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Three tris-heteroleptic mononuclear Ru(II) complexes with dual fluorescence and phosphorescence-[Ru(dpma)(bpy)(phen)] 2+ ( 1 2+ ), [Ru(dpma)(bpy)(dppz)] 2+ ( 2 2+ ), and [Ru(dpma)(phen)(dppz)] 2+ ( 3 2+ )-have been designed and used as ratiometric light-response probes for DNA, where dpma is di(pyrid-2-yl)(methyl)-amine, bpy is 2,2'-bipyridine, phen is 1,10-phenanthroline, and dppz is dipyridophenazine, respectively. Single crystals of complex 2 (PF 6 ) 2 have been obtained and studied by X-ray analysis. The interactions of these complexes with different DNAs are investigated by means of spectroscopic methods, viscosity measurements, and molecular modeling. In the presence of calf thymus DNA, complexes 2 (PF 6 ) 2 and 3 (PF 6 ) 2 show the emergence of a new lower-energy phosphorescence emission band; meanwhile, the higher-energy fluorescence emission band is essentially unchanged, functioning as an intrinsic internal reference. These two complexes exhibit stronger preference for calf thymus DNA over single-strand DNA (d(A) 16 and d(C) 16 ). In contrast, no binding interaction between 1 (PF 6 ) 2 and calf thymus DNA is observed. The intrinsic binding constants ( K b ) of 2 (PF 6 ) 2 and 3 (PF 6 ) 2 with calf thymus DNA are determined to be (1.4 ± 0.4) × 10 5 and (9.5 ± 0.15) × 10 4 M -1 , respectively. In addition, these spectroscopic results are compared with those of the prototype complex [Ru(bpy) 2 (dppz)] 2+ ( 4 2+ ), and density functional theory and time-dependent density functional theory calculations are employed to elucidate these experimental findings.

A dual-emissive tris-heteroleptic ruthenium complex is designed, synthesized and applied for the ratiometric photoluminescent detection of amyloid-β (Aβ) aggregation in both steady and transient states. The Aβ aggregation is supported by transmission electron microscopy and confocal laser scanning microscopy analysis. In addition, molecular docking calculations have been performed to gain insights into the interaction mode between the ruthenium complex and Aβ fibrils.

Four bis-tridentate ruthenium complexes with 5,5′′-divinyl-4′-tolyl-2,2′:6′,2′′-terpyridine (dvtpy) have been synthesized. Among them, 3(PF6) ([(dvtpy)Ru(Mebib)](PF6)) and 4(PF6) ([(dvtpy)Ru(dpb)](PF6)) are cyclometalated, and 5(PF6)2 ([(dvtpy)Ru(Mebip)](PF6)2) and 6(PF6)2 ([(dvtpy)Ru(tpy)](PF6)2) are noncyclometalated, where Mebib is 2-deprotonated-1,3-bis(N-methylbenzimidazolyl)benzene, dpb is 2-deprotonated-1,3-di(2-pyridyl)benzene, Mebip is 2,6-bis(N-methylbenzimidazolyl)pyridine, and tpy is 2,2′:6′,2′′-terpyridine, respectively. Reductive electropolymerization of these complexes and copolymerization of 4(PF6) and 5(PF6)2 proceeded smoothly, both on glassy carbon and ITO glass electrodes, to afford stable metallopolymeric films with well-defined redox processes. On the basis of the monomer structures, electrochemical properties, and polymerization mechanism, the polymer chains of these materials are supposed to be composed of organic frameworks with the metal ions laterally chelated to the main backbones. The polymeric films on ITO surfaces display promising electrochromism in the visible region with good reversibility and moderate contrast ratio. Besides, the apparent diffusion constants of films of 3(PF6)–6(PF6)2 were measured by potential step chronoamperometry and the typical surface morphology of poly-5(PF6)2/ITO film was studied using SEM.

Seven bis-tridentate osmium complexes with Mebib or Mebip (Mebib is the 2-deprotonated form of 1,3-bis(N-methylbenzimidazolyl)benzene and Mebip is bis(N-methylbenzimidazolyl)pyridine) have been prepared, and their electrochemical and spectroscopic properties are compared with ruthenium structural analogues. Among them, four complexes have the [Os(NCN)(NNN)]-type coordination, including [Os(Mebib)(Mebip)](PF6)2 (1(PF6)2), [Os(dpb)(Mebip)](PF6) (2(PF6), dpb is the 2-deprotonated form of 1,3-di(pyrid-2-yl)benzene), [Os(Mebib)(ttpy)](PF6) (3(PF6), ttpy = 4'-tolyl-2,2':6',2"-terpyridine), and [Os(dpb)(ttpy)](PF6) (4(PF6)). The other three complexes are [Os(Mebip)2](PF6)2 (5(PF6)2), [Os(Mebip)(tpy)](PF6)2 (6(PF6)2, tpy = 2,2':6',2"-terpyridine), and [Os(ttpy)2](PF6)2 (7(PF6)2) with the [Os(NNN)(NNN)]-type coordination. Single crystals of 2(PF6) and 6(PF6)2 have been obtained, and their structures are studied by X-ray crystallographic analysis. The Os(II/III) redox potentials of 1(PF6)2 to 7(PF6)2 progressively increase from +0.04, +0.23, +0.24, +0.36, +0.56, +0.79 to +0.94 V vs Ag/AgCl, which are 200-300 mV less positive relative to the Ru(II/III) potentials of their ruthenium counterparts. The highest occupied molecular orbital energy levels of 1(+)-7(2+) are calculated to vary in a descending order. The ruthenium and osmium complexes have singlet metal-to-ligand charge-transfer (MLCT) transitions of similar energies and band shapes, while the osmium complexes display additional (3)MLCT transitions in the lower-energy region. Complexes 6(PF6)2 and 7(PF6)2 emit weakly at 780 and 740 nm, respectively. Complex 1(PF6)2 was synthesized as the oxidized Os(III) salt because of the low Os(II/III) potential. The transformation of 1(2+) to 1(+) by chemical reduction or electrolysis led to the emergence of the (1)MLCT transitions in the visible region.

Six dinuclear cyclometalated ruthenium complexes, 1-6, based on diphenylanthracene (DPA) and anthracene (AN) as bridging ligands have been synthesized and fully characterized electrochemically and spectroscopically. The anodic electrochemistry of the homobinuclear ruthenium complexes, 1-6, has been examined in three different nonaqueous solvents (ACN, DMF, and CH(2)Cl(2)). The ability of the anthracene derivatives to transmit electronic effects between the two redox units has been demonstrated by the observed splitting of the voltammetric signals ascribed to the metal centers. The electronic communication has also been evidenced by the presence of intervalence charge transfer transition bands in the near-infrared region of the spectrum due to an intramolecular electron transfer process mediated by the bridge when the mixed valence species (Ru(II)/Ru(III)) are electrochemically generated. Cyclic voltammetric measurements have been carried out under different conditions of solvent and supporting electrolyte. Differences in DeltaE degrees', the potential separation of the formal potentials of the metal-based anodic processes, have been observed and found to depend on the medium employed. These differences have been ascribed to different degrees of ion pairing. Such effects can be, in turn, modulated as a function of not only the polarity and donor strength of the solvent but also of the coordinating capacity of the anion employed as a supporting electrolyte.

Three monoruthenium complexes 1(PF6)2–3(PF6)2 bearing an N(CH3)-bridged ligand have been synthesized and characterized. These complexes have a general formula of [Ru(bpy)2(L)](PF6)2, where L is a 2,5-di(N-methyl-N'-(pyrid-2-yl)amino)pyrazine (dapz) derivative with various substituents, and bpy is 2,2′-bipyridine. The photophysical and electrochemical properties of these compounds have been examined. The solid-state structure of complex 3(PF6)2 is studied by single-crystal X-ray analysis. These complexes show two well-separated emission bands centered at 451 and 646 nm (Δλmax = 195 nm) for 1(PF6)2, 465 and 627 nm (Δλmax = 162 nm) for 2(PF6)2, and 455 and 608 nm (Δλmax = 153 nm) for 3(PF6)2 in dilute acetonitrile solution, respectively. The emission maxima of the higher-energy emission bands of these complexes are similar, while the lower-energy emission bands are dependent on the electronic nature of substituents. These complexes display two consecutive redox couples owing to the stepwise oxidation of the N(CH3)-bridged ligand and ruthenium component. Moreover, these experimental observations are analyzed by computational investigation. [ABSTRACT FROM AUTHOR]

Keywords: dibenzo[ f, h ]quinolones; polycyclic aromatic hydrocarbons; C-H arylation; reductive cyclodehydrogenation; ruthenium EN dibenzo[ f, h ]quinolones polycyclic aromatic hydrocarbons C-H arylation reductive cyclodehydrogenation ruthenium 2779 2785 7 08/17/23 20230901 NES 230901 Graph Polycyclic aromatic hydrocarbons (PAHs) typically contain two or more fused benzene rings and are structurally characterized by a high degree of rigidity and -conjugation. We present in this work a new approach to synthesize dibenzo[ I f i , I h i ]quinolines via a two-step procedure involving the ruthenium-catalyzed C-H arylation followed by the potassium-mediated reductive cyclodehydrogenation (Figure 1e). For the substituents, only the relatively electron-rich groups such as OMe, Me, and Ph were used, because electron-deficient substituents, e.g., Cl and CO SB 2 sb Et, are not tolerated in the subsequent reductive cyclodehydrogenation reaction with potassium. Zhang and co-workers developed a palladium-catalyzed double cross-coupling reaction between cyclic diaryliodonium salts and 2-chloropyridinyl acids to access dibenzo-[ I f i , I h i ]quinolines and their derivatives (Figure 1a). [Extracted from the article]

A star‐shaped N C N‐pincer tri‐RuII complex 3 with a triarylamine core, capped with three 2,2':6',2''‐terpyridine‐4,4',4''‐tricarboxylic acid terminal ligands, has been synthesized. The single‐crystal X‐ray structure of a precursor ester complex 7 is presented. By using the Zr‐mediated layer‐by‐layer assembly, multilayer films FTO/SnO2:Sb/(3)n(Zr)n‐1 (n = 1–4) have been prepared on Sb‐doped SnO2 nanocrystalline substrates. These films have been characterized by XPS and SEM analysis. The electrochromism of these films in the near‐infrared region were examined by oxidative spectroelectrochemical measurements and douple‐potential‐step chronoamperometry. The two‐layered film displays the best overall performance with a contrast ratio (ΔT%) of 36 % at 1550 nm and response time of shorter than 2 s. After 1000 switching cycles, around 11 % loss of the contrast ratio is observed, suggesting good cyclic stability of these films. In addition, a comparison of the electrochromic performance of these multilayer films with respect to the previously reported electropolymerized films of a related tri‐RuII complex and monolayer films of two mono‐RuII complexes on SnO2:Sb is presented. [ABSTRACT FROM AUTHOR]

Two bis-tridentate pincer complexes [Ru(H 2 bip)(Mebib)](PF 6 ) 2 ( 1 (PF 6 ) 2 ) and [Ru(H 2 bip)(H 2 bib)](PF 6 ) 2 ( 2 (PF 6 ) 2 ) were prepared and studied, where H 2 bip is 2,6-bis(benzimidazol-2-yl)pyridine, Mebib is the 2-deprotonated 1,3-bis( N -methylbenzimidazol-2-yl)benzene, and H 2 bib is 2-deprotonated 1,3-bis(benzimidazol-2-yl)benzene. These complexes were isolated as cyclometalated Ru(III) salts with a [(NCN)(NNN)] coordination due to a low Ru(III/II) redox potential. Complex 1 (PF 6 ) 2 has two N−H protons on the NNN ligand side, while complex 2 (PF 6 ) 2 has four N−H protons. Absorption spectral analysis showed that two deprotonation steps were distinguished for 1 (PF 6 ) 2 with p K a1 and p K a2 of 3.46 and 5.88, respectively. In comparison, four deprotonation steps were observed for 2 (PF 6 ) 2 with four p K a values of 3.45, 5.95, 8.95, and 10.98, respectively. When the solution was changed from acidic to basic, the Ru(III/II) redox wave of 1 (PF 6 ) 2 and 2 (PF 6 ) 2 shifted from +0.20 V vs Ag/AgCl to a less positive region by 540 and 850 mV, respectively. These studies suggest that the electronic absorption and electrochemical properties of these complexes are very sensitive to pH effect. [ABSTRACT FROM AUTHOR]

Three tris(bidentate) monoruthenium complexes [Ru(dpma)(bpy)2](PF6)2 [1(PF6)2; dpma = di(pyrid-2-yl)(methyl)- amine, bpy = 2,2'-bipyridine], [Ru(dpma)2(bpy)](PF6)2 [2(PF6)2], and [Ru(dpma)3](PF6)2 [3(PF6)2] with the electron-rich ligand dpma were synthesized and characterized. The single-crystal Xray structures of 1(PF6)2 to 3(PF6)2 are presented. The electrochemical and spectroscopic properties of these complexes were examined and compared with those of the reference complex [Ru(bpy)3](PF6)2. Complexes 1(PF6)2 to 3(PF6)2 show a decreased RuIII/II redox potential by 140-310 mV with respect to [Ru(bpy)3](PF6)2. The strong emission property of [Ru(bpy)3]- (PF6)2 is maintained in 1(PF6)2 and 2(PF6)2. However, complex 3(PF6)2 is only weakly emissive at room temperature. In addition, density functional theory (DFT) and time-dependent DFT calculations were performed to complement these experimental results. [ABSTRACT FROM AUTHOR]

A series of cyclometalated diruthenium complexes with a redox-active amine bridge were synthesized. Depending on the terminal ligands of the ruthenium components and the substituent on the amine unit, the one-electron-oxidized state can be either in the form of a weakly or strongly coupled mixed-valence diruthenium complex, a fully charge-delocalized three-center system, or a bridge-biased electrophore. This transition among different electronic forms was supported by electrochemistry, near-infrared absorption, electron paramagnetic resonance, and density functional theory analysis. [ABSTRACT FROM AUTHOR]

In response to the application of low electrochemical potentials, ruthenium-tris(bipyridine) complexes decorated with multiple electron-rich and redox-active amine substituents show reversible absorption and emission spectral changes in the deep-red to NIR region. The number of amine substituents strongly affects the electrochemical and spectroscopic properties and the spin density distributions of the complex in the one-electron-oxidized state. [ABSTRACT FROM AUTHOR]

Monometallic and dimetallic complexes with the ruthenium-amine conjugated structural unit have been prepared. These complexes display consecutive redox waves with low potentials and rich and intense absorptions in the near-infrared region. The electrochemical and spectroscopic properties can be modulated using substituents or auxiliary ligands with different electronic natures. Through simple functionalization, electropolymerized or monolayer thin films of these complexes have been prepared. These films display multistate near-infrared electrochromism with good contrast ratios and long optical retention times. In addition, flip-flop and flip-flap-flop memories have been demonstrated on the basis of these thin films. [ABSTRACT FROM AUTHOR]

Hybrid films of functional molecules and metal nanoparticles have been considered to be novel photo-functional devices. Here we have successfully constructed hybrid films of silver nanoparticles and ruthenium polypyridine derivatives on substrates. In order to hybridise them on a surface, a self-assembled monolayer method via chemical bond formation and electro-reductive polymerisation (thick layers) via physical attachment have been employed. These methods have the advantage of convenient and reproducible fabrication of complicated hybrid films. Furthermore, it has been clarified that these hybrid films show unique photo-functional behaviours, such as enhanced photocurrent generation. [ABSTRACT FROM AUTHOR]

A diruthenium complex with a redox-active amine bridge has been designed, synthesized, and studied by single-crystal X-ray analysis and DFT and TDDFT calculations. It shows three well-separated redox processes with exclusive near-infrared (NIR) absorbance at each redox state. The electropolymerized film of a related vinyl-functionalized complex displays multistate NIR electrochromism with low operational potential, good contrast ratio, and long retention time. Flip-flop, flip-flap-flop, and ternary memories have been realized by using the obtained film (ca. 15-20 nm thick) with three electrochemical inputs and three NIR optical outputs that each displays three levels of signal intensity. [ABSTRACT FROM AUTHOR]

A diruthenium complex with a redox-active amine bridge has been designed, synthesized, and studied by single-crystal X-ray analysis and DFT and TDDFT calculations. It shows three well-separated redox processes with exclusive near-infrared (NIR) absorbance at each redox state. The electropolymerized film of a related vinyl-functionalized complex displays multistate NIR electrochromism with low operational potential, good contrast ratio, and long retention time. Flip-flop, flip-flap-flop, and ternary memories have been realized by using the obtained film (ca. 15-20 nm thick) with three electrochemical inputs and three NIR optical outputs that each displays three levels of signal intensity. [ABSTRACT FROM AUTHOR]

Six cyclometalated diruthenium complexes bridged by 3,3′,5,5′-tetra(pyrid-2-yl)biphenyl have been prepared, in which 12+, 32+, and 52+ are symmetric complexes with different terminal ligands [2,6-bis( N-methylbenzimidazolyl)pyridine (Mebip), 4′-tolyl-2,2′:6′,2″-terpyridine (ttpy), and trimethyl-4,4′,4″-tricarboxylate-2,2′:6′,2″-terpyridine (Me3tctpy), respectively]. Three other complexes with mixed terminal ligands (Mebip-Me3tctpy for 62+; Mebip-ttpy for 72+; ttpy-Me3tctpy for 82+) are structurally nonsymmetric. These complexes display two consecutive Ru(III/II) redox couples between 0.20 and 0.90 V vs. Ag/AgCl, with the potential splitting ranging from 150 (for 52+) to 280 mV (for 62+). The mixed-valent states of these complexes have been generated by stepwise electrolysis. The symmetric complexes show intervalence charge transfer (IVCT) transitions at similar energy ( Eop ≈ 5750 cm-1), with the electronic coupling parameter Vab of 1240, 1220, and 970 cm-1 for 13+, 33+, and 53+, respectively. The nonsymmetric series show significantly different Eop (7600, 5850, and 6650 cm-1 for 63+, 73+, and 83+, respectively) but Vab values that were comparable to that of 13+. DFT and TDDFT calculations have been performed to complement these experimental results. [ABSTRACT FROM AUTHOR]

Through Ru(ii)-catalyzed C–H bond activation, a methodology for the synthesis of 2- or 2,7-functionalized pyrene derivatives has been developed using the substrate 1-(pyrid-2-yl)pyrene or 1,6-di(pyrid-2-yl)pyrene. [ABSTRACT FROM AUTHOR]

Bis-triarylamine 2 and cyclometalated diruthenium 6(PF6)2 with a linear trans, trans-urea bridge have been prepared, together with the bis-triarylamine 3 and cyclometalated diruthenium 8(PF6)2 with a folded cis, cis- N, N-dimethylurea bridge. The linear or folded conformations of these molecules are supported by single-crystal X-ray structures of 2, 3, and other related compounds. These compounds display two consecutive anodic redox waves (N .+/0 or RuIII/II processes) with a potential separation of 110-170 mV. This suggests that an efficient electronic coupling is present between two redox termini through the cross-conjugated urea bridge. The degree of electronic coupling has been investigated by using spectroelectrochemical measurements. Distinct intervalence charge-transfer (IVCT) transitions have been observed for mixed-valent (MV) compounds with a linear conformation. The IVCT transitions can also be identified for the folded MV compounds, albeit with a much weaker intensity. DFT results support that the electronic communication occurs by a through-bond and through-space pathway for the linear and folded compounds, respectively. The IVCT transitions of the MV compounds have been reproduced by TDDFT calculations. For the purpose of comparison, a bistriarylamine and a diruthenium complex with an imidazolidin-2-one bridge and a urea-containing mono-triarylamine and monoruthenium complex have been synthesized and studied. [ABSTRACT FROM AUTHOR]

Nine cyclometalated ruthenium complexes with a redox-active diphenylamine unit in the para position to the RuC bond were prepared. MeO, Me, and Cl substituents on the diphenylamine unit and three types of auxiliary ligands-bis( N-methylbenzimidazolyl)pyridine (Mebip), 2,2′:6′,2′′-terpyridine (tpy), and trimethyl-4,4′,4′′-tricarboxylate-2,2′:6′,2′′-terpyridine (Me3tctpy)-were used to vary the electronic properties of these complexes. The derivative with an MeO-substituted amine unit and Me3tctpy ligand was studied by single-crystal X-ray analysis. All complexes display two well-separated redox waves in the potential region of +0.1 to +1.0 V versus Ag/AgCl, and the potential splitting ranges from 360 to 510 mV. Spectroelectrochemical measurements show that these complexes display electrochromism at low potentials and intense near-infrared (NIR) absorptions. In the one-electron oxidized form, the complex with the Cl-substituted amine unit and Mebip ligand shows a moderate ligand-to-metal charge transfer at 800 nm. The other eight complexes show asymmetric, narrow, and intense intervalence charge-transfer transitions in the NIR region, which are independent of the polarity of the solvent. The Mebip-containing complexes display rhombic or broad isotropic EPR signals, whereas the other seven complexes show relatively narrow isotropic EPR signals. In addition, DFT and time-dependent DFT studies were performed to gain insights into the spin distributions and NIR absorptions. [ABSTRACT FROM AUTHOR]

A common bridging ligand, 3,3′,5,5′-tetrakis( N-methylbenzimidazol-2-yl)biphenyl, and four terpyridine terminal ligands with various substituents (amine, tolyl, nitro, and ester groups) have been used to synthesize ten cyclometalated diruthenium complexes 12+- 102+. Among them, compounds 12+- 62+ are redox nonsymmetric, and others are symmetric. These complexes show two RuIII/II processes and an intervalence charge transfer (IVCT) transition in the one-electron oxidized state. The potential separation (Δ E) of 12+- 102+ has been correlated to the energy difference Δ G0, the energy of the IVCT band Eop, and the ground-state delocalization coefficient α2. Time-dependent (TD)DFT calculations suggest that the absorptions in the visible region of 12+- 62+ are mainly associated with the metal-to-ligand charge-transfer transitions from both ruthenium ions and to both terminal ligands and the bridging ligand. However, the energies of these transitions vary significantly. DFT calculations have been performed on 12+- 62+ and 13+- 63+ to give information on the electronic structures and spin populations of the mixed-valent compounds. The TDDFT-predicted IVCT excitations reproduce well the experimental trends in transition energies. In addition, three monoruthenium complexes have been synthesized for a comparison study. [ABSTRACT FROM AUTHOR]

Four heterodimetallic complexes [Ru(Fcdpb)(L)](PF6) (Fcdpb=2-deprotonated form of 1,3-di(2-pyridyl)-5-ferrocenylbenzene; L=2,6-bis-( N-methylbenzimidazolyl)-pyridine (Mebip), 2,2′:6′,2′′-terpyridine (tpy), 4-nitro-2,2′:6′,2′′-terpyridine (NO2tpy), and trimethyl-4,4′,4′′-tricarboxylate-2,2′:6′,2′′-terpyridine (Me3tctpy)) have been prepared. The electrochemical and spectroelectrochemical properties of these complexes have been examined in CH2Cl2, CH3NO2, CH3CN, and acetone. These complexes display two consecutive redox couples owing to the stepwise oxidation of the ferrocene (Fc) and ruthenium units, respectively. The potential difference, Δ E1/2 ( E1/2(RuII/III)− E1/2(Fc0/+)), decreased slightly with increasing solvent donocity. The mixed-valent states of these complexes have been generated by and the resulting intervalence charge-transfer (IVCT) bands have been analyzed by Hush theory. Good linear relationships exist between the energy of the IVCT band, Eop, and Δ E1/2 of four mixed-valent complexes in a given solvent. [ABSTRACT FROM AUTHOR]

Two series of linear ruthenium coordination oligomers, [(Ntpy)Ru n(tppz) n−1(tpy)]2 n+ (mono-Ntpy series, n=1-3) and [(Ntpy)2Ru n(tppz) n−1]2 n+ (bis-Ntpy series, n=1-3) have been prepared, where Ntpy is the capping ligand 4′-di- p-anisylamino-2,2′:6′,2′′-terpyridine, tppz is tetra-2-pyridylpyrazine, and tpy is 2,2′:6′,2′′-terpyridine. The electrochemical measurements evidence oxidation events from both the amine segments and the metal centers and reduction waves from tppz and the capping ligands. Both series complexes display much enhanced light absorption with respect to model complexes without terminal amine units. Density functional theory (DFT) calculations have been performed on both series and time-dependent DFT (TD-DFT) calculations have been performed on the bis-Ntpy-series compounds ( n=1-4) to characterize their electronic structures and excited states and predict the electronic properties of long-chain polymers. Upon one-electron oxidation, the mono-Ntpy-series monoruthenium and diruthenium complexes display N+-localized transitions and metal-to-nitrogen charge-transfer (MNCT) transitions in the near-infrared (NIR) region. DFT and TD-DFT computations on the one-electron-oxidized forms of the mono-Ntpy-series compounds ( n=1-4) provide insight into the nature of the MNCT transitions and the degree of charge delocalization. [ABSTRACT FROM AUTHOR]

A new bridging ligand, 2,3-di(2-pyridyl)-5-phenylpyrazine (dpppzH), has been synthesized. This ligand was designed so that it could bind two metals through a NN-CNN-type coordination mode. The reaction of dpppzH with cis-[(bpy)2RuCl2] (bpy=2,2′-bipyridine) affords monoruthenium complex [(bpy)2Ru(dpppzH)]2+ ( 12+) in 64 % yield, in which dpppzH behaves as a NN bidentate ligand. The asymmetric biruthenium complex [(bpy)2Ru(dpppz)Ru(Mebip)]3+ ( 23+) was prepared from complex 12+ and [(Mebip)RuCl3] (Mebip=bis( N-methylbenzimidazolyl)pyridine), in which one hydrogen atom on the phenyl ring of dpppzH is lost and the bridging ligand binds to the second ruthenium atom in a CNN tridentate fashion. In addition, the RuPt heterobimetallic complex [(bpy)2Ru(dpppz)Pt(CCPh)]2+ ( 42+) has been prepared from complex 12+, in which the bridging ligand binds to the platinum atom through a CNN binding mode. The electronic properties of these complexes have been probed by using electrochemical and spectroscopic techniques and studied by theoretical calculations. Complex 12+ is emissive at room temperature, with an emission λmax=695 nm. No emission was detected for complex 23+ at room temperature in MeCN, whereas complex 42+ displayed an emission at about 750 nm. The emission properties of these complexes are compared to those of previously reported Ru and RuPt bimetallic complexes with a related ligand, 2,3-di(2-pyridyl)-5,6-diphenylpyrazine. [ABSTRACT FROM AUTHOR]

Abstract: This review first summarizes various synthetic approaches to vinyl-substituted polypyridine ligands. Based on the polymerization efficiency of vinyl-substituted complexes and stability of the resulting polymeric films, four categories of substrates are distinguished and representative examples are then given. The characterizations of metallopolymeric films using different electrochemical, spectroscopic, and microscopic methods are introduced. Finally, recent applications of the title films in electrode coatings, electrocatalysis, electrogenerated chemiluminescence, and electrochromism are discussed. [Copyright &y& Elsevier]

Three bis-tridentate ferrocene-containing cyclometalated ruthenium complexes, [(Fcdpb)Ru(tpy)]+ ( 1+), [(Fctpy)Ru(dpb)]+ ( 2+), and [(Fcdpb)Ru(Fctpy)]+ ( 3+), have been prepared and characterized, where Fcdpb is the 2-deprotonated form of 1,3-di(2-pyridyl)-5-ferrocenylbenzene, tpy is 2,2′:6′,2'-terpyridine, dpb is the 2-deprotonated form of 1,3-di(2-pyridyl)benzene, and Fctpy is 4′-ferrocenyl-2,2′:6′,2'-terpyridine. Single crystals of compounds 2+ and 3+ have been studied by X-ray analysis. Complexes 1+ and 2+ displayed two anodic redox waves, whilst three well-separated redox couples were observed for compound 3+. A combined experimental and computational study suggested that the ferrocene unit on the Fcdpb moiety in compounds 1+ and 3+ was oxidized first. In contrast, the order of the oxidation of ruthenium and ferrocene in complex 2+ was reversed. Metal-to-metal-charge-transfer transitions (MM′CT) have been observed for the singly oxidized states 12+, 22+, and 32+ in the near-infrared region. Hush analysis showed that the metal-metal electronic couplings in compounds 12+ and 32+ were much stronger than those in compound 22+. [ABSTRACT FROM AUTHOR]

• A ruthenium polypyridyl complex with 2-picolinamide as an anionic N^N bidentate ligand is presented for the selective recognition of H 2 PO 4 − by spectroscopic and electrochemical response. • In response to the presence of H 2 PO 4 −, the Ru(II/III) redox couple of 4 (PF 6) displays a "two-wave behavior" accompanied by a large negative shift from +0.74 to +0.45 V vs Ag/AgCl. • 1H NMR spectral titration analyses suggest that effective hydrogen-bonding interactions are present between 4 and H 2 PO 4 −, which are believed responsible for the observed spectroscopic and electrochemical response of 4 (PF 6) toward H 2 PO 4 −. A ruthenium polypyridyl complex 4 (PF 6) with 2-picolinamide as an anionic N^N bidentate ligand is synthesized and characterized, including single-crystal X-ray analysis. As an effective anion receptor in CH 2 Cl 2 , complex 4 (PF 6) shows selective spectroscopic and electrochemical recognition towards H 2 PO 4 − over other anions tested (F−, Cl−, Br−, I−, HP 2 O 7 3−, HSO 4 −, AcO− and NO 3 −). Job's plot and mass spectral analyses support that an adduct is formed between 4 and H 2 PO 4 − with a 1:2 binding stoichiometry. The absorption spectral titration of 4 (PF 6) with H 2 PO 4 − yields a global association constant in the order of 108 L2⋅mol−2 and an optical detection limit of 1.4 × 10−6 mol⋅L−1. In response to the presence of H 2 PO 4 −, the Ru(II/III) redox couple of 4 (PF 6) displays a "two-wave behavior" accompanied by a large negative shift from +0.74 to +0.45 V vs Ag/AgCl. 1H NMR spectral titration analyses suggest that effective hydrogen-bonding interactions are present between 4 and H 2 PO 4 −, which are believed responsible for the observed spectroscopic and electrochemical response of 4 (PF 6) toward H 2 PO 4 −. A Ru(II) polypyridyl complex with 2-picolinamide is shown to selectively recognize H 2 PO 4 − by distinct spectroscopic and electrochemical signal changes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Review: 206 refs. [ABSTRACT FROM AUTHOR]

A series of mononuclear cyclometalated ruthenium complexes with 1,2,4,5-tetrakis(N-methylbenzimidazolyl)benzene have been prepared, where two N-methylbenzimidazoles bind to the metal center and others remain intact. Electronic properties of these complexes were investigated by electrochemical and spectroscopic studies and DFT/TDDFT computations. The RuII/III redox potentials of theses complexes can be modulated by attaching substituents of various electronic natures on the non-cyclometalating ligand. These complexes display enhanced visible light absorption compared to those without two free-standing N-methylbenzimidazolyl units as a result of the three-chromophore effect. [ABSTRACT FROM AUTHOR]

The linear bis-cyclometalated Ru(II) complex [(ttpy)Ru(ttabp)Ru(ttpy)]2+was prepared from the oxidative coupling of the monometalliccomplex [(ttpy)Ru(dtab)]+in good yield, where ttpy is4′-tolyl-2,2′:6′,2″-terpyridine, ttabpis 3,3′,5,5′-tetrakis(1-butyl-1H-1,2,3-triazol-4-yl)biphenyl,and dtab is 1,3-bis(1-butyl-1H-1,2,3-triazol-4-yl)benzene.The electronic properties of these two complexes were studied andcompared by electrochemical and spectroscopic methods and DFT/TDDFTcalculations. The complex [(ttpy)Ru(ttabp)Ru(ttpy)]2+showedtwo consecutive RuII/IIIredox waves at +0.34 and +0.51V vs Ag/AgCl with a comproportionation constant Kcof 760. One-electron oxidation of [(ttpy)Ru(ttabp)Ru(ttpy)]2+by electrochemical methods produced the mixed-valent complex[(ttpy)Ru(ttabp)Ru(ttpy)]3+, which exhibited a symmetricintervalence charge transfer band at 1800 nm (νmax= 5550 cm–1, εmax= 5100 M–1cm–1, Δν1/2= 3580 cm–1). The energy and shape of this bandare very similar in the different solvents studied (CH3CN, DMF, CH2Cl2). [(ttpy)Ru(ttabp)Ru(ttpy)]3+was determined to be a class II/III borderline system withthe electronic coupling parameter Hab=530 cm–1. It displayed a metal-centered rhombicEPR signal at 77 K with an isotropic gfactor of2.109 and total ganisotropy of 0.256, which pointsto an appreciable spin distribution on the bridging ligand in additionto the metal centers. [ABSTRACT FROM AUTHOR]

The excited state properties of a series of ruthenium(II) amine-substituted bipyridyl complexes, [Ru(bpy) n (NNbpy) 3−n ] 2+ , were investigated by steady-state and transient absorption spectroscopy, as well as quantum chemical calculations. The steady-state absorption spectra of these complexes in CH 3 CN show a distinct red-shift of the 1 MLCT absorption with increasing numbers of amine substituent, whereas the emission spectra indicate an energy gap order of [Ru(bpy) 3 ] 2+ > [Ru(bpy) 2 (NNbpy)] 2+ > [Ru(NNbpy) 3 ] 2+ > [Ru(bpy)(NNbpy) 2 ] 2+ . Nanosecond, femtosecond transient absorption and electrochemical measurements suggest that NNbpy ligand has a strong influence on the electronic and emission properties of these complexes, due to electron-rich amine substituent. We illustrate how the numbers of amine substituent modulate the spectroscopic properties of transition metal complexes, which is related to the design of new electro-active systems with novel photoelectrochemical properties. [ABSTRACT FROM AUTHOR]

• Cyclometalated ruthenium complexes with two amine substituents are synthesized. • Three consecutive redox couples are observed between 0 and +1.5 V vs Ag/AgCl. • Three-step NIR absorption spectral changes are observed upon stepwise oxidations. Two structurally asymmetric cyclometalated ruthenium complexes 3 (PF 6) and 4 (PF 6), with an amine substituent on the cyclometalating and noncyclometalating ligand of each complex respectively, have been prepared and characterized. Three consecutive anodic redox couples are observed for these complexes in the potential window of 0 ~ +1.5 V vs Ag/AgCl, assigned to the stepwise oxidations of the ruthenium component and the two amine substituents. Upon stepwise oxidations with SbCl 5 , these complexes exhibit three-step absorption spectral changes in the near-infrared (NIR) region. At the singly-oxidized state, single-line or axial-like EPR signals are detected for 3 2+ and 4 2+, respectively. The NIR absorptions of 3 n+ and 4 n+ at different charge states (n = 2 – 4) are rationalized by time-dependent density functional theory calculations. [Display omitted] [ABSTRACT FROM AUTHOR]