NLO active CuII/RuII and CdII/RuII coordination-organometallic complexes: synthesis,structural characterization and photoluminescence properties

Cu^II/Ru^II and Cd^II/Ru^II hybrid complexes [Cu(L_1–3)(NC₅H₄C≡CRu(dppe)₂Cl)] (1a-3a) and [Cd(L_1-3)(NC₅H₄C≡CRu(dppe)₂Cl)] (1b–3b) have been prepared by reaction of trans-[RuCl(dppe)₂(C≡C-py-3)] (1) with copper or cadmium acetate in the presence of Schiff base ligands L_H1–3 (where L_H = 2-(pyrrole-2-yl-methylidine)aminophenol (L_H1), 5-bromo-2-(pyrrole-2-yl-methylidine)aminophenol (L_H2) and 5-nitro-2-(pyrrole-2-yl-methylidine)aminophenol (L_H3)). The hybrid materials were characterized on the basis of elemental analyses, TEM, IR, UV–visible, ¹H NMR, and ³¹P NMR spectral studies. TEM overview observations revealed well-dispersed spherical nanoparticles of ~60 nm are formed. Quasireversible redox behavior is observed for Cu^II/Ru^II complexes corresponding to Cu^I/Cu^II and Ru^II/Ru^III couples. All the complexes exhibit blue-green emission as a result of fluorescence from the intraligand (π → π*) emission excited state with good quantum yield. The second-order nonlinear optical (NLO) properties of Cu^II/Ru^II and Cd^II/Ru^II complexes have been investigated by the Kurtz-powder method. The second harmonic generation efficiency of these complexes show that these complexes are NLO active and display good second-order nonlinear optical activity.     

Ruthenium(II)/(III) complexes of bidentate acetyl hydrazide Schiff bases

A series of octahedral Ru^II/Ru^III complexes of the type [Ru(Y)(CO)(BAX)(PPh₃)₂] and [RuCl₂(BAX)(PPh₃)₂] (Y = H or Cl; BAX = benzaldehydeacetylhydrazone anion; X = H, Me, OMe, OH, Cl or NO₂) have been prepared and characterised by spectral, magnetic and cyclic voltammetric studies. The Ru^II complexes are low spin diamagnetic (S = 0) whereas the Ru^III complexes are low spin and paramagnetic (S = 1/2). These Ru^II and Ru^III complexes absorb in the visible region respectively at ca. 16,000 and 28,000 cm^–1 which bands are assigned to the MLCT. The correlation of the _max values of the Ru^III complexes with the ⁺ Hammett parameter, is linear, indicating the profound effect of substituents on the electron density of the central metal. I.r. spectral data reveals that the hydrazone is chelated to ruthenium through the hydrazinic nitrogen and the deprotonated enolic oxygen. The rhombic nature of the e.s.r. spectra of the Ru^III complexes indicates an asymmetry in the electronic environment around the Ru atom. Ru^II complexes in CH₂Cl₂ show an irreversible Ru^II/III redox couple at ca. 0.9–0.5 V, while the Ru^III complexes show two reversible redox couples in the –0.1–0.1 and 0.8–0.6 V range, indicating that the higher oxidation state of ruthenium is stabilised by hydrazones.     

Redox properties of ruthenium(III/II)–edta complexes with o-phenylenediamine and o-benzoquinone diimine ligands

The reaction of [Ru^III(edta)(H₂O)]⁻ with o-phenylenediamine (opda) in water, under aerobic conditions, affords the diamagnetic [Ru^II(edta)(bqdi)]²⁻ product (where edta stands for the ethylenediaminetetraacetate co-ligand, and bqdi represents the non-innocent o-benzoquinone α,α^′-diimine ligand). In the current communication, the redox chemistry of this system in aqueous solution is described in details on the basis of electrochemical and spectroelectrochemical studies. The electrochemical behavior of “free” opda is rather complicated with further chemical reactions following the irreversible two-proton/two-electron oxidation (opda→bqdi+2e⁻+2H⁺), whereas its complex is electrochemically well-behaved with two chemically reversible redox processes: the monoelectronic couple associated with the metal ion (Ru^III/Ru^II) and another bielectronic step centered on the coordinated ligand (bqdi/opda). The set of UV–Vis electronic spectra were obtained by electrolytical generation, in situ, of all the redox species accessible in the CV working conditions (i.e., the starting [Ru^II(edta)(bqdi)]²⁻, the fully oxidized [Ru^III(edta)(bqdi)]⁻, and the fully reduced [Ru^II(edta)(opda)]²⁻ species), which are stable and totally interconvertible. The electrochemistry and absorption spectroscopy of these complexes in water were found to be comparable with the tetraammine counterparts. A remarkable difference in redox behavior between the diimine- and the analogous dioxolene-complexes was also revealed by comparison of the system reported herein with the one derived from catechol, and rationalized in terms of the quite efficient π-accepting electronic nature of the bqdi ligand.     

Spectroscopic,Electrochemical and Computational Characterisation of Ru Species Involved in Catalytic Water Oxidation: Evidence for a [RuV(O)(Py2Metacn)] Intermediate

A new family of ruthenium complexes based on the N‐pentadentate ligand Py₂^Metacn (N‐methyl‐N′,N′′‐bis(2‐picolyl)‐1,4,7‐triazacyclononane) has been synthesised and its catalytic activity has been studied in the water‐oxidation (WO) reaction. We have used chemical oxidants (ceric ammonium nitrate and NaIO₄) to generate the WO intermediates [Ru^II(OH₂)(Py₂^Metacn)]²⁺, [Ru^III(OH₂)(Py₂^Metacn)]³⁺, [Ru^III(OH)(Py₂^Metacn)]²⁺ and [Ru^IV(O)(Py₂^Metacn)]²⁺, which have been characterised spectroscopically. Their relative redox and pH stability in water has been studied by using UV/Vis and NMR spectroscopies, HRMS and spectroelectrochemistry. [Ru^IV(O)(Py₂^Metacn)]²⁺ has a long half‐life (>48 h) in water. The catalytic cycle of WO has been elucidated by using kinetic, spectroscopic, ¹⁸O‐labelling and theoretical studies, and the conclusion is that the rate‐determining step is a single‐site water nucleophilic attack on a metal‐oxo species. Moreover, [Ru^IV(O)(Py₂^Metacn)]²⁺ is proposed to be the resting state under catalytic conditions. By monitoring Ce^IV consumption, we found that the O₂ evolution rate is redox‐controlled and independent of the initial concentration of Ce^IV. Based on these facts, we propose herein that [Ru^IV(O)(Py₂^Metacn)]²⁺ is oxidised to [Ru^V(O)(Py₂^Metacn)]²⁺ prior to attack by a water molecule to give [Ru^III(OOH)(Py₂^Metacn)]²⁺. Finally, it is shown that the difference in WO reactivity between the homologous iron and ruthenium [M(OH₂)(Py₂^Metacn)]²⁺ (M=Ru, Fe) complexes is due to the difference in the redox stability of the key M^V(O) intermediate. These results contribute to a better understanding of the WO mechanism and the differences between iron and ruthenium complexes in WO reactions.     

N,N′-Bis(aryl)pyridine-2,6-dicarboxamide complexes of ruthenium: Synthesis,structure and redox properties

Reaction of five N,N′-bis(aryl)pyridine-2,6-dicarboxamides (H₂L-R, where H₂ denotes the two acidic protons and R (R = OCH₃, CH₃, H, Cl and NO₂) the para substituent in the aryl fragment) with [Ru(trpy)Cl₃](trpy = 2,2′,2″-terpyridine) in refluxing ethanol in the presence of a base (NEt₃) affords a group of complexes of the type [Ru^II(trpy)(L-R)], each of which contains an amide ligand coordinated to the metal center as a dianionic tridentate N,N,N-donor along with a terpyridine ligand. Structure of the [Ru^II(trpy)(L-Cl)] complex has been determined by X-ray crystallography. All the Ru(II) complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on the [Ru^II(trpy)(L-R)] complexes shows a Ru(II)–Ru(III) oxidation within 0.16–0.33 V versus SCE. An oxidation of the coordinated amide ligand is also observed within 0.94–1.33 V versus SCE and a reduction of coordinated terpyridine ligand within −1.10 to −1.15 V versus SCE. Constant potential coulometric oxidation of the [Ru^II(trpy)(L-R)] complexes produces the corresponding [Ru^III(trpy)(L-R)]⁺ complexes, which have been isolated as the perchlorate salts. Structure of the [Ru^III(trpy)(L-CH₃)]ClO₄ complex has been determined by X-ray crystallography. All the Ru(III) complexes are one-electron paramagnetic, and show anisotropic ESR spectra at 77 K and intense LMCT transitions in the visible region. A weak ligand-field band has also been shown by all the [Ru^III(trpy)(L-R)]ClO₄ complexes near 1600 nm.     

DNA-Targeting RuII-Polypyridyl Complex with a Long-Lived Intraligand Excited State as a Potential Photodynamic Therapy Agent

Subtle ligand modifications on Ru^II-polypyridyl complexes may result in different excited-state characteristics, which provides the opportunity to tune their photo-physicochemical properties and subsequently change their biological functions. Here, a DNA-targeting Ru^II-polypyridyl complex (named Ru1 ) with highly photosensitizing ³IL (intraligand) excited state was designed based on a classical DNA-intercalator [Ru(bpy)₂(dppz)] ⋅ 2 PF₆ by incorporation of the dppz (dipyrido[3,2-a:2′,3′-c]phenazine) ligand tethered with a pyrenyl group, which has four orders of magnitude higher potency than the model complex [Ru(bpy)₂(dppz)] ⋅ 2 PF₆ upon light irradiation. This study provides a facile strategy for the design of organelle-targeting Ru^II-polypyridyl complexes with dramatically improved photobiological activity.     

Ruthenium(II) and ruthenium(III) complexes derived from O,O-donor ligands

The new [Ru¹¹(PPh₃)₂L₂] complexes [L=monoanion of tropolone, benzoylacetone, or 3-hydroxy-2-pyridinone (hypy)], [RuH(PPh₃)₃L′][HL′=maltol, dibenzoylmethane or 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdmhypy)] and [Ru^IIIX₂(EPh₃)₂L″] complexes (X=Cl, Br; E=As or P; L″=hypy, dmhypy) have been prepared, and characterized by spectroscopic techniques. Their redox behaviour was studied by cyclic voltammetry. Most of the complexes were found to be effective catalysts for the oxidation ofp-methoxybenzyl alcohol to the corresponding aldehyde in the presence ofN-methylmorpholine-N-oxide as co-oxidant.     

The Tunable Luminescence of Ruthenium(II) Complexes Containing Different Tetrazolate Ligands

Three luminescent mononuclear Ru^II compounds, [Ru^II(bpy)₂( L¹ )](BF₄) ( 1 ), [Ru^II(bpy)₂( L² )](BF₄) ( 2 ), and the neutral compound [Ru^II(bpy)₂( L³ )] ( 3 ), were obtained, by treatment of [Ru^II(bpy)₂Cl₂] with the tetrazolate (tz)-containing ligands L¹ – L³ . All the compounds were well characterized by IR, UV/Vis, and ¹H NMR and their redox properties were also investigated by cyclic voltammogram. The crystal structure of 3 was determined by X-ray crystallography and it clearly shows that the Ru^II ion is octahedrally coordinated by two bpy ligands and a deprotonated L³ ligand. After introduction of these tz ligands, 1 – 3 are more sensitive towards the change of micro-environment of solvents as compared with that of [Ru^II(bpy)₃]²⁺. This effect is most obvious in 3 , since it contains a 2^– ligand L³ . The slight modification of diimine ligand make these complexes have potential applications as sensors.     

Coordination Booster‐Catalyst Assembly: Remote Osmium Outperforming Ruthenium in Boosting Catalytic Activity

Presented herein is a set of bimetallic and trimetallic “coordination booster‐catalyst” assemblies in which the coordination complexes [Ru^II(terpy)₂] and [Os^II(terpy)₂] acted as boosters for enhancement of the catalytic activity of [Ru^II(NHC)(para‐cymene)]‐based catalytic site. The boosters accelerated the oxidative loss of para‐cymene from the catalytic site to generate the active catalyst during the oxidation of alkenes and alkynes into corresponding aldehydes, ketones and diketones. It was found that the boosting efficiency of the [Os^II(terpy)₂] units was considerably higher than its congener [Ru^II(terpy)₂] unit in these assemblies. Mechanistic studies were conducted to understand this unique improvement.     

Synthesis and characterization of stable thiazolylazo anion radical complexes of ruthenium(II)

Two stable thiazolylazo anion radical complexes of ruthenium(II), [Ru(L1^•−)(Cl)(CO)(PPh₃)₂] (1) and [Ru(L2^•−)(Cl)(CO)(PPh₃)₂] (2) (where L1 = 2′-Thiazolylazo-2-imidazole and L2 = 4-(2′-Thiazolylazo)-1-n-hexadecyloxy-naphthalene), have been synthesized and characterized by spectroscopic and electrochemical techniques. The radical nature of the complexes has been confirmed from their room temperature magnetic moments and X-band ESR spectra. The radical complexes display a moderately intense (ε ~ 10⁴ M⁻¹ cm⁻¹) and relatively broad band in 430–460 nm region. In the microcrystalline state, complexes (1) and (2) display strong ESR signals at g = 1.951 and g = 1.988, respectively. In CH₂Cl₂ solution, complexes (1) and (2) show a quasireversible one-electron response near −0.64 and −0.59 V, respectively, versus Ag/AgCl due to the radical redox couple [Ru^II(L)(Cl)(CO)(PPh₃)₂]/[Ru^II (L^•−)(Cl)(CO)(PPh₃)₂].     

Asymmetric 1,3‐Dipolar Cycloadditions of 2‐Diazocyclohexane‐1,3‐diones and Alkyl Diazopyruvates

The 1,3‐dipolar cycloaddition reactions of 2‐diazocyclohexane‐1,3‐dione ( 7a ; Table 1) and of alkyl diazopyruvates ( 11a – e ; Table 3) to 2,3‐dihydrofuran and other enol ethers have been investigated in the presence of chiral transition metal catalysts. With Rh^II catalysts, the cycloadditions were not enantioselective, but those catalyzed by [Ru^IICl₂( 1a )] and [Ru^IICl₂( 1b )] proceeded with enantioselectivities of up to 58% and 74% ee, respectively, when diazopyruvates 11 were used as substrates. The phenyliodonium ylide 7c yielded the adduct 8a in lower yield and poorer selectivity than the corresponding diazo precursor 7a (Table 2) upon decomposition with [Ru(pybox)] catalysts. This suggests that ylide decomposition by Ru^II catalysts, contrary to that of the corresponding diazo precursors, does not lead to Ru‐carbene complexes as reactive intermediates. Our method represents the first reproducible, enantioselective 1,3‐cycloaddition of these types of substrates.     

Ruthenium(II) complexes of 2-phenylimidazo[4,5-f] [1,10]phenanthroline. Synthesis,characterization and third order nonlinear optical properties

Three Ru^II complexes [Ru(bpy)₂(PIP)]²⁺, [Ru(PIP)₂(bpy)]²⁺ and [Ru(PIP)₃]²⁺ (PIP = 2-phenylimidazo[4,5-f][1,10]phenanthroline, bpy = 2,2-bipyridine) were prepared and characterized by electrospray mass spectrometry, ¹H-n.m.r, u.v.–vis. and electrochemistry. The nonlinear optical properties (NLO) of the Ru^II complexes were investigated by Z-scan techniques with 12 ns laser pulses at 540 nm, and all of them exhibit both NLO absorption and self-defocusing effects. The corresponding effective NLO susceptibility |³| of the complexes is in the (4.15 – 4.86) × 10^–12 e.s.u. range.     

Ru(II)–DMSO complexes containing aromatic and heterocyclic acid hydrazides: Structure,electrochemistry and biological activity

The reaction of cis-[RuCl₂(DMSO)₄] with a family of aromatic and heterocyclic acid hydrazides yielded new complexes of the general formula trans-[RuCl₂(DMSO)₂(hydrazide)] · nH₂O (n = 0; 1–6; n = 1; 7). The new complexes have been characterized by IR, UV–Vis and ¹H NMR spectroscopic methods. In addition, the structure of one of the complexes, [RuCl₂(DMSO)₂(tcah)] · H₂O (tcah = thiophene-2-carboxylic acid hydrazide), has been determined by single crystal X-ray diffraction. All the studies reveal the neutral bidentate coordination of the hydrazide ligands through the acyl oxygen and amine nitrogen atoms. The electron transfer properties of the complexes were studied by cyclic voltammetry and all the complexes except one show an irreversible/quasi-reversible reduction wave (Ru^II/Ru^I) and an uncoupled oxidation peak (Ru^III/ Ru^II). The preliminary DNA-binding ability of the complexes, studied with herring sperm DNA, shows the binding of the complexes with DNA with a lesser affinity than classical intercalators. The complexes have also been screened for their antibacterial activity against five pathogenic bacteria.     

Synthesis and Characterization of New Water‐Soluble Hydrides of RuII: A Step towards Dinitrogen Activation?

The basic aqueous coordination chemistry of Ru^II has been studied using the catalytically important TPPTS phosphine (TPPTS=trisodium salt of 3,3′,3″‐phosphinetriylbenzenesulfonic acid) and small gas molecules (H₂, CO, N₂) as ligands. As a result, new water‐soluble ruthenium mixed hydride complexes, presumably key species in many industrial catalytic processes, have been formed and identified. The Ru^II mixed hydrides were synthesized, and their formation was followed in situ by multinuclear NMR spectroscopy, pressurizing aqueous Ru^II? TPPTS systems with H₂ and CO gas in sapphire NMR tubes. The formation equilibrium of these complexes is highly dependant on the temperature and the gas pressures. Under 50 atm of N₂, the unique [RuH(CO)(N₂)(TPPTS)₂(H₂O)]⁺ complex has been identified, which could be the first step toward dinitrogen activation.     

Binuclear ruthenium complexes containing mPTA and alkyl-bis(8-thiotheophylline) derivatives (mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane)

The water-soluble complex [RuClCp(PPh₃)(mPTA)](CF₃SO₃) reacts with the thiopurines, bis(S-8-thiotheophylline)methane (MBTTH₂), 1,2-bis(S-8-thiotheophylline)ethane (EBTTH₂), and 1,3-bis(S-8-thiotheophylline)propane (PBTTH₂), to lead to the binuclear ruthenium(II) complexes [{RuCp(PPh₃)(mPTA)}₂-μ-(L-κS7,S′7)](CF₃SO₃)₂ where (L = MBTT^2? (1), EBTT^2? (2), and PBTT^2? (3)). All the complexes have been fully characterized by elemental analysis, IR, and multinuclear ¹H, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopy. The cyclic voltammetry of the complexes is characterized by two one-electron oxidative responses (Ru^II–Ru^II/Ru^III–Ru^II; Ru^III–Ru^II/Ru^III–Ru^III) that increase their redox potential when the bis(8-thiotheophylline)-alkyl-bridge growths. The reactivity against DNA and partition coefficient of the complexes were also determined.     

Tuning the Excited State of Water‐Soluble IrIII‐Based DNA Intercalators that are Isostructural with [RuII(NN)2(dppz)] Light‐Switch Complexes

The synthesis of two new Ir^III complexes which are effectively isostructural with well‐established [Ru(NN)₂(dppz)]²⁺ systems is reported (dppz=dipyridophenazine; NN=2,2′‐bipyridyl, or 1,10‐phenanthroline). One of these Ir^III complexes is tricationic and has a conventional N₆ coordination sphere. The second dicationic complex has a N₅C coordination sphere, incorporating a cyclometalated analogue of the dppz ligand. Both complexes show good water solubility. Experimental and computational studies show that the photoexcited states of the two complexes are very different from each other and also differ from their Ru^II analogues. Both of the complexes bind to duplex DNA with affinities that are two orders of magnitude higher than previously reported Ir(dppz)‐based systems and are comparable with Ru^II(dppz) analogues.     

Judicious Ligand Design in Ruthenium Polypyridyl CO2 Reduction Catalysts to Enhance Reactivity by Steric and Electronic Effects

A series of Ru^II polypyridyl complexes of the structural design [Ru^II(R?tpy)(NN)(CH₃CN)]²⁺ (R?tpy=2,2′:6′,2′′‐terpyridine (R=H) or 4,4′,4′′‐tri‐tert‐butyl‐2,2′:6′,2′′‐terpyridine (R=tBu); NN=2,2′‐bipyridine with methyl substituents in various positions) have been synthesized and analyzed for their ability to function as electrocatalysts for the reduction of CO₂ to CO. Detailed electrochemical analyses establish how substitutions at different ring positions of the bipyridine and terpyridine ligands can have profound electronic and, even more importantly, steric effects that determine the complexes’ reactivities. Whereas electron‐donating groups para to the heteroatoms exhibit the expected electronic effect, with an increase in turnover frequencies at increased overpotential, the introduction of a methyl group at the ortho position of NN imposes drastic steric effects. Two complexes, [Ru^II(tpy)(6‐mbpy)(CH₃CN)]²⁺ (trans‐[ 3 ]²⁺; 6‐mbpy=6‐methyl‐2,2′‐bipyridine) and [Ru^II(tBu?tpy)(6‐mbpy)(CH₃CN)]²⁺ (trans‐[ 4 ]²⁺), in which the methyl group of the 6‐mbpy ligand is trans to the CH₃CN ligand, show electrocatalytic CO₂ reduction at a previously unreactive oxidation state of the complex. This low overpotential pathway follows an ECE mechanism (electron transfer–chemical reaction–electron transfer), and is a direct result of steric interactions that facilitate CH₃CN ligand dissociation, CO₂ coordination, and ultimately catalytic turnover at the first reduction potential of the complexes. All experimental observations are rigorously corroborated by DFT calculations.     

Recent Chemistry Based on the [RuCp(CH3CN)3]+ Cation: Reappraisalof an Old Precursor

 This article gives an overview of recent chemistry based on the tris-acetonitrile complex [RuCp(CH₃CN)₃]⁺. Due to the labile nature of the CH₃CN ligands, substitution reactions are a dominant feature of this complex. Important derivatives are the highly reactive complexes [RuCp(PR ₃)(CH₃CN)₂]⁺ which are a source of the 14e⁻ fragment [RuCp(PR ₃)]⁺. These species are catalytically active in the redox isomerization of allyl alcohols to give aldehydes and ketones. Furthermore, the cationic complex [RuCp(κ¹(P),η²-PPh₂CH₂CH₂CH*CH₂)(CH₃CN)]PF₆ derived from the reaction of [RuCp(CH₃CN)₃]⁺ with PPh₂CH₂CH₂CH*CH₂ is a model compound for studying coupling reactions of olefins and acetylenes. In addition, [RuCp(CH₃CN)₃]⁺ is a valuable precursor for the synthesis of configurationally stable chiral three-legged piano-stool ruthenium complexes. These are currently being intensively investigated as Lewis acid catalysts in asymmetric synthesis.     

Synthesis, characterization, catalytic, electrochemical and thermal properties of tetradentate Schiff base complexes

In this study, the Schiff base ligands H₂L¹–H₂L³ and their Cu^II, Co^II, Ni^II, Fe^III Ru^III and VO^IV complexes have been prepared and characterized by spectroscopic and analytical techniques. All the complexes are mononuclear. Keto-enol tautomeric forms of the ligands have been investigated in polar and apolar solvents. The ligands favor the keto-form in the C₇H₈ and C₆H₁₄. The C–C coupling reaction of the 2,6-di-t-butylphenol has been investigated by the Co^II and Cu^II complexes. Thermal properties of the complexes have been assessed using thermal techniques and similar properties were found. In the Fe^III and Ru^III complexes, firstly, the coordinated water molecule is lost from the complex; in the second step, the chloride ion leaves the molecule in the 300–350 °C temperature range. Finally, the complexes decompose to the appropriate metal oxide at the higher temperature ranges. The electrochemical properties of the complexes have been studied in the two different solvents (DMF and CH₃CN).     

Tuning the Photo-electrochemical Performance of RuII-Sensitized Two-Dimensional MoS2

Covalently tethering photosensitizers to catalytically active 1T-MoS₂ surfaces holds great promise for the solar-driven hydrogen evolution reaction (HER). Herein, we report the preparation of two new Ru^II-complex-functionalized MoS₂ hybrids [Ru^II(bpy)₂(phen)]-MoS₂ and [Ru^II(bpy)₂(py)Cl]-MoS₂. The influence of covalent functionalization of chemically exfoliated 1T-MoS₂ with coordinating ligands and Ru^II complexes on the HER activity and photo-electrochemical performance of this dye-sensitized system was studied systematically. We find that the photo-electrochemical performance of this Ru^II-complex-sensitized MoS₂ system is highly dependent on the surface extent of photosensitizers and the catalytic activity of functionalized MoS₂. The latter was strongly affected by the number and the kind of functional groups. Our results underline the tunability of the photovoltage generation in this dye-sensitized MoS₂ system by manipulation of the surface functionalities, which provides a practical guidance for smart design of future dye-sensitized MoS₂ hydrogen production devices towards improved the photofuel conversion efficiency.