单核钌催化剂化学催化和光催化水氧化反应

合成了一系列含有不同对位取代基团的吡啶轴向配体的单核钌化合物Ru(bda)(pic)₂ (H₂bda=2,2''-联吡啶-6,6''-二羧酸; pic=对甲基吡啶),对化合物的结构进行了核磁、质谱和X射线单晶衍射表征,并在中性和酸性条件下研究了这些化合物的电化学性质.以硝酸铈铵为氧化剂,对催化剂的催化活性进行了测试,并以[Ru(bpy)₃]²⁺为光敏剂,S₂O₈^2-为电子牺牲剂,在三组分体系中考察了这些化合物的光催化活性.研究发现,在化学法水氧化反应中,化合物1由于其轴向配体4,4''-联吡啶在酸性条件下能够发生质子化,从而增强了吸电子效应,因此表现出最高的催化活性,催化循环数达到4000.在光催化水氧化反应中,化合物2因其轴向配体具有最强的吸电子能力而表现出最高的催化活性,反应2h的催化循环数达到270.结果表明,轴向配体的吸电子能力明显提高了这类Ru催化剂催化水氧化反应活性.     

Factors affecting the electrochemical and spectroelectrochemical properties of diruthenium(III,II) complexes containing four identical unsymmetrical bridging ligands

Factors affecting the electrochemical and spectroelectrochemical properties of diruthenium(III,II) complexes containing four unsymmetrical bridging ligands are reported for seven related compounds which were isolated in one or two of the four possible isomeric forms. The investigated compounds are represented as Ru(2)(2-CH(3)ap)(4)Cl, Ru(2)(2,5-F(2)ap)(4)Cl, Ru(2)(2,6-F(2)ap)(4)Cl, and Ru(2)(2,4,6-F(3)ap)(4)Cl where 2-CH(3)ap, 2,5-F(2)ap, 2,6-F(2)ap, and 2,4,6-F(3)ap are, respectively, the 2-(2-methylanilino)pyridinate anion, the 2-(2,5-difluoroanilino)pyridinate anion, the 2-(2,6-difluoroanilino)pyridinate anion, and the 2-(2,4,6-trifluoroanilino)pyridinate anion. Ru(2)(2-CH(3)ap)(4)Cl and Ru(2)(2,5-F(2)ap)(4)Cl exist only in a (4,0) conformation while Ru(2)(2,4,6-F(3)ap)(4)Cl is present in both (3,1) and (4,0) isomeric forms. Ru(2)(2,6-F(2)ap)(4)Cl also exists in two isomeric forms, but only the (3,1) isomer was generated in sufficient quantities to be isolated and structurally characterized. This series of seven closely related metal-metal bonded complexes thus provides the first possibility to systematically examine how differences in position and number of the electron-donating or electron-withdrawing groups on the anionic bridging ligands might be related to the electronic properties and structural features of the compound as well as the type and number of geometric isomers which are formed. Each diruthenium derivative undergoes three one-electron transfers in CH(2)Cl(2) containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The first reduction and first oxidation products were characterized by thin-layer UV-vis spectroelectrochemistry, and the spectroscopic data, along with E(1/2) values, were then related via linear free energy relationships to the type of isomer and/or position of the electron-donating or electron-withdrawing substituents on the anionic ap bridge. The electrogenerated Ru(2)(6+) and Ru(2)(4+) forms of the compounds were assigned on the basis of electrochemical and UV-vis spectroscopic data as having the electronic configuration sigma(2)pi(4)delta(2)pi(2) and sigma(2)pi(4)delta(2)pi(3)delta, respectively, and seemed to be independent of the isomer type ((3,1) or (4,0)). The spectral and electrochemical properties of the compounds both vary substantially as a function of the isomer type, but this is not reflected in the structural features of the compounds which are within the range of what is seen for other Ru(2)(5+) species described in the literature. The Ru-Ru bond lengths of the four structurally characterized (4,0) isomers of the ap complexes range from 2.275 to 2.296 A while those of the three structurally characterized (3,1) isomers of ap derivatives fall in the range 2.284-2.286 A and show no significant difference among the three compounds. The Ru-Cl bond lengths of the (3,1) isomers do not vary significantly with the bridging ligand and range from 2.458 to 2.471 A whereas those of the (4,0) isomers range from 2.437 to 2.487 A and show larger variations among the compounds. The Ru-Ru-Cl bond angle is virtually independent of the bridging ligand in the case of the (4,0) isomers but decreases with the electron-withdrawing effect of the substituent in the case of the (3,1) isomers.     

Synthesis, structure, and electronic properties of RuN6 dinuclear Ru-Hbpp complexes

A series of RuN(6) dinuclear Ru-Hbpp complexes (Hbpp is the dinucleating tetraaza ligand 3,5-bis(pyridyl)pyrazole) of general formula {[Ru(II)(R(2)-trpy)(MeCN)](2)(μ-R(1)-bpp)}(3+), 10(3+)-14(3+), (R(1) = H, Me, or NO(2). and R(2) = H, Me, MeO; see Scheme 1) has been prepared from their Cl(-) or AcO(-) bridged precursors. The complexes have been characterized by UV-vis, NMR, CV, and some by X-ray. Complexes 10(3+)-14(3+), Ru(2)(II,II), were oxidized by 1 equiv in solution, leading to the mixed valence Ru(2)(II,III) complexes 10(4+)-14(4+) containing one unpaired electron and were characterized by EPR and UV-vis-near-IR, which showed metal-centered spin and the presence of low-energy IVCT bands. The H(ab) parameter indicates a relatively strong electronic coupling between the two ruthenium centers (class II). Further two electron oxidation in solution of the 10(3+)-14(3+) led to the formation of EPR silent Ru(2)(III,III) complexes 10(5+)-14(5+), that were further characterized by UV-vis-NIR. TD-DFT calculations are employed to assign the nature of the UV-vis transitions for the complexes in the various oxidation states, which are of metal to ligand charge transfer (MLCT) type for Ru(2)(II,II) and ligand to metal charge transfer (LMCT) type for Ru(2)(III,II) and Ru(2)(III,III).     

Density functional theory/time-dependent DFT studies on the structures, trend in DNA-binding affinities, and spectral properties of complexes [Ru(bpy)2(p-R-pip)]2+ (R = -OH, -CH3, -H, -NO2)

Studies on the electronic structures and trend in DNA-binding affinities of a series of Ru(II) complexes [Ru(bpy)2(p-R-pip)]2+ (bpy = 2,2-bipyridine; pip = 2-phenylimidazo[4,5-f] [1,10]-phenanthroline; R = -OH, -CH3, -H, -NO2) 1-4 have been carried out, using the density functional theory (DFT) at the B3LYP/LanL2DZ level. The electronic absorption spectra of these complexes were also investigated using time-dependent DFT (TDDFT) at the B3LYP//LanL2DZ/6-31G level. The computational results show that the substituents on the parent ligand (pip) have a significant effect on the electronic structures of the complexes, in particular, on the energies of the lowest unoccupied molecular orbital (LUMO) and near some unoccupied molecular orbitals (LUMO+x, x = 1-4). With the increase in electron-withdrawing ability of the substituent in this series, the LUMO+x (x = 0-4) energies of the complexes are substantially reduced in order, for example, epsilon(LUMO)(1) approximately epsilon(LUMO)(2) > epsilon(LUMO)(3) > epsilon(LUMO)(4), whereas the pi-component populations of the LUMO+x (x = 0-4) are not substantially different. Combining the consideration of the bigger steric hindrance of complex 2, the trend in DNA-binding affinities (K(b)) of the complexes, that is, K(b)(2) < K(b)(1) < K(b)(3) < K(b)(4) can be reasonably explained. In addition, the experimental singlet metal-to-ligand charge transfer ((1)MLCT) spectra of these complexes can be well simulated and discussed by the TDDFT calculations.     

Experimental and theoretical evaluation of the charge distribution over the ruthenium and dioxolene framework of [Ru(OAc)(dioxolene)(terpy)] (terpy = 2,2':6',2' '-terpyridine) depending on the substituents

A series of ruthenium complexes [Ru(OAc)(dioxolene)(terpy)] having various substituents on the dioxolene ligand (dioxolene = 3,5-t-Bu2C6H2O2 (1), 4-t-BuC6H3O2 (2), 4-ClC6H3O2 (3), 3,5-Cl2C6H2O2 (4), Cl4C6O2 (5); terpy = 2,2':6'2' '-terpyridine) were prepared. EPR spectra of these complexes in glassy frozen solutions (CH2Cl2:MeOH = 95:5, v/v) at 20 K showed anisotropic signals with g tensor components 2.242 > g1 > 2.104, 2.097 > g2 > 2.042, and 1.951 > g3 > 1.846. An anisotropic value, Deltag = g1 - g3, and an isotropic g value, g = [(g1(2) + g2(2) + g3(2))/3]1/2, increase in the order 1 < 2 < 3 < 4 < 5. The resonance between the Ru(II)(sq) (sq = semiquinone) and Ru(III)(cat) (cat = catecholato) frameworks shifts to the latter with an increase of the number of electron-withdrawing substituents on the dioxolene ligand. DFT calculations of 1, 2, 3, and 5 also support the increase of the Ru spin density (Ru(III) character) with an increase of the number of Cl atoms on the dioxolene ligand. The singly occupied molecular orbitals (SOMOs) of 1 and 5 are very similar to each other and stretch out the Ru-dioxolene frameworks, whereas the lowest unoccupied molecular orbital (LUMO) of 5 is localized on Ru and two oxygen atoms of dioxolene in comparison with that of 1. Electron-withdrawing groups decrease the energy levels of both the SOMO and LUMO. In other words, an increase in the number of Cl atoms in the dioxolene ligand results in an increase of the positive charge on Ru. Successive shifts in the electronic structure between the Ru(II)(sq) and Ru(III)(cat) frameworks caused by the variation of the substituents are compatible with the experimental data.     

Redox pathways in DNA oxidation: kinetic studies of guanine and sugar oxidation by para-substituted derivatives of oxoruthenium(IV)

The oxidation of nucleotides and DNA by a series of complexes based on Ru(tpy)(bpy)O2+ (1) was investigated (tpy = 2,2':6',2"-terpyridine; bpy = 2,2'-bipyridine). These complexes were substituted with electron-donating or-withdrawing substituents in the para positions of the polypyridyl ligands so that the oxidation potentials of the complexes were affected but the reaction trajectory of the oxo ligand with DNA was the same throughout the series. The prepared complexes were (with E1/2(III/II) and E1/2(IV/III) values in volts versus Ag/AgCl) Ru(4'-EtO-tpy)(bpy)O2+ (2; 0.47, 0.60), Ru(4'-Cl-tpy)(bpy)O2+ (3; 0.55, 0.63), Ru(tpy)(4,4'-Me2-bpy)O2+ (4; 0.48, 0.62), and Ru(tpy)(4,4'-Cl2-bpy)O2+ (5; 0.58, 0.63). The complexes oxidized deoxycytosine 5'-monophosphate at the sugar moiety (k = 0.24-0.47 M-1 s-1) and guanosine 5'-monophosphate at the base moiety (k = 6.1-15 M-1 s-1). The rate constants increase across these ranges in the order 3 > 1 > 4 > 2, which is the same order as the redox potentials of the complexes. The effect of the base on these reactions was also studied, and xanthine was found to react with 1 much faster than guanine while hypoxanthine was less reactive than the sugar moiety. The complexes all oxidized oligonucleotides to generate base-labile lesions at guanine and a combination of spontaneous and base-labile scission at the sugar functionalities. The selectivity of cleavage in duplex and single-stranded DNA was not a strong function of the substituents on the metal complex.     

Spectral, structural, and electrochemical properties of ruthenium porphyrin diaryl and aryl(alkoxycarbonyl) carbene complexes: influence of carbene substituents, porphyrin substituents, and trans-axial ligands

A wide variety of ruthenium porphyrin carbene complexes, including [Ru(tpfpp)(CR(1)R(2))] (CR(1)R(2) = C(p-C(6)H(4)Cl)(2) 1 b, C(p-C(6)H(4)Me)(2) 1 c, C(p-C(6)H(4)OMe)(2) 1 d, C(CO(2)Me)(2) 1 e, C(p-C(6)H(4)NO(2))CO(2)Me 1 f, C(p-C(6)H(4)OMe)CO(2)Me 1 g, C(CH==CHPh)CO(2)CH(2)(CH==CH)(2)CH(3) 1 h), [Ru(por)(CPh(2))] (por=tdcpp 2 a, 4-Br-tpp 2 b, 4-Cl-tpp 2 c, 4-F-tpp 2 d, tpp 2 e, ttp 2 f, 4-MeO-tpp 2 g, tmp 2 h, 3,4,5-MeO-tpp 2 i), [Ru(por)[C(Ph)CO(2)Et]] (por=tdcpp 2 j, tmp 2 k), [Ru(tpfpp)(CPh(2))(L)] (L = MeOH 3 a, EtSH 3 b, Et(2)S 3 c, MeIm 3 d, OPPh(3) 3 e, py 3 f), and [Ru(tpfpp)[C(Ph)CO(2)R](MeOH)] (R = CH(2)CH==CH(2) 4 a, Me 4 b, Et 4 c), were prepared from the reactions of [Ru(por)(CO)] with diazo compounds N(2)CR(1)R(2) in dichloromethane and, for 3 and 4, by further treatment with reagents L. A similar reaction of [Os(tpfpp)(CO)] with N(2)CPh(2) in dichloromethane followed by treatment with MeIm gave [Os(tpfpp)(CPh(2))(MeIm)] (3 d-Os). All these complexes were characterized by (1)H NMR, (13)C NMR, and UV/Vis spectroscopy, mass spectrometry, and elemental analyses. X-ray crystal structure determinations of 1 d, 2 a,i, 3 a, b, d, e, 4 a-c, and 3 d-Os revealed Ru==C distances of 1.806(3)-1.876(3) A and an Os==C distance of 1.902(3) A. The structure of 1 d in the solid state features a unique "bridging" carbene ligand, which results in the formation of a one-dimensional coordination polymer. Cyclic voltammograms of 1 a-c, g, 2 a-d, g-k, 3 b-d, 4 a, b, and 3 d-Os show a reversible oxidation couple with E(1/2) values in the range of 0.06-0.65 V (vs Cp(2)Fe(+/0)) that is attributable to a metal-centered oxidation. The influence of carbene substituents, porphyrin substituents, and trans-ligands on the Ru==C bond was examined through comparison of the chemical shifts of the pyrrolic protons in the porphyrin macrocycles ((1)H NMR) and the M==C carbon atoms ((13)C NMR), the potentials of the metal-centered oxidation couples, and the Ru==C distances among the various ruthenium porphyrin carbene complexes. A direct comparison among iron, ruthenium, and osmium porphyrin carbene complexes is made.     

Chemical control on the coordination mode of benzaldehyde semicarbazone ligands. synthesis, structure, and redox properties of ruthenium complexes

Reaction of benzaldehyde semicarbazone (HL-R, where H is a dissociable proton and R is a substituent (R = OMe, Me, H, Cl, NO(2)) at the para position of the phenyl ring) with [Ru(PPh(3))(3)Cl(2)] and [Ru(PPh(3))(2)(CO2)Cl2] has afforded complexes of different types. When HL-NO(2) and [Ru(PPh(3))(3)Cl2] react in solution at ambient temperature, trans-[Ru(PPh(3))(2)(L-NO2Cl] is obtained. Its structure determination by X-ray crystallography shows that L-NO2 is coordinated as a tridentate C,N,O-donor ligand. When reaction between HL-NO2 and [Ru(PPh(3))(3)Cl2] is carried out in refluxing ethanol, a more stable cis isomer of [Ru(PPh(3))(2)(L-NO2)Cl] is obtained. The trans isomer can be converted to the cis isomer simply by providing appropriate thermal energy. Slow reaction of HL-R with [Ru(PPh(3))(2)(CO2)Cl2] in solution at ambient temperature yields 5-[Ru(PPh(3))(2)(L-R)(CO)Cl] complexes. A structure determination of 5-[Ru(PPh(3))(2)(L-NO2)(CO)Cl] shows that the semicarbazone ligand is coordinated as a bidentate N,O-donor, forming a five-membered chelate ring. When reaction between HL-R and [Ru(PPh(3))(2)(CO2Cl2] is carried out in refluxing ethanol, the 4-[Ru(PPh(3))(2)(L-R)(CO)Cl] complexes are obtained. A structure determination of 4-[Ru(PPh(3))(2)(L-NO2)(CO)Cl] shows that a semicarbazone ligand is bound to ruthenium as a bidentate N,O-donor, forming a four-membered chelate ring. All the complexes are diamagnetic (low-spin d(6), S = 0). The trans- and cis-[Ru(PPh(3))(2)(L-NO2)Cl] complexes undergo chemical transformation in solution. The 5- and 4-[Ru(PPh(3))(2)(L-R)(CO)Cl] complexes show sharp NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry of the 5-[Ru(PPh(3))(2)(L-R)(CO)Cl] and 4-[Ru(PPh(3))(2)(L-R)(CO)Cl] complexes show the Ru(II)-Ru(III) oxidation to be within 0.66-1.07 V. This oxidation potential is found to linearly correlate with the Hammett constant of the substituent R.     

Mechanism of oxidation of benzaldehyde by polypyridyl oxo complexes of Ru(IV)

The oxidation of benzaldehyde and several of its derivatives to their carboxylic acids by cis-[Ru(IV)(bpy)2(py)(O)]2+ (Ru(IV)=O2+; bpy is 2,2'-bipyridine, py is pyridine), cis-[Ru(III)(bpy)2(py)(OH)]2+ (Ru(III)-OH2+), and [Ru(IV)(tpy)(bpy)(O)]2+ (tpy is 2,2':6',2'-terpyridine) in acetonitrile and water has been investigated using a variety of techniques. Several lines of evidence support a one-electron hydrogen-atom transfer (HAT) mechanism for the redox step in the oxidation of benzaldehyde. They include (i) moderate k(C-H)/k(C-D) kinetic isotope effects of 8.1 +/- 0.3 in CH3CN, 9.4 +/- 0.4 in H2O, and 7.2 +/- 0.8 in D2O; (ii) a low k(H2O/D2O) kinetic isotope effect of 1.2 +/- 0.1; (iii) a decrease in rate constant by a factor of only approximately 5 in CH3CN and approximately 8 in H2O for the oxidation of benzaldehyde by cis-[Ru(III)(bpy)2(py)(OH)]2+ compared to cis-[Ru(IV)(bpy)2(py)(O)]2+; (iv) the appearance of cis-[Ru(III)(bpy)2(py)(OH)]2+ rather than cis-[Ru(II)(bpy)2(py)(OH2)]2+ as the initial product; and (v) the small rho value of -0.65 +/- 0.03 in a Hammett plot of log k vs sigma in the oxidation of a series of aldehydes. A mechanism is proposed for the process occurring in the absence of O2 involving (i) preassociation of the reactants, (ii) H-atom transfer to Ru(IV)=O2+ to give Ru(III)-OH2+ and PhCO, (iii) capture of PhCO by Ru(III)-OH2+ to give Ru(II)-OC(O)Ph+ and H+, and (iv) solvolysis to give cis-[Ru(II)(bpy)2(py)(NCCH3)]2+ or the aqua complex and the carboxylic acid as products.     

Complexes of substituted derivatives of 2-(2-pyridyl)benzimidazole with Re(I), Ru(II) and Pt(II): structures, redox and luminescence properties

N,N'-Chelating ligands based on the 2-(2-pyridyl)benzimidazole (PB) core have been prepared with a range of substituents (phenyl, pentafluorophenyl, naphthyl, anthracenyl, pyrenyl) connected to the periphery via alkylation of the benzimidazolyl unit at one of the N atoms. These PB ligands have been used to prepare a series of complexes of the type [Re(PB)(CO)(3)Cl], [Pt(PB)(CCR)(2)](where -CCR is an acetylide ligand) and [Ru(bpy)(2)(PB)][PF(6)](2)(bpy = 2,2'-bipyridine). Six of the complexes have been structurally characterised. Electrochemical and luminescence studies show that all three series of complexes behave in a similar manner to the analogous complexes with 2,2'-bipyridine in place of PB. In particular, all three series of complexes show luminescence in the range 553-605 nm (Pt series), 620-640 nm (Re series) and 626-645 nm (Ru series) arising from the (3)MLCT state, with members of the Pt(II) series being the most strongly emissive with lifetimes of up to 500 ns and quantum yields of up to 6% in air-saturated CH(2)Cl(2) at room temperature. In the Re and Ru series there was clear evidence for inter-component energy-transfer processes in both directions between the (3)MLCT state of the metal centre and the singlet and triplet states of the pendant organic luminophores (naphthalene, pyrene, anthracene). For example the pyrene singlet is almost completely quenched by energy transfer to a Re-based MLCT excited state, which in turn is completely quenched by energy transfer to the lower-lying pyrene triplet state. For the analogous Ru(II) complexes the inter-component energy transfer is less effective, with (1)anthracene --> Ru((3)MLCT) energy transfer being absent, and Ru((3)MLCT)-->(3)anthracene energy transfer being incomplete. This is rationalised on the basis of a greater effective distance for energy transfer in the Ru(II) series, because the MLCT excited states are localised on the bpy ligands which are remote from the pendant aromatic group; in the Re series in contrast, the MLCT excited states involve the PB ligand to which the pendant aromatic group is directly attached, giving more efficient energy transfer.     

1,10]-Phenanthrolin-2-yl ketones and their coordination chemistry

A synthetic protocol involving the Friedl?nder reaction of 8-amino-7-quinolinecarbaldehyde followed by potassium dichromate oxidation was applied to 2,3,4-pentanetrione-3-oxime and 1-(pyrid-2'-yl)propane-1,2-dione-1-oxime to provide the ligands di-(phenathrolin-2-yl)-methanone (1) and phenanthrolin-2-yl-pyrid-2-yl-methanone (8), respectively. Ligand 1 complexed as a planar tetradentate with Pd(II) to form [Pd(1)](BF4)2 and with Ru(II) and two 4-substituted pyridines (4-R-py) to form [Ru(1)(4-R-py)2](PF6)2 where R = CF3, CH3, and Me2N. With [Ru(bpy)2Cl2], the dinuclear complex [(bpy)2Ru(1)Ru(bpy)2](PF6)4 was formed (bpy = 2,2'-bipyridine). Ligand 8 afforded the homoleptic Ru(II) complex [Ru(8)2](PF6)2, as well as the heteroleptic complex [Ru(8)(tpy)](PF6)2 (tpy = 2,2';6,2'-terpyridine). The ligands and complexes were characterized by their NMR and IR spectra, as well as an X-ray structure determination of [Ru(1)(4-CH3-py)2](PF6)2. Electrochemical analysis indicated metal-based oxidation and ligand-based reduction that was consistent with results from electronic absorption spectra. The complexes [Ru(1)(4-R-py)2](PF6)2 were sensitive to the 4-substituent on the axial pyridine: electron donor groups facilitated the oxidation while electron-withdrawing groups impeded it.     

Monometallic and dimetallic ruthenium(II)-terpyridine complexes employing the tetradentate ligands dipyridylpyrazolyl,dipyridyloxadiazole, and their dimethyl derivatives

The tetradentate ligands, 2,2'-(1H-pyrazole-3,5-diyl)bis(4- methylpyridine) (4,4'-Me2dppzH), 2,2'-(1H-pyrazole-3,5-diyl)bis(6-methylpyridine) (6,6'-Me2dppzH), 3,5-di(pyrid-2-yl)pyrazole (dppzH), and dipyridyloxadiazole (dpo) react with either Ru(trpy)Cl3 or trans-Ru(trpy)Cl2(NCCH3), where trpy is 2,2',2'-terpyridine, to form a variety of Ru(II) complexes. Among these are the symmetrical chloro-bridged Ru(II) dimer and the "in" and "out" geometric isomers of the monometallic Ru(II) containing species where "in" and "out" refer to the orientation of the Ru-Cl vector relative to the centroid of the ligand backbone. Thirteen complexes were prepared and painstakingly purified by careful recrystallization and/or exhaustive column chromatography. These complexes were characterized by 1H and 13C NMR, electronic absorption, and infrared spectroscopy. Additionally, [Ru2(tryp)2(6,6'-Me2dppz)mu-Cl](BF4)2 (3b(BF4)2), [Ru2(trpy)2(4,4'-Me2dppz)mu-Cl](PF6)2.0.5MeOH (3c), [Ru2(trpy)2(6,6'-Me2dppz)(CH2C(O)CH3)](PF6)2.0.5(CH3)2CO (9b), "in"-[Ru(trpy)(4,4'-Me2dppz)Cl](PF6).(CH3)2CO (1c), and "out"-[Ru(trpy)(dpo)Cl](PF6).(CH3)2CO (2d) were characterized by X-ray crystallography. Several ligand substitution reactions were attempted. For example, [Ru2(trpy)2(6,6'-Me2dppz)mu-Cl](BF4)2 (3b) was reacted with hydroxide ion to produce [Ru2(trpy)2(6,6'-Me2dppz)mu-OH](PF6)2 (6b). Complex 6b reacts with benzyl bromide to produce [Ru2(trpy)2(6,6'-Me2dppz)mu-Br](PF6)2 (7b) or with (CH3)3Sil to produce [Ru2(trpy)2(6,6'-Me2dppz)mu-I](PF6)2 (8b). of 6b with acetone forms the methyl enolate complex [Ru2(trpy)2(6,6'-Me2dppz)(CH2COCH3)](PF6)2 (9b) while, analogously to a Cannizarro reaction, the reaction with benzaldehyde forms the bridging benzoate complex [Ru2(trpy)2(6,6'-Me2dppz)(C6H4CO2)](PF6)2 (11b). The bridging azide complex [Ru2(trpy)2(6,6'-Me2dppz)mu-N3](PF6)2 (10b) is formed by reaction of 6b with (CH3)3-SiN3. Additionally, the chloride ligands of the monometallic complexes of "in"-[Ru(trpy)(dpo)Cl](PF6) (1d), "in"-[Ru(trpy)(4,4'-Me2dpo)Cl](PF6)] (1e), and "out"-[Ru(trpy)(dpo)Cl](PF6) (2d) were substituted with water to form their respective aqua complexes, 4d, 4e, and 5d. All of the complexes exhibit broad unsymmetrial absorption bands in the visible portion of the electromagnetic spectrum. The dimetallic complexes 3b and 3c exhibit two, 1e- reversible oxidation waves at +0.72 and +1.15 V, and at +0.64 and +1.13 V, respectively. These complexes were not emissive.     

Organoactinides promote the dimerization of aldehydes: scope, kinetics, thermodynamics, and calculation studies

Surprising catalytic activities have been found for the actinide complexes Cp*(2)ThMe(2) (1), Th(NEtMe)(4) (2), and Me(2)SiCp'(2)Th(C(4)H(9))(2) (3) toward oxygenated substrates. During the catalytic dimerization of benzaldehydes to their corresponding esters, complexes 1 and 2 gave 65 and 85% yield in 48 h, respectively, while the geometry-constrained complex 3 gave 96% yield in 24 h. Exploring the effect of substituents on benzaldehyde, it has been found that, in general, electron-withdrawing groups facilitate the reaction. Kinetic study with complexes 1 and 3 reveals that the rate of the reaction is first order in catalyst and substrate, which suggests the rate equation "rate = k[catalyst](1)[aldehyde](1)". The activation energy of the reaction was found to be 7.16 ± 0.40 and 3.47 ± 0.40 kcal/mol for complexes 1 and 3 respectively, which clearly indicates the advantage of the geometry-constrained complex. Astonishing are the reactivity of the organoactinide complexes with oxygen-containing substrates, and especially the reactivity of complex 3, toward the dimerization of substrates like p-methoxybenzaldehyde, m/p-nitrobenzaldehyde, and furanaldehyde and the reactivity toward the polymerization of terephthalaldehyde. Density functional theory mechanistic study reveals that the catalytic cycle proceeds via an initially four-centered transition state (+6 kcal/mol), followed by the rate-determining six-centered transition state (+13.5 kcal/mol), to yield thermodynamically stable products.     

Substituent effect on the photophysical properties, electrochemical properties and electroluminescence performance of orange-emitting iridium complexes

A series of bis(2-phenylbenzothiozolato-N,C(2'))iridium(acetylacetonate) [(bt)(2)Ir(acac)] derivatives, 1-4, were synthesized. Different substituents (CF(3), F, CH(3), OCH(3)) were introduced in the benzothiazole ring to study the substituent effect on the photophysical, electrochemical properties and electroluminescent performance of the complexes, and finally to select high-performance phosphors for use in organic light-emitting diodes (OLEDs). All complexes 1-4 and (bt)(2)Ir(acac) are orange-emitting with tiny spectral difference, despite the variation of the substituent. However, the phosphorescent quantum yield increases with the electron-withdrawing ability of the substituent. This is in contrast to the previous observation that the substituent in the phenyl ring bonded to the metal center of (bt)(2)Ir(acac) not only affected the luminescent quantum efficiency but also greatly tuned the emission color of the complexes. Quantum chemical calculations revealed that the substituents in this position do not make a significant contribution to both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), which probably accounts for the fact that they do no strongly influence the bandgap and emission color of the complexes. Orange OLEDs were fabricated using 1-4 as doped emitters. The electron-withdrawing CF(3) and F groups favor improving the electroluminescence efficiency in comparison with that of the parent (bt)(2)Ir(acac), while electron-donating CH(3) and OCH(3) are not favorable for light emission. The complex 1 based OLED exhibited a maximum luminance efficiency of 54.1 cd A(-1) (a power efficiency of 24 lm W(-1) and an external quantum efficiency of 20%), which are among the best results ever reported for vacuum deposited orange OLEDs so far.     

Electrochemical and spectroelectrochemical characterization of Ru(2)(4+) and Ru(2)(3+) complexes under a CO atmosphere

Eleven different Ru(2)(4+) and Ru(2)(3+) derivatives are characterized by thin-layer FTIR and UV-visible spectroelectrochemistry under a CO atmosphere. These compounds, which were in-situ electrogenerated from substituted anilinopyridine complexes with a Ru(2)(5+) core, are represented as Ru(2)(L)(4)Cl where L = 2-CH(3)ap, ap, 2-Fap, 2,3-F(2)ap, 2,4-F(2)ap, 2,5-F(2)ap, 3,4-F(2)ap, 3,5-F(2)ap, 2,4,6-F(3)ap, or F(5)ap. The Ru(2)(5+) complexes do not axially bind CO while mono- and bis-CO axial adducts are formed for the Ru(2)(4+) and Ru(2)(3+) derivatives, respectively. Six of the eleven investigated compounds exist in a (4,0) isomeric form while five adopt a (3,1) geometric conformation. These two series of compounds thus provide a large enough number of derivatives to examine trends and differences in the spectroscopic data of the two types of isomers in their lower Ru(2)(4+) and Ru(2)(3+) oxidation states. UV-visible spectra of the Ru(2)(4+) derivatives and IR spectra of the Ru(2)(3+) complexes under CO are both isomer dependent, thus suggesting that these data can be used to reliably predict the isomeric form, i.e., (3,1) or (4,0), of diruthenium complexes containing four unsymmetrical substituted anilinopyridinate bridging ligands; this was confirmed by X-ray crystallographic data for seven compounds whose structures were available.     

Synthesis, structure, and reactivity of ruthenium carboxylato and 2-oxocarboxylato complexes bearing the bis(3,5-dimethylpyrazol-1-yl)acetato ligand

A series of ruthenium(II) acetonitrile, pyridine (py), carbonyl, SO2, and nitrosyl complexes [Ru(bdmpza)(O2CR)(L)(PPh3)] (L = NCMe, py, CO, SO2) and [Ru(bdmpza)(O2CR)(L)(PPh3)]BF4 (L = NO) containing the bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) ligand, a N,N,O heteroscorpionate ligand, have been prepared. Starting from ruthenium chlorido, carboxylato, or 2-oxocarboxylato complexes, a variety of acetonitrile complexes [Ru(bdmpza)Cl(NCMe)(PPh3)] (4) and [Ru(bdmpza)(O2CR)(NCMe)(PPh3)] (R = Me (5a), R = Ph (5b)), as well as the pyridine complexes [Ru(bdmpza)Cl(PPh3)(py)] (6) and [Ru(bdmpza)(O2CR)(PPh3)(py)] (R = Me (7a), R = Ph (7b), R = (CO)Me (8a), R = (CO)Et (8b), R = (CO)Ph) (8c)), have been synthesized. Treatment of various carboxylato complexes [Ru(bdmpza)(O2CR)(PPh3)2] (R = Me (2a), Ph (2b)) with CO afforded carbonyl complexes [Ru(bdmpza)(O2CR)(CO)(PPh3)] (9a, 9b). In the same way, the corresponding sulfur dioxide complexes [Ru(bdmpza)(O2CMe)(PPh3)(SO2)] (10a) and [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b) were formed in a reaction of the carboxylato complexes with gaseous SO2. None of the 2-oxocarboxylato complexes [Ru(bdmpza)(O2C(CO)R)(PPh3)2] (R = Me (3a), Et (3b), Ph (3c)) showed any reactivity toward CO or SO2, whereas the nitrosyl complex cations [Ru(bdmpza)(O2CMe)(NO)(PPh3)](+) (11) and [Ru(bdmpza)(O2C(CO)Ph)(NO)(PPh3)](+) (12) were formed in a reaction of the acetato 2a or the benzoylformato complex 3c with an excess of nitric oxide. Similar cationic carboxylato nitrosyl complexes [Ru(bdmpza)(O2CR)(NO)(PPh3)]BF4 (R = Me (13a), R = Ph (13b)) and 2-oxocarboxylato nitrosyl complexes [Ru(bdmpza)(O2C(CO)R)(NO)(PPh3)]BF4 (R = Me (14a), R = Et (14b), R = Ph (14c)) are also accessible via a reaction with NO[BF4]. X-ray crystal structures of the chlorido acetonitrile complex [Ru(bdmpza)Cl(NCMe)(PPh3)] (4), the pyridine complexes [Ru(bdmpza)(O2CMe)(PPh3)(py)] (7a) and [Ru(bdmpza)(O2CC(O)Et)(PPh3)(py)] (8b), the carbonyl complex [Ru(bdmpza)(O2CPh)(CO)(PPh3)] (9b), the sulfur dioxide complex [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b), as well as the nitrosyl complex [Ru(bdmpza)(O2C(CO)Me)(NO)(PPh3)]BF4 (14a), are reported. The molecular structure of the sulfur dioxide complex [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b) revealed a rather unusual intramolecular SO2-O2CPh Lewis acid-base adduct.     

Ruthenium(II) complexes containing 8-(dimethylphosphino)quinoline (Me(2)Pqn): preparation,crystal structures,and electrochemical and spectroscopic properties of [Ru(bpy or phen)(3)(-)(n)(Me(2)Pqn)(n)](PF(6))(2) (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline; n = 1, 2, or 3)

Several new ruthenium(II) complexes containing 8-(dimethylphosphino)quinoline (Me(2)Pqn) were synthesized, and their structures and electrochemical/spectroscopic properties have been investigated. In addition to the mono(Me(2)Pqn) complex [Ru(bpy or phen)(2)(Me(2)Pqn)](PF(6))(2) (1 or 1'; bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline), the geometrical isomers trans(P)- and C(1)-[Ru(bpy)(Me(2)Pqn)(2)](PF(6))(2) (tP-2 and C(1)-2) and mer- and fac-[Ru(Me(2)Pqn)(3)](PF(6))(2) (m-3 and f-3) were also selectively synthesized and isolated. It was found that complexes tP-2 and m-3 were converted quantitatively to the corresponding C(1)-2 and f-3 isomers, respectively, by irradiation of light corresponding to the MLCT transition energy. The strong trans influence of the Me(2)P- donor group of Me(2)Pqn was confirmed by the X-ray structural analyses for 1, tP-2, m-3, and f-3. Cyclic voltammetry of a series of complexes, [Ru(bpy)(3)](PF(6))(2), 1, C(1)-2, and f-3, exhibited a reversible one-electron oxidation wave and two or three one-electron reduction waves. The oxidation potentials of the complexes gave a large positive shift with increasing number of coordinated Me(2)Pqn molecules, indicating a larger pi-acceptability of the Me(2)P- group compared with bpy or qn. Complex f-3 in EtOH/MeOH (4:1) glass at 77 K exhibited an intense long-lived (tau = 920 microseconds) emission arising from the quinoline-based (3)(pi-pi) excited state. In contrast, the mixed-ligand complexes 1, 1', and C(1)-2 showed a characteristic dual emission, giving a double-exponential emission decay, and the dual emission originates from both the bpy-based (3)MLCT and the quinoline-based (3)(pi-pi) emitting states.     

Diastereoselective Synthesis, Spectroscopy, and Electrochemistry of Ruthenium(II) Complexes of Substituted Pyrazolylpyridine Ligands

We report the synthesis of the hetero- and homoleptic ruthenium(II) complexes Ru(bpy)(2)L(2+), Ru(bpy)L(2)(2+) (bpy is 2,2'-bipyridine), and RuL(3)(2+) of six new bidentates L, the substituted pyrazolylpyridines 1-6 (1-substituted-3-(2-pyridinyl)-4,5,6,7-tetrahydroindazoles with substituents R = H, CH(3), Ph, or C(6)H(4)-4"-COOX where X = H, CH(3), or C(2)H(5)). These were fully characterized by (1)H- and (13)C-NMR spectroscopy and elemental analysis. The UV-visible spectra and redox properties of the complexes, some in the ruthenium(III) and reduced bipyridine oxidation states, are also discussed. The substituents R played a role in determining the stereochemistry of the Ru(bpy)L(2)(2+) and RuL(3)(2+) products. The reaction of Ru(DMSO)(4)Cl(2) with 3 equiv of L bearing aromatic substituents gave only meridional RuL(3)(2+) isomers. The one-step reaction of Ru(bpy)Cl(3).H(2)O with 2 equiv of L provided a mixture of the three possible Ru(bpy)L(2)(2+) isomers, from which one symmetric isomer (labeled beta) was isolated pure. A trans arrangement of the pyrazole groups was deduced by (1)H-NMR and confirmed by X-ray crystallography for one such stereomer (beta-[Ru(bpy)(5)(2)](PF(6))(2), R = C(6)H(4)-4"-COOC(2)H(5)). In contrast, Ru(DMSO)(4)Cl(2) reacted with 2 equiv of L and then 1 equiv of bpy to selectively form the other symmetric isomer (labeled alpha) where the pyridine groups of L are trans. Crystal data for beta-[Ru(bpy)(5)(2)](PF(6))(2) (C(52)H(50)N(8)O(4)F(12)P(2)Ru) with Mo Kalpha (lambda = 0.710 73 ?) radiation at 295 K: a = 28.442(13) ?, b = 18.469(15) ?, c = 23.785(9) ?, beta = 116.76(0) degrees, monoclinic, space group C2/c, Z = 8. Fully anisotropic (except for H and disordered F atoms), full-matrix, weighted least-squares refinement on F(2) gave a weighted R on F(2) of 0.2573 corresponding to R on F of 0.1031 for data where F > 4sigma(F ).     

Separating innocence and non-innocence of ligands and metals in complexes [(L)Ru(acac)2](n) (n = -1, 0, +1; L = o-iminoquinone or o-iminothioquinone)

The diamagnetic title complexes were obtained from Ru(acac)(2)(CH(3)CN)(2) and 2-aminophenol or 2-aminothiophenol. X-ray structure analysis of (L(1))Ru(acac)(2) (L(1) = o-iminoquinone) revealed C-C intra-ring, C-O, and C-N distances which suggest a Ru(III)-iminosemiquinone oxidation state distribution with antiparallel spin-spin coupling. One-electron oxidation and reduction of both title compounds to paramagnetic monocations [(L)Ru(acac)(2)](+) or monoanions [(L)Ru(acac)(2)](-) occurs reversibly at widely separated potentials (deltaE > 1.3 V) and leads to low-energy shifted charge transfer bands. In comparison with clearly established Ru(II)-semiquinone or Ru(III)-catecholate systems the g tensor components 2.23 > g(1) > 2.09, 2.16 > g(2) > 2.07, and 1.97 > g(3) > 1.88 point to considerable metal contributions to the singly occupied MO, corresponding to Ru(III) complexes with either o-quinonoid (--> cations) or catecholate-type ligands (--> anions) and only minor inclusion of Ru(IV)- or Ru(II)-iminosemiquinone formulations, respectively. The preference for the Ru(III) oxidation state for all accessible species is partially attributed to the monoanionic 2,4-pentanedionate (acac) co-ligands which favor a higher metal oxidation state than, e.g., neutral 2,2'-bipyridine (bpy).     

Linkage and redox isomerism in ruthenium complexes of catecholate, semiquinone, and o-acylphenolate ligands derived from 1,2-dihydroxy-9,10-anthracenedione (alizarin) and related species: syntheses, characterizations, and photophysics

The complexes Ru(CO)2L2(AL-2H) (AL = alizarin; L = PPh3, PCyc3, PBu3, P(m-NaSO3C6H4)3), Ru(CO)(dppe)(PBu3)(AL-2H), and RuH(CO)L2(AL-H) (L = PPh3, PCyc3), and Ru(CO)2L2(AR-2H) (AR = anthrarobin; L = PBu3) were prepared by reactions of Ru3(CO)12, L, and AL, and the complexes RuH(CO)(PPh3)2(AL-H), RuH(CO)(PPh3)2(QN-H) (QN = quinizarin), and RuH(CO)(PPh3)2(LQN-H) (LQN = leucoquinizarin) are prepared by reactions of RuH2(CO)(PPh3)3 with AL or QN. The AL-2H and AR-2H ligands act as 1,2-catecholates, whereas the AL-H, QN-H, LQN-H ligands are 1,9-o-acylphenolate ligands. RuH(CO)(PPh3)2(AL-H) is characterized by X-ray crystallography. The electrochemistry of these complexes is examined, and the semiquinone complexes [Ru(CO)2L2(AL-2H)]+ (L = PPh3, PCyc3, PBu3) and [Ru(CO)(dppe)(PBu3)(AL-2H)]+ are generated by chemical oxidation and were characterized by EPR and IR spectroscopy. The photophysical properties are also reported.