin‐Orbit Coupling: A Study Based on High‐Resolution Optical Spectroscopy

AbstractReview: 141 refs.

Rodlike Fluorescent π-Conjugated 3,3′-Bipyridazine Ligand: Optical, Electronic, and Complexation Properties

We report on the design and synthesis of a new quadrupolar pi-conjugated 3,3'-bipyridazine D-A-D ligand. Its electronic and optical properties were investigated. Besides high fluorescence and pronounced solvatochromism, it exhibits an inherent electroactivity exploited to build an organic green light emitting device. Moreover, the ability of this ligand to complex metallic centers (Cu(I), Ni(II), Pt(II), and Ir(III)) was also investigated to access different geometries and to tune their electronic and optical properties. These preliminary results open up the synthesis of heavy-metal complexes to obtain phosphorescent emitters.

Synthesis, Characterization, Absorption Spectra, and Luminescence Properties of Multinuclear Species Made of Ru(II) and Ir(III) Chromophores

A series of new mixed-metal Ru(II)-Ir(III) trinuclear complexes have been prepared and characterized, together with their mononuclear parents and a series of closely related dinuclear and trinuclear homometallic Ru(II) and Ir(III) species, and their absorption spectra and luminescence properties (both at 77 K in rigid matrix and at room temperature in fluid solution) have been studied. The absorption spectra and luminescence properties of the Ru(II) species and subunits are dominated by metal-to-ligand charge-transfer (MLCT) transitions and excited states, whereas ligand centered (LC) transitions and excited states govern the spectroscopic and photophysical properties of most of the Ir(III) species here studied, with MLCT states playing an important role when cyclometalated Ir(III) subunits are present. Each metal-based subunit retains in the multinuclear arrays its own spectroscopic properties, but in the case of the mixed Ru-Ir species an efficient, additional decay channel is opened for the excited states involving the Ir-centered subunits, that is, photoinduced energy transfer to the lower-lying MLCT state(s) involving the Ru centers.

A Synthetic, Structural, Spectroscopic and DFT study of ReI, CuI, RuII and IrIII Complexes Containing Functionalised Dipyrido[3,2‐a:2′,3′‐c]phenazine (dppz)

The ligands 11-cyanodipyrido[3,2-a:2',3'-c]phenazine and 2-(11-dipyrido[3,2-a:2',3'-c]phenazine)-5-phenyl-1,3,4-oxadiazole have been coordinated to Re(I), Cu(I), Ru(II) and Ir(III) metal centres. Single-crystal X-ray analyses were performed on fac-chlorotricarbonyl(11-cyanodipyrido[3,2-a:2',3'-c]phenazine)rhenium (C(22)H(9)ClN(5)O(3)Re, a=6.509(5), b=12.403(5), c=13.907(5) A, alpha=96.88(5), beta=92.41(5), gamma=92.13(5) degrees , triclinic, P1, Z=2) and bis-2,2'-bipyridyl(2-(11-dipyrido[3,2-a:2',3'-c]phenazine)-5-phenyl-1,3,4-oxadiazole)ruthenium triflate2 CH(3)CN (C(52)H(36)F(6)N(12)O(8)RuS(2), a=10.601(5), b=12.420(5), c=20.066(5) A, alpha=92.846(5), beta=96.493(5), gamma=103.720(5) degrees , triclinic, P1, Z=2). The ground- and excited-state properties of the ligands and complexes have been investigated with a range of techniques, including electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and excited-state lifetime studies. Spectroscopic, time-resolved and DFT studies reveal that the ligand-centred (LC) transitions and their resultant excited states play an important role in the photophysical properties of the complexes. Evidence for the presence of lower-lying metal-to-ligand charge-transfer transitions is obtained from resonance Raman spectroscopy, but nanosecond transient Raman experiments suggest that once excited, the (3)LC state is populated.

Transfer Hydrogenation of α‐Branched Ketimines: Enantioselective Synthesis of Cycloalkylamines via Dynamic Kinetic Resolution

AbstractThe transfer hydrogenation of 2‐substituted bicyclic and monocyclic ketimines using HCO2H/ Et3N as the hydrogen source and TsDPEN‐based Ru(II) and Ir(III) catalysts proceeds with dynamic kinetic resolution to afford the corresponding cis‐cycloalkylamines with moderate to excellent levels of diastero‐ and enantioselectivity. A “one‐pot” procedure starting from ketones as starting materials with in situ formation of the reacting imines has also been developed.

Two-color luminescence from a tetranuclear Ir(iii)/Ru(ii) complex

A new tetranuclear compound containing Ru(II) and Ir(III) polypyridine subunits exhibits two independent emissions at room temperature, as a consequence of weak interchromophoric coupling; in contrast, at 77 K energy transfer from Ir-based chromophores to the Ru-based ones is quantitative.

Boronic acid-substituted metal complexes: versatile building blocks for the synthesis of multimetallic assemblies

Polypyridyl complexes of Ru(II) and Ir(III) incorporating a boronic acid substituent undergo cross-coupling with bromo-substituted complexes, and a sequential coupling-bromination-coupling strategy permits the controlled synthesis of a luminescent Y-shaped heterometallic assembly, in which efficient energy transfer to the terminus occurs.

Molecularly doped polymer light emitting diodes utilizing phosphorescent Pt(II) and Ir(III) dopants

The use of molecular phosphorescent dyes in polymer-based organic light emitting diodes (OLED) of different architectures was investigated by incorporating several phosphorescent dopants into poly(N-vinylcarbazole) (PVK)-based single layer and single heterostructure light emitting diodes (LEDs). In particular, cis-bis[2-(2-thienyl)pyridine-N,C3] platinum(II) (Pt(thpy)2) and platinum(II) 2,8,12,17-tetraethyl-3,7,13,18-tetramethyl porphyrin (PtOX), and an Ir(III) compound, fac-tris[2-(4′,5′-difluorophenyl)pyridine-C′2,N] iridium(III) (FIrppy) were used. The maximum external quantum efficiency of phosphorescent devices exceeds 0.6% for the two Pt dopants and reaches ≈1.8% for FIrppy. An overall increase in LED efficiency compared to similar devices based on fluorescence is attributed to the fact that phosphorescent dopants allow both singlet and triplet excitons to be involved in emission. In addition to finding an energetically suitable dopant, such parameters as dopant concentration and organic layer thickness influence the performance of the LEDs. Introduction of an electron injecting layer of tris(8-hydroxyquinoline) aluminum(III) causes an increase of quantum efficiency of up to 1.8–2.8%. The second order quenching process present in these OLEDs, which is prevalent at high current densities, is most likely not due to T–T annihilation of excitons trapped at dopant sites in these OLEDs. T–T annihilation in the PVK matrix or trapped charge-triplet annihilation are more likely explanations for the decrease.

Metal complexes of biologically important ligands, CXIV ferrocenyl–oxazolones as N and C donors in Pd(II), Pt(II) and Ir(III) complexes and ferrocenoyl–dipeptides

2-Ferrocenyl-4R-5(4H)-oxazolones 1– 5 were obtained from N-ferrocenoyl-α-amino acids and function as N donors in dichloro–phosphine–palladium(II) and platinum(II) complexes 6– 18. The reaction of ferrocenyl–oxazolone and ferrocenyl–bis(oxazolone) with [Cp*IrCl 2] 2 afforded trimetallic and pentametallic complexes 19 and 20 with a C,N bridging oxazolone. Ring opening of the ferrocenyl–oxazolones 1, 2 and 4 with α-amino acid esters gave N-ferrocenoyl–dipeptide esters 21– 26. In the ferrocene bis(dipeptides) the two peptide esters are aligned parallel by hydrogen bonding. The structures of 6 and 19 were determined by X-ray diffraction.

Absorption, Circular Dichroism, and Luminescence Spectroscopy of Electrogenerated Delta-[Ru(bipy)(3)](+/0/)(-) and Delta-[Os(bipy)(3)](+/0/)(-) (bipy = 2,2'-Bipyridine).

The electronic absorption and circular dichroism (CD) spectra of the complexes produced by the one, two, and three electron reduction of Delta-[Ru(bipy)(3)](2+) and Delta-[Os(bipy)(3)](2+) are reported. The CD spectra give unequivocal proof that the added electrons are localized on individual bipiridine ligands and thus that the complexes are correctly formulated [M(bipy)(2)(bipy(-))](+), [M(bipy)(bipy(-))(2)](0), and [M(bipy(-))(3)](-). The absorption spectra of the triply reduced species [M(bipy(-))(3)](-) (M = Ru, Os) are compared to those of the Fe(II) and Ir(III) analogs. The luminescence spectra of the two triply reduced complexes [Ru(bipy(-))(3)](-) and [Os(bipy(-))(3)](-). are also presented. The MLCT luminescence found in the parent complexes is completely quenched and is replaced by a weak luminescence attributed to the pi(10) --> pi(7) transition of the (coordinated) [bipy](-) ion.

Evaluation of the Ionic Radii of Ru(II) and Ir(III) in Oxide Solid Solution by the Elastic Matrix Approach

Article Evaluation of the Ionic Radii of Ru(II) and Ir(III) in Oxide Solid Solution by the Elastic Matrix Approach was published on January 1, 1981 in the journal Zeitschrift für Physikalische Chemie (volume 125, issue 1).