Equimolar Reaction Research Articles

Design, spectral characterization, DFT and biological studies of transition metal complexes of Schiff base derived from 2-aminobenzamide, pyrrole and furan aldehyde

A series of two biologically active Schiff base ligands L1, L2 have been synthesized in equimolar reaction of 2-aminobenzamide with pyrrol-2-carboxaldehyde and furan-2-carboxaldehyde. The synthesized Schiff bases were used for complexation with different metal ions like Co(II), Ni(II) and Cu(II) by using a molar ratio of ligand: metal as 2:1. The characterization of newly formed complexes was done by 1H NMR, UV–Vis, TGA, IR, mass spectrophotometry, EPR and molar conductivity studies. The thermal studies suggested that the complexes are more stable as compared to ligand. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31+g(d,p) basis set. On the basis of the spectral studies an octahedral geometry has been assigned for Co(II) and Ni(II) complexes and distorted octahedral geometry for Cu(II) complexes. All the synthesized compounds, were studied for their in vitro antimicrobial activities, against four bacterial strains and two fungal strains by using serial dilution method. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination.

Reactivity of Traditional Metal–Carbon (Alkyl) versus Nontraditional Metal–Carbon (Cage) Bonds in Organo-Rare-Earth Metal Complexes [η5:σ-(C9H6)(C2B10H10)]Ln(CH2C6H4-o-NMe2)(THF)2

Equimolar reaction of 1-indenyl-1,2-carborane with Ln(CH2C6H4-o-NMe2)3 in THF gave highly constrained-geometry complexes [η5:σ-(C9H6)C2B10H10]Ln(CH2C6H4-o-NMe2)(THF)2 (Ln = Y (1a), Gd (1b), Dy (1c)). They reacted with RN═C═NR or 2,6-Me2C6H3NCS to generate the Ln–Calkyl insertion products [η5:σ-(C9H6)C2B10H10]Ln[η2-(RN)2C(CH2C6H4-o-NMe2)](THF) (R = TMS, Ln = Y (2a), Gd (2b); R = tBu, Ln = Y (3a)) or [η5:σ-(C9H6)C2B10H10]Dy[η2-(2,6-Me2C6H3)NC(CH2C6H4-o-NMe2)S](THF)2 (4c). Treatment of 2a with 1 equiv of R′N═C═NR′ to give the Y–Ccage insertion complexes [η5:σ-(C9H6){N(R′)C(═NR′)}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)] (R′ = Cy (5a), iPr (6a)). Similarly, unsaturated compounds Ph2C═C═O and Py2C═O (Py = 2-pyridyl) also inserted into the Y–Ccage bond in 2a to yield [η5:σ-(C9H6){OC(═CPh2)}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)] (7a) and [η5:σ-(C9H6){OC(Py)2}C2B10H10]Y[η2-{(TMS)N)}2C(CH2C6H4-o-NMe2)](THF) (8a), respectively. In sharp contrast to the earlier reports that the nontraditional metal–Ccage σ bonds ...

Chemistry of heterocyclic-2-thiones: in situ generated 1-(4,5-dihydro-3-alkyl-imidazolidin-2-yl)-3-alkyl-imidazolidine-2-thione and triiodide form novel mixed valent CuI–II/CuIIcomplexes

Copper(i) iodide transformsN-n-butyl-imidazolidine-2-thione in air into 1-(4,5-dihydro-3-butyl-imidazolidin-2-yl)-3-butyl-imidazolidine-2-thione (L-NBun) which formed novel complex, [Cu(κ2-N,S-L-NBun)2](I3)2.

From plant oils to plant foils: Straightforward functionalization and crosslinking of natural plant oils with triazolinediones

With the aid of triazolinedione (TAD) chemistry, an additive-free, straightforward functionalization and crosslinking strategy for numerous plant oils was developed. In a first step, model studies on the most common natural fatty acids were performed with the aid of monofunctional TAD moieties. These equimolar functionalization reactions were readily monitored by NMR and MS analysis, further facilitated by the disappearance of the characteristic red colour of the TAD molecule. Then, a series of synthesized, bifunctional TAD molecules were used for the chemical crosslinking of crude plant oils, a process that was typically finished within minutes. In this way, a large variety of polymer networks could be obtained, such as plant oil-based foils, showing a wide range of thermal properties, which can be tuned and rationalized by the chemical structure of the different plant oils.

Versatile Reactivity of β-Diketiminato-Supported Yttrium Dialkyl Complex toward Aromatic N-Heterocycles

The reactions of β-diketiminatoyttrium dialkyl complex LY(CH2Ph)2(THF) (1, L = [{N(2,6-iPr2C6H3)C(Me)}2CH]−) with a series of aromatic N-heterocycles such as 2-phenylpyridine, benzothiazole, and benzoxazole were studied and displayed discrete reactivity including C–H activation, C–C coupling, ring-opening/insertion, and dearomatization. The reaction of 1 with 2-phenylpyridine in 1:2 molar ratio in THF at 30 °C for 14 days afforded a structurally characterized metal complex, LY(η2-N,C-C5H4NC6H4-2)[C5H4N(CH2Ph-4)Ph] (2), in 73% isolated yield, indicating the occurrence of phenyl ring C(sp2)–H activation and pyridine ring 1,4-addition/dearomatization. However, when this reaction was done at 5 °C for 7 days, it gave the pyridine ring 1,2-addition product LY(η2-N,C-C5H4NC6H4-2)[C5H4N(CH2Ph-2)Ph] (3) in 54% isolated yield. Further investigations revealed that complex 2 is the thermodynamic controlled product and complex 3 is the kinetically controlled product; 3 converted slowly into 2, as confirmed by 1H NMR spectroscopy. The equimolar reaction of 1 with benzothiazole or benzoxazole produced two C–C coupling/ring-opening/insertion products, LY[η2-S,N-SC6H4NCH(CH2Ph)2](THF) (4) and {LY[μ-η2:η1-O,N-OC6H4NCH(CH2Ph)2]}2 (5), in 84% and 78% isolated yields, respectively.

Conformational Analysis of the 1,3‐Oxaphosphorinanes Formed from α,β‐Unsaturated Aldehydes and the (Hydroxymethyl)phosphines RP(CH2OH)2 (R = Ph or CH2OH)

Equimolar reactions of cinnamaldehyde or its 3,5‐dimethoxy‐4‐hydroxy derivative (sinapaldehyde) with RP(CH2OH)2 (R = Ph or CH2OH) were studied in MeOH or CD3OD at room temperature by NMR spectroscopy. In MeOH, nucleophilic attack of the phosphine at the CC bond, with concomitant loss of CH2O, affords the tertiary phosphine HOCH2P(R)CH(Ar)CH2CHO (3) that rapidly converts mainly into a 1,3‐oxaphosphorinane derivative (5) formed as a mixture of four diastereomers. Conformational analysis reveals that the Ar group in these is exclusively in an equatorial position while the OH and R groups can be equatorial‐oriented or axial‐oriented. In CD3OD, 1,3‐oxaphosphorinanes monodeuterated in the C5 position are obtained as a mixture of eight diastereomers where the dominate diastereomers have an axial D‐atom. Diastereomeric ratios depend on the nature of the Ar and R groups.

Reactivity of boryllithium with AlMe3, AlEt3, and GaMe3, including the synthesis of a lanthanum heterogallate complex.

Treatment of boryllithium (THF)2Li[B(NDippCH)2] (Dipp = 2,6-diisopropylphenyl) with various amounts of AlMe3 or GaMe3 leads to the formation of inter group 13 compounds. Equimolar reactions result in ate complexes of the type (THF)nLi(Me3M)[B(NDippCH)2] (M = Al, Ga) with discrete (n = 2, 3) or eight-membered ring structures (n = 1). We reported previously that use of excessive amounts of group 13 metal methyl compounds can result in four-coordinate THF-adducts (THF)(Me2M)[B(NDippCH)2] or unsolvated complexes {(Me2M)[B(NDippCH)2]}x (M = Al, x = 2; M = Ga, x = 1) via separation of LiMMe4. Polymeric [(THF)Li(Et3Al){B(NDippCH)2}]n is formed when boryllithium is reacted with an equimolar amount of AlEt3. The discrete THF-adduct (THF)Et2Al[B(NDippCH)2] can be isolated when using a boryllithium/AlEt3 ratio of 1 : 5. The reaction of THF-adduct (THF)Me2Ga[B(NDippCH)2] with La(AlMe4)3 affords the heterogallate complex La[(Me3Ga){B(NDippCH)2}]3, according to a donor-assisted tetramethylaluminate/alkylgallate exchange. The obtained complexes feature rare examples of crystallographically characterized non-cluster compounds with unsupported B-Al and B-Ga contacts.

Iridium-Promoted Conversion of Chlorosilanes to Alkynyl Derivatives in a One-Pot Reaction Sequence

By making use of the catalytic potential of the iridium system [{Ir(μ-Cl)(CO)2}2]/NEt(i-Pr)2 in the synthesis of silyl-functionalized alkynes via silylative coupling of terminal alkynes/diynes with iodosilanes, we propose a new protocol allowing employment of various mono- and dichlorosilanes as reagents. The process is based on a sequence of two reactions occurring simultaneously: i.e., conversion of initial chlorosilane (SiR1nCl4–n) to the appropriate iodosilane via Cl/I nucleophilic substitution and its further conversion to a silylalkyne derivative ((SiR1n(C≡CR2)4–n) via iridium-catalyzed silylative coupling with terminal alkyne. Under optimum conditions, the method has proved to be effective and versatile in the conversion of a wide range of chlorosilanes to a rich portfolio of various corresponding alkynyl-functionalized silicon derivatives. Additionally, NMR studies of the equimolar reaction of a well-defined iridium(I) alkynyl precursor with Me3Si–I revealed that ≡Si–I bond activation in iodosilan...

Synthesis, Spectroscopy and Crystal Structure of a New Copper Complex Built Up by Cationic (Dimethylphosphoryl)methanaminium Ligands

A new transition metal complex of the mono-protonated ligand (dimethylphosphoryl)methanamine (dpmaH+) was obtained by equimolar reaction of copper(II) chloride dihydrate and dpma in concentrated hydrochloric acid. The asymmetric unit of the title structure, [CuCl2(C3H11NOP)4][CuCl4]2, consists of one half of a fourfold charged trans-dichloridotetrakis[(dimethylphosphoryl)methanaminium]copper(II) complex with the copper atom located on an inversion centre and one tetrachloridocuprate(II) dianion found in a general position. The copper centre in the cationic complex shows a tetragonally distorted octahedral environment composed of four oxygen atoms in a square plane and two trans-coordinated chlorido ligands. This 4+2-coordination causes elongated Cu-Cl distances because of the Jahn-Teller effect. The geometry of the tetrachloridocuprate(II) dianion is best described as a seriously distorted tetrahedron. Analysis of the hydrogen bonding scheme by graph-set theory shows three patterns of rings in the title compound. The cationic copper complex reveals intramolecular hydrogen bonds between two aminium groups and the two axial chlorido ligands. Further hydrogen bonding among the cations and anions, more precisely between four aminium groups and the chlorido ligands of four adjacent tetrachloridocuprate(II) anions, lead to a chain-type structure. Comparing the coordination chemistry of the title structure with an analogue cobalt(II) compound only disclose differences in hydrogen bonding pattern resulting in an unusual chain propagation. Besides the crystal structure received spectroscopic data are in accordance with appropriate literature.

Syntheses and Structures of Bis-Amidinate–Alane Complexes

Insertion reactions of α,ω-bis-carbodiimides (RNCN)2X (1–5: R = Et, t-Bu, Ph; X = C3H6, C4H8) with 2 equiv of AlMe3 yielded the dinuclear tethered bis-amidinate–alane complexes [RNC(Me)NAlMe2]2X (R = Et, X = C4H8 (6); R = t-Bu, X = C3H6 (7), C4H8 (8)). Analogous reactions with 4 equiv of AlMe3 resulted in the coordination of two additional AlMe3 molecules, yielding the tetranuclear bis-amidinate complexes [EtN(AlMe3)C(Me)NAlMe2]2X (X = C3H6 (9), C4H8 (10)) and [t-BuNC(Me)N(AlMe3)AlMe2]2X (X = C3H6 (11), C4H8 (12)). In addition, equimolar reactions between (RNCN)2X (R = Et, X = C3H6, C4H8; R = Ph, X = C4H8) and 2 equiv of AlMe3 at elevated temperatures occurred with intramolecular cyclization and formation of [EtNC(Me)NC3H6N(AlMe3)CNEt]AlMe2 (13) and [RNC(Me)NC4H8N(AlMe3)CNR]AlMe2 (R = Et (14), Ph (15)). Hydrolysis of 11 gave the protonated free ligand PhNC(Me)NC4H8N(H)CNPh (16) in high yield. 6–16 were characterized by elemental analyses, multinuclear NMR (1H, 13C) and IR spectroscopy, and single-crystal X-ray diffraction (7, 10–14, 16).

Fluoride Ion Sensing and Caging by a Preformed Molecular D4R Zinc Phosphate Heterocubane

Double-4-ring (D4R) zinc phosphate [Zn(dipp)(DMSO)]4 (1, dipp = 2,6-di-iso-propylphenylphosphate, DMSO = dimethyl sulfoxide), on treatment with a free fluoride ion source, exhibited ability to sense and capture fluoride ions from a variety of sources, as evidenced by extensive solution (31)P and (19)F NMR spectral titration studies. The fluoride ion-encapsulated cage [(n)Bu4N][F@{Zn(dipp)(DMSO)}4] (2) was isolated in good yield from an equimolar reaction between 1 and (n)Bu4NF in methanol and characterized by analytical and spectroscopic methods. When 1-methyl-4,4'-bipyridin-1-ium fluoride (MeQ-F) was used as the fluoride ion source a zwitterionic cage [F@{Zn4(dipp)4(MeQ)(DMSO)3}] (3) was isolated. Crystal structure determination for 3 confirmed not only fluoride incorporation inside the D4R cage but also a weak interaction of the central fluoride ion with all four zinc centers of the cubane, resulting in a trigonal bipyramidal geometry around the zinc centers. To establish the selectivity, cubane 1 was treated with 2 equiv of MeQ-X (X = various anions) under similar conditions to isolate [F@{Zn4(dipp)4(MeQ)2(MeOH)2}][X] (X = I 4; BF4 5; PF6 6) in good yields. The crystal structure determination of 4 and 5 showed that the iodide and tetrafluoroborate anions are found outside the cage while fluoride ion has entered the cavity. The final fluoride encapsulated D4R cage is anionic in 2, neutral in 3, and cationic in 4-6, showing the versatility of the cubane framework to stabilize fluoride ions in all three forms. NMR titrations showed that 1 can sense even 1 ppm level of fluoride ions and sequester them from fluoridated water and toothpaste extract.

P–Cl bond-induced lactamization of 2(2′-hydroxyl)phenyloxazoline to form a cyclic phosphinite, 3-(2-chloroethyl)-2-phenyl-2H-benzo[e][1,3,2]oxaza-phosphinin-4(3H)-one: synthesis, structural studies and transition metal complexes

The equimolar reaction between 2(2'-hydroxy)phenyloxazoline (1) and PPhCl2 in the presence of triethylamine afforded an unexpected cyclic product, phenyl-benzo-oxazaphosphininone (2), instead of a simple phosphinite derivative A. A similar reaction between 1 and PPhCl2 in 2 : 1 ratio also yielded the same product 2, but with one equivalent of 2(2'-hydroxy)phenyloxazoline (1) left unreacted. The formation of the cyclic product 2 is due to the P-Cl bond induced oxazoline ring opening followed by the formation of a six-membered γ-lactam type product, 3-(2-chloroethyl)-2-phenyl-2H-benzo[e][1,3,2]oxazaphosphinin-4(3H)-one (2 also referred to as L). The reactions of 2 with H2O2, elemental sulphur or elemental selenium yielded the corresponding chalcogenides, LE (3, E = O; 4, E = S; 5, E = Se) in quantitative yield. Treatment of 2 with [Ru(η(6)-Cymene)Cl2]2, [Pd(COD)Cl2] and [Pd(η(3)-C3H5)Cl]2 resulted in the formation of [RuCl2(η(6)-cymene)(L)] (6), [PdCl2{L}2] (7), and [Pd(η(3)-C3H5)Cl(L)] (8), respectively. The compound 2 obtained in the 2 : 1 reaction when treated with [Pd(η(3)-C3H5)Cl]2 gave the same palladium complex 8 (referred to as 9a), but co-crystallized with bis(oxazolyl)palladacycle (9b) as confirmed by single crystal X-ray analysis.

1,4-Dialkyl-1,4-diazabutadienes: their reactions with aluminum and indium halides

Reactions of 1,4-bis[(S) methylbenzyl]-1,4-diazabutadiene (1), 1,4-bis[(R) 1′-chlorobutan-2′-yl]-1,4-diazabutadiene (2), 1,4-bis[(S,S) 1′-chloro-1′-phenyl-propan-2′-yl]-1,4-diazabutadiene (3), and 1,4-di-tert-butyl-1,4-diazabutadiene (4) with aluminum and indium halides were performed. Reaction of 1,4-diazabutadienes 1–4 with two equivalents of aluminum halides in toluene afforded ionic aluminum coordination compounds (5–10) which in THF solution are transformed into 1,3-dialkyl-2-methaneiminealkyl imidazolium heterocycles (11–14) by condensation of two 1,4-diazabutadienes and elimination of amine hydrochloride. Equimolar reactions of 1–4 with InCl3 in dry acetonitrile at −78 °C afforded the neutral and diamagnetic InCl3 coordination compounds (15–18), which are stable in the solid state under dry conditions, but in THF solution are slowly transformed into the corresponding 1,3-dialkyl-imidazolium heterocycles 19–22. The X-ray diffraction analyses of compounds 2, 3, 10, 11, 14 and 17 are described. Quantum mechanical calculations were performed in order to find the minimum energy conformers of 1,4-diazabutadienes, 1,3-dialkyl-2-methaneiminealkyl imidazolium and 1,3-dialkyl-imidazolium derivatives as well as the aluminum and indium coordination compounds.

Hemilabile imino-phosphine palladium(II) complexes: synthesis, molecular structure, and evaluation in Heck reactions

AbstractThe ligands 2-(diphenylphosphino)benzyl-(2-thiophene)methylimine (V) and 2-(diphenylphosphino) benzyl-(2-thiophene)ethylimine (VI) were prepared from 2-(diphenylphosphino)benzaldehyde and thiophene amines with very good yields. An equimolar reaction of V and VI with either PdCl2(cod) (cod = cyclooctadiene) or PdClMe(cod) afforded palladium(II) complexes I–IV. The molecular structure of II was confirmed by X-ray crystallography. The coordination geometry around the palladium atom exhibited distorted square planar geometry at the palladium centre. Complexes I, II, and IV were evaluated as catalysts for Heck coupling reactions of iodobenzene with methyl acrylate under mild reaction conditions; 0.1 mole % catalyst, Et3N base, MeCN reflux for 8 h, 80°C; isolated yield on a 10 mmol scale with catalyst I (64 %), II (68 %), and IV (58 %). They all exhibited significant activities.

Reactivity of Yttrium Carboxylates Toward Alkylaluminum Hydrides

Yttrocene-carboxylate complex [Cp*2Y(OOCAr(Me))] (Cp*=C5Me5, Ar(Me) =C6H2Me3-2,4,6) was synthesized as a spectroscopically versatile model system for investigating the reactivity of alkylaluminum hydrides towards rare-earth-metal carboxylates. Equimolar reactions with bis-neosilylaluminum hydride and dimethylaluminum hydride gave adduct complexes of the general formula [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] (R=CH2SiMe3, Me). The use of an excess of the respective aluminum hydride led to the formation of product mixtures, from which the yttrium-aluminum-hydride complex [{Cp*2Y(μ-H)AlMe2(μ-H)AlMe2(μ-CH3)}2] could be isolated, which features a 12-membered-ring structure. The adduct complexes [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] display identical (1)J(Y,H) coupling constants of 24.5 Hz for the bridging hydrido ligands and similar (89)Y NMR shifts of δ=-88.1 ppm (R=CH2SiMe3) and δ=-86.3 ppm (R=Me) in the (89)Y DEPT45 NMR experiments.

Imino-phosphine palladium(II) and platinum(II) complexes: Synthesis, molecular structures and evaluation as antitumor agents

The imino-phosphine ligands L1 and L2 were prepared via condensation reaction of 2-(diphenylphosphino)benzaldehyde with substituted anilines and obtained in very good yields. An equimolar reaction of L1 and L2 with either PdCl2(cod) or PtCl2(cod) gave new palladium(II) and platinum(II) complexes 1–4. The compounds were characterized by elemental analysis, IR, 1H and 31P NMR spectroscopy. The molecular structures of 2, 3 and 4 were confirmed by X-ray crystallography. All the three molecular structures crystallized in monoclinic C2/c space system. The coordination geometry around the palladium and platinum atoms in respective structures exhibited distorted square planar geometry at the metal centers. The complexes were evaluated in vitro for their cytotoxic activity against human breast (MCF-7) and human colon (HT-29) cancer cells, and they exhibited growth inhibitory activities and selectivity that were superior to the standard compound cisplatin.

Synergy in co-pyrolysis of oil shale and pine sawdust in autoclaves

Synergistic effects (Δ) in low temperature co-pyrolysis of Kukersite oil shale and pine (Pinus sylvestris) sawdust were studied in autoclaves in the ranges of blend composition xi=0–1g/g, nominal temperature 360–400°C and duration 2–4h. The value of Δ was estimated as the difference between the actual yield of pyrolysis products (gas, pyrogenetic water, subsequent extracts into hexane, benzene and tetrahydrofurane, and organic solid residue) and the additive value calculated as linearly proportional to the contributions of the individual components. The amplitude of Δ was explained based on the stability of a new cross-compound AnB formed between the liquid and solid decomposition products of the components. An equimolar synergy reaction (n=1) was proved to result synergies in the yields of the co-pyrolysis products. The extent of synergy was quantitatively evaluated by means of positive and negative values of a new characteristic, synergy factor (δ) expressing proportionality between the synergy and product of the shares of the components in the blend (Δ=δxAxB). The maximum synergistic increase in the yield of total oil (sum of hexane and benzene extracts), by 21.6%, was revealed for xi=0.5g/g when the primary thermal decomposition of kerogen was not completed (360°C, 2h). Lack of synergy prevailed under the optimum conditions for thermobituminization (380°C, 2–4h). A decrease in the oil yield from the additive value by 9% was evident when the secondary coke formation from thermobitumen and oil took place (400°C, 2–3h).

A novel approach for selective cross aldol condensation using reusable NaOH-cationic micellar systems

The efficiency of NaOH-cationic micellar systems was demonstrated for selective cross aldol condensation of benzaldehyde with n-heptanal (as model reaction, which involves cross and self condensation reactions) in equimolar amount to synthesize jasminaldehyde (cross product) with high selectivity. In comparison of biphasic reactions in NaOH aqueous solution (in absence of surfactant), the aldol reactions in NaOH-micellar solution were faster and selective to cross product without consumption of NaOH. The reaction rate and jasminaldehyde selectivity was observed to be influenced by surfactant concentration and reaction temperature. The equimolar reaction of both aldehydes in NaOH-cetyltrimethyl ammonium bromide (CTAB: 200mM) aqueous solution resulted to highest conversion of n-heptanal (99%) with 90% selectivity to jasminaldehyde within 4h. The reusability of NaOH-CTAB system was examined for five reaction cycles.

Large-Scale Capture of Peptides Containing Reversibly Oxidized Cysteines by Thiol-Disulfide Exchange Applied to the Myocardial Redox Proteome

Redox regulation is emerging as an important post-translational modification in cell signaling and pathogenesis. Cysteine (Cys) is the most redox active of the commonly coded amino acids and is thus an important target for redox-based modifications. Reactions that oxidize the Cys sulfur atom to low oxidation states (e.g., disulfide) are reversible, while further reactions to higher oxidation states (e.g., sulfonic acid) may be irreversible under biological conditions. Reversible modifications are particularly interesting as they mediate redox signaling and regulation of proteins under physiological conditions and during adaptation to oxidant stress. An enrichment method that relied on rapid and specific alkylation of free Cys, followed by thiol-based reduction and resin capture by thiol-disulfide exchange chemistry was applied to isolate reversibly modified Cys-containing peptides. Chromatographic conditions were optimized to provide increased specificity by removal of noncovalent interactions. The technique was highly efficient, based on near equimolar reactions with the resin, reproducible and linear for peptide elution, as quantified by label-free mass spectrometry. The method was applied to a complex protein lysate generated from rat myocardial tissue and 6559 unique Cys-containing peptides from 2694 proteins were identified. Comparison with the rat database and previous studies showed effective enrichment of proteins modified by S-nitrosylation, disulfide formation, and Cys-sulfenic acid. Analysis of amino acid sequence features indicated a preference for acidic residues and increased hydrophilicity in the regions immediately up- or downstream of the reactive Cys. This technique is ideally suited for the enrichment and profiling of reversible Cys modifications on a proteome-wide scale.

Mono- and dinuclear rhenium(I) compounds with bidentate benzimidazole chelators

Abstract A mononuclear rhenium(I) complex, fac-[Re(CO)3(bzch)Cl] (1), where bzch = 2-benzimidazole-4H-chromen-4-one, was isolated from the equimolar reaction between the Schiff base ligand 2-(2-aminophenyliminomethyl)-4H-chromen-4-one (H2pch) and [Re(CO)5Cl]. The 1:2 molar ratio reactions between [Re(CO)5Cl] and N-(2-hydroxybenzylidene)-benzimidazole (Hbzp) afforded a dinuclear rhenium(I) compound, (μ-bzp)2[Re(CO)3]2 (2). These new rhenium(I) compounds were characterized by NMR, UV–vis, IR, and emission spectroscopy, as well as conductance measurements and single crystal X-ray diffraction. The emission spectra for 1 in dichloromethane were well-resolved and could be deconvoluted into three main bands. The emission spectra for 2 were red-shifted by > 140 nm and markedly broadened relative to those of 1.