bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesen und Ringerweiterungsreaktionen von 2‐(4‐Hydroxyalkyl)‐2‐nitrocycloalkanonen
Authors: Stach Hans , Hesse Manfred 
Published: December 2004

Syntheses and Ring‐Enlargement Reactions of 2‐(4‐Hydroxyalkyl)‐2‐nitrocycloalkanonesSyntheses of the title compounds were achieved by [Pd{P(C6H5)3}4]‐catalyzed reaction of 2‐nitrocycloalkanones 3 with vinyloxirane followed by catalytic hydrogenation. By another route, the known methyl 4‐(1‐nitro‐2‐oxocycloalkyl)butanoates 6 were reduced to the corresponding aldehydes 7 which by NaBH4 reduction or methylation with (CH3)2Ti(i‐Pr)2 were transformed to the alcohols 5 and 8, respectively (Saheme 1). Treatment of 5 and/or 8 with KH/THF under reflux gave, via a 7‐membered intermediate, the nitrolactones 12 and oxolactones 13 (Scheme 3). Compared with similar reactions running via 5‐ or 6‐membered intermediates (see 1 and 2), the yields are distinctly lower. The natural occurring 12‐tridecanolid (14) was synthesized.
Eine einheitlich verlaufende aliphatische Benzilsäure‐Typ‐Umlagerung
Authors: Schaltegger Alexander , Bigler Peter 
Published: December 2004

An Uniformly Occurring Aliphatic Benzil‐Benzilic‐Acid‐Type RearrangementTreatment of 6‐bromo‐2,2,5,5‐tetramethylcyclohex‐3‐enone (2) with aqueous alkaline and air affords 1‐hydroxy‐2,2,5,5‐tetramethylcyclopent‐3‐enecarboxylic acid (8) as the major product of a benzil‐benzilic‐acid‐type rearrangement. The key compound is 2,2,5,5‐tetramethylcyclohex‐3‐ene‐1,2‐dione (11). The by‐product of the reaction is (E)‐2,2,5,5‐tetramethylhex‐3‐enedioic acid (9) as the result of an oxidative cleavage of the 6‐membered ring and the isomerization of the double bond.
Asymmetric and ‘anti’‐Selective Aldolisations of Acetates and Propionates. Preliminary Communication
Authors: Oppolzer Wolfgang , Marco‐Contelles José 
Published: December 2004

AbstractStarting from acetates 1 and propionates 6, TiCl4‐mediated addition of their silyketene acetals 2 and 7 to aldehydes gave aldols 4 and 9, respectively, with high π‐face and ‘anti’ differentiation (Schemes, and Tables 1 and 2). Alternation of the (E/Z)‐enolate geometry led to reversed α‐ and β‐inductions (7 → 9b, 8 → 10b). Non‐destructive removal of the auxiliary yielded enantiomerically pure β ‐hydroxycarboxylic acids 13.
Enantiomerenreine Pyrrolidin‐Derivate aus trans‐4‐Hydroxy‐L‐prolin durch elektrochemische oxidative Decarboxylierung und Titantetrachlorid‐vermittelte Umsetzung mit Nukleophilen
Authors: Renaud Philippe , Seebach Dieter 
Published: December 2004

Enantiomerically Pure Pyrrolidine Derivatives from trans‐4‐Hydroxy‐L‐proline by Electrochemical Oxidative Decarboxylation and Titanium‐Tetrachloride‐Mediated Reaction with NucleophilesPreparative electrolysis of N‐methoxycarbonyl‐O‐[(t‐butyl)dimethylsilyl]hydroxyproline 4 in MeOH leads to substitution of the COOH by a MeO group (oxidative decarboxylation). The mixture 5 of the two diastereoisomers (ca 1:1) thus obtained was reacted in CH2Cl2 with nucleophilic silylated compounds (such as allylsilane, silyl cyanide and 1‐phenyl‐1‐silyloxyethane) or with trimethyl phosphite in the presence of TiCl4 to give 2‐allyl‐, 2‐cyano‐, 2‐(2‐oxo‐2‐phenylethyl)‐ and 2‐phosphono‐substituted hydroxypyrrolidines, respectively, with high diastereoselectivities (≥ 90%, products 6‐12). The configuration of two of the products (6/7 and 8/9) was shown to be cis.
Synthetic applications of electrochemically produced α‐methoxyamides. Part 2. Oxidation of hydroxyproline derivatives
Authors: Thaning Mikkel , Wistrand Lars‐G. 
Published: December 2004

AbstractThe electrochemical methoxylation of N‐acetyl‐4‐hydroxyproline esters has been investigated. Both the free alcohol 3 and the corresponding 4‐acetoxy derivative 4 as well as the cis‐4‐acetoxyproline 17 are methoxylated anodically preferentially at C(5), giving a mixture of stereoisomeric methoxy compounds. These mixtures can be used for further substitution as exemplified by the allylation of the methoxylated 4‐acetoxy derivatives, giving substitution products preferentially trans to the acetoxy group although with low selectivity. The low selectivity is discussed in terms of kinetic vs. thermodynamic control.
New Synthetic Routes to β‐Olefinic Trialkoxyphosphonium Salts and Phosphonates: Organometallic Variants of the Michaelis‐Arbuzov Reaction
Authors: Hafner Andreas , Von Philipsborn Wolfgang , Salzer Albrecht 
Published: December 2004

AbstractThe low‐temperature addition of tertiary phosphites to [(allyl)Fe (CO)4]+X− complexes proceeds regio‐ and stereospecifically and produces metal‐coordinated β‐olefinic trialkoxyphosphonium ions. These can be converted by various routes into the uncomplexed phosphonium salts or phosphonates. Similar reactions of acyclic [(dienyl)Fe(CO)3]+X− compounds give metal‐coordinated (2,4‐dien‐1‐yl)trialkoxyphosphonium salts or dialkyl (2,4‐dien‐1‐yl)phosphonates. The mechanisms and their relationship to the classical Michaelis‐Arbuzov reaction are discussed. The new compounds are characterized, if possible, by 1H‐, 13C‐, and 31P‐NMR spectra. The new phosphonium salts and phosphonates, potentially useful for Wittig‐Horner reactions, are difficult to obtain by conventional routes.
3,7‐Dioxaazelaamides as Ionophores for Lithium Ion Selective Liquid Membrane Electrodes
Authors: Metzger Erich , Aeschimann Roland , Egli Martin , Suter Gaby , Dohner René , Ammann Daniel , Dobler Max , Simon Wilhelm 
Published: December 2004

AbstractLipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1:1 Li+/ionophore complex of one representative (N,N,N′,N′‐tetracyclohexyl‐5,5‐dimethyl‐3,7‐dioxaazelaamide) has been prepared, and its structure was elucidated by X‐ray analysis.
Carbophile Additionen von Organocupraten mit 1,3‐Thiazol‐5(4H)‐thionen
Authors: Jenny Christjohannes , Wipf Peter , Heimgartner Heinz 
Published: December 2004

Carbophilic Additions of Organocuprates and 1,3‐Thiazole‐5(4H)‐thionesOrganocuprates and 1,3‐thiazole‐5(4H)‐thiones 1 react in THF at 0° via carbophilic addition onto the CS bond to give 4,5‐dihydro‐1,3‐thiazole‐5‐thiols 3 (Scheme 3). This observation is in marked contrast to the previously described reaction of organolithium compounds and 1, which undergo a thiophilic addition onto the exocyclic S‐atom. As an exception, treatment of the 1,3‐thiazole‐5(4H)‐thione 1a with tert‐butyl cuprate leads to 7a (Scheme 3).
Chiral Diaminodiamide Copper(II) Complexes for the Enantioselective Recognition of Amino Acids: Synthesis of the Ligands and Formation Constants
Authors: Armani Elisabetta , Marchelli Rosangela , Dossena Arnaldo , Casnati Giuseppe , Dallavalle Francesco 
Published: December 2004

Abstract(S,S)‐N,N′ ‐Bis(aminoacyl)ethane‐ and (S,S)‐N,N′ ‐bis(aminoacyl)propanediamines (AA‐NN‐2 and AA‐NN‐3, respectively, AA = alanine, phenylalanine, valine) were synthesized as the dihydrochlorides, and their complexes with Cu(II) studied potentiometrically. Since these ligands in the presence of Cu(II) are able to perform chiral resolution of D,L‐dansylamino acids in HPLC (reversed phase), in a certain pH range (6.5–8.5), it is important to know the equilibria existing between ligands and copper in aqueous solution. For AA‐NN‐2, four species, CuLH3+, CuL2+, Cu2L2H, and CuLH−2, were detected, whereas for AA‐NN‐3, only CuLH3+, CuL2+, and CuLH−2 were found. The aim is to find out which complexes may be involved in the recognition process.
Stereochemical Analysis of an Aromatic Triplet Di‐π‐methane Rearrangement
Authors: Scholl Bernhard , Hansen Hans‐JÜRgen 
Published: December 2004

AbstractIt is shown that (−)‐(S)‐N,N‐dimethyl‐2‐(1′‐methylallyl)aniline ((−)‐(S)‐4), on direct irradiation in MeCN at 20°, undergoes in its lowest‐lying triplet state an aromatic di‐π‐methane (ADPM) rearrangement to yield (−)‐(1′R,2′R)‐ and (+)‐(1′R,2′S)‐N,N‐dimethyl‐2‐(2‐methylcyclopropyl)aniline ((−)‐trans‐ and (+)‐cis‐7) in an initial trans/cis ratio of 4.71 ± 0.14 and in optical yields of 28.8 ± 5.2% and 15 ± 5%, respectively. The ADPM rearrangement of (−)‐(S)‐4 to the trans‐ and cis‐configurated products occurs with a preponderance of the path leading to retention of configuration at the pivot atom (C(1′) in the reactant and C(2′) in the products) for (−)‐trans‐7 and to inversion of configuration for (+)‐cis‐7, respectively. The results can be rationalized by assuming reaction paths which involve the occurrence of discrete 1,4‐ and 1,3‐diradicals (cf. Schemes 10, 12, and 13). A general analysis of such ADPM rearrangements which allows the classification of these photochemical reactions in terms of borderline cases is presented (Scheme 14). It is found that the optical yields in these ‘step‐by‐step’ rearrangements are determined by the first step, i.e. by the disrotatory bond formation between C(2) of the aromatic moiety and C(2′) of the allylic side chain leading to the generation of the 1,4‐diradicals. Moderation of the optical yields can occur in the ring closure of the 1,3‐diradicals to the final products, which may take place with different trans/cis‐ratios for the individual 1,3‐diradicals. Compounds (−)‐trans‐7 as well as (+)‐cis‐7 easily undergo the well‐known photochemical trans/cis‐isomerization. It mainly leads to racemization. However, a small part of the molecules shows trans/cis‐isomerization with inversion of configuration at C(1′), which is best explained by a photochemical cleavage of the C(1′)–C(3′) bond.
Metal complexes of macrocyclic ligands. Part XXIII. Synthesis, properties, and structures of mononuclear complexes with 12‐ and 14‐membered tetraazamacrocycle‐N,N′,N″,N‴‐tetraacetic Acids
Authors: Riesen Andreas , Zehnder Margareta , Kaden Thomas A. 
Published: December 2004

AbstractThe two tetraazamacrocycle‐N,N′,N″,N‴‐tetraacetic acids H4dota and H4teta form with Ni2+, Cu2+, and Zn2+ (M2+) mononuclear complexes MLH2 and M′[ML], M′ being an alkaline earth ion. The structures of Ni(H2dota) and Cu(H2dota) have been solved by X‐ray structure analysis. The metal ions are in a distorted octahedral geometry coordinated by four amino N‐atoms and two carboxylates. In the case of Cu2+, the distortions are more pronounced than for Ni2+ indicating that the Jahn‐Teller effect is operating. Starting from these two structures, the coordination geometry of the other complexes is discussed using VIS and IR spectra.
Neue Cyclosporine aus Tolypocladium inflatum. Die Cyclosporine K–Z
Authors: Traber René , Hofmann Hans , Loosli Hans‐Rudolf , Ponelle Monique , von Wartburg Albert 
Published: December 2004

Novel Cyclosporins from Tolypocladium inflatum. The Cyclosporins K–ZThe fungus T. inflatum produces a plethora of oligopeptides, the cyclosporins, which exhibit remarkable biological activities. Cyclosporin A, the main metabolite, represents a potent immunosuppressant which opened new ways in the immunotherapy of bone marrow and organ transplantations. In addition to the already described cyclosporins A–I, we report now the isolation of the cyclosporins K–Z. The structural assignments of these novel congeners are based on chemical degradation, correlation reactions, mass spectra, and extensive analysis of 1H‐ and 13C‐NMR spectra. All cyclosporins are cyclic undecapeptides differing from each other by minor variations in the amino‐acid sequence. Comparison of the immunosuppressive and antifungal effects furnished new information concerning structure‐activity relationships.
Addition of Chiral Glycine, Methionine, and Vinylglycine Enolate Derivatives to Aldehydes and Ketones in the Preparation of Enantiomerically Pure α‐Amino‐β‐Hydroxy Acids
Authors: Seebach Dieter , Juaristi Eusebio , Miller David D. , Schickli Christof , Weber Theodor 
Published: December 2004

AbstractChiral enolates of imidazolidinones and oxazolidinones from the title amino acids react with carbonyl compounds to afford the corresponding alcohols in excellent yields (see Scheme 5). Furthermore, the addition to aldehydes proceeds with high diastereoselectivity to give, after acid hydrolysis, threo‐α‐amino‐β‐hydroxy acids of high enantiomeric purity. Some of the threo‐α‐amino‐β‐hydroxy acids prepared in this work are the proteinogenic (S)‐threonine (26), the naturally occurring (S)‐3‐phenylserine (28), and (S)‐3‐hydroxyleucine (27) as well as the unnatural (S)‐4,4,4‐trifluorothreonine (30) and (S)‐3‐(4‐pyridyl)serine (31). The N‐methylamide of (2S,3R,4R,6E)‐3‐hydroxy‐4‐methyl‐2‐(methylamino)‐6‐octenoic acid (32), the unique amino acid in the immunosuppressive cyclosporine, was prepared by the new method. This report presents also information suggesting that both steric and stereoelectronic effects are responsible for the good stereoselectivities observed.
Revised Structure of the Fungal Germination Self‐Inhibitor Gloeosporone
Authors: Meyer Walter L. , Schweizer W. Bernd , Beck Albert K. , Scheifele Werner , Seebach Dieter , Schreiber Stuart L. , Kelly Sarah E. 
Published: December 2004

AbstractGloeosporone, the germination self‐inhibitor from the fungus Colletotrichum gloeosporioides f.sp. jussiaea, is shown by spectroscopic data and X‐ray analysis to have the constitution and relative configuration as shown in Formula 2 (either (1S,6R,12R)‐1‐hydroxy‐6‐pentyl‐5,15‐dioxabicyclo[10.2.1]pentadecan‐4,13‐dione or its enantiomer), rather than the previously assigned constitution 1.
A Liquid‐Crystal Study of Heptalene
Authors: Gottarelli Giovanni , Hansen Hans‐Jürgen , Spada Gian Piero , Weber Roland H. 
Published: December 2004

AbstractThe chiral structure of heptalene is characterised, for a given configuration, by helicities, which are opposite in the direction (x) of the central C(5a)‐C(10a) bond and in the direction (y) of a line perpendicular to it, passing through the C(3)‐and C(8)‐atoms. These two helicities can be experimentally established and differentiated by the handedness of the cholesteric mesophases induced in a biphenyl‐type liquid crystal (LC) by chiral heptalenes with substituents favouring the x or y orientation along the nematic director of the LC.
Nucleoside und Nucleotide Teil 27 Festphasensynthese eines Tridecanucleosid‐dodecaphosphats, das die unnatürliche Base 4‐Amino‐2(1H)‐pyridinon enthält, und eines Octanucleosid‐heptaphosphats zur Untersuchung der DNA‐Polymerase‐Spezifität
Authors: Charczuk Roland , Tamm Christoph 
Published: December 2004

Nucleosides and Nucleotides. Solid Phase Synthesis of a Tridecanucleoside Dodecaphosphate Containing the Unnatural Base 4‐Amino‐2(1H)‐pyridinone and of a Octanucleoside Heptaphosphate for the Determination of the DNA‐Polymerase SpecificityThe tridecanucleoside dodecaphosphate d (T‐T‐Z‐C‐G‐T‐C‐A‐A‐A‐A‐T‐C) incorporating the modified nucleoside 4‐amino‐1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐2(1H)‐pyridinone (Zd, 1) and the octanucleoside heptaphosphate d (G‐A‐T‐T‐T‐T‐G‐A) were synthesized by the solid‐phase method using the triester method. The carrier material was a copolymer consisting of styrene with 1% divinylbenzene.
Synthese und NMR‐Spektren von Nonafulven sowie Vergleich mit 10‐Phenylnonafulven
Authors: Furrer Jürg , Bönzli Peter , Frey Alfred , Neuenschwander Markus , Engel Peter 
Published: December 2004

Synthesis and NMR Spectra of Nonafulvene and Comparison with 10‐PhenylnonafulveneExperimental procedures for the reaction of cis,cis,cis,trans‐cyclononatetraenide (ccct‐CNT−; see 4) with bromomethyl acetate (1a, R = H, X = Br) to give (cyclononatetraenyl)methyl acetate (5a; 84% yield) as well as for the base‐induced elimination of HOAc from 5a to give nonafulvene (6a; 44% yield) are described. Spectroscopic as well as chemical evidence for 6a and 6b is presented. An approximate high‐field‐NMR analysis of 6a and 6b has been completed. The results are in favour of a fast interconversion of the type 6A⇄6B (Scheme 4), and supported by the MNDO‐optimised geometry of 6a. The first X‐ray analysis of a cyclononatetraene (i.e. of 5b) has been accomplished: 5b is a polyolefinic molecule with largely alternating bond lengths and with a nine‐membered ring deviating strongly from planarity.
Structures and Electrical Properties of Some New Organic Conductors Derived from the Donor Molecule TMET (S,S,S,S,‐Bis(dimethylethylenedithio) tetrathiafulvalene)
Authors: Karrer Andreas , Wallis John D. , Dunitz Jack D. , Hilti Bruno , Mayer Carl W. , Bürkle Markus , Pfeiffer Jürgen 
Published: December 2004

AbstractCrystal structures and electrical properties of radical‐cation salts of the chiral organic donor TMET (S,S,S,S,‐bis‐(dimethylethylenedithio)tetrathiafulvalene) are described. Two structural types, 2:1 with octahedral anions Pf, AsF, SbF, I (incommensurate), and 3:2 with tetrahedral anions BF−4, CIO−4, ReO−4 are observed. Resistivity measurements between 2 and 298 K indicate that the 3:2 types are organic metals, while the other compounds are semiconductors. (TMET)3(CIO4)2 is metallic down to about 120 K at ambient pressure and remains metallic down to 2 K at 8 kbar.
Isolation and Structure Elucidation of Some Components of the Antitumor Antibiotic Mixture ‘Rubiflavin’
Authors: Nadig Heinz , Sèquin Urs 
Published: December 2004

AbstractThe antitumor antibiotic ‘rubiflavin’ was investivated. It was shown to be a mixture of several compounds, nine of which ‐ after isolation by HPLC ‐ could be identified by 1H‐NMR spectroscopy. The rubiflavins A (4), B (5), C‐1(6), C‐2(7), D(8), and E(9) are pluramycin antibiotics differing only in their side chains at C(2). Rubiflavin B(5) was found to be identical with kidamycin, rubiflavin F(10) with isokidamycin. Two unpolar compounds isolated which lack the two sugar rings typical for pluramycin antibiotics were called rubiflavinone C‐1 (2) and C‐2 (3); they are the ‘aglycones’ of the corresponding rubiflavins.
Binding of AMP, ADP, and ATP Nucleotides by Polyammonium Macrocycles
Authors: Hosseini Mir Wais , Lehn Jean‐Marie 
Published: December 2004

AbstractThe macrocyclic polyamines 4–6, when protonated, bind strongly and selectively nucleotides (AMP, ADP, ATP) and pyrophosphate in aqueous solution. The stoichiometry of the complexes formed was determined by titration experiments followed by 31P‐NMR spectroscopy. Compounds 4 and 5 form 1:1 complexes with ATP, ADP, and pyrophosphate, whereas 6 forms complexes with ATP and ADP involving 2 nucleotides and 1 receptor molecule. The stability constants of these complexes have been determined by pH‐metric measurements. At pH 7, both 5 and 6 give complexes of mainly the fully protonated species 5.6H+ and 6.8H+, whereas 4 yields predominantly complexes of 4.5H+ and 4.4H+.
Morphological and Thermal Investigations of the ‘Active’ Dimer Hydroxide of Chromium(III)
Authors: Spiccia Leone , Marty Werner , Giovanoli Rudolf 
Published: December 2004

AbstractThe ‘active’ dimer hydroxide, [Cr2(μ‐OH)2(OH)4(OH2)4]·2 H2O, has been characterised by means of IR spectroscopy, thermal analysis, X‐ray powder diffraction, and electron microscopy. Thermogravimetric measurements and the Cr content of the hydroxide are in agreement with this composition. The IR spectrum supports the notion that this hydroxide is composed of unaltered dimer fragments linked through hydrogen bonds of ca. 2.8 Å. The compound is microcrystalline in nature with an X‐ray powder diffraction pattern distinctly different from that of the isomeric ‘active’ monomer hydroxide. Electron micrographs of the ‘active’ dimer hydroxide indicate that this material consists of platelets the sie of which is dependent on the pH of precipitation.
2,3‐Bis(diphenylphosphino)‐1,3‐butadien
Authors: Schmidbaur Hubert , Dziwok Klaus , Reber Gabriele , Müller Gerhard 
Published: December 2004

2,3‐Bis(diphenylphosphino)‐1,3‐butadieneA method for synthesis of the title compound is described, using the readily available 2,3‐bis(diphenylphosphinoyl)‐1,3‐butadiene (1) as the starting material. For the protection of the diene system, 1 is first converted into the 1,4‐dibromo‐ and 1,4‐dichloro derivatives 2a and b, respectively, by addition of Br2 or Cl2, respectively. The structure of 2b has been determined by single‐crystal X‐ray diffraction. The molecule has a centrosymmetrical (E)‐configuration. Reduction of the phosphinoyl groups by HSiCl3(to give the bis(diphenylphosphino)compound 3), followed by removal of the Cl‐atoms using Zn powder, affords the bis(diphenylphosphino)butadiene 4. Compounds 3 and 4 give quaternary phosphonium salts 5 and 6, respectively, on addition of CH3OSO2F or CH3I. The sulfur analogue of 1 is formed on treatment of 4 with elemental sulfur.
Synthesis of (±)‐trans‐2,5‐Dialkylpyrrolidines from the Lukes‐Šorm Dilactam: Efficient Preparation of (±)‐trans‐2‐Butyl‐5‐heptylpyrrolidine and Analogs Present in Ant Venoms
Authors: Gessner Wieslaw , Takahashi Kimio , Brossi Arnold , Kowalski Marek , Kaliner Michael A. 
Published: December 2004

AbstractA 7‐step synthesis of (±)‐trans‐2‐butyl‐5‐heptylpyrrolidine (14) from the Lukes‐Šorm dilactam 1 was accomplished in 6% overall yield without counting for a reconversion of cis‐isomer 13 into trans‐isomer 14 which was also accomplished. Reduction of pyrroline 12, the precursor of 14, with NaBH4 afforded a 1:1 mixture of cis‐isomer 13 and trans‐isomer 14 separated by chromatography. Reductive N‐methylation of 14 afforded the N‐methyl analog 15, another ant alkaloid. The synthetic route to 14 was extended to a similar synthesis of analogs 23–25 and is representative for the synthesis of trans‐2,5‐diakyl‐substituted pyrrolidines. Results on the screening of a few compounds for the effect on vascular permeability are reported.
Spectroscopic, Electrochemical, and Kinetic Characterization of New Ruthenium(II) Tris‐chelates Containing Five‐Membered Heterocyclic Moieties
Authors: Orellana Guillermo , Quiroga María L. , Braun André M. 
Published: December 2004

AbstractSynthesis, redox, photophysical, and photochemical properties of Ru(NN) complexes NN = 2‐((2′‐pyridyl)thiazole (pyth), 2‐(2′‐pyrazyl)thiazole (pzth), 2,2′‐bithiazole (bth), 5‐(2′‐pyridyl)‐1,2,4‐thiadiazole (pytda), 2‐(2′‐pyridyl)imidazole (pyim), 1‐methyl‐2‐(2′‐pyridyl)imidazole (Mepyim), and 2‐(2′‐pyridyl)oxazole (pyox)) are described. Oxidation potentials for the Ru3+/2+ couples in MeCN varied from about 0.80 V to 1.60 V vs. NHE. Three reduction waves were observed in all the cases except for Ru(pyim) and Ru(Mepyim) complexes and asigned to the one‐electron reduction of each bidentate ligand. Absorption spectra contained bands in the UV (280–325 nm) and VIS (437–481 nm) regions which have been assigned to ligand‐centered π‐π* and metal‐to‐ligand charge‐transfer dπ‐π* transitions, respectively. Emission spectra at 77 K were determined for all the complexes presenting maxima in the 580–650‐nm region, with vibrational progression in some of them. Only pyth, pzth, bth, and pytda tris‐chelates showed luminescence at room temperature in aqueous solution, with quantum yields ranging from 0.0013 to 0.0095 and excited‐state lifetimes from 55 to 390 ns, as determined from pulsed laser techniques. Their E0–0 spetroscopic energies have been estimated from emission wavelength maxima at 77 K which, in turn, have allowed calculation of excited‐state redox potentials. A plot of E0–0 vs. ΔE1/2, where ΔE1/2 = E1/2(3+/2+) − E1/2(2+/+), was linear with a slope of ca. 1.1 and a correlation coefficient of 0.999, demonstrating an identical nature of the orbital involved in spectroscopic and electrochemical processes. Photochemical properties of Ru(NN) complexes have been tested using methyl viologen (MV2+) in Ar‐purged aqueous solution at pH 5. Stern‐Volmer treatment has led to the determination of bimolecular quenching constants (0.5 to 2 × 109m−1·s−1) which parallel electron‐transfer free‐energy changes. Homogeneous back‐reaction of primarily produced MV+· and Ru(NN) has been measured resulting to be slightly higher than diffusion control and independent of ligand nature. Rate constants for the scavenging of Ru(NN) by added edta have been also determined (1.7 to 8.2 × 108M−1 · S−1). Under such conditions, net production of MV+· is attained with quantum yields varying from 0.003 to 0.038 (single‐shot laser results).