bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Absolute Configurations and Biogenesis of Some New Halogenated Chamigrenes from the Sea Hare Aplysia dactylomela
Authors: Sakai Ryuichi , Higa Tatsuo , Jefford Charles W. , Bernardinelli GéRald 
Published: December 2004

AbstractFour new halogenated chamigrenes have been isolated from the sea hare, the (E)‐ and (Z)‐9‐(bromomethylidene)‐1,2,5‐trimethylspiro[5.5]undeca‐1,7‐dien‐3‐ones (11 and 10, resp.) the structures of which were deduced by NMR spectroscopy and by comparison with a known relative, the (8R,9R)‐8‐bromo‐9‐chloro‐5,5,9‐trimethyl‐1‐methylidenespiro[5,5]undec‐3‐en‐2‐one (12), and its (11 R)‐11‐acetoxy‐substituted derivative 13. Their structures and absolute configurations were determined and deduced by X‐ray using the absolute‐structure parameter. The configurations were remarkable in being enantiomeric to those of the tertiary chlorochamigrenes isolated so far. Consequently, a more general scheme is proposed to account for their biogenesis.
An ESR Study of the Radical Cations of Tetrathiafulvalene (TTF) and Electron Donors Containing the TTF Moiety
Authors: Ćavara Luka , Gerson Fabian , Cowan Dwaine O. , Lerstrup Knud 
Published: December 2004

AbstractHyperfine data and g factors are reported for the radical cations of tetrathiafulvalene (TTF; 1) and of its derivatives 2–13. From the intense satellite spectra of 1+–13+ not only the coupling constants of the 33S isotopes in the TTF moiety could be determined, but also, in favourable cases, those of the 13C isotopes in the central double bond. The former values range from 0.370 (8+) to 0.470 mT (4+) and the latter from 0.255 (8+) to 0.360 mT (4+) in the radical cations of bis(ethylenedithio)‐TTF (8+) and tetracyano‐TTF (4+). The radical cation of TTF (1+) exhibits intermediate values, 0.425 for the 33S and 0.285 mT for the 13C isotopes. The spin population in 1+–13+ resides, to a large extent, in the central S2C  CS2 part of the π‐system. It tends to increase (decrease) by substitution with electron‐accepting (donating) groups in the 2,3,6,7‐positions of TTF.
Influence of N,N′‐Substituents on the FeCl3‐Catalyzed Photo‐oxidation of 2,5‐Dibenzylpiperazine‐3,6‐Diones
Authors: Barbier Michel 
Published: December 2004

AbstractReactions carried out on benzoyl (2) and hydroxybenzyl (10) derivatives of L‐phenylalanine‐cycloanhydride 1 lead to the conclusion that the structure 3, previously proposed for picroroccellin (a metabolite from the lichen Roccella fuciformis), should be revised to 6, While the FeCl3‐catalyzed photo‐oxidation of 1 gives 2, the N,N′‐dimethyl derivative 7 leads to N,N′‐dimethyl‐2‐benzylpiperazine‐3,5,6‐trione (9). N,N′ ‐diacetyl‐L‐phenylalanine‐cycloanhydride 11 remains unchanged. It is established that N,N′ ‐substitutions of 2,5‐dibenzylpiperazines‐3,6‐diones considerably influence their photo‐oxidations under the reported conditions.
Stoffwechselprodukte von Mikroorganismen. 233. Mitteilung. Danoxamin, der eisenbindende Teil des Sideromycin‐Antibioticums Danomycin
Authors: Huber Peter , Leuenberger Heinz , Keller‐Schierlein Walter 
Published: December 2004

Danoxamine, the Iron‐Binding Moiety of the Sideromycin Antibiotic DanomycinThe antibiotic danomycin was separated into its components, danomycin A and B (1 and 2, resp.), by various methods. Danomycin A is a carbamate of danomycin B and can be transformed to the latter by boiling with H2O. Both danomycins can be hydrolyzed by alkali to the Fe‐containing moiety, danoxamine (3). The structure of the latter was determined by spectroscopy and chemical degradation as the Fe(III) complex of 5,16,27,32‐tetrahydroxy‐4,12,15,23,26‐pentaoxo‐5,11,16,22,27‐pentaaza‐dotriacontanoic acid. It belongs thus to the ferrioxamine family of siderophores. In the danomycins, this moiety is linked by an ester bond to a disaccharide moiety of unknown structure. One of the sugars is believed to be an aminohexane methyl ether. Chromatographically homogenous danomycins A and B are still mixtures of isomers, a neutral sugar being glucose or mannose.
Nucleophilic additions to N‐glycosylnitrones part IV Asymmetric synthesis of N‐hydroxy‐α‐aminophosphonic and α‐aminophosphonic acids
Authors: Huber Rolf , Vasella Andrea 
Published: December 2004

AbstractThe addition of phosphite anions and of tris(trimethylsilyl) phosphite (P(OSiMe3)3) to N‐glycosyl‐C‐arylnitrones was examined. While these nitrones proved inert towards the phosphite anions, they reacted with P(OSiMe3)3 under catalysis by Lewis acids. Thus, P(OSiMe3)3 reacted with the crystalline (Z)‐N‐glycosylnitrones 2 and 8 to give the optically active N‐hydroxy‐α‐aminophosphonic acids 4 and 10, respectively, and hence the α‐aminophosphonic acids 5 and 11 in yields up to 92% and with an enantiomeric excess (e.e.) up to 97% (Scheme 1). The absolute configuration of the phosphonates depend upon the nature and – in one case – upon the quantity of the catalyst (Figure). Upon catalysis by HCIO4 or Zn(OTF)2, p(OSiMe3)3 added to 2 to give, in both cases, the (+)‐(R)‐phenylphosphaglycine 5 (optical purity 79–84 and 90–93%, resp.). The optical purity (o.p.) was hardly influenced by the amount of these catalysts (0.02‐;1 equiv.). However, catalysis by ZnCl2 gave, with trace quantities of the catalyst, (–)‐(S)‐5 (o.p. 79%), while an equimolar amount of ZnCl2 yielded (+)‐(R)‐5 (o.p. 82%). The HClO4‐catalyzed addition of P(OSiMe3)3 to the nitrone 14 (Scheme 2) led to (+)‐(R)‐N‐hydroxyphosphavaline 15 (78%) and hence to (–)‐(R)‐phosphavaline 16 (71% from 14 e.e. 95%). Under conditions leading from the nitrones 2, 8, 14, and 20 (Schemes 1 and 2) predominantly to (R)‐α‐aminophosphonic acids, the addition of P(OSiMe3)3 to nitrone 18, possessing a benzyloxy substituent as an additional potential ligand for the catalyst, gave (S)‐phosphaserine 19. The addition of P(OSiMe3)3 to the nitrone 20, catalyzed by Zn(OTf)2, led to (+)‐(R)‐N‐hydroxyphosphamehionine 21 (71%, e.e. 77%) and hence to (–)‐(R)‐phosphamethionine 22 (77% from 20, e.e. 79%). Catalysis by trace quantities of ZnCl2 gave (+)‐(S)‐22 (85%, e.e. 61%). The enantiomerically pure aminophosphonic acids 5, 11, and 16 were obtained by recrystalliztion. The e.e. of the N‐hydroxyaminosphosphonic acids 10, 15, and 21 and the aminophosphonic acids 5, 11, 16, and 22 were determined by the HPLC analysis of the dimethyl N‐naphthoyl‐α‐aminophosphonats 7, 13, 17, and 23, on a chiral stationary phase.
Protonated diolefin complexes: Model systems for C;h activation via metal complexation
Authors: Piantini Umberto , Philipsborn Wolfgang Von , Salzer Albrecht , Buchmann Brigitte 
Published: December 2004

AbstractOn protonation of the diolefin complexes [M(C5R5)(diene)] (R = H, CH3; M = Co, Rh, Ir; diene = 2,3‐dimethylbutadiene, 1,3‐cyclohexadiene) with HBF4, cationic species are isolated which, at room temperature, show fluxional behaviour on the NMR time scale. Depending on R and M, three different ground states are observed for these cationic complexes in the NMR spectra at low temperatures. While for M = Ir a classical metal‐hydride structure M–H is observed, the Co and Rh complexes show ground states with ‘agostic’ H‐bridges M‥H‥C. The protonated species are characterized by 1H‐, 13C‐ and 103Rh‐NMR spectra. Total line‐shape analysis of the 1H and 13C spectra in the 298–154 K range gave the free enthalpies of activation ΔG ≠ for methyl rotation and 1, 4‐H shift in the agostic structures 2b, 2b′, 2c, and 2c′. The Rh complexes show the lowest ΔG± values for the 1,4‐H shift, and the strength of the agostic bond appears to decrease in the order CoC5H5 > CoC5Me5 > RhC5H5 > RhC5Me5. Only for R = H and M = Rh and in the presence of traces of Lewis bases (H2O, Pyridine, or acetone), variable amounts of coordinatively saturated allyl complexes competing with the agostic species are observable. Morethan equimolar amounts of basic solvents lead to irreversible deprotonation and recovery of the starting complexes. Stable allyl‐halide complexes are formed on reaction with HCI, while protonation with HBF4, in the presence of CO, gives high yields of complexes [M(CO)(allyl)(C5R5)] [BF4]. The different ground states observed for the protonated complexes and the dynamic behaviour in solution are compared with other hydride‐transfer reactions observed in organometallic chemistry, specifically with the β‐hydride elimination and the catalytic hydrogenation of olefins.
Über den Einfluss des Donor‐Teilchromophors bei Dimethinmerocyanin‐Farbstoffen auf das Aggregationsverhalten in wässriger Lösung
Authors: Kussler Manfred , Balli Heinz 
Published: December 2004

On the Influence of the Donor Part of the Chromophor of Dimethinmerocyanine Dyes upon the Aggregation Tendency in Aqueous SolutionA series of novel long‐chain alkyl‐dimethinmerocyanine dyes containing the (rhodaninyl)benzenesulfonate or (cyanoacetoxy)alkanesulfonate group is synthesized in good yield and their aggregation tendency in H2O and/or in various organic solvents/H2O mixtures without addition of salt investigated. Except for the merocyanine 2h, all dyes give J‐aggregation in H2O or in organic solvents containing H2O. The Lambert‐Beer rule is proved for the solution of 3a(4) in H2O. The degree of aggregation of 3a(4) in H2O is investigated by ultracentrifugation. The kind of the aggregation (J‐ or H‐type) can be found out very quickly by dissolving the dye in H2O with the help of ultra‐sound.
Isolierung und Strukturaufklärung epimerer 1(5),6‐Guaiadiene aus Tolubalsam
Authors: Friedel Horst Dieter , Matusch Rudolf 
Published: December 2004

Isolation and Structure Elucidation of Epimeric 1(5,)6‐Guaiadienes from TolubalsamTwo epimeric 1(5),6‐guaiadienes, which have very similar spectroscopic properties, were isolated from tolubalsam. Their structures were elucidated by NMR spectroscopy, acid‐catalyzed isomerization of γ‐gurjunene, and Diels‐Alder reactions.
Acid‐Catalyzed Rearrangement of 3‐Aza‐8‐oxatricyclo[3.2.1. 02,4]octan‐6‐one Acetals. Highly Stereoselective Total Synthesis of 3‐Amino‐3‐deoxy‐D‐altrose and Derivatives
Authors: Nativi Cristina , Reymond Jean‐Louis , Vogel Pierre 
Published: December 2004

AbstractEthyl and tert‐butyl azidoformate added to 7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐one dimethyl (5) and dibenzyl (6) acetals to give mixtures of regioisomeric triazolines. The latter gave the corresponding aziridines (6,6‐dialkoxy‐3‐aza‐8‐oxatricyclo[3.2.1.02,4]octane‐3‐carboxylates 15, 19, 23, and 27 and 31) on UV irradiation. In the presence of protic acids, the aziridines were rearranged into protected amines ([3‐endo‐alkoxy‐5‐oxo‐7‐oxabicyclo[2.2.1]hept‐2‐exo‐yl]carbamates 16, 20, 24, and 28 and 33). Using (+)‐(1R, 4R)‐5,5‐bis(benzyloxy)7‐oxabicyclo[2.2.1]hept‐2‐ene((+)‐6) derived from furan and l‐cyanovinyl (1S)‐camphanate, the method was applied to prepare 2‐O‐benzyl‐3‐[(tert‐butoxy)carbonyiamino]‐5‐O‐(3‐chlorobenzoyl)‐3‐deoxy‐β‐D‐altrofuranurono‐6,1‐lactone ((−)‐37). This compound was converted to methyl 3‐amino‐3‐deoxy‐α‐D‐altropyranoside hydrochloride (44) and several derivatives.
Photochemical Reactions 151st Communication. Photo‐oxygenation of (E)‐ and (Z)‐7‐Methyl‐β‐ionone
Authors: Nishio Takehiko , Mathies Peter , Job Kurt , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractPhoto‐oxygenation of (E)‐7‐methyl‐β‐ionone ((E)−1) and (E)‐8‐methyl‐β‐ionone ((E)−2) gave rise to the formation of the hydroperoxy‐enones (E)−10 and (E)−15, respectively, which, in part, underwent intramolecular epoxidation to the hydroxy‐epoxy‐ketones 11 and 16, respectively, The product distribution of the photo‐oxidation of (Z)−1 shows a marked influence of the skewed ground‐state conformation of the dienone chromophore. Thus, singlet oxygen (1O2) was added to C(γ) of the dienone chromophore leading to the spirocyclic peroxy‐hemiacetal 12 and to the endoperoxide 13. In addition, the tricyclic peroxide 14 was formed as a new type of product via primary addition of 1O2 to C(γ) of the dienone chromophore. The structure of 14 was established by X‐ray crystal‐structure analysis of the hemiacetal 22.
Notiz über Ellagitannine und Flavonol‐glycoside aus Rosenblüten
Authors: Nayeshiro Kyosuke , Eugster Conrad Hans 
Published: December 2004

AbstractNote on Ellagitannins and Flavonol Glycosides from Rose PetalsPetals from two garden roses proved to be very rich in ellagitannins and flavonol glycosides. Rutin (1), spiraeoside (2), quercitrin (3), isoquercitrin (4), nicotiflorin (5), eugeniin (6), rugosin A (7), rugosin D (10), casuarictin (8), and tellimagrandin I (9) were isolated. Spiraeoside, at physiological pH, exerts a pronounced stabilisation of the anthocyanin colour with enhancement of extinction and bathochromic shift of the absorption maximum in the visible range. The abundance of gallic‐acid derivatives 6–10 is in contrast to the apparent inability of rose flowers to produce anthocyanins with a trihydroxylated ring B, a prerequisite in breeding true blue‐coloured roses.
A New Route to Crystalline Salts of the Hydrolytic Dimer of Chromium(III)
Authors: Merakis Thomas , Murphy Annette , Spiccia Leone , Beguin Alan , Marty Werner 
Published: December 2004

AbstractCrystalline salts of the hydrolytic dimer of Cr(III), [Cr2(μ‐OH)2(H2O)8]X4·n H2O (X = p‐toluenesulfonate (tos) or mesitylene‐2‐sulfonate (dmtos)) have been prepared in good yields via a simple two‐step procedure: H+ oxidation of Cr metal to give Cr2+ (T ≈︁ 70°) followed by O2 oxidation, of Cr2+ to give the dimer (T ≈︁ 25°). The mechanism of conversion of Cr2+ into the dimer is discussed.
The Synthesis of Racemic Ambrox®
Authors: Büchi George , Wüest Hans 
Published: December 2004

Abstract(±)‐Ambrox (10), the racemic form of (−)‐Ambrox®, the commercially most important ambergris odorant has been synthesized from a readily available bicyclic keto ester in five steps. The racemic ether retains the characteristic scent of fine‐quality ambergis, and the odor threshold of the racemate and the (−)‐enantiomer prepared from natural sclareol were found to be essentially identical.
Synthesis and NMD A Antagonistic Properties of the Enantiomers of 4‐(3‐phosphonopropyl)piperazine‐2‐carboxylic acid (CPP) and of the unsaturated analogue (E)‐4‐(3‐phosphonoprop‐2‐enyl)piperazine‐2‐carboxylic acid (CPP‐ene)
Authors: Aebischer Bernard , Frey Peter , Haerter Hans‐Peter , Herrling Paul L. , Mueller Werner , Olverman Henry J. , Watkins Jeffrey C. 
Published: December 2004

AbstractThe (R)‐ and (s)‐enantiomers of 4‐(3‐phosphonopropyl)piperazine‐2‐carboxylic acid (D‐ and L‐CPP, resp.; 15 and 16, resp.), and of its unsaturated analogue (E)‐4‐(3‐phosphonoprop‐2‐enyl)piperazine‐2‐carboxylic acid (D‐ and L‐CPP‐ene, resp.; 13 and 14, resp.) were prepared. The absolute configuration of the enantiomers was determined by a chemical correlation of the menthyl ester 7 with D‐asparagine. The affinity of these derivatives for the NMDA receptor was determined by displacement of [3H]CPP in rat cerebral cortical membranes. In two functional tests (the frog hemisected spinal cord preparation and the sodium efflux test from rat brain slices), D‐CPP‐ene appears to be the most potent, enantiomerically pure, competitive NMDA antagonist known to date.
Chloride Binding by Polyammonium Receptor Molecules: 35Cl‐NMR Studies
Authors: Hosseini Mir Wais , Kintzinger Jean‐Pierre , Lehn Jean‐Marie , Zahidi Assou 
Published: December 2004

AbstractBinding of chloride anion by protonated polyamines was investigated by 35ClNMR spectroscopy. The presence of protonated macro(poly)cyclic polyamines caused downfield shifts and significant line broadening of the 53ClNMR signals. 35ClNMR spectroscopy was used for complex‐formation stoichiometry determination and revealed the formation of a binuclear chloride complex with the fully protonated ditopic hexaazamacrocyclic receptor 6. 35ClNMR spectroscopy was also applied in competition experiments between Cl and SO42− and demonstrated that the fully protonated macrocyclic hexaamine 4 forms a strong complex with SO4−2 with 1:1 stoichiometry.
Diastereoface Selectivity During Pthalimidonitrene Additions to (E)‐and (Z)‐configurated α, β‐unsaturated esters, induced by a chiral center in the γ‐position
Authors: Chilmonczyk Zdzislaw , Egli Markus , Behringcr Christoph , Dreiding AndréS. 
Published: December 2004

AbstractIn‐situ‐generated phthalimidonitrene was added to five α, β‐unsaturated esters containing a chiral secondary O‐function at C(γ). The additions were fully suprafacial, inasmuch as the (E)‐isomers 1 afforded only the trans‐aziridines 2 and 3 (J(β, γ) = 4.8−5.1 Hz) and the (Z)‐isomers 4 only the cis‐aziridines 5 and 6 (8.2−8.5 Hz). The products 2, 3, 5, and 6 where shown to possess the arabino‐, xylo‐, ribo‐, and lyxo‐ configuration, respectively, by X‐ray structure analysis of 2b, 2d, and 6a. The diastereoface selectivity of the nitrene additions, induced by the chiral substructure around C(γ), resulted in more 2 than 3 from 1, but more 6 than 5 from 4, which means that the preference of attack at the double bond switches from one side to the other depending on the C=C configuration. The preferences were higher at lower temperature. The aziridines 2a, 2d, and 3d exhibit 1H‐NMR‐visible isomerism at the ring N‐atom; the major (78−95 %)invertomer A is always the one with the phthalimido group in trans‐position to the (larger) substructure around C(γ). The other aziridines only show 1H‐NMR signals of one invertomer, which – by steric reasoning ‐ ought to be A; this is confirmed by a 1H‐NMR argument for 3a, 5a, 6a, 5c, and 6c.
An Eclipsed C(sp3)‐CH3 Bond in a Crystalline Hydrated Tricyclic Orthoamide: Evidence for CH…︁O hydrogen bonds
Authors: Seiler Paul , Dunitz Jack D. 
Published: December 2004

AbstractAccurate, low‐temperature (81 K) X‐ray analyses have been made for two crystalline modifications of the tricyclic orthoamide 1b: a cubic trihydrate in space group Pa3 (Z = 8), where the molecule has crystallographic threefold rotation symmetry, and an anhydrous monoclinic form in space group P21/c (Z = 8) where two symmetry‐independent molecules have different configurations, one ail‐trans. (as in the cubic trihydrate), the other cis, cis, trans. In the cubic trihydrate, each orthoamide molecule is attached to a triad of H2o molecules by OH…︁N H‐bonds. A remarkable feature of this structure is the nearly eclipsed conformation about the central C‐CH3 bond. In the anhydrous crystal, both types of molecule have the normal staggered orientation of their Me groups. The reversal of the Me orientation in the trihydrate is attributed to CH…︁O H‐bonding, which must be much stronger and more directionally specific than has been previously assumed.
Dichotomy of Fe+‐Mediated Sequential Activation of CH/CC Bonds of Aldimines: A Case of Efficient Reaction Control by Chain‐Length Effects Preliminary Communication
Authors: Prüsse Tilmann , Schwarz Helmut 
Published: December 2004

AbstractThe metastable ions of Fe+ complexes of aldimines R1NCHR2 exhibit a unique behaviour in that sequential loss of olefin/H2 follows two distinct pathways: one corresponds to the familiar pattern of double remote functionalization, involving either alkyl chain R1 and R2. In addition, based on labeling studies, evidence is presented demonstrating that the consecutive elimination of C2H4/H2 from the Fe+ complex of C6H13NCHC3H7 involves exclusively the C6H13 part of the substrate. These and other Fe+‐mediated CH/CC bond activations of aldimines are controlled by chain‐length effects, reflecting the preferential formation of metallacyclic intermediates of particular ring sizes.
Determination of the Chemical Structure of Linden Ether
Authors: Blank Imre , Grosch Werner , Eisenreich Wolfgang , Bacher Adelbert , Firl Joachim 
Published: December 2004

AbstractThe chemical structure of the novel monoterpene 1, named ‘linden ether’ and isolated from linden honey and the blossoms of lime tree (Tilia cordata), was studied by two‐dimensional NMR spectroscopy, by high‐resolution MS as well as by hydrogenation experiments and by GC on a chiral phase. Thus, linden ether was identified as a racemic mixture, i.e. (7aRS)‐2, 4, 5, 7a‐tetrahydro‐3, 6‐dimethylbenzofuran.
Synthesis of Optically Active Bifunctional Isoprenoid Building Blocks by Rhodium(I)‐Catalyzed Asymmetric Allylamine to Enamine Isomerization
Authors: Schmid Rudolf , Hansen Hans‐Jürgen 
Published: December 2004

AbstractThe application of the known asymmetric allylamine to enamine isomerization methodology to bifunctional C5‐isoprenoid allylic amines of types IId and IIe (Scheme 1) is described. It is shown that a number of such substrates can be isomerized with enantioselectivities of > 90% ee. using cationie Rh1 complexes containing (6. 6′‐dimethylbiphenyl′2, 2′‐diyl)bis(dipheny phosphine) (BIPHEMP; 9) as asymmetry‐inducing ligand (Scheme 2, Tables 1 and 2). Synthetically most useful is the isomerization of the benzyloxy derivative 10a into the (E)‐enamine 11a. This isomerization proceeds with very high enantioselectivity (98‐99% ee) and affords, after enamine hydrolysis, the optically active 4‐(benzyloxy)‐3‐methylbutanals ((R)‐ or (S)‐12) in chemical yields of ca. 90%. In conjunction, a short synthetic route to the starting material 10a has been developed which has a Pd‐catalyzed amination of isoprene epoxide (30) as the key step. Thus, convenient and practical access to the optically active aldehydes (R)‐and (S)‐12 is now at hand. These aldehydes are useful optically active bifunctional building blocks for isoprenoid homologation.
A New Convergent Synthesis of Thiamine Hydrochloride
Authors: Contant Pierre , Forzy Liliane , Hengartner Urs , Moine Gérard 
Published: December 2004

AbstractThiamine hydrochloride (1a; 3‐[(4‐amino‐2‐methylpyrimidin‐5‐yl)methyl]‐5‐(2‐hydroxyethyl)‐4‐methylthia‐zolium chloride hydrochloride; vitamin B1) has been synthesized in excellent yield by condensation of 3‐mercapto‐4‐oxopentyl acetate (5a) with 3, 4‐dihydro‐7‐methylpyrimido[4, 5‐d]pyrimidine (4) in formic acid. The two intermediates 5a and 4 are prepared from 3‐chloro‐4‐oxopentyl acetate (3) and 4‐amino‐2‐methyl‐5‐(aminomethyl)‐pyrimidine (Grewe diamine; 2a), respectively.
Spectroscopical and Electrochemical Behavior of New Mixed‐Ligand Cyclometalated Rh(III) Complexes
Authors: Sandrini Diana , Maestri Mauro , Ciano Mauro , Maeder Urs , von Zelewsky Alex 
Published: December 2004

AbstractThe absorption spectra, luminescence spectra, excited‐state lifetimes, and electrochemical behavior of the cyclometalated [Rh(ppz)2bpy]+, [Rh(3‐Cl‐ppz)2(bpy)]+, [Rh(4‐NO2‐ppz)2(bpy)]+, [Rh(ppz)2(biq)]+ and [Rh(4‐NO2‐ppz)2(biq)]+ complexes (ppz−, 3‐Cl‐ppz−, and 4‐NO2‐ppz− are the ortho‐C‐deprotonated forms of 1‐phenylpyrazole, l‐(3‐chlorophenyl)pyrazole and l‐(4‐nitrophenyl)pyrazole, respectively) have been investigated. The results obtained have been compared with those concerning the free protonated ligands and some previously studied mixed‐ligand cyclometalated Rh(III) complexes. Luminescence originates from the lowest ligand‐centered (LC) excited state, which involves the diimine ligands in all cases except for [Rh(4‐NO2‐ppz)2(bpy)]+, where it involves the ortho‐metalating ligand. s. In the absorption spectra, LC and metal‐to‐ligand charge‐transfer (MLCT) bands, involving the diimine and/or the ortho‐metalating ligands, have been assigned, and correlations between spectroscopic and electrochemical data are discussed.