Axial Azide Research Articles

Effect of carrier and axial ligand on the photocatalytic activity of cobalt thioporphyrazine

The photocatalytic activity of cobalt octakis(butylthio) porphyrazine (CoPz(BuS)8) was assessed through photodegradation of the dye rhodamine B (RhB) in water under irradiation with a Xe lamp and aerated conditions. The photocatalytic activity of CoPz(BuS)8 loaded on Al2O3 or SiO2@Fe3O4 nanoparticles or coordinated with an axial azide ligand was also investigated. The results demonstrated that the photocatalytic activity of CoPz(BuS)8 loaded on Al2O3 was higher than that loaded on SiO2@Fe3O4. The kinetic curves of RhB degradation in aqueous solutions at different pH indicated the pseudo first-order kinetics of the reaction. The highest degradation rate for CoPz(BuS)8 loaded Al2O3 at pH = 4 after 160 min was 84.6%. However, the advantages of easier separation and recycling as well as the ability to terminate the reaction at any time for the CoPz(BuS)8 loaded SiO2@Fe3O4 cannot be ignored. When electron-rich NaN3 was coordinated with CoPz(BuS)8 as an axial ligand and loaded on Al2O3, the resulting catalyst produced more active oxygen species such as O2− and HO• to promote the quicker degradation of RhB than that by the other catalysts. For the N3-coordinated CoPz(BuS)8 loaded on Al2O3, the reactions at pH = 4 and 7 distinctly deviated from first-order kinetics, and the degradation rate reached 77.6% after 80 min at pH = 4.

Stereoselective Synthesis of 5-epi-α-Sialosides Related to the Pseudaminic Acid Glycosides. Reassessment of the Stereoselectivity of the 5-Azido-5-deacetamidosialyl Thioglycosides and Use of Triflate as Nucleophile in the Zbiral Deamination of Sialic Acids.

With a view to the eventual synthesis of glycosyl donors for the stereocontrolled synthesis of pseudaminic acid glycosides, the stereocontrolled synthesis of a d-glycero-d-gulo sialic acid adamantanylthioglycoside carrying an axial azide at the 5-position is described. The synthesis employs levulinic acid as nucleophile in the oxidative deamination of an N-acetylneuraminic acid thioglycoside leading to the formation of a 3-deoxy-d-glycero-d-galacto-2-nonulosonic acid (KDN) derivative selectively protected as 5-O-levulinate. Replacement of the levulinate by triflate enables introduction of the axial azide and hence formation of the glycosyl donor. A shorter synthesis uses trifluoromethanesulfonate as nucleophile in the oxidative deamination step when the 5-O-triflyl KDN derivative is obtained directly. Glycosylation reactions conducted with the 5-azido-d-glycero-d-gulo-configured sialyl adamantanylthioglycoside at -78 °C are selective for the formation of the equatorial glycosides, suggesting that the synthesis of equatorial pseudaminic acid glycosides will be possible as suitable donors become available. A comparable N-acetylneuraminic acid adamantanylthioglycoside carrying an equatorial azide at the 5-position was also found to be selective for equatorial glycoside formation under the same conditions, suggesting that reinvestigation of other azide-protected NeuAc donors is merited. Glycosylation stereoselectivity in the d-glycero-d-gulo series is discussed in terms of the side-chain conformation of the donor.

Ultrafast 2DIR spectroscopy of ferric azide precursors for high-valent iron. Vibrational relaxation, spectral diffusion, and dynamic symmetry breaking

Femtosecond mid-infrared pump-probe and two-dimensional mid-infrared spectroscopy have been used to investigate the dynamics of vibrational relaxation and vibrational spectral diffusion of the asymmetric N3-stretching vibration of pseudo-octahedral azidoiron(III) complexes, [L6-nFe(N3)n](+) with n = 1 or 2 and L being an auxiliary ligand of denticity 6-n, in acetonitrile at room temperature. Compared to the free azide anion in acetonitrile solution, the vibrational relaxation dynamics are considerably accelerated. Vibrational energy transfer to the solvent is accelerated by virtue of a resonance with an overtone transition of the solvent. Intramolecular vibrational redistribution is found to be accelerated by virtue of a coupling between the initial azide stretching vibration and the torsional modes involving the axial ligands. Vibrational spectral diffusion within the asymmetric N3-stretching resonance was found to be insensitive to solvent fluctuations because the axial azide ligands are only partially accessible to the solvent. The particular role of intramolecular structural relaxations of the complex for shaping the linear and nonlinear two-dimensional infrared spectra is discussed in terms of ultrafast symmetry-breaking torsional fluctuations and on the basis of density functional theory calculations.

Facile Preparation of Mono‐, Di‐ and Mixed‐Carboxylato Platinum(IV) Complexes for Versatile Anticancer Prodrug Design

Facile strategies were developed for the versatile functionalization of platinum(IV) axial sites, allowing for easy accessibility to unsymmetric mono- and mixed-carboxylato, as well as symmetric di-substituted platinum(IV) complexes. The first method involves the direct oxidation and carboxylation of the platinum(II) center using an appropriate peroxide and the carboxylate of choice to firstly yield a monocarboxylato monohydroxido platinum(IV) complex. This platinum(IV) intermediate can undergo further carboxylation to give rise to a mixed-carboxylato platinum(IV) complex. The second method involves the activation of the carboxylate of choice by a common carbodiimide coupling reagent, and its reaction with a dihydroxido platinum(IV) precursor to give the monocarboxylato platinum(IV) complex. Uronium salts can be employed to promote efficient dicarboxylation of the dihydroxido platinum(IV) precursor. Lastly, an axial azide pendant group was demonstrated to be suitable for orthogonal "click" conjugation reactions.

Di-μ-azido-bis(μ-1,4,7,10,13,16-hexaoxacyclooctadecane)bis(5,10,15,20-tetraphenylporphyrinato)dicadmiumdisodium

The asymmetric unit of the title compound, [Cd2Na2(N3)2(C44H28N4)2(C12H24O6)2], consists of one half of the dimeric complex; the tetra­nuclear mol­ecule lies about an inversion centre. The CdII atom is coordinated by the four pyrrole N atoms of the 5,10,15,20-tetra­phenyl­porphyrinate ligand and one N atom of the axial azide ligand in a square-pyramidal geometry. The azide group is also linked to the NaI atom, which is surrounded by one 18-crown-6 molecule and additionally bonded to a second 18-crown-6 molecule trans to the azide group. The porphyrin core exhibits a major doming distortion (∼40%) and the crystal structure is stabilized by weak C—H⋯π inter­actions. The mol­ecular structure features weak intra­molecular hydrogen bonds: two O—H⋯O inter­actions within the 18-crown-6 mol­ecule and one C—H(18-crown-6)⋯N(azido) contact.

Spinosyn G: Proof of Structure by Semisynthesis

[reaction: see text] Spinosyn G was isolated in the late 1980s as a minor component from the broth of our potent, fermentation-derived insecticide spinosad. Its structure was then tentatively identified as 5' '-epispinosyn A (3) on the basis of (1)H and (13)C NMR data, but the 4' '-epi compound 4 could not be conclusively ruled out with the data available. Described herein are unambiguous syntheses of both 3 and 4, whereby 3 was proved identical to the natural product. Compound 4 was prepared from intact spinosyn A by a novel F-TEDA-promoted oxidative deamination to the 4' '-ketone 5, stereoselective reduction to the equatorial alcohol 6, and nitrogen incorporation via the axial azide 7. Compound 3 was obtained by coupling spinosyn A 17-pseudoaglycone (9) with the N-protected dihydropyran 16 derived from methyl l-ossaminide (14). This gave an approximately 2:1 mixture of anomeric products 17 with the desired equatorial glycoside predominating, which was then converted to 3 by N-deprotection and methylation.

Unusual ferromagnetic couplings in single end-to-end azide-bridged cobalt(II) and nickel(II) chain systems.

Two new one-dimensional single azide-bridged metal(II) compounds [[M(5-methylpyrazole)4(N3)]n](ClO4)n(H2O)n [M = Co (1a), Ni (2a)] were prepared by treating an M(II) ion with stoichiometric amount of sodium azide in the presence of four equivalents of the 3(5)-methylpyrazole ligand. The isostructural compounds 1a and 2a crystallize in the monoclinic space group P2(1)/n. The azide bridging ligands have a unique end-to-end coordination mode that brings two neighboring metal centers into a cis-position with respect to the azide unit to form single end-to-end azide-bridged cobalt(II) and nickel(II) chains. The two neighboring metal atoms at inversion centers adopt octahedral environments with four equatorial 3(5)-methylpyrazole ligands and two axial azide bridges. Two adjacent equatorial least-squares planes form dihedral angles of 60.5 degrees and 60.6 degrees for Co and Ni, respectively. In addition, the metal-azide-metal units form large M-N3-M torsion angles, which are magnetically important geometrical parameters, of 71.6 degrees for M=Co and 75.7 degrees for M=Ni. It should also be noted that the M-N-N angles associated with end-to-end azide group, another magnetically important structural parameter, fall into the experimentally observed range of 120-140 degrees as 128.3(3) and 147.8(3) degrees for cobalt species and 128.4(2) and 146.1(3) degrees for nickel species; these values deviate from the theoretical value of around 164 degrees at which the incidental orthogonality is achieved under the torsion angle of 0 degrees. The compounds 1a and 2a have unique magnetic properties of ferromagnetism, zero-field splitting, and spin canting. The MO calculations indicate that the quasiorthogonality between the magnetic orbitals of metal ions and the p atomic orbitals of the bridging azide is possible in the observed structures and leads to the ferromagnetism. The spin canting related to the perturbation of ferromagnetism arises from the magnetic anisotropy and antisymmetric interactions judged by the structural parameters of the zero-field splitting and the tilted MN4 planes in a chain. The enhancement of magnetic interactions was accomplished by dehydrating the chain compounds to afford two soft magnets with critical temperature T(C) and coercive field of 2 K and 35 G for 1b and 2.3 K and 20 G for 2b, respectively.

A New Dinuclear Copper (II) Complex of a Bis‐macrocyclic Ligand: Synthesis, Characterization, Crystal Structure and Magnetic Properties

AbstractA new dinuclear Cu(II) complex, [Cu2L(N3)2](ClO4)1.5 (OH)4.5 · 2H2O 0.5C2H5OH (1), of a bis‐macrocyclic ligand, 2,6‐bis(l,4,7,10‐tetraazacyclododecan‐10‐ylmethyl)‐methoxybenzene (L), has been synthesized, characterized and structurally determined by X‐ray diffraction analysis. Complex 1 crystallizes in orthorhombic crystal system, Pca2(l) space group with a = 1.5371(3), b = 1.6641(3), c = 3.0950(6) nm, V = 7.917(3) nm3, Fw = 904.62, Z=8, Dc= 1.529 g/cm3 and final R = 0.0568, wR = 0.1406 for 10410 observed reflections with I≥2σ (I). Both Cu(II) centers in the structure are coordinated by four nitrogen atoms of 1,4,7, 10‐tetraazacyclododecane (cyclen) and a nitrogen donor of the axial azide anion. Each Cu(II) center is in a square‐pyramidal coordination environment, and the intra‐and nearest inter‐molecular CuCu nonbonding distances are 0.9855 and 0.7298 nm, respectively. Variable temperature magnetic susceptibility measurements in the range of 4.2–300 K indicate mat there exists weak intra‐ and inter‐molecular antiferromagnetic coupling between the Cu(II) centers with 27= −4.2 cm−1 and Θ = −0.47 K.

Catalyzed autoxidation of azide by cobalt(II) (2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) 2+

The catalytic autoxidation of azide by Co(tim) 2+ was studied. In the presence of dioxygen Co(tim)(H 2O) 2 2+ (tim=2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) reacts with azide in a complex process to produce Co(tim)(N 3) x (3− x)+ ( x=1 or 2) ( λ max at 340 nm) and dinitrogen. The reaction is clearly catalytic with up to several hundred turnovers. The dioxygen dependence of the reaction implies the involvement of an oxygen adduct, stabilized by an axial azide ligand.

Azide promotion of alkane oxidations catalyzed by metal complexes in solution

The oxidation of light alkanes catalyzed by metal complexes in solution is promoted by Group 1 metal azides. Yields of oxygenated reaction products are greatly enhanced when catalytic amounts of azides are added to the reaction mixture. The addition of sodium azide to oxidations catalyzed by transition metal acetylacetonates, heteropolyacids, polyoxometallates, phthalocyanines, bis-(pyridylimino)isoindolines, porphyrins and Schiff bases significantly enhances rates of low-temperature catalytic oxidation reactions in the liquid phase. Earlier work showed that Cr(III), Mn(III), Fe(III) and Co(III) complexes of electron-deficient macrocyclic complexes exhibited remarkable catalytic activity for oxidizing light alkanes. Such complexes bearing axial azide ligands were far more active than their axial chloride or acelate counterparts.

Effect of axial azide on the selective, low temperature metalloporphyrin-catalysed reactions of isobutane with molecular oxygen

Azido(tetraphenylporphyrinato) complexes of CrIII, MnIII, and FeIII catalyse selective, low temperature hydroxylation of isobutane with molecular oxygen and provide many turnovers in the absence of added co-reductants.

ChemInform Abstract: First Example of Organic Reaction Implying the Axial Ligand in Metalloporphyrin Series. Synthesis, Characterization of 4‐Substituted (Tetrazolato)indium(III) Porphyrin Complexes, and Molecular Structure of (4‐Phenyltetrazolato)‐(2,3,7,8,12,13,17,18‐octaethylporphinato)indium(III).

AbstractThe axial azide ligand in (I) undergoes a classical organic reaction with nitriles to give the complexes (III), which are characterized by MS, electronic, IR, and 1H NMR spectroscopy.

O.R.D. characteristics of azido derivatives of pentoses

O.r.d. curves of some methyl 4-azido-4-deoxypentopyranosides have been measured. Although it is not possible to predict, on the basis of analysis by an azide octant rule, the sign of the Cotton effect exhibited by these derivatives, several empirical observations are noteworthy. Those derivatives in the C1 ( d) conformation and having an axial azide substituent exhibit positive Cotton effects, whereas those having an equatorial azide substituent show negative Cotton effects. Azide derivatives in the 1C ( d) conformation and having an equatorial azide group exhibit a negative Cotton effect, whereas those having an axial azide substituent show a positive Cotton effect. There is a marked dependence of the magnitude of the background rotation on the configuration of the substituent at C-1; an axial, glycosidic, methoxyl group causes a much higher background rotation than does an equatorial substituent.