Photochemical reactions of trans-[Ru(NH3)4L(NO)] complexes

The photochemical behavior of a series of trans-[Ru(NH₃)₄L(NO)]³⁺ complexes, where L=nitrogen bound imidazole, L-histidine, 4-picoline, pyridine, nicotinamide, pyrazine, 4-acetylpyridine, or triethylphosphite is reported. In addition to ligand localized absorption bands (<300 nm), the electronic spectra of these complexes are dominated by relatively low intensity bands assigned as ligand field (LF) and metal to ligand (d_π → NO) charge transfer (MLCT) transitions. Irradiation of aqueous solutions of these complexes with near-UV light (300-370 nm) labilizes NO, i.e.,

     

trans-[Ru(NO)(NH3)4(py)](BF4)3.H2O encapsulated in PLGA microparticles for delivery of nitric oxide to B16-F10 cells: Cytotoxicity and phototoxicity

The NO donor trans-[Ru(NO)(NH(3))(4)(py)](BF(4))(3).H(2)O (py=pyridine) was loaded into poly-lactic-co-glycolic acid (PLGA) microparticles using the double emulsification technique. Scanning electron microscopy (SEM) and dynamic light scattering revealed that the particles are spherical in shape, have a diameter of 1600nm, and have low tendency to aggregate. The entrapment efficiency was 25%. SEM analysis of the melanoma cell B16-F10 in the presence of the microparticles containing the complex trans-[Ru(NO)(NH(3))(4)(py)](BF(4))(3).H(2)O (pyMP) showed that the microparticles were adhered to the cell surface after 2h of incubation. The complex with concentrations lower than 1x10(-4)M did not show toxicity in B16-F10 murine cells. The complex in solution is toxic at higher concentrations (>1x10(-3)M), with cell death attributed to NO release following the reduction of the complex. pyMP is not cytotoxic due to the lower bioavailability and availability of the entrapped complex to the medium and its reducing agents. However, pyMP is phototoxic upon light irradiation. The phototoxicity strongly suggests that cell death is due to NO release from trans-[Ru(NO)(NH(3))(4)(py)](3+). This work shows that pyMP can serve as a model for a drug delivery system carrying the NO donor trans-[Ru(NO)(NH(3))(4)(py)](BF(4))(3).H(2)O, which can release NO locally at the tumor cell by irradiation with light only.     

Syntheses, spectra and crystal structures of ruthenium(II) complexes with polypyridyl: [Ru(bipy)2(phen)](ClO4)2 · H2O and [Ru(bipy)2(Me-phen)](ClO4)2

Two ruthenium(II) complexes with polypyridyl, Ru(bipy)₂(phen)](ClO₄)₂·H₂O (1) and [Ru(bipy)₂(Me-phen)](ClO₄)₂ (2), (phen = 1,10-phenanthroline, bipy = 2,2′-bipyridine, Me-phen = 5-methyl-1,10-phenanthroline), were synthesized and characterized by IR, MS and NMR spectra. Their structures were determined by single crystal X-ray diffraction techniques. The strong steric interaction between the polypyridyl ligands was relieved neither by the elongation of the Ru---N bonds nor increase of the N---Ru---N bite angles. The coordination sphere was distorted to relieve the ligand interaction by forming specific angles (δ) between the polypyridyl ligand planes and coordination planes (N---Ru---N), and forming larger twisted angles between the two pyridine rings for each bipy. The bond distances of Ru---N(bipy) and Ru---N(phen) were virtually identical with experimental error, as expected of π back-bonding interactions which statistically involve each of the ligands present in the coordination sphere.     

The macrocyclic effect and vasodilation response based on the photoinduced nitric oxide release from trans-[RuCl(tetraazamacrocycle)NO](2+)

Irradiation of trans-[RuCl(cyclam)(NO)](2+), cyclam is 1,4,8,11-tetraazacyclotetradecane, at pHs 1-7.4, with near UV light results in the release of NO and formation of trans-[Ru(III)Cl(OH)(cyclam)](+) with pH dependent quantum yields (from approximately 0.01 to 0.16 mol Einstein(-1)) lower than that for trans-[RuCl([15]aneN(4))(NO)](2+), [15]aneN(4) is 1,4,8,12-tetaazacyclopentadecane, (0.61 mol Einstein(-1)). After irradiation with 355 nm light, the trans-[RuCl([15]aneN(4))(NO)](2+) induces relaxation of the aortic ring, whereas the trans-[RuCl(cyclam)(NO)](2+) complex does not. The relaxation observed with trans-[RuCl([15]aneN(4))(NO)](2+) is consistent with a larger quantum yield of release of NO from this complex.     

Influence of ancillary ligand L in the nitric oxide photorelease by the [Ru(L)(tpy)NO] complex and its vasodilator activity based on visible light irradiation

The photochemical and pharmacological studies of the novel [Ru(L)(tpy)NO]³⁺ L = bpy (2,2′-bipyridine), NH · NHq (quinonediimine) and NH₂.NH₂cat (o-phenylenediamine) were investigated in aqueous medium. The synthesized nitrosyl ruthenium complexes showed nitric oxide (NO) release under light irradiation at 355 nm for [Ru(L)(tpy)NO]³⁺ complex with quantum yield of 0.14 ± 0.02, 0.47 ± 0.03 and 0.46 ± 0.02 mol Einstein⁻¹ for L = bpy, NH · NHq and NH₂ · NH₂cat, respectively, and 0.0065 ± 0.001 mol Einstein⁻¹ for light irradiation at 532 nm for [Ru(NH · NHq)(tpy)NO]³⁺ complex. The photochemical pathway at 355 nm light irradiation was described as a multi-step mechanism, although at 532 nm it was better attributed to a photo-induced electron transfer. The vasorelaxation induced by NO release produced by light irradiation in visible region from physiological solution of [Ru(NH · NHq)(tpy)NO]³⁺ complex was evaluated and compared with sodium nitroprusside (SNP). The results showed very similar vasodilator power between both species.     

Structure-dependent in vitro cytotoxicity of the isomeric complexes [Ru(L)2Cl2] (L=o-tolylazopyridine and 4-methyl-2-phenylazopyridine) in comparison to [Ru(azpy)2Cl2]

The dichlorobis(2-phenylazopyridine)ruthenium(II) complexes, [Ru(azpy)(2)Cl(2)], are under renewed investigation due to their potential anticancer activity. The three most common isomers alpha-, beta- and gamma-[RuL(2)Cl(2)] with L= o-tolylazopyridine (tazpy) and 4-methyl-2-phenylazopyridine (mazpy) (alpha indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual cis, trans, cis positions, beta indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual cis, cis, cis positions, and gamma indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual trans, cis, cis positions) are synthesized and characterized by NMR spectroscopy. The molecular structures of gamma-[Ru(tazpy)(2)Cl(2)] and alpha-[Ru(mazpy)(2)Cl(2)] are determined by X-ray diffraction analysis. The IC(50) values of the geometrically isomeric [Ru(tazpy)(2)Cl(2)] and [Ru(mazpy)(2)Cl(2)] complexes compared with those of the parent [Ru(azpy)(2)Cl(2)] complexes are determined in a series of human tumour cell lines (MCF-7, EVSA-T, WIDR, IGROV, M19, A498 and H266). These data unambiguously show for all complexes the following trend: the alpha isomer shows a very high cytotoxicity, whereas the beta isomer is a factor 10 less cytotoxic. The gamma isomers of [Ru(tazpy)(2)Cl(2)] and [Ru(mazpy)(2)Cl(2)] display a very high cytotoxicity comparable to that of the gamma isomer of the parent compound [Ru(azpy)(2)Cl(2)] and to that of the alpha isomer. These biological data are of the utmost importance for a better understanding of the structure-activity relationships for the isomeric [RuL(2)Cl(2)] complexes.     

Synthesis, DNA-binding and photocleavage studies of ruthenium complexes [Ru(bpy)2(mitatp)] and [Ru(bpy)2(nitatp)]

Two new ruthenium complexes [Ru(bpy)₂(mitatp)](ClO₄)₂1 and [Ru(bpy)₂(nitatp)](ClO₄)₂2 (bpy = 2,2′-bipyridine, mitatp = 5-methoxy-isatino[1,2-b]-1,4,8,9-tetraazatriphenylene, nitatp = 5-nitro-isatino[1,2-b]-1,4,8,9-tetraazatriphenylene) have been synthesized and characterized by elemental analysis, ¹H NMR, mass spectrometry and cyclic voltammetry. Spectroscopic and viscosity measurements proved that the two Ru(II) complexes intercalate DNA with larger binding constants than that of [Ru(bpy)₂(dppz)]²⁺ (dppz = dipyrido[3,2-a:2′,3′-c]phenazine) and possess the excited lifetime of microsecond scale upon binding to DNA. Both complexes can efficiently photocleave pBR322 DNA in vitro under irradiation. Singlet oxygen (¹O₂) was proved to contribute to the DNA photocleavage process, the ¹O₂ quantum yields was determined to be 0.43 and 0.36 for 1 and 2, respectively. Moreover, a photoinduced electron transfer mechanism was also found to be involved in the DNA cleavage process.     

On the lability of dimethylsulfoxide (DMSO) coordinated to the [Ru(II)-NO(+)] species: X-ray structures of mer-[RuCl(3)(DMSO)(2)(NO)] and mer-[RuCl(3)(CD(3)CN)(DMSO)(NO)

The syntheses of nitrosyl–dimethylsulfoxide–ruthenium(II) complexes with general formula mer-[RuCl₃(L)(DMSO)(NO)] (L=DMSO or CD₃CN) is reported. The mer-[RuCl₃(DMSO)₂(NO)] (1) complex was obtained from the reaction of [RuCl₃(NO)] with the sulfoxide ligand in acetone. The mer-[RuCl₃(CD₃CN)(DMSO)(NO)] (2) compound was obtained from mer-[RuCl₃(DMSO)₂(NO)] maintained in deuterated acetonitrile. These data suggest a slow kinetic reaction due the low lability of the DMSO ligand coordinated to the {Ru^II–NO⁺} species. The crystal and molecular structures of (1) and (2) have been determined from X-ray studies. Crystal data: for (1), monoclinic, P2₁/c, a=8.8340(2) Å, b=12.0230(3) Å, c=13.7064(4) Å, β=114.546(2)°, Z=4, R1=0.0429; for (2), monoclinic, P21/n, a=10.0180(7) Å, b=9.5070(7) Å, c=13.3340(9) Å, β=102.264(4)°, Z=4, R1=0.0472. The spectroscopic characterization of (1), in solid state (infrared spectrum) and in solution (nuclear magnetic resonance and cyclic voltammetry) is also described.     

Electrospray mass spectrometry of trans-[Ru(NO)Cl(dpaH)2] (dpaH=2,2′-dipyridylamine) and ‘caged NO’, [RuCl3(NO)(H2O)2]: loss of HCl and NO from positive ions versus NO and Cl from negative ions

The positive ion electrospray mass spectrometry (ESI-MS) of trans-[Ru(NO)Cl)(dpaH)₂]Cl₂ (dpaH=2,2′-dipyridylamine), obtained from the carrier solvent of H₂O–CH₃OH (50:50), revealed 1+ ions of the formulas [Ru^II(NO⁺)Cl(dpaH)(dpa)]⁺ (m/z=508), [Ru^IIICl(dpaH)(dpa⁻)]⁺ (m/z=478), [Ru^II(NO⁺)(dpa)₂]⁺ (m/z=472), [Ru^III(dpa)₂]⁺ (m/z=442), originating from proton dissociation from the parent [Ru^II(NO⁺)Cl(dpaH)₂]²⁺ ion with subsequent loss of NO (17.4% of dissociative events) or loss of HCl (82.6% of dissociative events). Further loss of NO from the m/z=472 fragment yields the m/z=442 fragment. Thus, ionization of the NH moiety of dpaH is a significant factor in controlling the net ionic charge in the gas phase, and allowing preferential dissociation of HCl in the fragmentation processes. With NaCl added, an ion pair, {Na[Ru^II(NO)Cl(dpa)₂]}⁺ (m/z=530; 532), is detectable. All these positive mass peaks that contain Ru carry a signature ‘handprint’ of adjacent m/z peaks due to the isotopic distribution of ¹⁰⁴Ru, ¹⁰²Ru, ¹⁰¹Ru, ⁹⁹Ru, ⁹⁸Ru and ⁹⁶Ru mass centered around ¹⁰¹Ru for each fragment, and have been matched to the theoretical isotopic distribution for each set of peaks centered on the main isotope peak. When the starting complex is allowed to undergo aquation for two weeks in H₂O, loss of the axial Cl⁻ is shown by the approximately 77% attenuation of the [Ru^II(NO⁺)Cl(dpaH)(dpa)]⁺ ion, being replaced by the [Ru^II(NO⁺)(H₂O)(dpa)₂]⁺ (m/z=490) as the most abundant high-mass species. Loss of H₂O is observed to form [Ru^II(NO⁺)(dpa)₂]⁺ (m/z=472). No positive ion mass spectral peaks were observed for RuCl₃(NO)(H₂O)₂, ‘caged NO’. Negative ions were observed by proton dissociation forming [Ru^II(NO)Cl₃(H₂O)(OH)]⁻ in the ionization chamber, detecting the parent 1− ion at m/z=274, followed by the loss of NO as the main dissociative pathway that produces [Ru^IIICl₃(H₂O)(OH)]⁻ (m/z=244). This species undergoes reductive elimination of a chlorine atom, forming [Ru^IICl₂(H₂O)(OH)]⁻ (m/z=208). The ease of the NO dissociation is increased for the negative ions, which should be more able to stabilize a Ru^III product upon NO loss.     

Studies on electronic structures and related properties of [Ru(bpy)2(dpq)] and its 9,9′-substituted derivates with DFT method

Studies on electronic structures and related properties of [Ru(bpy)₂(dpq)]²⁺ and its 9,9′-substituted derivates are carried out using DFT method at B3LYP/LanL2DZ level. The substituent effects caused by the electron-pushing group (OH) and the electron-withdrawing groups (F) on the electronic structures and its related properties, e.g. the energies and components of some frontier molecular orbitals, the spectral properties, and the net charge populations of some main atoms of the complexes, etc. have been investigated. The computational results show that: first, the substituents have some important effects on the first excited state properties. Both electron-withdrawing group (F) and the electron-pushing group (OH) can all activate the main ligand and passivate the co-ligands in the first excited states of [Ru(bpy)₂(9,9′-2R-dpq)]²⁺, and both can lead to a little red shift in the electronic ground bands of the substitutive derivates, respectively, in particular, the electron-pushing group (OH) can lead to that more. Secondly, the most negative charges are populated on N1 or N5, and the next most negative charges are populated on C8 among all atoms of aromatic ring skeleton. In addition, the substituents have slight effects on coordination-bond lengths of complexes. The above theoretical results should be important to further inquire into the interaction mechanism between the complexes and DNA active units from the interactions between molecular orbitals, or from the interactions between atomic charges.     

Substitution of chloride by nitrosyl ligand in a scorpionate ruthenium(III) compound: A theoretical study

A theoretical study of the ruthenium(III) complex [RuCl₂(pz₂CHSO₃)(en)] and of its nitrosyl-substituted product [Ru(NO)Cl(pz₂CHSO₃)(en)]⁺ is presented, based on density functional calculations. Several isomers of each compound differing in the position of the anionic tail of a bis(3,4-dimethyl-1-yl)methanesulfonate scorpionate ligand, pz₂CHSO₃⁻, relative to the monodentate ligands have been optimized. A two-step mechanism is proposed for the ligand substitution reaction that is consistent with the computational results and the weak coordination of the sulfonate group.     

Synthesis and characterization of [Ru(NO)(bpp)Cl · 2H2O] [bpp = N,N′-bis(2-pyridinecarboxamide)-1,3-propane dianion] and [Ru(NO)(bpe)Cl · 2H2O] [bpe = N,N′-bis(2-pyridinecarboxamide)-1,2-ethane dianion]

Two ruthenium nitrosyl bis-pyridyl/biscarboxamido compounds, [Ru(NO)(bpp)Cl · 2H₂O] [bpp = N,N′-bis(2-pyridinecarboxamide)-1,3-propane dianion] and [Ru(NO)(bpe)Cl · 2H₂O] [bpe = N,N′-(bis-2-pyridinecarboxamide)-1,2-ethane dianion] have been characterized by ¹H NMR, ¹³C{¹H} NMR, and IR spectroscopies, electrospray ionizaton mass spectrometry, and X-ray crystallography.     

A theoretical study of Ru(II) polypyridyl DNA intercalators: Structure and electronic absorption spectroscopy of [Ru(phen)2(dppz)] and [Ru(tap)2(dppz)] complexes intercalated in guanine-cytosine base pairs

The structural and spectroscopic properties of [Ru(phen)₂(dppz)]²⁺ and [Ru(tap)₂(dppz)]²⁺ (phen = 1,10-phenanthroline; tap = 1,4,5,8-tetraazaphenanthrene; dppz = dipyridophenazine ) have been investigated by means of density functional theory (DFT), time-dependent DFT (TD-DFT) within the polarized continuum model (IEF-PCM) and quantum mechanics/molecular mechanics (QM/MM) calculations. The model of the Δ and Λ enantiomers of Ru(II) intercalated in DNA in the minor and major grooves is limited to the metal complexes intercalated in two guanine-cytosine base pairs. The main experimental spectral features of these complexes reported in DNA or synthetic polynucleotides are better reproduced by the theoretical absorption spectra of the Δ enantiomers regardless of intercalation mode (major or minor groove). This is especially true for [Ru(phen)₂(dppz)]²⁺. The visible absorption of [Ru(tap)₂(dppz)]²⁺ is governed by the MLCT_tap transitions regardless of the environment (water, acetonitrile or bases pair), the visible absorption of [Ru(phen)₂(dppz)]²⁺ is characterized by transitions to metal-to-ligand-charge-transfer MLCT_dppz in water and acetonitrile and to MLCT_phen when intercalated in DNA. The response of the IL_dppz state to the environment is very sensitive. In vacuum, water and acetonitrile these transitions are characterized by significant oscillator strengths and their positions depend significantly on the medium with blue shifts of about 80 nm when going from vacuum to solvent. When the complex is intercalated in the guanine-cytosine base pairs the ¹IL_dppz transition contributes mainly to the band at 370 nm observed in the spectrum of [Ru(phen)₂(dppz)]²⁺ and to the band at 362 nm observed in the spectrum of [Ru(tap)₂(dppz)]²⁺.     

A comparative study of the spectroscopy and oxidative spectroelectrochemistry of a series of homo- and heterobimetallic Ru(II) and Os(II) polypyridine complexes

A spectroscopic and spectroelectrochemical comparison is made among homo- and heterobimetallic complexes of the form [(bpy)₂Ru(BL)Os(byp)₂]⁴⁺, [(bpy)₂Ru(BL)Ru(bpy)₂]⁴⁺ and [(bpy)₂Os(BL)Os(bpy)₂]⁴⁺ (BL = 2,3,-bis(2′-pyridyl)pyrazzine(dpp),2,3-bis(2′-pyridyl)quinoxaline(dpq) or 2,3-bis(2′-pyridyl)benzoquinoxaline(dpb); bpy = 2,2′-bipyridine). It has been postulated that the spectroscopy of the mixed-metal bimetallic complexes bridged by polyazine bridging ligands can be assigned by comparison to those of the homobimetallic analogs. We have in hand a unique series of complexes where such a postulate can be tested. Utilizing the visible spectra of the homobimetallic Os,Os and Ru,Ru systems, we have been able to generate the spectra of the mixed-metal complexes. Some differences have been seen, particularly in the energy of the Os → dpp ³MLCT. Oxidative spectroelectrochemistry studies on the homobimetallic ruthenium or osmium based systems indicate that upon complete oxidation of both metal centers, transitions in the visible are lost. Hence, partial oxidation of the ruthenium based homobimetallics and Os, Ru mixed-metal bimetallics allows for the direct comparison of the spectroscopic character of the one remaining ruthenium chromophore within these mixed-valence systems. Oxidation to form the Os(III)/Ru(II) species and the Ru(III)/Ru(II) species resulted in similar spectra. This establishes further that the visible spectroscopy of mixed-metal systems of this nature can be accurately interpreted by comparison to the homobimetallic analogs.     

Molecular structure, bioavailability and bioactivity of [Cu(o-phen)2(cnge)](NO3)2.2H2O and [Cu(o-phen)(cnge)(H2O)(NO3)2] complexes

Two Cu(II) complexes with cyanoguanidine (cnge) and o-phenanthroline, [Cu(o-phen)(2)(cnge)](NO(3))(2).2H(2)O (1) and [Cu(o-phen)(cnge)(H(2)O)(NO(3))(2)] (2), have been synthesized using different experimental techniques and characterized by elemental analyses, FTIR, diffuse and UV-vis spectra and EPR and magnetic moment measurements techniques. The crystal structures of both complexes were solved by X-ray diffraction methods. Complex (1) crystallizes in the monoclinic space group C2/c with a=12.621(5), b=31.968(3), c=15.39(1)A, beta=111.68(4) degrees, and Z=8 and complex (2) in the monoclinic space group P2(1)/n with a=10.245(1), b=13.923(2), c=12.391(2)A, beta=98.07(1) degrees, and Z=4. The environments of the copper(II) center are trigonal bipyramidal (TBP) for [Cu(o-phen)(2)(cnge)](2+) and an elongated octahedron for [Cu(o-phen)(cnge)(H(2)O)(NO(3))(2)]. Solution studies have been performed to determine the species distribution. The superoxide dismutase (SOD) activities of both complexes have also been tested in order to determine if these compounds mimic the enzymatic action of the enzyme SOD that protects cells against peroxide radicals.     

Interaction of [Ru(bpy)2(dppz)] with human telomeric DNA: Preferential binding to G-quadruplexes over i-motif

Inspired by the enormous importance attributed to the structure and function of human telomeric DNA, we focus our attention on the interaction of [Ru(bpy)₂(dppz)]²⁺ with the guanine-rich single-strand oligomer 5′-AGGGTTAGGGTTAGGGTTAGGG-3′ (22AG) and the complementary cytosine-rich strand (22CT). In Na⁺ buffer, 22AG may adopt an antiparallel basket quadruplex, whereas, it favours a mixed parallel/antiparallel structure in K⁺ buffer. 22CT may self-associate at acidic pH into an i-motif. In this paper, the interaction between [Ru(bpy)₂(dppz)]²⁺ and each unusual DNA was evaluated. It was interesting that [Ru(bpy)₂(dppz)]²⁺ could promote the human telomeric repeat 22AG to fold into intramolecular antiparallel G-quadruplex without any other cations. What's more, [Ru(bpy)₂(dppz)]²⁺ was found to have a strong preference for binding to G-quadruplexes that were induced through either Na⁺ or K⁺, while weak binding to i-motif was observed. The results also indicated that [Ru(bpy)₂(dppz)]²⁺ could serve as a prominent molecular “light switch” for both G-quadruplexes, revealing a potential application of the title complex in luminescent signaling of G-quadruplex DNA.     

The Effects of Grafting of 2-Pyridyl to [Ru(bpy)2(Hpip)]2+ on Acid-Base and DNA-Binding Properties: Experimental and DFT Studies

Abstract

A new Ru(II) complex of [Ru(bpy)₂(Hppip)]²⁺ {bpy = 2,2′-bipyridine; Hppip = 2-(4-(pyridin- 2-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} has been synthesized by grafting of 2-pyridyl to parent complex [Ru(bpy)₂(Hpip)]²⁺ {Hppip = 2-(4-phenyl)-1H-imidazo[4,5-f] [1,10]phenanthroline}. The acid-base properties of [Ru(bpy)₂(Hppip)]²⁺ studied by UV-visible and luminescence spectrophotometric pH titrations, revealed off-on-off luminescence switching of [Ru(bpy)₂(Hppip)]²⁺ that was driven by the protonation/deprotonation of the imidazolyl and the pyridyl moieties. The complex was demonstrated to be a DNA intercalator with an intrinsic DNA binding constant of (5.56 ± 0.2) × 10⁵ M^?1 in buffered 50 mM NaCl, as evidenced by UV-visible and luminescence titrations, reverse salt effect, DNA competitive binding with ethidium bromide, steady-state emission quenching by [Fe(CN)₆]^4-, DNA melting experiments and viscosity measurements. The density functional theory method was also used to calculate geometric/electronic structures of the complex in an effort to understand the DNA binding properties. All the studies indicated that the introduction of 2-pyridyl onto Hpip ligand is more favorable for extension of conjugate plane of the main ligand than that of phenyl, and for greatly enhanced ct-DNA binding affinity accordingly.     

Cyclometalated ruthenium(II) complexes of benzo[h]quinoline (bzqH)[Ru(bzq)(NCMe)4], [Ru(bzq)(LL)(NCMe)2], and [Ru(bzq)(LL)2] (LL = bpy, phen)

Cyclometalation of benzo[h]quinoline (bzqH) by [RuCl(μ-Cl)(η⁶-C₆H₆)]₂ in acetonitrile occurs in a similar way to that of 2-phenylpyridine (phpyH) to afford [Ru(bzq)(MeCN)₄]PF₆ (3) in 52% yield. The properties of 3 containing ‘non-flexible’ benzo[h]quinoline were compared with the corresponding [Ru(phpy)(MeCN)₄]PF₆ (1) complex with ‘flexible’ 2-phenylpyridine. The [Ru(phpy)(MeCN)₄]PF₆ complex is known to react in MeCN solvent with ‘non-flexible’ diimine 1,10-phenanthroline to form [Ru(phpy)(phen)(MeCN)₂]PF₆, being unreactive toward ‘flexible’ 2,2′-bipyridine under the same conditions. In contrast, complex 3 reacts both with phen and bpy in MeCN to form [Ru(bzq)(LL)(MeCN)₂]PF₆ {LL = bpy (4) and phen (5)}. Similar reaction of 3 in methanol results in the substitution of all four MeCN ligands to form [Ru(bzq)(LL)₂]PF₆ {LL = bpy (6) and phen (7)}. Photosolvolysis of 4 and 5 in MeOH occurs similarly to afford [Ru(bzq)(LL)(MeCN)(MeOH)]PF₆ as a major product. This contrasts with the behavior of [Ru(phpy)(LL)(MeCN)₂]PF₆, which lose one and two MeCN ligands for LL = bpy and phen, respectively. The results reported demonstrate a profound sensitivity of properties of octahedral compounds to the flexibility of cyclometalated ligand. Analogous to the 2-phenylpyridine counterparts, compounds 4-7 are involved in the electron exchange with reduced active site of glucose oxidase from Aspergillus niger. Structure of complexes 4 and 6 was confirmed by X-ray crystallography.     

Synthesis and properties of the dichloro [tetramethyl (trifluoromethyl)cyclopentadienyl]ruthenium dimer: X-ray structure of [M2(η-C5Me4CF3)2Cl2(μ-Cl)2] (M=Ru, Rh)

The reaction of RuCl₃(H₂O), with C₅Me₄CF₃J in refluxing EtOH gives [Ru₂(η⁵-C₅Me₁CF₂)₂ (μ-Cl₂] (20 in 44% yield. Dimer 2 antiferromagnetic (−2J=200 cm¹). The crystal structures of 2 (rhombohedral system, R3 space group, Z=9, R=0.0589) and [Rh₂(η⁵-C₅Me₄CF₃(₂Cl₂(μ-Cl)₂] (3) (rhombohedral system. space group, Z = 9, R = 0.0641) were solved; both complexes have dimeric structures with a trans arrangement of the η⁵-C₅Me₄CF₄ rings. Comparison of the geometry of 2 and 3 with those of the corresponding η⁵-C₅Me₅ complexes shows that lowering the ring symmetry causes significant distortion of the M₂(μ-Cl)₂ moiety. The analysis of the MCl₃ fragment conformations in 2 and 3 and in the η⁵-C₅ME₅ analogues shows that they are correlated with the M---M distances. The Cl atoms are displaced by Br on reaction of 2 with KBr in MeOH to give the diamagnetic dimer [Ru₂(η⁵-C₅Me₄CF₃)₂Br₂ (μ-Br₂] (4). Complex 2 reacts with O₂ in CH₂Cl₂ solution at ambient temperature to form a mixture of isomeric η⁶-fulvene dimers [Ru₂(η⁶-C₅Me₃CF₃ = CH₂)₂Cl₂(μ-Cl)₂] (5). Reactions of 5 with CO and allyl chloride give Ru(η⁵-C₅Me₃CF₃CH₂Cl)(CO)₂Cl (6) and Ru(η⁵-C₅Me₃CF₃CF₃CH₂Cl)(η³-C₃H₅)Cl₂ (7) respectively.     

Synthesis, characterization and application of Ru(BINAP) (Acac) (MNAA) (MeOH), a highly effective catalyst for the asymmetric hydrogenation of 2-(6′-methoxynaphth-2′-yl)acrylic acid

Ru(S-BINAP) (Acac) (MNAA) (MeOH) (1) (where MNAA (2) = 2-(6′-methoxynaphth-2′-yl)acrylate anion), a highly effective catalyst for the asymmetric hydrogenation of 2-(6′-methoxynaphth-2′-yl) acrylic acid (3), was isolated from a dichloromethane/methanol (vol./vol. = 1/4) solution of Ru(S-BINAP) (Acac)₂ and excess of 2-(6′-methoxynaphth-2′-yl)acrylic acid after the solution was exposed to visible light for 2 weeks. On side by side comparison studies, the rate of the hydrogenation of 3 catalyzed by 1 was found to be substantially faster than the same reaction catalyzed by Ru(S-BINAP) (OAc)₂. The molecular structure of 1 was unambiguously characterized by single crystal X-ray diffraction.