Stability, thermal homolysis and intermediate phases of solid hydroazafullerene C59HN

Density functional (DFT) calculations, high-temperature electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM) results suggest that thermal homolysis of C59HN involves a remarkably stable intermediate C59N-C59HN* structure characterised by charge redistribution from a C59N* radical to a bonded C59HN.     

自由基C59N及双体(C59N)2的理论研究

用INDO系列方法对自由基C59N及双体(C59N)2进行了理论研究,结果表明: N的掺入使C60笼发生畸变, N向笼外突出, 碳氮6-6键上的C自旋密度较大, 两C59N自由基在这个碳上以C-C单键连接形成双体为C2h, C2v对称性。其中C2v构型更稳定, 且N与附近的三个碳均以单键连接。理论计算的电子光谱与实验吻合较好。(C59N)2易分解为单体C59N。     

Synthesis and characterization of HN(SPiPr2)(SePPh2) and [Te[N(SPiPr2)(SePPh2)]2

The compound HN(SP(i)Pr(2))(SePPh(2)) has been synthesized from the reaction of Ph(2)P(Se)NH(2) with (i)()Pr(2)P(S)Cl in the presence of NaH in THF. HN(SP(i)Pr(2))(SePPh(2)) crystallizes with eight formula units in space group Pbca of the orthorhombic system in a cell of dimensions at -120 degrees C of a = 9.9560(6) A, b = 17.9053(10) A, c = 22.4156(13) A, and V = 3995.9(4) A(3). The square-planar Te(II) complex [Te[N(SP(i)Pr(2))(SePPh(2))](2)] has been isolated from the reaction of Te(tu)(4)Cl(2) x 2H(2)O (tu = thiourea) with the anion [N(SP(i)Pr(2))(SePPh(2))](-), generated in situ from HN(SP(i)Pr(2))(SePPh(2)) in the presence of KO(t)Bu. [Te[N(SP(i)Pr(2))(SePPh(2))](2)] is dimorphic, crystallizing with one formula unit in space group P1 of the triclinic system in a cell of dimensions at -120 degrees C of a = 9.8476(9) A, b = 10.3296(9) A, c = 11.3429(10) A, alpha = 101.903(1) degrees, beta = 115.471(1) degrees, gamma = 92.281(2) degrees, and V = 1008.4(2) A(3) and also crystallizing with two formula units in space group P2(1)/n of the monoclinic system in a cell of dimensions at -120 degrees C of a = 8.7931(5) A, b = 17.1830(10) A, c = 14,1026(9) A, beta = 104.696(1) degrees, and V = 2061.1(2) A(3). In each instance, the [Te[N(SP(i)Pr(2))(SePPh(2))](2)] molecule possesses a center of symmetry, comprising a Te center liganded in a trans manner by two bidentate N(SP(i)Pr(2))(SePPh(2)) groups. However, the (31)P, (77)Se, and (125)Te NMR spectra of [Te[N(SP(i)Pr(2))(SePPh(2))](2)] show two sets of resonances at 25 degrees C. The (31)P VT NMR spectra show two sets of resonances between -50 and +50 degrees C that coalesce between 80 and 100 degrees C, consistent with the presence of the cis as well as the trans isomer in solution.     

ChemInform Abstract: Crystal Structure of Azafullerene (C59N)2.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Resonant processes and Coulomb interactions in (C59N)2

We have determined the on-site molecular Coulomb interaction energy U of a (C59N)2 bulk film and find values ranging from 1.10+/-0.10 eV for the highest occupied molecular orbital to 1.35+/-0.10 eV for the deeper lying orbitals, comparable to values found in C60. The on-site Coulomb interaction between a carbon core hole and valence electrons, Uc, is, however, substantially lower than in C60 at 1.35+/-0.07 eV. Resonant photoemission (RESPES) results show a weakened participator decay channel, especially around the N 1s threshold, where resonance of the highest occupied molecular orbital shoulder is absent. Near-edge x-ray absorption fine structure and constant initial state measurements, taken in parallel with the RESPES data, indicate, however, that matrix element effects cannot be ruled out.     

Synthesis,molecular and electronic structure of [ReCl2(N2COPh)(C4N2H4)(PPh3)2]

A new organodiazenido rhenium complex, [ReCl₂(N₂COPh)(C₄N₂H₄)(PPh₃)₂] has been obtained from the direct reaction of [ReCl₂(η²–N₂COPh–N′,O)(PPh₃)₂] with pyrazine in acetone. The complex has been characterized by spectroscopic methods and its structure determined using single-crystal X-ray diffraction techniques.     

From fullerene-mixed peroxide to open-cage oxafulleroid C(59)(O)(3)(OH)(2)(OO(t)()Bu)(2) embedded with furan and lactone motifs

[reaction: see text] Removal of one carbon atom from the C60 cage is achieved under mild conditions. The process involves the formation of fullerene-mixed peroxide, subsequent Lewis acid induced cleavage of O-O and C-O bonds, and thermolysis at 75 degrees C. In the proposed mechanism, the carbon atom is deleted as CO and an oxygen atom occupies the vacancy to form a furan ring. Single-crystal X-ray analysis confirmed the results.     

The syntheses,crystal, molecular and electronic structures of two polymorphs of [ReCl2(N2COPh)(C3N2H4)(PPh3)2] and [ReCl2(N2COPh)(py)(PPh3)2] complexes

The [ReCl₂(η²-N₂COPh–N^′,O)(PPh₃)₂] complex reacts with pyridine and pyrazole to give [ReCl₂(N₂COPh)(py)(PPh₃)₂] and [ReCl₂(N₂COPh)(C₃N₂H₄)(PPh₃)₂], respectively. Two monoclinic polymers of [ReCl₂(N₂COPh)(C₃N₂H₄)(PPh₃)₂] and [ReCl₂(N₂COPh)(py)(PPh₃)₂] have been characterized by IR, UV–Vis, ¹H NMR, magnetic measurements and X-ray structure.     

Synthesis,spectroscopic investigation,crystal and molecular structure of [ReCl2(N2COPh)(C10H14N2)(PPh3)2]

[ReCl₂(N₂COPh)(C₁₀H₁₄N₂)(PPh₃)₂] has been obtained in the reaction of benzoylhydrazido-Re(V) with an excess of nicotine. The [ReCl₂(N₂COPh)(C₁₀H₁₄N₂)(PPh₃)₂] complex crystallizes in the monoclinic space group P2₁/n. The complex was characterized by infrared, Ultaviolet-visible, ¹H NMR and magnetic measurements.     

Direct detection of singlet oxygen sensitized by nalidixic acid: the effect of pH and melanin

Abstract— Singlet oxygen yields are reported for the antibiotic nalidixic acid in D₂O at pH values above and below its pK., in water. The φ_Δincreases on lowering the pH. The effect of eumelanin on the φ_Δ values is shown to be substantial at pH 4.4, but virtually zero above the pK_n value. Human serum albumin seems to have little effect on the singlet oxygen yield at high pH in the presence of melanin. The results are correlated with the experimental and clinical observations relating to the photosensitizing activity of the drug.     

Study of singlet oxygen equilibrium in dioctadecyldimethylammonium chloride vesicles employing 2-(n-(N,N,N-trimethylamine)-n-alkyl)-5-alkylfuryl halides

Steady state photolysis and time resolved near infrared luminescence detection were employed to study the reaction kinetics of singlet oxygen with three different lipid-soluble probes incorporated in large unilamellar dioctadecyldimethylammonium chloride (DODAC) vesicles. The probes: 2-(4-(N,N,N-trimethylamine)-butyl)-5-dodecylfuryl bromide (DFTA), 2-(12-(N,N,N-trimethylamine)-dodecyl)-5-hexylfuryl bromide (HFDA) and 2-(1-(N,N,N-trimethylamine)-methyl)-5-methylfuryl iodide (MFMA) are useful in studying both singlet oxygen dynamics and its equilibrium in microcompartmentalized systems because they are actinometers in lipidic microphases. These probes contain a reactive furan ring, which will be located at different depths in the bilayer of DODAC vesicles. In the limit of the approximations, the result indicates an inhomogeneous equilibrium distribution of singlet oxygen across the bilayer. The calculated mean partitioning constant of singlet oxygen equals 2.8 and 8.3 at 20 degrees C and 40 degrees C, respectively, in the order of the previously reported constants for other microorganized systems such as sodium dodecylsulfate and cetyltrimethylammonium halide micelles and water/oil microemulsions.     

Photochemical reduction of oxygen adsorbed to nanocrystalline TiO(2) films: a transient absorption and oxygen scavenging study of different TiO(2) preparations

Transient absorption spectroscopy (TAS) has been used to study the interfacial electron-transfer reaction between photogenerated electrons in nanocrystalline titanium dioxide (TiO(2)) films and molecular oxygen. TiO(2) films from three different starting materials (TiO(2) anatase colloidal paste and commercial anatase/rutile powders Degussa TiO(2) P25 and VP TiO(2) P90) have been investigated in the presence of ethanol as a hole scavenger. Separate investigations on the photocatalytic oxygen consumption by the films have also been performed with an oxygen membrane polarographic detector. Results show that a correlation exists between the electron dynamics of oxygen consumption observed by TAS and the rate of oxygen consumption through the photocatalytic process. The highest activity and the fastest oxygen reduction dynamics were observed with films fabricated from anatase TiO(2) colloidal paste. The use of TAS as a tool for the prediction of the photocatalytic activities of the materials is discussed. TAS studies indicate that the rate of reduction of molecular oxygen is limited by interfacial electron-transfer kinetics rather than by the electron trapping/detrapping dynamics within the TiO(2) particles.     

Sensitized photo-redox reaction: VII. The Synthesis,FAB mass spectrum,stationary absorption,emission, transient absorption spectra,redox potential of dihydroxy-tin (IV)-mesoporphyrin dimethyl ester and its sensitized photo-reduction of methyl viologen

In DMSO/water (4:1), photolysis of the dihydroxy-Sn (IV)-mesoporphyrin dimethyl ester (SnP)/methyl viologen (MV²⁺)/ethylene diamine tetraacetic acid (EDTA) ternary system produces methyl viologen cation radical with a quantum yield of 0.67, much higher than that of systems with other metal complexes of mesoporphyrin dimethyl ester. Neither EDTA nor MV²⁺ quenches the stationary fluorescence of SnP, implying that the reaction does not take place at the singlet state. With flash photolysis we obtain the T-T absorption spectrum of SnP (λ_max 440 nm). By following the decay of this absorption, the triplet life time of SnP is estimated to be 41 μs. The life time is related to the concentration of either MV²⁺ or EDTA. Good linear relationships are obtained by plotting τ₀τ vs. the concentration of MV²⁺ or EDTA (Stern-Volmer plot), from which we determine the quenching constants: _kq(MV²⁺) =5.5 × 10⁷ mol^?1, s^?1; k_q (EDTA) =2.7 × 10⁷ mol^?1, s^?1. The data suggests that upon photolysis of the above ternary system, both oxidative quenching and reductive quenching of the triplet state of the sensitizer are occurring. From the measured phosphorescence spectrum (λ_max 704 nm) and the ground state redox, potentials (E^red_1/2?-0.84V, E^ox_1/2?+1.43 V, vs. Ag/AgCl, KCl (sat.)), we obtain the redox potential of triplet SnP to be E(P⁺/P*_T)?-0.33 V, E(P*_T+/P^?)?+0.92 V. Matching this data with the redox potential of MV²⁺ and EDTA, we establish the fact that during the photolysis of the SnP/MV²⁺/EDTA ternary system, both oxidative and reductive quenching are thermodynamically favorable processes. This is also the reason why the SnP sensitized reaction is much more efficient relative to other mesoporphyrin derivatives.