Redox and spectroscopic orbitals in Ru(II) and Os(II) phenolate complexes

A detailed spectroscopic and electrochemical study of a series of novel phenolate bound complexes, of general formulas [M(L-L)(2)(box)](PF(6)), where M is Os and Ru, L-L is 2,2-bipyridine or 2,2-biquinoline, and box is 2-(2-hydroxyphenyl)benzoxazole, is presented. The objectives of this study were to probe the origin of the LUMOs and HOMOs in these complexes, to elucidate the impact of metal and counter ligand on the electronic properties of the complex, and to identify the extent of orbital mixing in comparison with considerably more frequently studied quinoid complexes. [M(L-L)(2)(box)](PF(6)) complexes exhibit a rich electronic spectroscopy extending into the near infrared region and good photostability, making them potentially useful as solar sensitizers. Electrochemistry and spectroscopy indicate that the first oxidation is metal based and is associated with the M(II)/(III) redox states. A second oxidative wave, which is irreversible at slow scan rates, is associated with the phenolate ligand. The stabilities of the oxidized complexes are assessed using dynamic electrochemistry and discussed from the perspective of metal and counter ligand (LL) identity and follow the order of increasing stability [Ru(biq)(2)(box)](+) < [Ru(bpy)(2)(box)](+) < [Os(bpy)(2)(box)](+). Electronic and resonance Raman spectroscopy indicate that the lowest energy optical transition for the ruthenium complexes is a phenolate (pi) to L-L (pi) interligand charge-transfer transition (ILCT) suggesting the HOMO is phenolate based whereas electrochemical data suggest that the HOMO is metal based. This unusual lack of correlation between redox and spectroscopically assigned orbitals is discussed in terms of metal-ligand orbital mixing which appears to be most significant in the biquinoline based complex.     

Electrochemical, spectroscopic, and photophysical properties of structurally diverse polyazine-bridged Ru(II),Pt(II) and Os(II),Ru(II),Pt(II) supramolecular motifs

Five new tetrametallic supramolecules of the motif [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) and three new trimetallic light absorbers [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) (TL = bpy = 2,2'-bipyridine or phen = 1,10-phenanthroline; M = Ru(II) or Os(II); BL = dpp = 2,3-bis(2-pyridyl)pyrazine, dpq = 2,3-bis(2-pyridyl)quinoxaline, or bpm = 2,2'-bipyrimidine) were synthesized and their redox, spectroscopic, and photophysical properties investigated. The tetrametallic complexes couple a Pt(II)-based reactive metal center to Ru and/or Os light absorbers through two different polyazine BL to provide structural diversity and interesting resultant properties. The redox potential of the M(II/III) couple is modulated by M variation, with the terminal Ru(II/III) occurring at 1.58-1.61 V and terminal Os(II/III) couples at 1.07-1.18 V versus Ag/AgCl. [{(TL)(2)M(dpp)}(2)Ru(BL)](PF(6))(6) display terminal M(dπ)-based highest occupied molecular orbitals (HOMOs) with the dpp(π*)-based lowest unoccupied molecular orbital (LUMO) energy relatively unaffected by the nature of BL. The coupling of Pt to the BL results in orbital inversion with localization of the LUMO on the remote BL in the tetrametallic complexes, providing a lowest energy charge separated (CS) state with an oxidized terminal Ru or Os and spatially separated reduced BL. The complexes [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) and [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) efficiently absorb light throughout the UV and visible regions with intense metal-to-ligand charge transfer (MLCT) transitions in the visible at about 540 nm (M = Ru) and 560 nm (M = Os) (ε ≈ 33,000-42,000 M(-1) cm(-1)) and direct excitation to the spin-forbidden (3)MLCT excited state in the Os complexes about 720 nm. All the trimetallic and tetrametallic Ru-based supramolecular systems emit from the terminal Ru(dπ)→dpp(π*) (3)MLCT state, λ(max)(em) ≈ 750 nm. The tetrametallic systems display complex excited state dynamics with quenching of the (3)MLCT emission at room temperature to populate the lowest-lying (3)CS state population of the emissive (3)MLCT state.     

Contemporary progresses on neutral, highly emissive Os(II) and Ru(II) complexes

This tutorial review highlights recent and current advances in Os(II) and Ru(II) based luminescent complexes in view of their potential in providing models for photophysical properties and in serving as active materials in optoelectronic devices. It starts with a discussion of the fundamentals of pyridyl azolate chromophores and presents several prototypical designs that allow subtle variation of their basic properties. The third section of this article concerns the preparation of Os(II) and Ru(II) metal complexes and discusses the key factors that control their phosphorescence efficiencies and peak wavelengths. Attention is focused on the properties of their lowest lying excited states. In the last section, we present a series of related Os(II) complexes possessing pyridyl azolate, cyclometalated benzo[h]quinoline, beta-diketonates and quinolinates to demonstrate the power of fundamental basis to chemistry and theoretical approaches in rationalizing the corresponding photophysical behavior and hence to discuss the implications regarding their possible routes for future research.     

Dendrimers made of Ru(II) and Os(II) polypyridine subunits as artificial light-harvesting antennae

Dendrimers based on Ru(II) and Os(II) polypyridine complexes as building blocks and 2,3–dpp (2,3–dpp = 2,3–bis(2′–pyridyl)pyrazine) as bridging ligands are presented and their properties as light-harvesting antenna systems are illustrated. The dendrimers exhibit a huge absorption in the visible region and energy migration patterns whose direction and efficiency depend on the synthetically determined topography of the systems. New recent developments are also discussed, with particular regard towards ultrafast energy transfer processes and long-range electron transfer within the dendritic arrays. To cite this article: S. Serroni et al., C. R. Chimie 6 (2003).     

Donor/acceptor interactions in systematically modified Ru(II)-Os(II) oligonucleotides

Donor/acceptor (D/A) interactions are studied in a series of doubly modified 19-mer DNA duplexes. An ethynyl-linked Ru(II) donor nucleoside is maintained at the 5' terminus of each duplex, while an ethynyl-linked Os(II) nucleoside, placed on the complementary strands, is systematically moved toward the other terminus in three base pair increments. The steady-state Ru(II)-based luminescence quenching decreases from 90% at the shortest separation of 16 A (3 base pairs) to approximately 11% at the largest separation of 61 A (18 base pairs). Time-resolved experiments show a similar trend for the Ru(II) excited-state lifetime, and the decrease in the averaged excited-state lifetime for each duplex is linearly correlated with the fraction quenched obtained by steady-state measurements. Analysis according to the F?rster dipole-dipole energy transfer mechanism shows a reasonable agreement. Deviation from idealized behavior is primarily attributed to uncertainty in the orientation factor, kappa(2). Analyzing D/A interactions in an analogous series of doubly modified oligonucleotides, where the ethynyl-linked Ru(II) center is replaced with a saturated two-carbon linked complex, yields an excellent correlation with the F?rster mechanism. As this simple change partially relaxes the rigid geometry of the donor chromophore, these results suggest that the deviation from idealized F?rster behavior observed for the duplexes containing the rigidly held Ru(II) center originates, at least partially, from ambiguities in the orientation factor. Surprisingly, analyzing both quenching data sets according to the Dexter mechanism also shows an excellent correlation. Although this can be interpreted as strong evidence for a Dexter triplet energy transfer mechanism, it does not imply that this electron exchange mechanism is operative in these D/A duplexes. Rather, it suggests that systems that transfer energy via the F?rster mechanism can under certain circumstances exhibit Dexter-like "behavior", thus illustrating the danger of imposing a single physical model to describe D/A interactions in such complex systems. While we conclude that the F?rster dipole-dipole energy transfer mechanism is the dominant pathway for D/A interactions in these modified oligonucleotides, a minor contribution from the Dexter electron exchange mechanism at short distances is likely. This complex behavior distinguishes DNA-bridged Ru(II)/Os(II) dyads from their corresponding low molecular-weight and covalently attached counterparts.     

Synthesis, structural characterization, and photophysical, electrochemical, intercomponent energy-transfer, and anion-sensing studies of imidazole 4,5-bis(benzimidazole)-bridged Os(II)Os(II) and Ru(II)Os(II) bipyridine complexes

Homo- and heterobimetallic complexes of composition [(bpy)(2)M(II)(H(2)Imbzim)M'(II)(bpy)(2)](ClO(4))(3)·nH(2)O, where M(II) = M'(II) = Os (1), M(II) = Ru and M'(II) = Os (2), H(3)Imbzim = 4,5-bis(benzimidazole-2-yl)imidazole, and bpy = 2,2'-bipyridine, have been synthesized and characterized using standard analytical and spectroscopic techniques. Both of the complexes crystallized in monoclinic form with the space group P2(1)/m for 1 and P2(1)/n for 2. The absorption spectra, redox behavior, and luminescence properties of the complexes have been thoroughly investigated. The complexes display very intense, ligand-centered absorption bands in the UV region and moderately intense metal-to-ligand charge-transfer (MLCT) bands in the visible region. The bimetallic complexes show two successive one-electron reversible metal-centered oxidations. The strong fluorescence of free H(3)Imbzim is completely quenched in the metal complexes by energy transfer to the metal-based units, which exhibit their characteristic MLCT phosphorescence. The luminescence data of the heterometallic complex 2 show that electronic energy transfer takes place from the ruthenium center to the osmium-based component. The anion binding properties of the complexes have been studied in solutions using absorption, emission, and (1)H NMR spectral measurements. The metalloreceptors act as sensors for F(-) and AcO(-) ions. Sensing studies indicate the presence of two successive anion-induced deprotonation steps, leading to the formation of [(bpy)(2)M(HImbzim)M'(bpy)(2)](2+) and [(bpy)(2)M(Imbzim)M'(bpy)(2)](+) species. Double deprotonation is also observed in the presence of hydroxide. The binding affinities of different anions toward the receptors have been evaluated. Cyclic voltammetry measurements carried out in acetonitrile have provided evidence in favor of anion-dependent electrochemical responses of the bimetallic metalloreceptors with F(-) and AcO(-) ions.     

Preparation and structural characterization of Os(II) and Ru(II) complexes,MCl2(vdpp)2 [M = Os or Ru,vdpp = 1,1-bis(diphenylphosphino)ethene]

A reaction between Os₂(O₂CCH₃)₄Cl₂ and vdpp [vdpp = 1,1-bis(diphenylphosphino) ethene] was investigated. When the reactants, in the presence of LiCl, were heated in toluene OsCl₂(vdpp)₂,1, was formed. In a similar reaction Ru₂(O₂CCH₃)₄Cl with vdpp afforded RuCl₂(vdpp)₂,2. The molecular structures of1 and2 were elucidated using X-ray crystallography. Single crystals of1 and2 grown from dichloromethanehexane crystallize in the space group P2₁/c with these cell dimensions: a = 11.046(2)Å, b = 18.168(3)Å, c = 12.678(3)Å, β = 110.24(2)° and V = 2387(2)ų for1 and a = 11.055(1)Å, b = 18.199(3)Å, c = 12.693(2)Å, β = 110.16(1)°, V = 2392(1)ų for2. The molecules of1 and2 are isostructural. Metal atoms reside on inversion centers relating the two halves of the molecules. The complexes are six-coordinate with two four-membered chelate rings and trans chlorine atoms. For RuCl₂(vdpp)₂ the PMP angle in the chelate ring is 73.13(2)° and the PCP angle in the chelate ring is 98.6(1)°. These values are 72.74(3)° and 97.9(2)°, respectively, for OsCl₂(vdpp)₂. There is a disordered dichloromethane solvent molecule present in the lattice and there are no unusual intermolecular contacts.     

Photophysics and electron transfer in poly(3-octylthiophene) alternating with Ru(II)- and Os(II)-bipyridine complexes

A series of soluble metal-organic polymers that contain Ru(II)- and Os(II)-polypyridine complexes interspersed within a pi-conjugated poly(3-octylthiophene) backbone are prepared. Detailed electrochemical and photophysical studies are carried out on the polymers and two model complexes to determine the extent that the metal-polypyridine units interact with the pi-conjugated system. The results indicate that there is a strong electronic interaction between the metal-based chromophores and the pi-conjugated organic segments, and consequently the photophysical properties are not simply based on the sum of the properties of the individual components. In the Ru(II) polymers, the metal-to-ligand charge-transfer (MLCT) excited state is slightly higher in energy than the 3 pi,pi* state of the poly(3-octylthiophene) backbone. This state ordering results in a material that displays only a weak MLCT luminescence and a long-lived transient absorption spectrum that is dominated by the 3 pi,pi* state. In the Os(II) polymer the MLCT state is lower in energy than the polythiophene-based 3 pi,pi* state and the "unperturbed" MLCT emission is observed. Finally, all of the metal-organic polymers undergo photoinduced bimolecular electron-transfer (ET) reactions with the oxidative quencher dimethyl viologen. Transient absorption spectroscopy reveals that photoinduced ET to dimethyl viologen produces the oxidized polymers, and in most cases, the transient spectra are dominated by features characteristic of a poly(3-octylthiophene) polaron.     

Os(II)-nitrosyl and Os(II)-dinitrogen complexes from reactions between Os(VI)-nitrido and hydroxylamines and methoxylamines

Reactions between the Os(VI)-nitrido salts (e.g., trans-[Os(VI)(tpy)(Cl)(2)(N)]PF(6) (tpy = 2,2':6',2"-terpyridine), cis-[Os(VI)(tpy)(Cl)(2)(N)]PF(6), and fac-[Os(VI)(tpm)(Cl)(2)(N)]PF(6) (tpm = tris(pyrazol-1-yl)methane)) and the hydroxylamines (e.g., H(2)NOH and MeHNOH) and the methoxylamines (e.g., H(2)NOMe and MeHNOMe) in dry MeOH at room temperature give three different types of products. They are Os(II)-dinitrogen (e.g., trans-, cis-, or fac-[Os(II)-N(2)]), Os(II)-nitrosyl [Os(II)-NO](+) (e.g., trans- or cis-[Os(II)-NO](+)), Os(IV)-hydroxyhydrazido (e.g., cis-[Os(IV)-N(H)N(Me)(OH)](+)), and Os(IV)-methoxyhydrazido (e.g., trans-/cis-[Os(IV)-N(H)N(H)(OMe)](+), and trans-/cis-[Os(IV)-N(H)N(Me)(OMe)](+)) adducts. The products depend in a subtle way on the electron content of the starting nitrido complexes, the nature of the hydroxylamines, the nature of the methoxylamines, and the reaction conditions. Their appearance can be rationalized by invoking the formation of a series of related Os(IV) adducts which are stable or decompose to give the final products by two different pathways. The first involves internal 2-electron transfer and extrusion of H(2)O, MeOH, or MeOMe to give [Os(II)-N(2)]. The second which gives [Os(II)-NO](+) appears to involve seven-coordinate Os(IV) intermediates based on the results of an (15)N-labeling study.     

Photophysical behavior of Ru(II) and Os(II) terpyridyl phenylene vinylene complexes: perturbation of MLCT state by intra-ligand charge-transfer state

The photophysical behavior of novel bimetallic Ru(II) and Os(II) complexes having a bridging ligand consisting of two terpyridyl moieties covalently linked in the 4′ position through a distyrylbenzene bridge (tp vp vpt) is reported. The Ru(II) complex has a unique red emission with an excited state lifetime nearly 2000-times longer than the parent complex, [Ru(mpt)₂](PF6)₂ (mpt=4′-(methylphenyl)-2,2′,6′,2″-terpyridine). Combined spectral data suggest the presence of an emissive intra-ligand charge-transfer (ILCT) state lower in energy than the metal-to-ligand charge transfer (MLCT) state. The Os(II) complex exhibits red emission that is similar to that of the parent complex [Os(mpt)₂](PF₆)₂. However, the excited state absorption spectrum reveals a unique transient absorption in the far red that suggests perturbation of the MLCT state by the ILCT state.     

Towards inert and preorganized d-block-containing receptors for trivalent lanthanides: the synthesis and characterization of triple-helical monometallic Os(II) and bimetallic Os(II)-Ln(III) complexes

The mononuclear Os(II) complex [Os()(3)](PF(6))(2) ( = 5-methyl(1-methylbenzimidazol-2-yl)pyridine) is an obvious candidate for the design of an inert d-block-based tripodal receptor capable of binding and photosensitizing trivalent lanthanides (Ln(III)). It has thus been prepared and its two enantiomeric meridional (Delta-mer and Lambda-mer) and facial (rac-fac) isomers have been separated by ion-exchange chromatography. The optical isomers have been characterized by CD spectroscopy and assignments of absolute configuration confirmed by an X-ray crystallographic study of Lambda-mer-[Os()(3)](PF(6))(2).1.5MeCN (monoclinic, P2(1), Z = 4). Comparison of the latter structure with that of racemic fac-[Os()(3)](PF(6))(2) (monoclinic, C2/c, Z = 8) and [Os(bipy)(3)](PF(6))(2) (where bipy = 2,2'-bipyridine) shows minimal structural variations, but differences are observed in the photophysical and electrochemical properties of the respective compounds. Luminescence emissions from Os(II) complexes of are typically lower in energy, with shorter lifetimes and lower quantum yields than their bipy analogues, whilst metal-centred oxidation processes are more facile due to the enhanced pi-donor ability of . The key relationships between these parameters are discussed. Finally, though challenged by (i) the low reactivity of many osmium precursors and (ii) the irreversible formation of competing side products, the synthesis and purification of the heterobimetallic triple-stranded helicate HHH-[OsLu()(3)](CF(3)SO(3))(5) has been realised, in which is a segmental ligand containing the same bidentate unit as that found in further connected to a tridentate binding site adapted for complexing Ln(III). Its solid-state structure has been established by X-ray crystallography (triclinic, P1, Z = 2).     

Photochromic dithienylethene derivatives containing Ru(II) or Os(II) metal units. Sensitized photocyclization from a triplet state

Efficient photocyclization from a low-lying triplet state is reported for a photochromic dithienylperfluorocyclopentene with Ru(bpy)3 units attached via a phenylene linker to the thiophene rings. The ring-closure reaction in the nanosecond domain is sensitized by the metal complexes. Upon photoexcitation into the lowest Ru-to-bpy 1MLCT state followed by intersystem crossing to emitting 3MLCT states, photoreactive 3IL states are populated by an efficient energy-transfer process. The involvement of these 3IL states explains the quantum yield of the photocyclization, which is independent of the excitation wavelength but decreases strongly in the presence of dioxygen. This behavior differs substantially from the photocyclization of the nonemissive dithienylperfluorocyclopentene free ligand, which occurs from the lowest 1IL state on a picosecond time scale and is insensitive to oxygen quenching. Cyclic voltammetric studies have also been performed to gain further insight into the energetics of the system. The very high photocyclization quantum yields, far above 0.5 in both cases, are ascribed to the strong steric repulsion between the bulky substituents on the dithienylperfluorocyclopentene bridge bearing the chelating bipyridine sites or the Ru(bpy)3 moieties, forcing the system to adopt nearly exclusively the reactive antiparallel conformation. In contrast, replacement of both Ru(II) centers by Os(II) completely prevents the photocyclization reaction upon light excitation into the low-lying Os-to-bpy 1MLCT state. The photoreaction can only be triggered by optical population of the higher lying 1IL excited state of the central photochromic unit, but its yield is low due to efficient energy transfer to the luminescent lowest 3MLCT state.     

Analogues of uracil nucleosides with intrinsic fluorescence (NIF-analogues): synthesis and photophysical properties

Uridine cannot be utilized as fluorescent probe due to its extremely low quantum yield. For improving the uracil fluorescence characteristics we extended the natural chromophore at the C5 position by coupling substituted aromatic rings directly or via an alkenyl or alkynyl linker to create fluorophores. Extension of the uracil base was achieved by treating 5-I-uridine with the appropriate boronic acid under the Suzuki coupling conditions. Analogues containing an alkynyl linker were obtained from 5-I-uridine and the suitable boronic acid in a Sonogashira coupling reaction. The uracil fluorescent analogues proposed here were designed to satisfy the following requirements: a minimal chemical modification at a position not involved in base-pairing, resulting in relatively long absorption and emission wavelengths and high quantum yield. 5-((4-Methoxy-phenyl)-trans-vinyl)-2'-deoxy-uridine, 6b, was found to be a promising fluorescent probe. Probe 6b exhibits a quantum yield that is 3000-fold larger than that of the natural chromophore (Φ 0.12), maximum emission (478 nm) which is 170 nm red shifted as compared to uridine, and a Stokes shift of 143 nm. In addition, since probe 6b adopts the anti conformation and S sugar puckering favored by B-DNA, it makes a promising nucleoside analogue to be incorporated in an oligonucleotide probe for detection of genetic material.     

Detection of adsorption of Ru(II) and Os(II) polypyridyl complexes on gold and silver nanoparticles by single-photon counting emission measurements

The present study describes a new application of ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) and osmium(II) tris(bipyridine) (Os(bpy)3(2+)) as phosphorescent labels for the quantification of surface binding of molecules to gold and silver nanoparticles. The fraction of Ru(bpy)3(2+) and Os(bpy)3(2+) that is in solution can be distinguished from the surface-bound fraction by the relative lifetimes and integrated emission yields as determined by time-correlated single-photon counting (TCSPC) spectroscopy. Complementary steady-state measurements were carried out to confirm surface attachment of the phosphorescent label molecules. Although the emission of solutions of Ru(bpy)3(2+) and Os(bpy)3(2+) is quenched proportional to the concentration of 10 nm Au or 20 nm Ag nanoparticles, the quenching is static and not diffusional quenching observed in Stern-Volmer plots. The results demonstrate that time-resolved spectroscopy provides a rapid method for the measurement of surface binding of labeled molecules on metallic nanoparticles. While steady-state measurements require the preparation of a series of samples with varying quencher concentrations and a reference, the method described herein requires a single sample plus reference. The mechanism for phosphorescence quenching on Au and Ag nanoparticles is discussed in terms of energy and electron transfer theories.     

Comparative study on the photophysical properties between carbene-based Fe (II) and Ru (II) complexes

The comparative study on the photophysical properties between cheap metal Fe (II) complexes and noble metal Ru (II) complexes with identical ligand coordination is performed by the combination of density functional theory (DFT) and time-dependent density functional theory (TDDFT) to evaluate the potential alternative applications of Fe (II) complexes. RuBIP (BIP = 2,6-bis (imidazol-2- ylidene)pyridine) is theoretically established that the radiative lifetime of the second lowest triplet state is more consistence with experimental value. However, FeBIP retains nonluminous because of low-lying ³MC originated from weak d orbital splitting. FeBIPC (FeBIP with carboxylic acid groups) has twice longer lifetime than its parent complex FeBIP due to the great decrease of the energy gap between ³MLCT and ³MC. What's more, the lifetimes of Fe (II) complexes detected in the experiments are more accessible to nonradiative decay lifetimes of ³MC. The carboxylic acid groups are beneficial for the improvement of luminescent possibility and controllability of Fe (II) complexes, while there is still a huge challenge for effective material replacement comparing with Ru (II) complexes.     

Parallel synthesis and rapid photochemical screening of organosoluble Ru(II) photosensitizers

Ru(II) complexes of heteroaromatic ligands are photosensitizers of interest in such applications as photovoltaic cells. Their bulk preparation is tedious, time-consuming, and expensive. Their assessments, by measurement of the individual excited-state lifetimes, is incomplete and requires specialized equipment and expertise, as well as time. The identification of new, promising photosensitizers would, therefore, greatly benefit from any time- and cost-saving protocol, if absolute purity is not required for assessment. This paper details a protocol for the fairly rapid preparation, in parallel and on a small scale, of organosoluble Ru(II) complexes in a state ready for screening for photosensitization ability. The protocol was tested with a small set of bidentate ligands, generating 20 possible complexes, many of which are known. The protocol was found to produce predominantly the desired species in all cases except those with three different ligands. The batch screening results for the remaining 16 complexes were entirely consistent with those obtained with pure samples of the most promising materials prepared in bulk and were consistent with known photophysical properties.     

Preparation and properties of stable protonation products of permethylmetallocenecarbaldehydes (M = Fe,Ru, Os)

The products ofO-protonation of metallocenecarbaldehydes C₅Me₅MC₅Me₄CHO (M = Fe, Ru, Os) with HBF₄ and CF₃COOH were obtained for the first time, the adducts [C₅Me₅MC₅Me₄CH(OH)]⁺BF^– being isolated in a pure state. The structures of the adducts depend on the nature of the metal and the anion and are governed by the correlation between their basicities. For example, the Fe-containing adducts have an open fulvenoid structure with an interionic hydrogen bond irrespective of the nature of the anion X (X = BF₄ ^–, CF₃COO^–). In the case of the Ru- and Os-containing adducts in which the metal atoms are more basic than iron, the competition between the metal atom and the anion for the formation of a hydrogen bond with the OH group is clearly manifested in the IR and¹H NMR spectra. In the presence of the weakly basic BF₄ ^– anion, a cyclic structure with an intramolecular M...HO hydrogen bond is formed, while in the presence of a more basic F^– or CF₃COO^– anion. it transforms to the open fulvenoid structure with an interionic hydrogen bond. The structures of the compounds obtained were determined by IR and¹H NMR spectra, and the structure of the (C₅Me₅RuC₅Me₄CHOH)⁺...F^– salt was proved by X-ray diffraction analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No.12, pp. 2486–2493, December, 1995.The work was carried out with financial support of the International Science Foundation (Grant Nos. JFN-100 and NSAW 000), the Russian Foundation for Basic Research (Grant No. 93-03-4610), and the Ministry of Science and Technical Policy of RF, whom the authors wish to thank.     

Complexes of (bpy)2Ru(II) and (Ph2bpy)2Ru(II) with a series of thienophenanthroline ligands: synthesis,characterization, and electronic spectra

A series of complexes (bpy)₂LRu(II) and (Ph₂bpy)₂LRu(II), where bpy is 2,2′-bipyridine, Ph₂bpy is 4,4′-diphenyl-2,2′-bipyridine and L is 1,10-phenanthroline (phen), [1]benzothieno[2,3-c][1,10]phenanthroline (btp), naphtho[1′,2′?:?5,4]thieno[2,3-c][1,10]phenanthroline [ntpl, l=linear], and naphtho[1′,2′?:?4,5]thieno[2,3-c][1,10]phenanthroline (ntph, h=helical) were synthesized and characterized using 2D COSY NMR spectra. The UV spectra were assigned to study their metal to ligand charge transfer (MLCT) excited states. Complexes of (bpy)₂LRu(II) showed identical absorption wavelengths (λ _max) for the MLCT of all four members of the series with the only variation being the intensity (log _ε ) for each. The MLCT of (Ph₂bpy)₂LRu(II) showed the similar behavior only with different wavelengths showing that in this heteroleptic series of complexes the MLCT is exclusively to the bpy ligands with none to thienophenanthroline (btp, ntpl, or ntph).