Regioselective intramolecular bridging of p-tert-butylcalix[7]arene

The first examples of singly bridged calix[7]arenes 2–4 have been obtained by base-promoted direct O-alkylation of p-tert-butylcalix[7]arene with a variety of bis-electrophiles including BrCH₂Cl, oligoethylene glycol ditosylates, and 1,4-bis(bromomethyl)benzene. 1,2-Bridging was favored with ‘short bite’ spanning elements, while the 1,4-isomer predominated with the others (yields up to 72% in the presence of Cs₂CO₃). Assignment of bridging pattern was mainly based on chemical shift of OH groups, in some cases confirmed by 2D NMR experiments. A hampered conformational mobility, depending on the position and nature of the bridge, was observed for compounds 2–4.     

The effect of p-tert-butylcalix[n]arene on γ-radiation degradation of polypropylene

The γ-radiation effect of polypropylene was investigated in the presence of three kinds of p-tert-butylcalix[n]arene (n=4, 6, 8) in air at ambient temperature. The influence of radiation dose and store time upon the mechanical properties of the irradiated PP sheets were measured. The results showed that the radiation stabilization was reduced with the increase of the ring size of calixarenes. Based on the mass spectra and the analysis of post-irradiated product, the mechanism of radiation degradation of p-tert-butylcalix[4]arene has been proposed.     

Electrochemistry and spectroelectrochemistry of tert-butylcalix[4]arene bridged bis double-decker lutetium(III) phthalocyanine, Lu2Pc4 and dimeric lutetium(III) phthalocyanine, Lu2Pc2(OAc)2

In this study, electrochemical, electrochromic and spectroelectrochemical properties of a tert-butylcalix[4]arene bridged bis double-decker lutetium(III) phthalocyanine (Lu₂Pc₄ 2) were investigated explicitly as compared with a tert-butylcalix[4]arene bridged dimeric lutetium(III) phthalocyanine [Lu₂Pc₂(OAc)₂ 1]. Distinctive differences between electrochemical and electrochromic properties of 1 and 2 were detected. Moreover, the properties of 1 and 2 were compared with previously reported S₄(CH₂)₄ bridged Lu₂Pc₂(OAc)₂ and Lu₂Pc₄. The calixarene bridged phthalocyanine (Pc) compounds, 1 and 2 showed well-defined electrochromic behaviour with green-blue and blue-purple colour transitions. The enhanced electrochromic properties of 2, as compared to 1, were attributed to its double-decker structure, probably allowing the formation of suitable ion channels for the counter ion movement in the solid film.     

Synthesis and structure of a novel molybdenum imido calix[6]arene

Treatment of p-tert-butylcalix[6]areneH₆ (H₆L) with [Mo(OBu^t)₂{[2,2′-(N)-C₆H₄]₂(CH₂CH₂)}] in refluxing toluene affords, after work-up, the complex [Mo(2-NC₆H₄CH₂CH₂C₆H₄NHC(Me)NH-2^/)LH₂]·4MeCN (1), which contains an 11-membered metallocyclic ring as characterised by Synchrotron X-radiation.     

A study of ortho- and para-siloxyanilines for the synthesis of mono-, bi-, and tetra-nuclear early transition metal–imido complexes

The siloxyanilines o-Me₃SiOC₆H₄NH₂ (1) and p-RMe₂SiOC₆H₄NH₂ (R=H (2); R=Me (3)), and their N-silylated derivatives p-Me₃SiOC₆H₄NHSiMe₃ (4) and p-Me₃SiOC₆H₄N(SiMe₃)₂ (5) have been prepared from ortho- or para-aminophenol and used in the synthesis of imido complexes. Thus, binuclear [{Ti(η⁵-C₅H₅)Cl}{μ-NC₆H₄(p-OSiMe₃)}]₂ (6) and mononuclear [TiCl₂{NC₆H₄(p-OSiMe₃)}(py)₃] (7) imido complexes have been obtained from the reaction of 3 and [Ti(η⁵-C₅H₅)Cl₃] or [TiCl₂(N^tBu)(py)₃], respectively. In contrast, the reaction of 1 with TiCl₄ and ^tBupy affords the titanocycle [TiCl₂{OC₆H₄(o-NH)---N,O}(^tBupy)₂] (8). Compound 5 has also been used to prepare the niobium imide complex [NbCl₃{NC₆H₄(p-OSiMe₃)}(MeCN)₂] (9), by its reaction with NbCl₅ in CH₃CN. These findings have been applied to the synthesis of polynuclear systems. Thus, chlorocarbosilane Si[CH₂CH₂CH₂Si(Me)₂Cl]₄ (CS–Cl) has been functionalized with the ortho- and para-aminophenoxy groups to give 10 and 11, respectively. The use of 11 has allowed the formation of the tetranuclear compound 12. Attempts to synthesize terminal imido titanium complexes from 10 and TiCl₄ in the presence of ^tBupy and Et₃N, give complex 8 and carbosilane CS–Cl.     

Syntheses and structural characterization of trivalent lanthanide complexes of p-sulfonatothiacalix[4]arene

The X-ray crystallographic studies are reported for the water-soluble trivalent lanthanide complexes of the macrocyclic p-sulfonatothiacalix[4]arene [Gd(H₂O)₆((CH₃)₂SO)(p-sulfonatothiacalix[4]arene)]·H₃O⁺·5H₂O (1) and Na[Nd(H₂O)₆((CH₃)₂SO)(p-sulfonatothiacalix[4]arene)]·3H₂O (2). The complexes are isostructural and belong to monoclinic system, C2/m space group. The Ln³⁺ metal ion is coordinated by the thiacalixarene ligand via the sulfonato group, and also ligated by an oxygen atom of a dimethyl sulfoxide (DMSO) molecule that occupies the cavity of the thiacalixarene and six aqua ligands. The thiacalixarenes are linked by the coordinated water molecules through hydrogen bonding to form a 2D polymer. The p-sulfonatothiacalixarenes maintain the clay-like bi-layer structure in the coordination network.     

Unprecedented cyclisations of calix[4]arenes under the Mitsunobu protocol. Part 3: Thiacalix[4]crowns versus dimers

Intermolecular couplings versus intramolecular ring closures were observed in the reaction of p-tert-butylthiacalix[4]arene and diethylene glycols affording dimers 2 and/or the inherently chiral 1,2-thiacalix[4]crown-3 derivatives 5 under the Mitsunobu protocol. The enantiomeric separation of 5a was achieved by chiral HPLC. The reaction of thiacalix[4]monocrowns 1 with diethylene glycols failed to give crowned thiacalix-tubes 7, instead biscrowns 8 were formed. Partially alkylated double thiacalix[4]arenes 10, 11 were obtained via the base promoted alkylations of a thiacalixarene dimer 2a containing diethyleneoxy linkers.     

Photodecomposition of several compounds commonly used as sunscreen agents

The photolysis reactions of three compounds commonly used as a sunscreen agents, Parsol 1789 (1-[4-(1,1-dimethylethyl)phenyl]-3-(4-methoxyphenyl)-1,3- propanedione), Oxybenzone ((2-hydroxy-4-methoxyphenyl)phenyl-methanone) and Padimate O (2-ethylhexyl-4-(dimethylamino)benzoate), were investigated to provide a chemical background to aid in the understanding of the photosensitization of the sunscreen agents. Photolysis was carried out in cyclohexane for 70–140 h using a mercury vapor lamp (450W) without excluding oxygen.

Irradation of Parsol 1789 in cyclohexane yielded tert-butylbenzene, p-tert-butylbenzoic acid and p-methoxybenzoic acid; products obtained from the combination of the sunscreen with the solvent included the cyclohexyl esters of p-methoxybenzoic acid, p-tert-butylbenzoic acid and methanoic acid; products obtained from the solvent included cyclohexanol, cyclohexanone and dicyclohexyl ether.

Irradiation of Oxybenzone in the cyclohexane for 100 h produced no detectable products by either gas or liquid chromatographic analysis. Oxybenzone was recovered unchanged and no products were observed from the photoinitiated reaction of oxygen with the solvent.

Irradiation of Padimate O in cyclohexane yielded the ethylhexyl esters of p-aminobenzoic acid, p-monomethylaminobenzoic acid and p-dimethylamino (o/m)-methylbenzoic acid, as well as products from the photoinitiated reaction of oxygen with the solvent.     

Tert-butylbenzamidate diruthenium(II, III) compounds. Crystal structure of [Ru2(μ-HNOCC6H4-p-CMe3)4(OPPh3)2]BF4

The reaction between Ru₂Cl(μ-O₂CCH₃)₄ and molten p-tert-butylbenzamide led to the formation of Ru₂Cl(μ-HNOCC₆H₄-p-CMe₃)₄. The polymeric structure of this insoluble compound was broken with AgBF₄, in anhydrous thf, giving [Ru₂(μ-HNOCC₆ H₄-p-CMe₃)₄(thf)₂]BF₄. The reaction of this cationic complex with OPPh₃ gave [Ru₂(μ-HNOCC₆H₄-p-CMe₃)₄(OPPh₃)₂]BF₄. The compounds have been characterized by elemental analysis, spectroscopic data and magnetic measurements and the crystal structure of [Ru₂(μ-HNOCC₆H₄-p-CMe₃)₄(OPPh₃)₂]BF₄ was determined by X-ray crystallography. The asymmetric unit is composed of halves of two different crystallographically independent centrosymmetric cations. Each ruthenium(II,III) dimer is bonded to four bridging p-tert-butylbenzamidate ligands and to two axial triphenylphosphine oxide molecules. The Ru---Ru distances in the two dimeric cations of the unit cell are 2.281(2) and 2.280(2) Å. The compound has a non-polar 2 : 2 arrangement of the tert-butylbenzamidate ligands.     

Synthesis and coordination of 2-diphenylphosphinopicolinamide

The synthesis and coordination of 2-diphenylphosphinopicolinamide (dpppa 1) is reported. Coordination complexes with Pd, Pt, Ru, Rh, Ir and Au are described. The ligand behaves as a monodentate P donor in complexes such as [PtCl₂(dpppa-P₂)], [PdCl(allyl)(dpppa-P)], [RuCl₂(p-Cymene)(dpppa-P)], cis-[PtCl₂(dpppa-P)(PR₃)] and [AuCl(dpppa-P)]. Bidentate P, O coordination was accomplished by reaction of BuLi with [RuCl₂(p-Cymene)(dpppa-P)], to give [RuCl(p-Cymene)(dpppa-P,O). P,N donor behaviour was achieved by reaction of a monodentate complex with a halide abstractor [AgBF₄] generating [RuCl(p-Cymene)(dpppa-P,N)][ClO₄] and[RhCl(η⁵-C₅Me₅)(dpppa-P,N)][BF₄]. The X-ray structures of dpppa, dpppaO, dpppaS, four monodentate complexes and [RuCl(p-Cymene)(dpppa-P,O) are reported. All of the structures contain intramolecular N–HN hydrogen bonding.     

Influence of the modification of the ligands on hex-1-ene hydroformylation catalyzed by [HRh{P(OPh)3}4] and [HRh(CO){P(OPh)3}3]. Catalytic activity of the sytem [HRh}P(OPh)3}4]+Cp2Zr(CH2PPh2)2

A study has been carried out of the catalytic activity of the systems formed by [HRh{P(OPh)₃}₄] or [HRh(CO){P(OPh)₃}₃] with the modifying ligands P(OPh)₃, PPh₃, diphos and Cp₂Zr(CH₂PPh₂)₂ in hydroformylation of hex-1-ene (at p = 5 bar). The best results were obtained with the system [HRh{P(OPh)₃}₄]+Cp₂Zr(CH₂PPh₂)₂ (75–85% yeild of aldehydes).     

Mercury(II) halide adducts of an olefinic double betaine: [{Hg2L2X4·6HgX2}n] [X = Cl, Br; L = cis-(p-Me2NC5H4N)2C2(COO)2]

Two polymeric mercury(II) halide adducts of an olefinic double betaine, cis-(p-Me₂NC₅H₄N⁺)₂C₂(COO⁻)₂ (L), have been prepared and characterized by X-ray crystallography. [{Hg₂L₂Cl₄·6HgCl₂}_n] (1) crystallizes in the monoclinic space group C2/c with Z = 4, and [{Hg₂L₂Br₄·HgBr₂}_n] (2) in the triclinic space group P with Z = 1. Complexes 1 and 2 are structurally similar, being composed of centrosymmetric fourteen-membered rings and nearly linear HgX₂ (X = Cl, Br) moieties that are further inter-linked by weak HgX [HgCl = 2.930–3.136(9) Å, HgBr = 3.057–3.310(6) Å] and HgO [2.64, 2.75(3) Å] bonds to generate a two-dimensional polymeric network.     

Reactivity of niobocene dihalogenides toward nitroso derivatives. EPR and IR characterization of the first niobium(IV) complexes containing an ArNO-N,O ligand

The reaction of [Nb(η⁵-C₅H₄R)₂X₂] [1: R = SiMe₃, X = Cl; 2: R = SiMe₃, X = Br; 3: R = H, X = Cl; 4: R =^t, X = Cl] with nitroso derivatives ArNO [a: Ar = Ph; b: Ar = o-CH₃-C₃H₄; c: Ar = p-(CH₃)₂NC₆H₄] yields paramagnetic complexes formulated as [Nb(η⁵-C₅H₄R)(η³-C₅H₄R)X₂(ArNO-N,O) 1a, 1b, 1c, 2a, 3a, 4a and 4c, which have been characterized by ESR and IR spectroscopy.     

Complexes of ytterbium(III) nitrate and triflate with homoazacalix[n]arenes (n=3, 4)

The synthesis and crystal structures of three ytterbium(III) complexes of homoazacalixarenes are reported. In all cases, the complexes are obtained without addition of a base, the protons of the complexing phenolic moieties being transferred to the amine groups upon complexation. The 1:1 complex between p-chloro-N-benzylhexahomotriazacalix[3]arene (1) and Yb(NO₃)₃ is analogous to the neodymium(III) complex reported previously, with the metal ion bound to three phenoxide groups and three nitrate ions. A second 1:1 complex is obtained with Yb(NO₃)₃ and p-methyl-N-benzyltetrahomodiazacalix[4]arene (2), in which the metal ion is bound to two phenoxide groups only. The replacement of nitrate by triflate counter-ions results in the formation of a 1:2 ‘sandwich’ complex with 1, in which two divergent calixarene molecules are bridged by the metal ion, the counter-ions being non-bonding.     

[C2B10]---[B12] double cage boron compounds—a new approach to the synthesis of water-soluble boron-rich compounds for BNCT

A new approach in the synthesis of water-soluble boron-rich compounds was proposed. The closo-dodecaborate cage is used as a hydrophilic substitutent providing for the water-solubility of the molecule whereas the carborane cage can be used for attachment to biomolecules using earlier developed methods. The double-cage molecules [o-, m-, and p-CB₁₀H₁₀C(CH₂)₄OB₁₂H₁₁]²⁻ were prepared by the reaction of the tetramethylene oxonium derivative of the closo-dodecaborate anion, [B₁₂H₁₁O(CH₂)₄]⁻, with the corresponding lithiated carboranes. The compounds obtained have doubled the boron contents and could serve for the synthesis of agents for boron neutron capture therapy (BNCT).     

The synthesis of novel polysiloxanes with pendant hand-basket type calix[6]crowns and their transporting properties for metal ions in a liquid membrane

Two novel polysiloxanes with pendant hand-basket type calix[6]-1,3-crown-3 and calix[6]-1,4-crown-4 were prepared by hydrosilylation of p-tert-butylcalix[6]-(2′-allyloxymethyl)-1,3-crown-3 (CA[6]C3) and p-tert-butylcalix[6]-[2′-(ω″-undecenyloxymethyl)]-1,4-crown-4 (CA[6]C4) followed by condensation reaction with silanol-terminated polydimethylsiloxane. The monomeric calix[6]crowns and two calix[6]crown-based polysiloxanes were used as carriers in a bulk membrane. All carriers showed the transport rate of the cations decreased in the order Li⁺ < Na⁺ < K⁺. The flux of K⁺ for the monomeric calix[6]crown was higher than that for polymeric carrier. In comparison with other carriers, the transport rate of calix[6]crown-4-functionalized polysiloxanes (CA[6]C4PS) towards cesium ions were increased greatly. Competitive transport experiments known to be more useful in industrial fields also revealed to give high cesium transfer rate.     

High-performance liquid chromatography of sulfonamides and quinolones on p-tert-butyl-calix[6]arene-bonded silica gel stationary phase

The high-performance liquid chromatographic behavior of some sulfonamides and quinolones was studied on a p-tert-butyl-calix[6]arene-bonded silica gel stationary phase. The effect of mobile phase variables such as methanol content, ionic strength and pH on their chromatographic behavior was investigated. The retention behavior of sulfonamides on the stationary phase was compared with that on both Zorbax C₁₈-bonded silica gel and γ-(ethylenediamino)propyltriethoxylsilane-bonded silica gel (diamino-bonded phase). The retention mechanism of sulfonamides and quinolones on the stationary phase was also discussed. The results indicate that the stationary phase behaves as a reversed-phase packing and its separation selectivity is much better than that of not only Zorbax C₁₈ phase but also diamino-bonded phase. Some sulfonamides and quinolones were separated on the stationary phase, but the separation of sulfonamides is far more successful.     

A thermochemical investigation of guest-host interactions in labile Werner clathrates of the [Ni(4-EtPy)4(NCS)2]·G type (G = Methyl derivatives of benzene)

The stoichiometry of thermal decomposition has been studied for (I): [Ni(4-EtPy)₄(NCS)₂] as a host complex as well as for its clathrates [Ni(4-EtPy)₄(NCS)₂]·G where guest molecule G - toluene, (II): T, (III): o-xylene (o-X) and (IV): p-xylene (p-X). The loss of volatile components proceeds in three steps (−2L, −1L, −1L) for I and in four steps (−G, −2L, −1L, −1L) for II, III and IV. DSC and X-ray powder measurements indicated a phase transition in all compounds under study. However, this process is overlapped by the escape of G in II and III. The differences in enthalpy changes are associated with different guest-host interactions in the particular clathrates.     

A piezoelectric quartz crystal sensor array self assembled calixarene bilayers for detection of volatile organic amine in gas

P-tert-butylcalix[n]arenes (n=4, 6, 8, abbreviated as CA[4], CA[6], CA[8], respectively) were immobilized on the Au surface of the piezoelectric quartz crystal by the reaction between CA[n] and the acid chloride terminated mercaptoacetic acid (MAA) self assembled monolayers to form MAA/CA[n] bilayers. The sensing films were not only immobilized easily and reproducibly, but also used to improve the reversibility of the sensor signal. The response characteristics show the response of CA to organic amine attributes to specific interaction between CA[n] (host) and organic amines (guest). The frequency shifts of n-butylamine and iso-butylamine are much larger than tert-butylamine and diethylamine because of shape-selection and hydrogen bonding. Compared to CA[6] and CA[4], CA[8] has highest sensitivity to organic amine due to having more flexibility to accommodate guest molecules. A sensor array with three-layer back-propagation neural network was applied to detect the binary mixture of n-butylamine in the range of 7.14–142 μl l⁻¹ and iso-butylamine in the range of 7.14–57 μl l⁻¹. The optimum values of learning rate (0.15) and momentum term (0.8) were determined by experiment. The best epoch of training was 1098. The root mean square error of prediction was 1.69 (μl l⁻¹) for n-butylamine, and 1.42 (μl l⁻¹) for iso-butylamine.     

硫代多联吡啶铂(Ⅱ)配合物的合成、性质及在光催化制氢中的应用

合成了2个新配体4-(4-硫代乙酸)甲苯基-6-苯基-2,2'-联吡啶HC^N^N(PhCH₂SCOCH₃)(L3)和6-(4-硫代乙酸)甲苯基-2,2'-联吡啶 HC^N^N (CH₂SCOCH₃)(L5)及其发光的铂(Ⅱ)配合物ClPtC^N^N(PhCH₂SCOCH₃)(C3)和ClPtC^N^N(CH₂SCOCH₃)(C5). 通过¹H NMR谱和质谱对它们的结构进行了表征, 采用X射线单晶衍射分析确定了C3的晶体结构. 利用紫外-可见吸收光谱、 发射光谱及激发态寿命测定研究了它们的光物理性质和电化学性质, 以及配合物作为光敏剂在光催化制氢中的应用. 通过系列配合物产氢效率的比较, 揭示了它们的产氢效率和激发态寿命的关系.