DFT study on [4+2] and [2+2] cycloadditions to [60] fullerene

The functionalisation of C₆₀ fullerene with 2,3-dimethylene-1,4-dioxane (I) and 2,5-dioxabicyclo [4.2.0]octa-1(8),6-diene (II) was investigated by the use of density functional theory calculations in terms of its energetic, structural, field emission, and electronic properties. The functionalisation of C₆₀ with I was previously reported experimentally. The I and II molecules are preferentially attached to a C—C bond shared and located between two hexagons of C₆₀ via [4+2] and [2+2] cycloadditions bearing reaction energies of ?15.9 kcal mol^?1 and ?72.4 kcal mol^?1, respectively. The HOMO-LUMO energy gap and work function of C₆₀ are significantly reduced following completion of the reactions. The field electron emission current of the C₆₀ surface will increase after functionalisation of either the I or II molecule.     

2-aryl(hetaryl)-4H-[1,2,4]triazolo[1,5-a]benzimidazoles

2-(4-Methylphenyl)-4H-[1,2,4]triazolo[1,5-a]benzimidazole and its previously unknown 2-(2-furyl)- and 2-(2-thienyl)-substituted analogs were synthesized by cyclization of benzimidazole-1,2-diamine with the corresponding carboxylic acid chlorides. The IR, ¹H, ¹³C, and ¹⁵N NMR, and mass spectra of the cyclization products in combination with the results of quantum-chemical calculations of NMR chemical shifts showed radical differences of [1,2,4]triazolo[1,5-a]benzimidazoles having no substituent on N⁴ from the recently reported low-melting products of oxidation of 2-amino-1-arylmethylideneaminobenzimidazoles with (diacetoxy-λ³-iodanyl)benzene, which, as we believe, were erroneously assigned analogous structure.     

[MoFe3S4]3+ and [MoFe3S4]2+ cubane clusters containing a pentamethylcyclopentadienyl molybdenum moiety

A series of organometallic molybdenum/iron/sulfur clusters of the general formula [Cp¹MoFe₃S₄L_n]^m (Cp¹ = η⁵-C₅Me₅; L = S^tBu, SPh, Cl, I, n = 3, m = 1−; L_n = I₂(P^tBu₃), m = 0; L = 2,6-diisopropylphenylisocyanide (ArNC), n = 7, m = 1+) have been synthesized. A cubane cluster (PPh₄)[Cp¹MoFe₃S₄(S^tBu)₃] (2) was isolated from a self-assembly reaction of Cp¹Mo(S^tBu)₃ (1), FeCl₃, LiS^tBu, and S₈ followed by cation exchange with PPh₄Br in CH₃CN, while an analogous cluster (PPh₄)[Cp¹MoFe₃S₄(SPh)₃] (3) was obtained from the Cp¹MoCl₄/FeCl₃/LiSPh/PPh₄Br reaction system or from a ligand substitution reaction of 2 with PhSH. Treatment of 2 with benzoyl chloride gave rise to (PPh₄)[Cp¹MoFe₃S₄Cl₃] (4), which was in turn converted to (PPh₄)[Cp¹MoFe₃S₄I₃] (5) by the reaction with NaI. A neutral cubane cluster Cp¹MoFe₃S₄I₂(P^tBu₃) (6) was generated upon treating 5 with P^tBu₃. Although reduction of 4 by cobaltocene under the presence of ArNC resulted in a disproportionation of the cubane core to give Fe₄S₄(ArNC)₉Cl (7), a similar reduction reaction of 5 produced [Cp¹MoFe₃S₄(ArNC)₇]I (8), where the MoFe₃S₄ core was retained. The crystal structures of 4–6, and 8 were determined by the X-ray analysis.     

[Me4N]2[(WOS3Ag)2]: a novel quasi-one-dimensional compound

Orange–yellow plate-like crystals of a new polymeric complex [Me₄N]₂[(WOS₃Ag)₂] were obtained at room temperature from the reaction of a suspension of [Me₄N]₂[WOS₃] in MeCN with solid AgCN. The new compound is obviously formed by cyanide elimination of primary [WOS₃(AgCN)]²⁻. It is monoclinic space group P2₁/c with unit cell parameters a=20.44(2) Å, b=9.655(6) Å, c=11.913(5) Å, β=99.06(2)°, Z=4. The crystal structure was determined from single crystal diffractometer data (Mo-Kα radiation) and refined to R=0.070 (2979 reflections, 199 variables). The structure is characterized by infinite anionic chains, ${}_{\mathrm{\infty }}{}^{\mathrm{<mspace\; xmlns="true"\; sp="0.3"\; width="2px"\; linebreak="nobreak"\; is="true"></mspace><mtext>1</mtext>}}$[(WOS₃Ag)₂]²⁻. The infrared spectrum of the complex (KBr powder) shows the terminal ν(WO) as strong absorption bands found at 913 and 905 cm⁻¹. The bridging ν(WS) shows bands at 438 (vs) and 434 (sh) cm⁻¹. The anionic mass spectrum shows a peak at m/z 404 for [WOS₃Ag]⁻. In addition, the primary formation of the potential monomeric precursor [WOS₃(AgCN)]²⁻ could be established in the filtrate by mass spectroscopy.     

Intensités des transitions optiques de [PtCl4]2−

The oscillator strengths of the “d-d” transitions of the ion [PtCl₄]^2? were calculated. The method, based on the evaluation of the MO of the distorted ion, gives results in good accordance with the experimental data. The transition to ¹ B _1g (a _1g →b _1g ^* ), as a consequence of the participation of the orbital 6s, mixed with \(5d_{z^2 } \) in \(a_{1_g } ,a_{1_g } \) is characterized by a very low intensity in the case of thex,y polarization.     

Synthesis of calix[4]arene(amido)monocrowns and their photoresponsive derivatives

A series of new calix[4]arene(amido)mono-crown compounds have been synthesized through aminolysis of calix[4]arene esters and intramolecular cyclization of the intermediates. The title compounds were converted into their nitro and azo substituted derivatives to provide novel photoresponsive molecular receptors for transition metal ions. Single crystal X-ray analysis of calix[4]arene(ethyleneamido)mono-crown (2a) revealed that the compound is present in a cone conformation with an amido loop that caps the lower rim of calix[4]arene cavity to result in stacking along axis a and axis c to provide supramolecular aggregates in the solid state. Evaluation of synthesized macrocycles in the solution phase for recognition of transition metal cations (Cr³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺, Hg⁺, Hg²⁺, Pd²⁺, and Pt²⁺) by UV-visible spectroscopy revealed that p-tert-butyl-calix[4]arene mono-(amidocrown) 1c selectively shows a blue shift at 38 nm on interaction with Hg⁺ ions.     

Formation of out of plane oxime metallacycles in [Cu2] and [Cu4] complexes

The reaction of Cu(ClO₄)₂·6H₂O with dimethylglyoxime (H₂dmg) in a 1:1 mole ratio in aqueous methanol at room temperature affords the dinuclear complex [Cu₂(μ-Hdmg)₄] (1). Reaction of 1 with [Cu(bpy)(H₂O)₂](ClO₄)₂ (bpy = 2,2′-bipyridine) in a 1:1 mole ratio in aqueous methanol at room temperature yields the tetranuclear complex [Cu₄(μ-Hdmg)₂(μ-dmg)₂(bpy)₂(H₂O)₂](ClO₄)₂ (2). The direct reaction of Cu(ClO₄)₂·6H₂O with H₂dmg and bpy in a 2:2:1 mole ratio in aqueous methanol at room temperature also yields 2 quantitatively. The complexes 1 and 2 were structurally characterized by X-ray crystallography. Unlike the binding in Ni/Co-dmg, two different types of N?O bridging modes during the oxime based metallacycle formation and stacking of square planar units have been identified in these complexes. The neutral dinuclear complex 1 has CuN₄O coordination spheres and complex 2 consists of a dicationic [Cu₄(μ-Hdmg)₂(μ-dmg)₂(bpy)₂(H₂O)₂]²⁺ unit and two uncoordinated ClO₄^? anions having CuN₄O and CuN₂O₃ coordination spheres. The two copper(II) ions are at a distance of 3.846(8) Å in 1 for the trans out of plane link and at 3.419(10) and 3.684(10) Å in 2 for the trans out of plane and cis in plane arrangements, respectively. The average Cu–N_oxime distances are 1.953 and 1.935 Å, respectively. The average basal and apical Cu?O_oxime distances are 1.945, 2.295 and 2.429 Å. The UV–Vis spectra of 2 is similar to the spectrum of the reaction mixture of 1 and [Cu(bpy)(H₂O)₂]²⁺. Variable temperature magnetic properties measurement shows that the interaction between the paramagnetic copper centers in complex 1 is antiferromagnetic in nature. The EPR spectra of frozen solution of the complexes at 77 K consist of axially symmetric fine-structure transitions (ΔM_S = 1) and half-field signals (ΔM_S = 2) at ca. 1600 G, suggesting the presence of appreciable Cu–Cu interactions.     

[Cu(mim)4]2[α-Mo8O26] – A layer-type octamolybdate framework

By reaction of (NH₄)₆Mo₇O₂₄·4H₂O, Cu(NO₃)₂·2.5H₂O and 1-methylimidazole (mim) under hydrothermal conditions the novel copper molybdate [Cu(mim)₄]₂[α-Mo₈O₂₆] is obtained in the form of blue, rectangular-shaped crystals. The title compound crystallizes with monoclinic lattice symmetry in the space group P2₁/n. The predominant structural feature of the title compound is a two-dimensional framework that is constituted by [α-Mo₈O₂₆]^4?octamolybdate units as framework nods and the copper complex [Cu(mim)₄]²⁺ as a linker. In addition to single-crystal structure analysis [Cu(mim)₄]₂[α-Mo₈O₂₆] is characterized by powder diffraction as well as by FT-IR and UV–vis spectroscopy.     

Synthesis and crystal structures of the dioxovanadium complexes [VO2L1] and [VO2L2]2

Two new oxovanadium complexes, [VO₂L¹] (I) and [VO₂L²]₂ (II), where L¹ and L² are the deprotonated forms of 4-bromo-2-[(2-diethylaminoethylimino)methyl]phenol (HL¹) and 4-bromo-2-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol (HL²), respectively, have been synthesized and characterized by IR spectra and single crystal X-ray diffraction. The crystal of I is monoclinic: space group P2₁/n, a = 14.300(3), b = 7.010(2), c = 15.460(2) ?, ?? = 107.401(2)°, V = 1478.7(5) ?³, Z = 4. The crystal of II is monoclinic: space group P2₁/c, a = 7.270(2), b = 15.373(3), c = 11.893(3) ?, ?? = 99.302(2)°, V = 1311.8(5) ?³, Z = 2. Complex I is a mononuclear dioxovanadium(IV) complex. Complex II is a centrosymmetric dinuclear dioxovanadium(V) complex with a V...V distance of 3.117(2) ?. The Vatom in I is in a distorted square-pyramidal coordination, and that in II is in an octahedral coordination. The difference in the structures of the complexes is largely induced by the hydrogen bonds during the self-assembly process.     

The Binary Group 4 Azides [PPh4]2[Zr(N3)6] and [PPh4]2[Hf(N3)6]

The binary zirconium and hafnium polyazides [PPh₄]₂[M(N₃)₆] (M=Zr, Hf) were obtained in near quantitative yields from the corresponding metal fluorides MF₄ by fluoride–azide exchange reactions with Me₃SiN₃ in the presence of two equivalents of [PPh₄][N₃]. The novel polyazido compounds were characterized by their vibrational spectra and their X‐ray crystal structures. Both anion structures provide experimental evidence for near‐linear M‐N‐N coordination of metal azides. The species [M(N₃)₄], [M(N₃)₅]^? and [M(N₃)₆]^2? (M=Ti, Zr, Hf) were studied by quantum chemical calculations at the electronic structure density functional theory and MP2 levels.     

Synthesis, characterization, solvatochromic behavior and crystal structures of complexes [CoIII(salophen)(thioacetamide)2]ClO4 and [CoIII(salophen)(thiobenzamide)2]ClO4

Two new cobalt(III) complexes of the Schiff base N,N′-disalicylidene-1,2-phenylendiimine dianion (salophen), trans- [Co^III(salophen)(ta)₂]ClO₄, (ta = thioacetamide) (1) and trans-[Co^III(salophen)(tb)₂]ClO₄, (tb = thiobenzamide) (2) were synthesized and characterized using single-crystal X-ray diffraction and spectroscopic techniques. Both complexes show solvatochromism in a variety of solvents. Complex (1) crystallized from CHCl₃ as a solvate of orthorhombic symmetry, space group Pca2₁ with a = 17.3480(10) Å, b = 18.7522(10) Å, c = 18.8128(11) Å, α = β = γ = 90°, and Z = 8. The cobalt(III) center lies in a distorted octahedral environment. The crystal structure of (1) consists of two independent [Co^III(salophen)(ta)₂]⁺ cations and ClO₄ ^- anions held together essentially via hydrogen bonds and π-π stacking interactions. Complex (2), forming also a CHCl₃ solvate, crystallized in the monoclinic space group P2₁/n with a = 14.710(3) Å, b = 13.506(3) Å, c = 18.595(4) Å, β = 100.295(4)°, and Z = 4. The geometry around cobalt(III) center is a distorted octahedron. The crystal structure of (2) contains a [Co^III(salophen)(tb)₂]⁺ complex with a remarkably twisted salophen ligand. Both complexes, (1) and (2), contain approximately one disordered CHCl₃ molecule per Co in the solid state.     

Synthesis and biological activity of fluorinated 2-amino-4-aryl-3,4-dihydro[1,3,5]triazino[1,2-a]benzimidazoles

The heterocyclic nucleus s-triazino[1,2-a]benzimidazole has been reported to exhibit antibacterial activity. In this study, seven new 3,4-dihydro[1,3,5]triazino[1,2-a]benzimidazole derivatives were prepared via cyclocondensation between 2-guanidinobenzimidazole and fluorine substituted (including trifluoromethyl) benzaldehydes. The structures of all the compounds were confirmed by ¹H, ¹³C NMR and IR spectral data. Spectral data also suggested the existence of various tautomeric forms of the fluorine-containing s-triazino[1,2-a]benzimidazole compounds. The synthesized compounds were also screened for antibacterial and bovine dihydrofolate reductase (DHFR) inhibitory activities. The compound 3g substituted with a 3′,5′-bis(trifluoromethyl)phenyl moiety demonstrated the best antibacterial activity in the series. None of the tested compounds significantly inhibited bovine DHFR.     

Selective sensing of Hg2+ by a proton-ionizable calix[4]arene fluoroionophore

A fluorogenic derivative of a calix[4]arene with two proton-ionizable N-(phenyl)sulfonyl carboxamide-containing side arms in the 1,3-positions on the lower rim is employed for the selective sensing of Hg²⁺ at low concentration levels in water/MeCN (1:1, v/v) solutions containing Pb²⁺ and Cd²⁺. All three metal ions quench the fluorescence of the ligand in pure MeCN. However, in water/MeCN mixed solvent, the recognition of such cations occurs differently as only Hg²⁺ complexation quenches the fluorescence of the calixarene. Experiments carried out in the presence of an acid and a bulky non-complexing cation shows that the quenching of the calixarene fluorescence upon Hg²⁺ addition is likely due to proton displacement from the proton-ionizable side arms of the ligand. The system may be employed as a simple tool for the selective and efficient mercury sensing in mixed water/organic solvent.     

1-aza-1,3-enynes in synthesis of substituted 4H-[1,3]thiazino[3,2-a]benzimidazol-4-ols

Reaction of N-tert-butyl-1-aza-1,3-enynes with symmetrically substituted 2-mercaptobenzimidazoles in water-alcohol solutions afford 4H-[1,3]thiazino[3,2-a]benzimidazol-4-ols. The structure of compounds obtained was proved by the ¹H and ¹³C NMR spectroscopy and X-ray diffraction data.     

Synthesis and crystal structures of Cd[AlCl4]2 and Cd2[AlCl4]2

Colorless single crystals of Cd[AlCl₄]₂ grow from the melt of CdCl₂ and AlCl₃ upon slow cooling from 250°C. The crystal structure [monoclinic, P1a1, Z = 2, a = 1288.7(2), b = 660.2(1), c = 705.1(1) pm, β = 92.89(1)º] may be derived from hexagonally closest packed layers of Cl^?. Octahedral and tetrahedral holes are filled with Cd²⁺ and Al³⁺ in a 1:2 ratio between all layers stacked in the [104] direction. Cd[GaCl₄]₂ and Cd[AlBr₄]₂ are isotypic. Reduction of Cd[AlCl₄]₂ with excess cadmium shot and slow cooling from 350°C yields plate-like very moisture-sensitive, colorless single crystals of Cd₂[AlCl₄]₂. The crystal structure [triclinic, C1 , Z = 2, a = 655.47(3), b = 1135.26(1), c = 935.23(6) pm, α = 89.70(2)º, β = 103.61(1)º, γ = 90.455(1)º] is built from slabs stacked in the [100] direction consisting of ethane-like [Cd₂Cl₆] units with a Cd? Cd distance of 256.1 pm sharing common vertices with [AlCl₄] tetrahedra.     

The experimental and DFT studies of 1,3-dimethyl-2-[4-chloro-styryl]-benzimidazolium iodide

1,3-Dimethyl-2-[4-chloro-styryl]-benzimidazolium iodide (1) was synthesized and characterized by X-ray diffraction, ¹H NMR, MS, IR, UV–vis spectra and elemental analysis. The crystals are monoclinic, space group P2₁/c, with a = 12.507(3) Å, b = 7.3259(19) Å, c = 36.705(9) Å, V = 3358.9(15) Å³, and Z = 4 (at 296(2) K). Crystal stacking scheme indicates the face-to-face π?π aromatic stacking interactions. Molecular geometries, frequencies, IR, ¹H NMR and UV–vis were calculated at DFT/TD-DFT level using two hybrid exchange–correlation functionals, B3LYP and PBE1PBE. The stability of the molecule arising from hyperconjugative interaction and charge delocalization had been analyzed using natural bond orbital (NBO) analysis. These calculations on (1) provide deep insight into its electronic structure and properties.     

On Tetrachlorophosphonium Chlorometallates of Rhenium and Molybdenum: Syntheses,Crystal Structures,and Magnetism of [PCl4]2[Re2Cl10] and [PCl4]3[ReCl6]2, and the Magnetic Properties of [PCl4]2[Mo2Cl10]

MoCl₄, ReCl₄, and ReCl₅ react with PCl₅ in sealed glass ampoules at temperatures between 220° and 320° to [PCl₄]₂[Mo₂Cl₁₀] ( 1 ) [PCl₄]₂[Re₂Cl₁₀] ( 2 ), and [PCl₄]₃[ReCl₆]₂ ( 3 ). 2 crystallizes isotypically to the previously reported 1 and the respective titanium and tin containing analogues. The structure (triclinic, P1, Z = 1, a = 897.3(2), b = 946.0(2), c = 687.13(9) pm, α = 95.59(2)°, β = 95.80(2)°, γ = 101.07(2)°, V = 565.4(2) 10⁶ pm³) is built of tetrahedral [PCl₄]⁺ and edge sharing double octahedral [Re₂Cl₁₀]^2– ions and can be derived from a hexagonal closest packing of Cl^– ions with tetrahedral and octahedral holes partially filled by P(V) and Re(IV), respectively. 3 crystallizes isotypically to [PCl₄]₃[PCl₆][MCl₆] (M = Ti, Sn) (tetragonal, P 4₂/mbc, Z = 4, a = 1496.2(1), c = 1363.2(2) pm). Because no evidence was found for the presence of [PCl₆]^– ions, Re in 3 has to be of mixed valency with Re^IV and Re^V sharing the same crystallographic site. The structure can be derived from a cubic closest packing or alternatively from an only sparsely distorted body centered cubic arrangement of Cl^– ions which is rarely found for anion arrays. The tetrahedral and octahedral holes are partially filled by P^V and M^IV/V, respectively. Magnetic measurements show all three compounds to be paramagnetic and confirm the oxidation state IV for Mo and Re in 1 and 2 and the mixed valence (IV/V) for Re in 3 .     

The study of radiolytic stability of 25,27-bis(2-propyloxy)calix[4]-26,28-crown-6(iPr-C[4]C-6)

The radiolytic stability of 25,27-bis(2-propyloxy)calix[4]-26,28-crown-6(iPr-C[4]C-6) was studied. The radiation source was ⁶⁰Co and its dose rate was 437?Gy/min and the total absorbed dose was from 10⁴ to 10⁶?Gy. The iPr-C[4]C-6 solid and 0.025?mol/L iPr-C[4]C-6/n-octanol which were pre-equilibrated with 0.01 and 3?mol/L nitric acid, respectively, were absorbed different dose and their extraction performance were researched. The degradation mechanism of them was investigated by mass spectrometry and infrared spectrum. The results show that radiolytic stability of the iPr-C[4]C-6 solid and 0.025?mol/L iPr-C[4]C-6/n-octanol are good when their absorbed dose was less than 10⁶?Gy. The extracting system of iPr-C[4]C-6/n-octanol is promising for separating cesium from high level liquid waste.     

Electrochemical behavior of [UO_2Cl_4]~(2-) in 1-ethyl-3-methylimidazolium based ionic liquids

In order to examine the chemical form of uranyl species in 1-ethyl-3-methylimidazolium(EMI) based ionic liquids,UV-visible absorption spectra of solutions prepared by dissolving [EMI] 2 [UO2Cl4] into a mixture of EMICl and EMIBF 4(50:50 mol%) were measured.As a result,it was confirmed that uranyl species in the mixture of EMICl and EMIBF 4 existed as [UO2Cl4]2-.Cyclic voltammograms(CVs) of [UO2Cl4]2-in the mixture were measured at 25 ℃ using a Pt working electrode,a Pt wire counter electrode,and an Ag/Ag + reference electrode(0.01 M AgNO 3,0.1 M tetrabutylammonium perchlorate in acetonitrile) in a glove box under an Ar atmosphere.Peaks corresponding to one redox couple were observed around-1.05 V(Epc) and-0.92 V(Epa) vs.ferrocene/ferrocenium ion(Fc/Fc +).The potential differences between two peaks(Ep) increased from 101 to 152 mV with an increase in the scan rate from 50 to 300 mV s-1,while the(Epc+Epa)/2 value was constant,-0.989 V vs.Fc/Fc + regardless of the scan rate.Furthermore,the diffusion coefficient of [UO2Cl4]2-and the standard rate constant were estimated to be 3.7 × 10-8 cm 2 s-1 and(2.7-2.8) × 10-4 cm s-1 at 25 oC.By using the diffusion coefficient and the standard rate constant,the simulation of CVs was performed based on the reaction,[UO2Cl4]2-+ e = [UO2Cl4]3-.The simulated CVs were found to be consistent with the experimental ones.From these results,it is concluded that [UO2Cl4]2-in the mixture of EMICl and EMIBF 4 is reduced to [UO2Cl4]3-quasi-reversibly at-0.989 V vs.Fc/Fc +.     

Anion receptors based on ureido-thiacalix[4]arenes

The regioselective ipso-nitration of tert-butylthiacalix[4]arene-tetrasulfone was used for the construction of thiacalixarene derivatives bearing one or two arylureido functions on the upper rim. The preorganization of ureido units using the thiacalix[4]arene moiety as a molecular scaffold leads to novel anion receptors with good complexation ability toward selected anions of various geometry (halides, carboxylates, HSO₄⁻, H₂PO₄⁻, NO₃⁻, CN⁻) in organic solvents.