Cationic Transition Metal Complexes Research Articles

Oxidation of Phenol by Tris(1,10-phenanthroline)osmium(III)

Outer-sphere oxidation of phenols is under intense scrutiny because of questions related to the dynamics of proton-coupled electron transfer (PCET). Oxidation by cationic transition-metal complexes in aqueous solution presents special challenges because of the potential participation of the solvent as a proton acceptor and of the buffers as general base catalysts. Here we report that oxidation of phenol by a deficiency of [Os(phen)(3)](3+), as determined by stopped-flow spectrophotometry, yields a unique rate law that is second order in [osmium(III)] and [phenol] and inverse second order in [osmium(II)] and [H(+)]. A mechanism is inferred in which the phenoxyl radical is produced through a rapid PCET preequilibrium, followed by rate-limiting phenoxyl radical coupling. Marcus theory predicts that the rate of electron transfer from phenoxide to osmium(III) is fast enough to account for the rapid PCET preequilibrium, but it does not rule out the intervention of other pathways such as concerted proton-electron transfer or general base catalysis.

Tailoring carrier injection efficiency to improve the carrier balance of solid-state light-emitting electrochemical cells

We study the influence of the carrier injection efficiency on the performance of light-emitting electrochemical cells (LECs) based on a hole-preferred transporting cationic transition metal complex (CTMC) [Ir(dfppz)(2)(dtb-bpy)](+)(PF(6)(-)) (complex 1) and an electron-preferred transporting CTMC [Ir(ppy)(2)(dasb)](+)(PF(6)(-)) (complex 2) (where dfppz is 1-(2,4-difluorophenyl) pyrazole, dtb-bpy is 4,4'-di(tert-butyl)-2,2'-bipyridine, ppy is 2-phenylpyridine and dasb is 4,5-diaza-9,9'-spirobifluorene). Experimental results show that even with electrochemically doped layers, the ohmic contacts for carrier injection could be formed only when the carrier injection barriers were relatively low. Thus, adding carrier injection layers in LECs with relatively high carrier injection barriers would affect carrier balance and thus would result in altered device efficiency. Comparison of the device characteristics of LECs based on complex 1 and 2 in various device structures suggests that the carrier injection efficiency of CTMC-based LECs should be modified according to the carrier transporting characteristics of CTMCs to optimize device efficiency. Hole-preferred transporting CTMCs should be combined with an LEC structure with a relatively high electron injection efficiency, while a relatively high hole injection efficiency would be required for LECs based on electron-preferred transporting CTMCs. Since the tailored carrier injection efficiency compensates for the unbalanced carrier transporting properties of the emissive layer, the carrier recombination zone would be located near the center of the emissive layer and exciton quenching near the electrodes would be significantly mitigated, rendering an improved device efficiency approaching the upper limit expected from the photoluminescence quantum yield of the emissive layer and the optical outcoupling efficiency from a typical layered light-emitting device structure.

Efficient solid-state white light-emitting electrochemical cells based on phosphorescent sensitization

Efficient phosphorescent sensitized white light-emitting electrochemical cells (LECs) based on a blue-emitting phosphorescent cationic transition metal complex (CTMC) doped with a red-emitting fluorescent dye are demonstrated. Blue phosphorescence and phosphorescence-sensitized red fluorescence contribute to white emission. Furthermore, the microcavity effect of the device structure is utilized to suppress the green part of the electroluminescence (EL) spectrum of the blue-emitting phosphorescent metal complex (1) via destructive interference. Hence, more saturated blue EL emission can be obtained. When combined with saturated red emission, white EL emission with Commission Internationale de l'Eclairage coordinates approaching (0.33, 0.33) can be obtained without the need for saturated deep-blue emitting CTMCs. Peak external quantum efficiency and power efficiency of the phosphorescence sensitized white LECs are up to 7.9% and 15.6 lm W−1, respectively. These efficiencies are among the highest reported for white LECs and reveal that phosphorescent sensitization is useful for improving device efficiencies of white LECs.

Improving the balance of carrier mobilities of host–guest solid-state light-emitting electrochemical cells

We report efficient host-guest solid-state light-emitting electrochemical cells (LECs) utilizing a cationic terfluorene derivative as the host and a red-emitting cationic transition metal complex as the guest. Carrier trapping induced by the energy offset in the lowest unoccupied molecular orbital (LUMO) levels between the host and the guest impedes electron transport in the host-guest films and thus improves the balance of carrier mobilities of the host films intrinsically exhibiting electron preferred transporting characteristics. Photoluminescence measurements show efficient energy transfer in this host-guest system and thus ensure predominant guest emission at low guest concentrations, rendering significantly reduced self-quenching of guest molecules. EL measurements show that the peak EQE (power efficiency) of the host-guest LECs reaches 3.62% (7.36 lm W(-1)), which approaches the upper limit that one would expect from the photoluminescence quantum yield of the emissive layer (∼0.2) and an optical out-coupling efficiency of ∼20% and consequently indicates superior balance of carrier mobilities in such a host-guest emissive layer. These results are among the highest reported for red-emitting LECs and thus confirm that in addition to reducing self-quenching of guest molecules, the strategy of utilizing a carrier transporting host doped with a proper carrier trapping guest would improve balance of carrier mobilities in the host-guest emissive layer, offering an effective approach for optimizing device efficiencies of LECs.

Synthesis of 4-(2-Indenylethyl)morpholine and their cationic transition metal complexes

The amido tethered ligand 4–(2–indenylethyl)morpholine (6) have been prepared in high yield (71%). All the compounds were fully characterized by NMR, IR, Mass Spec. and Microanalysis. Treatment of the lithio salt of (6) with TiCl4:2THF in THF afforded the new complex 4–(2–indenylethyl)morpholinetitanium dichloride (7a) in 26% yield as viscous green oil while, treatment with ZrCl22THF gave 4–(2–indenylethyl)morpholinezirconium dichloride (7b) in 63% yield as yellow solid. The new compounds (7a and 7b) were characterized by Mass Spectroscopy and Micro Analysis. Key words: 4–(2–indenylethyl)morpholine, 4–(2–indenylethyl)morpholinetitanium, 4–(2–indenylethyl)morpholinezirconium dichloride.

Tailoring balance of carrier mobilities in solid-state light-emitting electrochemical cells by doping a carrier trapper to enhance device efficiencies

We demonstrate the improving balance of carrier mobilities in neat-film light-emitting electrochemical cells (LECs) utilizing a cationic transition metal complex (CTMC) as the emissive material and a cationic near-infrared laser dye as the carrier trapper. This low-gap carrier trapper is judiciously chosen such that a significant energy offset in the highest occupied molecular orbital (HOMO) levels between the CTMC and the carrier trapper impedes hole transport in the emissive layers while similar lowest unoccupied molecular orbital (LUMO) levels of these two materials result in relatively unaffected electron transport. Since the CTMC neat films would intrinsically exhibit characteristics of preferred transport of holes, the balance of carrier mobilities would be improved by doping such carrier trapper. Electroluminescent measurements show that the peak external quantum efficiency (EQE) and the peak power efficiency of the neat-film LECs doped with the carrier trapper reach 12.75% and 28.70 lm W−1, respectively. These device efficiencies represent a 1.4 times enhancement as compared to those of the undoped neat-film LECs and approach the upper limit of EQE (∼15%) that one would expect from the photoluminescence quantum yield of the emissive layer (∼0.75) and an optical out-coupling efficiency of ∼20% from a typical layered device structure, consequently indicating superior balance of carrier mobilities in such a doped emissive layer. These results confirm that the balance of carrier mobilities in the CTMC neat films would be improved by doping a proper carrier trapper and this technique offers a general approach for optimizing device efficiencies of CTMC-based neat-film LECs.

Phosphorescent sensitized fluorescent solid-state near-infrared light-emitting electrochemical cells

We report phosphorescent sensitized fluorescent near-infrared (NIR) light-emitting electrochemical cells (LECs) utilizing a phosphorescent cationic transition metal complex [Ir(ppy)(2)(dasb)](+)(PF(6)(-)) (where ppy is 2-phenylpyridine and dasb is 4,5-diaza-9,9'-spirobifluorene) as the host and two fluorescent ionic NIR emitting dyes 3,3'-diethyl-2,2'-oxathiacarbocyanine iodide (DOTCI) and 3,3'-diethylthiatricarbocyanine iodide (DTTCI) as the guests. Photoluminescence measurements show that the host-guest films containing low guest concentrations effectively quench host emission due to efficient host-guest energy transfer. Electroluminescence (EL) measurements reveal that the EL spectra of the NIR LECs doped with DOTCI and DTTCI center at ca. 730 and 810 nm, respectively. Moreover, the DOTCI and DTTCI doped NIR LECs achieve peak EQE (power efficiency) up to 0.80% (5.65 mW W(-1)) and 1.24% (7.84 mW W(-1)), respectively. The device efficiencies achieved are among the highest reported for NIR LECs and thus confirm that phosphorescent sensitized fluorescence is useful for achieving efficient NIR LECs.

Catalyst Deactivation Reactions: The Role of Tertiary Amines Revisited

Decamethylzirconocene cation [Cp*2ZrMe](+) (2) decomposes in bromobenzene-d(5) solution to generate sigma-aryl species [Cp*Zr-2(2-C6H4Br-kappa Br,C)][B(C6F5)(4)] (3). This a-bond metathesis reaction is catalyzed by tertiary amines via a two-step mechanism, in which the amine acts as a proton relay. In benzene-d(6) compound 2 decomposes via C H bond activation of one of the Cp* ligands to generate tucked-in compound [Cp*{eta(5):eta(1)-C5Me4(CH2)}Zr](+) (4). In the presence of Et3N, no formation of tucked-in compound 4 is observed, but instead an overall double C-H bond activation and C-N bond cleavage of the tertiary amine is observed, resulting in [Cp*Zr-2{C(Me)NEt-kappa C,N}](+) (6). A mechanism is proposed that nominates [Cp*2ZrNEt2](+) as an intermediate, the result of a C-H bond activation of Et3N, followed by beta-amide elimination. Attempted synthesis of this species by treatment of Cp*Zr-2(NEt2)Me with [Ph3C][B(C6F5)(4)] results, again, in formation of compound [6](+). The presence of Et3N also has an effect on the stability of THF adduct [Cp*2ZrMe(THF)](+) as the amine performs a nucleophilic THF ring-opening to generate [Cp*2ZrMe{O(CH2)(4)NEt3}](+) (7). The results show that amine coproducts, often generated in the synthesis of cationic transition-metal complexes, are not necessarily innocent.

Five dimeric thiogermanates with transition metal complexes of multidentate chelating amines: Syntheses, structures, magnetism and photoluminescence

Five new thiogermanates, [Ni II(dien) 2] 2(Ge 2S 6) (dien = diethylenetriamine) ( 1), [Ni II(dien) 2](H 2pipe)(Ge 2S 6) (pipe = piperazine) ( 2), {[Mn II(tren)] 2( μ 2-Ge 2S 6)} (tren = N,N,N-tris(2-aminoethyl)amine) ( 3) and {[M II(tepa)] 2( μ 2-Ge 2S 6)} (M = Mn ( 4a), Ni ( 4b); tepa = tetraethylenepentamine), have been obtained solvothermally in the presence of tri-(L 3), tetra-(L 4) and penta-dentate (L 5) chelating amines and transition metal (TM) ions. Single-crystal X-ray diffraction analyses show that compounds 1– 2 are comprised of discrete (Ge 2S 6) 4− anions and TM complex (TMC) cations, while compounds 3– 4b are composed of each dimeric (Ge 2S 6) 4− anion bridging two TMC cations via TM–S bonds to form a neutral molecule. Notably, two interesting in situ metal/ligand reactions were observed in the solvothermal syntheses of 2 and 3. The present compounds exhibit wide optical gap ranging from 2.94 to 3.39 eV and photoluminescence with the emission maxima occurring around 440 ( 1, 2, 3 and 4b) and 489 nm ( 4a). Magnetic measurements show the presence of weak antiferromagnetic interactions between magnetic centers in the five compounds.

The impact of ion pair association upon the 1H NMR spectra of cationic complexes akin to Grubbs catalysts

A reconsideration of the (1)H NMR spectra of cationic transition metal complexes exhibiting the features of cyclophanes on the basis of Mislow's classification of topic groups arrives at the conclusion that the spectral changes triggered by chiral counterions reflect an intracationic diastereotopication of enantiotopic protons rather than the existence of pairs of long-lived diastereomeric ion pairs.

Transition Metal Complex Cations as Reagents for Gas-Phase Transformation of Multiply Deprotonated Polypeptides

Triply deprotonated DGAILDGAILD was reacted in the gas-phase with doubly charged copper, cobalt, and iron metal complexes containing either two or three phenanthroline ligands. Reaction products result from two major pathways. The first pathway involves the transfer of an electron from the negatively charged peptide to the transition-metal complex. The other major pathway consists of the displacement of the phenanthroline ligands by the peptide resulting in the incorporation of the transition-metal into the peptide to form [M - 3H + X(II)](-) ions, where X is Cu, Co, or Fe, respectively. The extent to which each pathway contributes is dependent on the nature of transition-metal complex. In general, bis-phen complexes result in more electron-transfer than the tris-phen complexes, while the tris-phen complexes result in more metal insertion. The metal in the complex plays a large role as well, with the Cu containing complexes giving rise to more electron transfer than the corresponding complexes of Co and Fe. The results show that a single reagent solution can be used to achieve two distinct sets of products (i.e., electron-transfer products and metal insertion products). These results constitute the demonstration of novel means for the gas-phase transformation of peptide anions from one ion type to another via ion/ion reactions using reagents formed via electrospray ionization.

Extended architectures based on sandwich-type polyanions and transition metal complex cations

Two new compounds based on Weakley-sandwich-type polyanion (WSP), H 2[Mn(en) 2] 2[Mn(en) 2(H 2O)] 2[Mn 4(H 2O) 2(PW 9O 34) 2]·9H 2O ( 1) and Na 2[Co(en) 2] 2[{Co(en) 2(H 2O)] 2[Co 4(H 2O) 2(PW 9O 34) 2]·9H 2O ( 2) (en = ethylenediamine), have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [ a- A-PW 9O 34] 9− with transition metal ions and en, and structurally characterized by routine physical methods and single-crystal X-ray diffraction. Compound 1 represents a 1D chain structure made up of WSPs and [Mn(en) 2] 2+ ions. Compound 2 represents a 2D layer structure formed by the interconnection of WSPs, [Co(en) 2] 2+ and Na + ions. Compounds 1 and 2 represent the first example of high-dimensional construction based on WSPs and transition metal complexes (TMCs), in which the water molecules located on the featured tetra-metal unit are still remained, and exhibit the property of sorption/desorption of water molecules.

Two Novel 1-D Organic–Inorganic Composite Phosphotungstates Constructed from [Ln(α-PW11O39)2]11− Units and [Cu(en)2]2+ Bridges (Ln = CeIII/ErIII)

Two novel organic–inorganic composite phosphotungstates, [H9{Ce(α-PW11O39)2}Cu(en)2] · 6H2O (1) and H7[Cu(en)2{Er(α-PW11O39)2}Cu(en)2] · 12H2O (2) (en = ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW9O34]9− with CeIII or ErIII ions in the presence of Cu2+ ions and en, and structurally characterized by IR spectra, elemental analysis and thermogravimetric analysis. X-ray crystallographic analyses indicate that they are all built by sandwich-type [Ln(α-PW11O39)2]11− (Ln = CeIII, ErIII) polyoxoanions and [Cu(en)2]2+ cations generating infinite one-dimensional arrangements. To our knowledge, this 1-D chain structures constituted by mono-Ln sandwiched POM units and transition-metal complex cations are very rare. Two novel organic–inorganic composite phosphotungstates, [H9{Ce(α-PW11O39)2}Cu(en)2] · 6H2O (1) and H7[Cu(en)2{Er(α-PW11O39)2}Cu(en)2] · 12H2O (2) (en = ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW9O34]9− with CeIII or ErIII ions in the presence of Cu2+ ions and en, and structurally characterized by IR spectra, elemental analysis and thermogravimetric analysis. X-ray crystallographic analyses indicate that they are all built by sandwich-type [Ln(α-PW11O39)2]11− (Ln = CeIII, ErIII) polyoxoanions and [Cu(en)2]2+ cations generating infinite one-dimensional arrangements. To our knowledge, this 1-D chain structures constituted by mono-Ln sandwiched POM units and transition-metal complex cations are very rare.

Influence of Ligands on the Dynamics of Hydrogen Elimination in Cationic Complexes of Co and Rh

The quantum dynamics of beta-hydrogen elimination in cationic transition metal complexes [CpML(C(2)H(4))H](+) (M = Co, Rh; L = PH(3), PF(3), PMe(3), P(OMe)(3)) is studied theoretically. The underlying potential energy profiles are obtained at the DFT level of theory; the nuclear motion is computed by the method of wave packet propagation (i.e., by integrating the time-dependent Schrodinger equation). For the Co as well as the Rh complexes, agostic intermediates relevant to the insertion/elimination process exist. Complexes containing each ligand are studied for both transition metals from an electronic structure point of view and, in addition, the ligand influence on the dynamics is compared. The results allow us to draw conclusions concerning the influence of the energetics as well as the different masses on vibrational periods and lifetimes of these complexes due to beta-elimination.

Structural Study of Organic−Inorganic Hybrid Thiogallates and Selenidogallates in View of Effects of the Chelate Amines

Four new gallium chalcogenides [H2dap]4Ga4Se10 (1), [Mn(dap)3]0.5GaSe2 (2), {[Ni(tepa)]2SO4}[Ni(tepa)(Ga4S6(SH)4)] (3) and [Mn(atep)]Ga2S4 (4) (dap = 1,2-diaminopropane, tepa = tetraethylenepentamine, atep = 4-(2-aminoethyl)triethylenetetramine) have been synthesized by solvothermal methods and structurally characterized. The effects of the strong chelating amines on the topology of gallium chalcogenidometalates have been enumerated. First, in the absence of transition metal ions, the chelating amine can offer more N−H groups than the monoamines to form hydrogen bonds; therefore, compound 1 takes a 2-D polymeric structure constructed by supertetrahedral clusters ([Ga4Se10]8−, T2). Second, when transition metals are incorporated into the chelating amine system, larger [M(dap)3]2+complex cations are formed, which force the anions of compound 2 to adopt a 1-D structure ([GaSe2]− chain). Third, when an appropriate chelating amine (e.g., tepa) is selected, unsaturated transition metal complex cations can be obtained, which not only act as a large cation but also form the covalently linked organic−inorganic hybrid compounds 3 and 4. The anion in 3 is a T2 {[Ga4S6(SH)4]4−} cluster connected to a [Ni(tepa)]2+ complex cation, while the structure of 4 consists of 1-D sinusoidal [Ga4S84−]n anion combined with [Mn(atep)]2+ complex cations.

Solid-State White Light-Emitting Electrochemical Cells Using Iridium-Based Cationic Transition Metal Complexes

White electroluminescent (EL) emission from single-layered solid-state light-emitting electrochemical cells (LECs) based on host-guest cationic iridium complexes has been successfully demonstrated. The devices show white EL spectra (Commission Internationale de l'Eclairage coordinates ranging from (x, y) = (0.45, 0.40) to (0.35, 0.39) at 2.9-3.3 V with high color rendering indices up to 80. Peak external quantum efficiency and peak power efficiency of the white LEC reach 4% and 7.8 lm/W, respectively. These results suggest that white LECs based on host-guest cationic transition metal complexes may be a promising alternative for solid-state lighting technologies.

Preparation of Monodispersed Nanoparticles by Electrostatic Assembly of Keggin‐Type Polyoxometalates and 1,4,7‐Triazacyclononane‐Based Transition‐Metal Complexes.

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Gas-Phase Ion/Ion Reactions of Transition Metal Complex Cations with Multiply Charged Oligodeoxynucleotide Anions

Multiply deprotonated hexadeoxyadenylate anions, (A6-nH)(n-), where n = 3-5, have been subjected to reaction with a range of divalent transition-metal complex cations in the gas phase. The cations studied included the bis- and tris-1,10-phenanthroline complexes of CuII, FeII, and CoII, as well as the tris-1,10-phenanthroline complex of RuII. In addition, the hexadeoxyadenylate anions were subjected to reaction with the singly charged FeIII and CoIIIN,N'-ethylenebis(salicylideneiminato) complexes. The major competing reaction channels are electron-transfer from the oligodeoxynucleotide anion to the cation, the formation of a complex between the anion and cation, and the incorporation of the transition-metal into the oligodeoxynucleotide. The latter process proceeds via the anion/cation complex and involves displacement of the ligand(s) in the transition-metal complex by the oligodeoxynucleotide. Competition between the various reaction channels is governed by the identity of the transition-metal cation, the coordination environment of the metal complex, and the oligodeoxynucleotide charge state. In the case of the divalent metal phenanthroline complexes, competition between electron-transfer and metal ion incorporation is particularly sensitive to the coordination number of the reagent metal complexes. Both electron-transfer and metal ion incorporation occur to significant extents with the bis-phenanthroline ions, whereas the tris-phenanthroline ions react predominantly by metal ion incorporation. To our knowledge this work reports the first observations of the gas-phase incorporation of multivalent transition-metal cations into oligodeoxynucleotide anions and represents a means for the selective incorporation of transition-metal counter-ions into gaseous oligodeoxynucleotides.

Preparation of Monodispersed Nanoparticles by Electrostatic Assembly of Keggin-Type Polyoxometalates and 1,4,7-Triazacyclononane-Based Transition-Metal Complexes

Complexation of Keggin-type polyoxometalates (POMs), [α-PW12O40]3- (PW), [α-SiW12O40]4- (SiW), and [γ-SiV2W10O38(OH)2]4- (SiVWH) with cationic transition-metal complexes having a triazacyclononane ligand, [M(tacn)2]n+ (M−tacn; M = CoIII and NiII; tacn = 1,4,7-triazacyclononane), yields fine particles of inorganic−organic composites. The strong electrostatic interaction between the highly negatively charged POMs and the +2- or +3-charged [M(tacn)2]n+ as well as the hydrophobicity of [M(tacn)2]n+ results in the formation of the water-insoluble binary composites. The crystal structure of the 1:1 (=the molar ratio of POM to M−tacn) composite [Co(tacn)2][α-PW12O40]·2H2O (1·H2O) shows the close packing of PW and Co−tacn in the crystal lattice. The guest sorption properties of the corresponding anhydrous compound 1 show that the amounts of hydrophobic molecules sorbed are comparable to that of water. The reaction of SiVWH with Co−tacn yields fine particles of [Co(tacn)2]2[γ-SiV2W10O40]·6H2O (2·H2O), and the mola...

Übergangsmetallionen in Iodostannaten: Die Kristallstrukturen von [Co(en)3]4[Sn3I12]I2 und $^{3}_{\infty}\rm [Co(en)_{4}SnI_{4}

AbstractTransition Metal Ions in Iodostannates: the Crystal Structures of [Co(en)3]4[Sn3I12]I2 and $^{3}_{\infty}\rm [Co(en)_{4}SnI_{4}]$Under solvothermal conditions SnI2 reacts with transition metal complex cations to form anionic iodostannates as well as neutral iodocomplexes with divalent tin. In the crystal lattice of [Co(en)3]4[Sn3I12]I2 (1, en = H2NCH2CH2NH2) isolated [Sn3I12]6− anions and additional non‐coordinating iodide ions are present. The charge is balanced by [Co(en)3]2+ cations. In contrast, in [Co(en)2SnI4] (2) [SnI4]2− chains are linked by Co(en)22+ groups to form a three dimensional network.[Co(en)3]4[Sn3I12]I2 (1): a = 2180.44(8), b = 1354.41(5), c = 2630.53(10) pm, V = 7768.5(5)·106 pm3, space group Pbca.[Co(en)2SnI4] (2): a = 1149.1(1), b = 1207.5(1), c = 1397.0(1) pm, α = 68.07(1), β = 68.26(1), γ = 85.83(1)°, V = 1665.2(7)·106 pm3, space group $P{\bar 1}$.