Synthesis and Characterization of Nickel(II) and Copper(II) Complexes with Non-symmetric Tetraaza[14]annulene Derivatives. X-ray Crystal Structure of Copper(II) Complex

The complexes 13,14-([X]benzo)-3-(p-[Y]benzoyl)-2,4,9,11-tetramethyl-1,5,8,12-tetraazacyclotetradeca-l,3,9,11-tetraenato(2-)nickel(II), wherein Y = CH₃, H, Cl, NO₂ or OCH₃, X = CH₃ or Cl, have been synthesized and characterized. IR spectra of the benzoylated complexes show intense bands in the regions 1641-1654 cm^?1 attributable to the stretching modes of C—O. Hammett plots of the l/γ _max of π→π ^? have positive slopes of 0.251 for A series (X = CH₃) and 0.233 for B series (X = Cl), respectively, which are quite similar to those based on the NMR resonances of methine protons. The cyclic voltammograms of the complexes show two one-electron irreversible oxidation processes in the potential range of +0.1 to +0.8 V and two, three or four reduction peaks between ?1.2 and ?2.8 V depending on the substituents. Hammett plots of first and second oxidation potentials are linear with the positive slopes (0.039 and 0.057 V for A series, 0.036 and 0.047V for B series). The structure of the copper(II) complex (orthorhombic, C222₁, a= 8.0994(11), b= 8.3187(10), c= 24.561(5)Å, α(=β=γ)= 90.0°, Z= 4, R ₁= 0.0474 and wR ₂= 0.1219) was characterized using single crystal X-ray diffraction method.     

Synthesis of an N-glycan decasaccharide of the hybrid type

A hybrid-type N-glycan decasaccharide GlcNAcMan₇GlcNAc₂ was synthesized from the pentasaccharide GlcNAcMan₂GlcNAc₂ as an advanced intermediate and an acyl-protected pentamannosyl donor. Benzyl mannoside was regioselectively benzoylated and glycosylated at OH-3 and OH-6 with a dimannoside to give the 3,6-branched pentamannoside. Coupling of the two pentasaccharides furnished the target decasaccharide in 60% yield. Deprotection of the base labile functions furnished a hybrid-type N-glycan decasaccharide functionalized for the conjugation with peptides or proteins.     

Synthesis and properties of BF2- & PO2-complexes of mono meso-heterocycle substituted 25-oxasmaragdyrins and derivatives

BF₂- and PO₂-smaragdyrins containing one five membered heterocycle such as pyrrole, thiophene and furan at one of the meso-position of corresponding 25-oxasmaragdyrins were synthesized by treating the appropriate mono meso-heterocycle substituted 25-oxasmaragdyrin with BF₃.OEt₂ and POCl₃ respectively in CH₂Cl₂ under mild reaction conditions. All macrocycles were thoroughly characterized by HR-MS and 1D and 2D NMR spectroscopy. The presence of a five membered heterocycle in place of a six membered aryl group significantly alters the electronic properties of the smaragdyrin macrocycle as reflected in their spectral and electrochemical properties. The meso-pyrrole BF₂-smaragdyrin was subjected to a Vilsmeier-Haack reaction to prepare meso-(α-formyl pyrrolyl) BF₂-smaragdyrin which was subsequently used to prepare meso-(α-dipyrromethanyl pyrrolyl) BF₂-smaragdyrin. The further use of meso-heterocycle substituted BF₂- and PO₂-oxasmaragdyrins was demonstrated by treating meso-pyrrolyl BF₂-smaragdyrin with pentafluorobenzaldehyde in CHCl₃ under mild acid catalysed conditions to afford an unusual dipyrromethanyl bridged BF₂-smaragdyrin dyad which exhibits excellent photophysical properties.     

Formate dehydrogenase–viologen-immobilized electrode for CO2 conversion,for development of an artificial photosynthesis system

Formate dehydrogenase (FDH)–viologen with a long alkyl chain (CH₃V(CH₂) _n COOH) immobilized on an indium–tin oxide (ITO) electrode, with the function of reduction of CO₂ to formic acid, was investigated as an artificial photosynthesis device based on CO₂ reduction. The amount of formic acid produced by use of FDH–CH₃V(CH₂) _n COOH immobilized on ITO in CO₂-saturated buffer solution, on application of a potential, as a result of one-electron reduction of viologen, depends on the carbon chain length of CH₃V(CH₂) _n COOH. When a CH₃V(CH₂)₉COOH–FDH/ITO electrode was used, production of formic acid was estimated to be 23 μmol after 3 h.     

High-Resolution Proton Magnetic Resonance Analysis of Polypropylenes

The dyad and triad tacticities of polypropylenes were determined quantitatively with the aid of a computer form the 100-MHz proton magnetic resonance spectra in o-dichlorobenzene solution at 165[ddot]C. The contents of tactic dyad and traid evaluated from the 100-MHz PMR spectra are in fair agreement with the values determined from the 220-MHz PMR and ¹³C-(¹H) spectra, respectively. The fraction soluble in boiling ethyl ether of polymer prepared with the Ti(O-n-Bu)Cl₃-AlEt₂ Cl catalyst shows a character of stereorandomness, and the ethyl ether-soluble portion of polymer polymerized with the TiCl₃-AlEt₂ Cl catalyst has a character of stereoblock sequence. Furthermore, by IR analysis, it has become apparent that the former has a (CH₂)₂ group formed by two propylene units in a tail-to-tail arrangement.     

Cyanoalkyl complexes of transition metals . : II. Preparation and properties of some platinum complexes containing phosphorus as a donor atom

cis-PtCl(CH₂CN)(PPh₃)₂ was obtained by the reaction of Pt(PPh₃)₄ with ClCH₂CN in acetone. A solution of Pt(PPh₃)₄ and ClCH₂CN in benzene was heated under reflux to give trans-PtCl(CH₂CN)(PPh₃)₂. The reaction of the trans-isomer with Br^?, I^?, Ph₂PCH₂CH₂ PPh₂, Ph₂PCH₂CH₂AsPh₂ and cisPh₂PCHCHPPh₂ has been examined. The trans-influence of a ligand trans to the CH₂CN group seems to be indicated by the ²J(PtH) of the CH₂CN protons. The τ values of trans-PtX(CH₂CN)(PPh₃)₂ and PtX(CH₂ CN)(PP) (X = Cl, Br, I) are related by a linear function.     

The chemistry of the transition metalcarbon σ-bond. Insertion reactions between stannous chloride and h1-allyl and h1-propargyl complexes of h5-cyclopentadienyldicarbonyliron

The reactions between h⁵-CpFe(CO)₂R (R = CH₂CHCH₂; CH₂CMe=CH₂; CH₂CHCHMe; CH₂CHCMe₂) and stannous chloride in tetrahydrofuran afford the insertion products h⁵-CpFe(CO)₂SnCl₂R. When treated with stannous chloride in methanol or with excess stannous chloride in tetrahydrofuran, h⁵-CpFe(CO)₂CH₂CMeCH₂ affords primarily h⁵-CpFe(CO)₂SnCl₃. The allenyl, 2-butynyl or cationic isobutylene complexes (R = CHCCH₂; CH₂ CCMe; CH₂CMe⁺₂) yield only h⁵-CpFe(CO)₂SnCl₃. Stannous iodide reacts with h⁵-CpFe(CO)₂CH₂CHCH₂ in benzene to form h⁵-CpFe(CO)₂I. Plumbous chloride in methanol fails to react with the above complexes.     

Synthesis and characterization of cationic silsesquioxane hybrids by hydrolytic condensation of triethoxysilane derived from 2-(dimethylamino)ethyl acrylate

A new family of silsesquioxane hybrids was synthesized by hydrolytic condensation of a triethoxysilane precursor, R-Si(OCH₂CH₃)₃, R = -CH₂CH₂CH₂N[CH₂CH₂COOCH₂CH₂N(CH₃)₂]₂, derived from 2-(dimethylamino)ethyl acrylate. Condensation of the triethoxysilane precursor proceeded as a homogeneous system in methanol in the presence of aqueous HF solution (3.2?%) to afford the water-soluble silsesquioxane hybrid having a high density of chemically bonded peripheral tertiary amino groups on the outermost surface, as confirmed by nuclear magnetic resonance and Fourier transform infrared analyses. The relatively low polydispersity (M _w/M _n ?=?1.33) and a reasonable molecular weight (M _n ?=?2700), corresponding to species having 6–12 silicon atoms, were confirmed by size exclusion chromatography. The size of the silsesquioxane hybrid (1.7?nm) was also determined by X-ray diffraction. Co-condensation of tetraethoxysilane (TEOS) with the triethoxysilane precursor was carried out under different feed ratios, and water-soluble products were obtained in the cases of TEOS molar ratio up to 40?%. Quaternization reaction of the tertiary amine-containing hybrids with methyl iodide led to cationic silsesquioxane hybrids containing quaternized amine functionalities, which showed good solubility in polar solvents. Scanning force microscopy measurements indicated the formation of the cationic silsesquioxane hybrids having relatively narrow size distribution with average particle diameter (about 2.0?nm) without aggregation.     

Aqueous ring opening of N-tosylaziridine with aniline derivatives

A series of N-(p-X-phenyl)-N′-(p-toluenesulfonyl)1,2-ethylenediamines compounds, TsN(H)CH₂CH₂N(H)PhX, were synthesized by the uncatalyzed ring opening reaction of N-tosylaziridine with p-X-aniline derivatives in pure water at 50 °C. No solvolysis product was observed and the only side product was that of a subsequent ring opening reactions of N-tosylaziridine with the product anilines leading to substituted diethylenetriamines, XPhN(CH₂CH₂NTs)₂.     

On the structure of lithium 2-(1-pyrrolidyl)ethoxide with benzyllithium

The structure of benzyllithium complexed with lithium 2–(1–pyrrolidyl)ethoxide was investigated by X-ray crystallographic analyses to afford (C₄H₈N–CH₂CH₂OLi)₆·(C₆H₅CH₂Li)₂ structure of a doubly capped hexagonal prism with C_i symmetry of heavily distorted structure. The crystal structure of C₄H₈N–CH₂CH₂OLi was also examined to give the distorted hexagonal prism of hexamer with S₆ symmetry.     

Effect of solvation on the dynamics of H + CH3 association

The gas phase association of CH₃ with the HAr₂ cluster to form a vibrationally/rotationally excited CH ₄ ^* molecule is used as a model to study microscopic solvation dynamics. A potential energy surface for the reactive system is constructed from a previously fitted H + CH₃ ab initio potential and 12-6 Lennard-Jones Ar-Ar, Ar-C, and Ar-H potentials. Classical trajectory calculations performed with the chemical dynamics computer program VENUS are used to investigate the CH₃ + HAr₂ → CH ₄ ^* + Ar₂ reaction dynamics. Reaction is dominated by a mechanism in which the CH₃ “strips” the H-atom from HAr₂ during large impact parameter collisions. For a large initial relative translational energy the CH₃ + HAr₂ → CH ₄ ^* + Ar₂ cross section is the same as that for H + CH₃ association, so that HAr₂ acts like a “heavy” H-atom. However, at a low initial relative translational energy, the long-range Ar₂—CH₃ attractive potential apparently makes the CH₃ + HAr₂ association cross section larger than that for H + CH₃. Partitioning of energy to the CH ₄ ^* and Ar₂ products is consistent with a stripping mechanism. The initial and final relative translational energies are nearly identical and the CH ₄ ^* rotational energy is controlled by the initial CH₃ rotational energy. The velocity and orbital tilt scattering angles, θ(v _i ,v _f ) and θ(l _i ,l _f ), respectively, are consistent with the stripping mechanism. On average only a small amount of the product energy is partitioned to Ar₂ vibration/rotation and CH ₄ ^* + Ar₂ relative translation.     

Novel perfluoroalkylated oligo(oxyethylene) methyl ethers with high hemocompatibility and excellent co-emulsifying properties for potential biomedical uses

Two series of novel perfluoroalkylated amphiphilic compounds were synthesized from monomethyl ethers of mono-, di- and tri-(oxyethylene) glycols. The first series CH₃(OCH₂CH₂)_nOCH₂CH(OH)CH₂-CF₂(CF₂CF₂)_nCF₃ (n = 1-3) bearing the hydroxy group at the spacer between hydrophilic and hydrophobic parts was prepared by the reactions of the monomethyl ethers with 2-(perfluoroalkylmethyl)oxiranes in 76-97% yields. The second series CH₃(OCH₂CH₂)_nOCH₂CH₂CH₂-CF₂(CF₂CF₂)_nCF₃ (n = 1-3) possessing the non-hydroxylated spacer was synthesized from allyl methyl ethers of oligo(oxyethylene) glycols using radical additions of perfluoroalkyl iodides and subsequent selective reductions of the C-I bond in the adducts in overall yields of 23-69%. Some of the novel amphiphilic compounds displayed very low hemolytic activity to erythrocytes and excellent co-emulsifying properties on testing on perfluorodecalin/Pluronic F-68 microemulsions. 1-O-(2-Hydroxy-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononyl)-d-xylitol was prepared by a novelized synthesis and employed as a standard compound in the testing.     

Self-assembly of the light-harvesting complex of photosystem II (LHCII) on alkanethiol-modified gold electrodes

A light-harvesting complex of photosystem II (LHCII), isolated from spinach, was immobilized onto a gold electrode modified with self-assembled monolayers (SAMs) of alkanethiols, NH₂–(CH₂) _n –SH, n = 2, 6, 8, 11; HOOC–(CH₂)₇–SH; and CH₃–(CH₂)₇–SH; and a bare electrode. The extent of LHCII complex adsorption according to surface treatment decreased in the order amino groups > carboxylic acid groups > methyl groups and increased with the methylene chain length in NH₂–(CH₂) _n –SH. Interestingly, the photocurrent density depended on the terminal group and the methylene chain length in NH₂–(CH₂) _n –SH and decreased in the order amino groups > methyl groups > carboxylic acid groups. An efficient photocurrent response of the LHCII complex on SAMs of NH₂–(CH₂) _n –SH, n = 8 was observed upon illumination at 680 nm. These results indicated that the LHCII complexes were well organized on the cationic surfaces of the gold electrodes modified with amino alkanethiols. The quantum yield depended on the methylene chain length (n), where the maximum photocurrent response was observed at n = 8, which corresponded to a distance of 1.7 nm between the terminal amino group in NH₂–(CH₂)₈–SH and the gold surface.     

Oxidative addition capability of triphosphine iron and ruthenium complexes with methyl iodide

The ruthenium and iron dicarbonyl complexes Ru(MeP(CH₂CH₂PMe₂)₂)(CO)₂ (1), Ru(MeP(CH₂CH₂CH₂PMe₂)₂)(CO)₂ (2) and Fe(MeP(CH₂CH₂CH₂PMe₂)₂)(CO)₂ (3) bearing strong donor tridentate phosphine ligands were prepared and fully characterised. The structures of the complexes have been established by X-ray diffraction studies. Oxidative addition of MeI to 1-3 proceeds instantaneously at room temperature and affords the corresponding octahedral cationic complexes fac,cis-[RuMe(MeP(CH₂CH₂PMe₂)₂)(CO)₂]I (5a) and mer,cis-[RuMe(MeP(CH₂CH₂PMe₂)₂)(CO)₂]I (5b), mer,trans-[MMe(MeP(CH₂CH₂CH₂PMe₂)₂)(CO)₂]I (6a (M=Ru); 7a (M=Fe)) and mer,cis-[MMe(MeP(CH₂CH₂CH₂PMe₂)₂)(CO)₂]I (6b (M=Ru); 7b (M=Fe)), respectively. The triphosphine preferentially adopts a facial arrangement in the case of the ethylene bridged tridentate ligand (5a) and a meridional arrangement in the case of the trimethylene bridged ligand (6a-7b). mer,cis-[RuMe(MeP(CH₂CH₂CH₂PMe₂)₂)(CO)₂]I (6a) undergoes CO insertion to the acetyl complex mer, trans-[Ru(COMe)(MeP(CH₂CH₂CH₂PMe₂)₂)(CO)₂]I (8). Attempts to produce a ketene complex from the deprotonation of 8 were not successful. The acetyl protons in 8 show very low acidity and no reaction occurred when the complex was reacted with bases such as DBU, BEMP (2-tert-Butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorine) or LDA.     

An examination of the product-catalyzed reaction of trimethylgallium with arsine

The reaction of (CH₃)₃Ga with AsH₃ at 203°C and 259°C has been examined over the product surfaces which were (CH₃)₃- GaAsH₃-x where the average values of x were 1.1 and 2.2 203°C and 259°C respectively. The surface reaction (catalyzed by the product surface) forming (CH₃)₂GaAsH₂ occurred on the surface between adsorbed molecules of (CH₃)₃Ga and ASH₃. The surface coverages of the reactants (gas pressures between 18 and 36 mmHg) were clearly less than monomolecular and for AsH₃ possibly as low as 0.01. For AsH₃ at a surface coverage of 0.12, adsorption data were consistent with AsH ₃ bound to the surface as a mobile film. The formation of GaAs via CH₄ elimination from (CH₃)₂GaAsH₂ or CH₃GaAsH was hindered by deposition of films of (CH₃)₃-x GaAsH₃-x even at 420°C. This was most significant for formation of GaAs (or even CH₃GaAsH) from (CH₃)₂-GaAsH₂ formed at 203°C and then heated at 420°C. The product surfaces also served as a catalyst for decomposition of AsH₃ to form H₂ and decomposition of (CH₃)₃Ga to form CH₄.     

Ethene elimination from CH3CH2NH=CH 2 + : Reaction pathways at the boundary between stepwise and concerted processes

The elimination of ethene from CH₃CH₂NH=CH ₂ ⁺ is characterized by ab initio procedures. This reaction occurs through several asynchronous stages, but without passing through formal intermediates. A potential energy barrier to hydrogen migration from the β carbon to N is largely determined by the energy required to cleave the CN bond, but is lowered slightly by H transfer from the β to the α carbon and then to N. The complex [C₂H ₅ ⁺ NH=CH₂] is bypassed, even though that complex could exist at energies only slightly above that of the transition state for ethene elimination. Furthermore, conversion of a substantial reverse activation energy into energy of motion causes CH₂=NH ₂ ⁺ and CH₂=CH₂ to dissociate faster than they can form [CH₂=NH ₂ ⁺ CH₂=CH₂]. Comparison of results for CH₃CH₂NH=CH ₂ ⁺ to ab initio ones for methane from CH₃CH₂CH ₃ ⁺ and elimination of ethene from CH₃CH₂O=CH ₂ ⁺ and CH₃CH₂CH=OH⁺ reveals that these dissociations occur in a similar but, in each case, a distinct series of asynchronous steps or stages, and that there is no sharp demarcation between concerted and stepwise eliminations as presently defined. In dissociations of CH₃CH₂NH=CH ₂ ⁺ , loss of electron density at the C in the breaking N bond leads the transfer of electron density to that carbon by migration of a hydrogen from the adjacent C. We attribute this to a requirement for the moving H to be close to Cα before the moving H can start to develop covalent bonding to Cα. It is also concluded that elimination of ethene from CH₃CH₂NH=CH ₂ ⁺ avoids a Woodward-Hoffmann symmetry-imposed barrier by H migrating sufficiently from the β to the α carbon on the way to N, so that the dissociation is essentially a 1,1 rather than a 1,2 elimination.     

Vibrational energy disposal in reactions of fluorine atoms with hydrides of groups III,IV and V

The HF infrared chemiluminescence from the reactions of F atoms with B₂H₆, CH₄, CH₃F, CH₂F₂, CH₂Cl₂, CH₃ONO. CH₃NO₂, NH₃ (and ND₃). PH₃ and HNCO has been observed from a 300 K flowing-afterglow reactor. Experiments were done for a range of CH₄ and F atom concentrations to identify conditions which were free of vibrational relaxation and secondary reactions, and these conditions were used to assign initial HF(v) vibrational distributions for each reaction. The emission intensity from each reaction also was compared to that from CH₄ in order to obtain the relative HF formation rate constants at 300 K. Since the absolute rate constant for F + CH₄ is well established, the combination of all of these data provides absolute rate constants for HF(v) formation at 300 K. The ND₃ reaction was studied to obtain information on more vibrational levels in order to better estimate the HF(v = 0) and DF(v = 0) components of the ammonia distributions. With NH₃ and ND₃ there is no significant isotope effect on the energy disposal. Except for NHCO, for which an addition-elimination channel is possible, the HF(v) distributions are inverted and <f_v > = 0.60. Differences between the HF(v) distributions reported here and some other reports in the literature are noted: the present data are discussed as representative of direct H atom abstraction for 300 K Boltzmann conditions. The HCl infrared chemiluminescence from the F + CHCl₂ secondary reaction also was observed; the HCl(v) distribution was v₁: v₂: v₃: v₄: v₅ - 0.47: 0.23: 0.18: 0.08: 0.04.     

The structure of the charge transfer complex in olefin quenching of benzophenone phosphorescence

The phosphorescence lifetimes of ω-alkenyl esters of p-benzophenone-carboxylic acid have been measured in dilute solution in degassed acetic acid solution. The lifetimes were extrapolated to infinite dilution. Intramolecular quenching was not very significant in benzophenone-4-CO₂(CH₂)_nCHCH₂ for n = 1, 2 or 4. For n = 9 the phosphorescence lifetime was found to be 2 μs compared to 70 μs for n = 1, 2. These results are interpreted to mean that the quenching complex has a specific geometric requirement with the CHCH₂ group approaching within a van der Waals distance of the ketone carbonyl group.     

Trimethylsilyl-substituted diazoalkanes : I. Trimethylsilyldiazomethane

Trimethylsilyldiazomethane was prepared by the action of aqueous KOH on nitroso-N-(trimethylsilylmethyl)urea. The spectroscopic properties of this stable, greenish-yellow liquid which can be isolated by gas chromatography are discussed. Its reaction with acetic acid gives the expected CH₃CO₂CH₂SiMe₃ in addition to SiC cleavage products, CH₃CO₂CH₃ and CH₃CO₂SiMe₃. Products of the 1,3-dipolar addition of Me₃SiCHN₂ to activated olefins were not very stable, and only the adduct with acrylonitrile was isolated as a pure material Trimethylsilyldiazomethane undergoes Me₃SiCH transfer to olefins, giving trimethylsilyl-substituted cyclopropanes, in the presence of CuCI in benzene, but other products are formed as well. Thus such a reaction with cyciohexenegave anti-7-trimethylsilylnorcarane (65%), syn-7-trimethylsilylnorcarane (7%), cis- and trans-l,2-bis(trimethylsilyl)ethylene (9% and 13%, respectively), and an unidentified Me₃SiCH trimer (2.3%).     

1,5-Migrations of silicon between oxygen centers in silyl β-diketones

A series of acyclic silyl diketonates, (CH₃)₃Si(dik), where dik = dipivaloyl-methanate, diisobutyrylmethanate and hexafluoroacetylacetonate, along with a new series of cyclic acetylacetonates of the type CH₃(-CH₂(CH₂)_xCH₂-)Si(acac), where x = 1, 2, and 3, have been shown to possess enol ether structures in which the acyl group is positioned cis or trans to the silyl group. The ratios of cis to trans configurations in the (CH₃)₃Si(dik) series increase from <0.02 to >50.0 in the order of diketonate substituents CF₃ < CH₃ <i-C₃H₇ < t-C₄H₉. The ratios for the CH₃(-CH₂(CH₂)xCH₂-)Si(acac) compounds increases in the order χ = 1 > 2 > 3. These data are interpreted in terms of incipient pentacoordination of silicon by the carbonyl oxygen atom in the cis isomer. Rates of 1,5-migration of silicon between oxygen centers in the cis isomers have been determined by NMR spectroscopy. The dependence of the rearrangement rates on diketonate substituent and angle strain at silicon indicate that the migration process is better viewed as an internal nucleophilic displacement, rather than a sigmatropic shift. 1,5-Migration in the chiral (C₆H₅CH₂)(CH₃)(C₆H₅)Si derivative of dipivaloylmethanate occurs exclusively with retention of configuration at silicon. The large difference in activation energy for migration and inversion (>18 kcal/mol) precludes the possibility of distinguishing between a stepwise and concerted displacement mechanism.