Chemical and Photochemical Water Oxidation Catalyzed by Mononuclear Ruthenium Complexes with a Negatively Charged Tridentate Ligand

Two mononuclear ruthenium complexes [RuL(pic)₃] ( 1 ) and [RuL(bpy)(pic)] ( 2 ) (H₂L=2,6‐pyridinedicarboxylic acid, pic=4‐picoline, bpy=2,2′‐bipyridine) have been synthesized and fully characterized. Both complexes could promote water oxidation chemically and photochemically. Compared with other known ruthenium‐based water oxidation catalysts using [Ce(NH₄)₂(NO₃)₆] (Ce^IV) as the oxidant in solution at pH 1.0, complex 1 is one of the most active catalysts yet reported with an initial rate of 0.23 turnover s^?1. Under acidic conditions, the equatorial 4‐picoline in complex 1 dissociates first. In addition, ligand exchange in 1 occurs when the Ru^III state is reached. Based on the above observations and MS measurements of the intermediates during water oxidation by 1 using Ce^IV as oxidant, [RuL(pic)₂(H₂O)]⁺ is proposed as the real water oxidation catalyst.     

Water Oxidation by Ruthenium Complexes Incorporating Multifunctional Bipyridyl Diphosphonate Ligands

We describe herein the synthesis and characterization of ruthenium complexes with multifunctional bipyridyl diphosphonate ligands as well as initial water oxidation studies. In these complexes, the phosphonate groups provide redox‐potential leveling through charge compensation and σ donation to allow facile access to high oxidation states. These complexes display unique pH‐dependent electrochemistry associated with deprotonation of the phosphonic acid groups. The position of these groups allows them to shuttle protons in and out of the catalytic site and reduce activation barriers. A mechanism for water oxidation by these catalysts is proposed on the basis of experimental results and DFT calculations. The unprecedented attack of water at a neutral six‐coordinate [Ru^IV] center to yield an anionic seven‐coordinate [Ru^IV?OH]^? intermediate is one of the key steps of a single‐site mechanism in which all species are anionic or neutral. These complexes are among the fastest single‐site catalysts reported to date.     

Photochemical,Electrochemical, and Photoelectrochemical Water Oxidation Catalyzed by Water‐Soluble Mononuclear Ruthenium Complexes

Two mononuclear ruthenium complexes [Ru(H₂tcbp)(isoq)₂] ( 1 ) and [Ru(H₂tcbp)(pic)₂] ( 2 ) (H₄tcbp=4,4′,6,6′‐tetracarboxy‐2,2′‐bipyridine, isoq=isoquinoline, pic=4‐picoline) are synthesized and fully characterized. Two spare carboxyl groups on the 4,4′‐positions are introduced to enhance the solubility of 1 and 2 in water and to simultaneously allow them to tether to the electrode surface by an ester linkage. The photochemical, electrochemical, and photoelectrochemical water oxidation performance of 1 in neutral aqueous solution is investigated. Under electrochemical conditions, water oxidation is conducted on the deposited indium‐tin‐oxide anode, and a turnover number higher than 15,000 per water oxidation catalyst (WOC) 1 is obtained during 10 h of electrolysis under 1.42 V vs. NHE, corresponding to a turnover frequency of 0.41 s^?1. The low overpotential (0.17 V) of electrochemical water oxidation for 1 in the homogeneous solution enables water oxidation under visible light by using [Ru(bpy)₃]²⁺ ( P1 ) (bpy=2,2′‐bipyridine) or [Ru(bpy)₂(4,4′‐(COOEt)₂‐bpy)]²⁺ ( P2 ) as a photosensitizer. In a three‐component system containing 1 or 2 as a light‐driven WOC, P1 or P2 as a photosensitizer, and Na₂S₂O₈ or [CoCl(NH₃)₅]Cl₂ as a sacrificial electron acceptor, a high turnover frequency of 0.81 s^?1 and a turnover number of up to 600 for 1 under different catalytic conditions are achieved. In a photoelectrochemical system, the WOC 1 and photosensitizer are immobilized together on the photoanode. The electrons efficiently transfer from the WOC to the photogenerated oxidizing photosensitizer, and a high photocurrent density of 85 μA cm^?2 is obtained by applying 0.3 V bias vs. NHE.     

Synthesis and Catalytic Water Oxidation Activities of Ruthenium Complexes Containing Neutral Ligands

Two dinuclear and one mononuclear ruthenium complexes containing neutral polypyridyl ligands have been synthesised as pre‐water oxidation catalysts and characterised by ¹H and ¹³C NMR spectroscopy and ESI‐MS. Their catalytic water oxidation properties in the presence of [Ce(NH₄)₂(NO₃)₆] (Ce^IV) as oxidant at pH 1.0 have been investigated. At low concentrations of Ce^IV (5 mM ), high turnover numbers of up to 4500 have been achieved. An ¹⁸O‐labelling experiment established that both O atoms in the evolved O₂ originate from water. Combined electrochemical study and electrospray ionisation mass spectrometric analysis suggest that ligand exchange between coordinated 4‐picoline and free water produces Ru aquo species as the real water oxidation catalysts.     

Efficient Water Oxidation Catalyzed by Mononuclear Ruthenium(II) Complexes Incorporating Schiff Base Ligands

Four new charge‐neutral ruthenium(II) complexes containing dianionic Schiff base and isoquinoline or 4‐picoline ligands were synthesized and characterized by NMR and ESI‐MS spectroscopies, elemental analysis, and X‐ray diffraction. The complexes exhibited excellent chemical water oxidation activity and high stability under acidic conditions (pH 1.0) using (NH₄)₂Ce(NO₃)₆ as a sacrificial electron acceptor. The high catalytic activities of these complexes for water oxidation were sustained for more than 10 h at low concentrations. High turnover numbers of up to 3200 were achieved. A water nucleophilic attack mechanism was proposed. A Ru^V?O intermediate was detected during the catalytic cycle by high‐resolution mass spectrometry.     

A Dinuclear Ruthenium‐Based Water Oxidation Catalyst: Use of Non‐Innocent Ligand Frameworks for Promoting Multi‐Electron Reactions

Insight into how H₂O is oxidized to O₂ is envisioned to facilitate the rational design of artificial water oxidation catalysts, which is a vital component in solar‐to‐fuel conversion schemes. Herein, we report on the mechanistic features associated with a dinuclear Ru‐based water oxidation catalyst. The catalytic action of the designed Ru complex was studied by the combined use of high‐resolution mass spectrometry, electrochemistry, and quantum chemical calculations. Based on the obtained results, it is suggested that the designed ligand scaffold in Ru complex 1 has a non‐innocent behavior, in which metal–ligand cooperation is an important part during the four‐electron oxidation of H₂O. This feature is vital for the observed catalytic efficiency and highlights that the preparation of catalysts housing non‐innocent molecular frameworks could be a general strategy for accessing efficient catalysts for activation of H₂O.     

Reactions of Ruthenium Complexes Containing Pentatetraenylidene Ligand

Two ruthenium acetylide complexes [Ru]?C≡C?C≡C?C(OR)(C₃H₅)₂ ( 2 , R=H and 2 a , R=CH₃; [Ru]=Cp(PPh₃)₂Ru) each with two cyclopropyl rings were synthesized from TMS?C≡C?C≡C?C(OH)(C₃H₅)₂ ( 1 ; TMS=trimethylsilyl). Treatments of 2 and 2 a with allyl halide in the presence of KPF₆ afforded the vinylidene complexes 3 and 3 a , respectively. When NH₄PF₆ was used, instead of KPF₆, additional ring‐opening reaction took place on one of the three‐membered ring. Treatment of [Ru]Cl with 1,3‐butadiyne ( 6 ), bearing an epoxide ring, afforded acetylide complex 7 with a furyl ring. Treatment of 2 a with Ph₃CPF₆ presumably afforded pentatetraenylidene complex {[Ru]=C=C=C=C=C(C₃H₅)₂}[PF₆] ( 10 ), which was not isolated. Additions of various alcohols in a solution of 10 generated a number of disubstituted allenylidene complexes {[Ru]=C=C=C(OR)?C=C(C₃H₅)₂}[PF₆] ( 11 ). Treatment of 11 with K₂CO₃ afforded the acetylide complex 12 bearing a carbonyl group, characterized by single X‐ray diffraction analysis. Addition of a primary amine to 10 caused cleavage of the farthermost C=C bond and several allenylidene complexes {[Ru]=C=C=C(Me)(NHR)}[PF₆] ( 18 ) were isolated.     

多齿胺膦钌配合物催化苯乙酮的氢转移氢化

利用Ｃ２－对称的双胺双膦钌（Ⅱ）配合物ＲｕＣｌ２（Ｐ２Ｎ２Ｈ４）为催化剂，研究了苯乙酮的氢转移还原反应。在苯乙酮、钌配合物和异丙氧基钾的摩尔比为２００：１：１２的条件下，于６５℃反应２ｈ后，苯乙酮的转化率高达９９％。讨论了苯乙酮的氢转移氢化机理。     

Luminescent Ruthenium(II) Polypyridyl Complexes as Nonviral Carriers for DNA Delivery

Two new luminescent ruthenium(II) polypyridyl complexes, [Ru(bpy)₂(tpt‐phen)]Cl₂ ( 1 ; bpy=2,2′‐bipyridine, tpt‐phen=triptycenyl‐1,10‐phenanthroline) and [Ru(phen)₂(tpt‐phen)]Cl₂ ( 2 ; phen=1,10‐phenanthroline), have been developed as potential nonviral vectors for DNA delivery. Photophysical and electrochemical properties of the complexes have been investigated and corroborated with electronic structure calculations. DNA condensation by these complexes has been investigated by UV/Vis and emission spectroscopy, circular dichroism spectroscopy, atomic force microscopy, dynamic light scattering, confocal microscopy, and electrophoretic mobility studies. These complexes interact with DNA and efficiently condense DNA into globular nanoparticles that are taken up efficiently by HeLa cells. DNA cleavage inability and biocompatibility of complexes have been explored. Both complexes have good gene transfection abilities.     

Ligand Modification Transforms a Catalase Mimic into a Water Oxidation Catalyst

The catalytic reactivity of the high‐spin Mn^II pyridinophane complexes [(Py₂NR₂)Mn(H₂O)₂]²⁺ (R=H, Me, tBu) toward O₂ formation is reported. With small macrocycle N‐substituents (R=H, Me), the complexes catalytically disproportionate H₂O₂ in aqueous solution; with a bulky substituent (R=tBu), this catalytic reaction is shut down, but the complex becomes active for aqueous electrocatalytic H₂O oxidation. Control experiments are in support of a homogeneous molecular catalyst and preliminary mechanistic studies suggest that the catalyst is mononuclear. This ligand‐controlled switch in catalytic reactivity has implications for the design of new manganese‐based water oxidation catalysts.     

Design of Mononuclear Ruthenium Catalysts for Low‐Overpotential Water Oxidation

Water oxidation is a key reaction in natural photosynthesis and in many schemes for artificial photosynthesis. Inspired by energy challenges and the emerging understanding of photosystem II, the development of artificial molecular catalysts for water oxidation has become a highly active area of research in recent years. In this Focus Review, we describe recent achievements in the development of single‐site ruthenium catalysts for water oxidation with a particular focus on the overpotential of water oxidation. First, we introduce the general scheme to access the high‐valent ruthenium–oxo species, the key species of the water‐oxidation reaction. Next, the mechanisms of the O? O bond formation from the active ruthenium–oxo species are described. We then discuss strategies to decrease the onset potentials of the water‐oxidation reaction. We hope this Focus Review will contribute to the further development of efficient catalysts toward sustainable energy‐conversion systems.     

Water Oxidation by In Situ Generated [RuII(OH2)(NCNHCO)(pic)2]+

A dinuclear ruthenium complex [Ru^II(NC^NHC O)(pic)₂]₂²⁺ ( 2 ) was firstly prepared and characterized spectroscopically and electrochemically. Instead of the conventional ligand exchange, complex 2 dissociates in situ to afford two single‐site Ru aqua complexes, [Ru^II(OH₂)(NC^NHC O)(pic)₂]⁺, which mediates water oxidation through proton‐coupled electron transfer events. In electrokinetic studies, complex 2 demonstrated a TOF of 150.3 s⁻¹ comparable to those state‐of‐the‐art catalysts at neutral conditions. TONs of 2173 and 217 were attained in chemical and photochemical water oxidation when 2 was used as a catalyst, exhibiting good stability. Notably, a TOF of 1.3 s⁻¹ was achieved at CAN‐driven water oxidation, which outperformed most of the reported single‐site Ru complexes, indicating that complex 2 is one of most active water oxidation catalysts (WOCs) to date. The unique coordination configuration and outstanding catalytic performance of complex 2 might shed light on the design of novel molecular WOCs.     

Charge‐Neutral Amidinate‐Containing Iridium Complexes Capable of Efficient Photocatalytic Water Reduction

Two new charge‐neutral iridium complexes, [Ir(tfm‐ppy)₂(N,N′‐diisopropyl‐benzamidinate)] ( 1 ) and [Ir(tfm‐ppy)₂(N,N′‐diisopropyl‐4‐diethylamino‐3,5‐dimethyl‐benzamidinate)] ( 2 ) (tfm‐ppy=4‐trifluoromethyl‐2‐phenylpyridine) containing an amidinate ligand and two phenylpyridine ligands were designed and characterised. The photophysical properties, electrochemical behaviours and emission quenching properties of these species were investigated. In concert with the cobalt catalyst [Co(bpy)₃]²⁺, members of this new class of iridium complexes enable the photocatalytic generation of hydrogen from mixed aqueous solutions via an oxidative quenching pathway and display long‐term photostability under constant illumination over 72 h; one of these species achieved a relatively high turnover number of 1880 during this time period. In the case of complex 1 , the three‐component homogeneous photocatalytic system proved to be more efficient than a related system containing a charged complex, [Ir(tfm‐ppy)₂(dtb‐bpy)]⁺ ( 3 , dtb‐bpy=4,4′‐di‐tert‐butyl‐2,2′‐dipyridyl). In combination with a rhodium complex as a water reduction catalyst, the performances of the systems using both complexes were also evaluated, and these systems exhibited a more efficient catalytic propensity for water splitting than did the cobalt‐based systems that have been studied previously.     

Control over Electrochemical Water Oxidation Catalysis by Preorganization of Molecular Ruthenium Catalysts in Self‐Assembled Nanospheres

Oxygen formation through water oxidation catalysis is a key reaction in the context of fuel generation from renewable energies. The number of homogeneous catalysts that catalyze water oxidation at high rate with low overpotential is limited. Ruthenium complexes can be particularly active, especially if they facilitate a dinuclear pathway for oxygen bond formation step. A supramolecular encapsulation strategy is reported that involves preorganization of dilute solutions (10^?5 m ) of ruthenium complexes to yield high local catalyst concentrations (up to 0.54 m ). The preorganization strategy enhances the water oxidation rate by two‐orders of magnitude to 125 s^?1, as it facilitates the diffusion‐controlled rate‐limiting dinuclear coupling step. Moreover, it modulates reaction rates, enabling comprehensive elucidation of electrocatalytic reaction mechanisms.     

Arene Control over Thiolate to Sulfinate Oxidation in Albumin by Organometallic Ruthenium Anticancer Complexes

Arene control : Anticancer complexes [Ru(arene)Cl(en)]⁺ (arene=p‐cymene or biphenyl; en=ethylenediamine) bind to surface histidine (His128, His247, His510) and methionine (Met298) residues in human albumin, but only the p‐cymene complex can gain entry to the crevice containing the free cysteine thiolate (Cys34) and induce oxidation to sulfinate.

     

氮杂环卡宾羰基氯钌配合物的合成、晶体结构及催化性质(英文)

合成了2个N-杂环卡宾钌配合物[RuCl2(L1)(CO)](1),L1=(2,6-二(甲基咪唑-2-鎓盐)吡啶)和[RuCl2(L2)(CO)](2),L2=(2,6-二(正丁基-2-鎓盐)吡啶),并通过元素分析、红外光谱、核磁共振氢谱和核磁共振碳谱对它们的结构进行了表征,X-射线单晶衍射测定了配合物2的分子结构,结果表明配合物2属单斜晶系,C2/c空间群,a=1.814 8(4)nm,b=1.129 2(3)nm,c=1.119 6(2)nm,β=108.862(3)°,且中心Ru(Ⅱ)离子是六配位,同时研究了配合物1和2在Suzuki-Miyaura偶联反应中的催化性质。