Indolocarbazole-based foldamers capable of binding halides in water

A series of indolocarbazole-based foldamers have been prepared which can fold into a helical array with an internal cavity encircled by multiple indole NHs, thus allowing for binding anions by hydrogen bonds. The helical folding has been confirmed by computer modeling, 1H NMR spectroscopy, 2D ROESY experiments, and binding studies. A water-soluble derivative binds small, hydrophilic anions in the order Cl- > F- > Br- but negligibly with large, diffuse anions such as I- and ClO4-. Interestingly, the relative binding affinities of the fluoride and chloride ions in water are opposite to each other in an organic medium 4:1 (v/v) DMSO/MeOH, possibly due to the difference in the competing solvation energy.     

Liquid crystalline properties of dissymmetric molecules IV. The substituent effect on thermal properties of nematic and smectic A phases in three aromatic ring systems with ester linkages

This paper describes the effect of substituent and ester linkage on smectic properties for some derivatives of 4-R -phenyl 4-(4-octyloxybenzoyloxy)benzoates (1 ), 4-octyloxyphenyl 4-(4-R-benzyloxy)benzoates (2), 4-(4-octyloxybenzoyloxy)phenyl 4- R -benzoates (3), and 4-R-phenyl 4-octyloxyphenyl terephthalates (4) where R = OCH₃, CH₃, OC₈H₁₇, C8H17, halogens, CF₃, OCF₃, CN, NO2, etc. The thermal properties are discussed in terms of the electrostatic nature of the substituents and the relative orientation of the ester groups with respect to both terminal substituents. The substituent effect on the layer structure of the smectic A phase is also examined by means of a small angle X-ray analysis.     

Halide-guided oligo(aryl-triazole-amide)s foldamers: receptors for multiple halide ions

We synthesized and characterized a series of oligo(phenyl-amide-triazole)s that can fold into a helical conformation guided by halide ions. Their binding models and affinities are highly dependent on the length of the foldamer, media and the inducing capability of halide ions. The short foldamer with one helical turn shows a 1:1 binding stoichiometry to all halides, while the longer foldamer with two or three helical turns in principle can form 1:2 complexes with chloride anions even bromide anions with an enhancement on binding affinities. A result of quantitative NOE calculations imply that the longer foldamer should increase its helical pitch so as to release the electrostatic repulsion between halide ions.     

Aggregation and counter ion binding ability of sulfonatomethylcalix[4]resorcinarenes in aqueous solutions

¹H NMR spectroscopy, ¹H NMR spin-lattice relaxation, conductivity and pH-metric titration data have been used to study the aggregation and counter-ion binding of tetrasulfonatomethylcalix[4]resorcinarenes with methyl (H₈XNa₄) and amyl (H₈YNa₄) substituents. The data obtained reveal the self-aggregation of H₈YNa₄ driven by hydrophobic interactions. The NMR relaxation data indicate that Gd³⁺ is bound by both H₈XNa₄ and H₈YNa₄. The Gd³⁺ ions were found to induce the aggregation of H₈YNa₄ with critical association concentration (CAC) value less than in case of its self-aggregation. Using Gd³⁺ as a probe of counter-ion binding with the aggregate interface it was found out that binding of quaternary ammonium cations (QUATSs) with H₈YNa₄ aggregates and SDS aggregates is quite different, while binding of inorganic ions by both types of aggregates is similar. The most outstanding peculiarity of QUATSs binding with H₈YNa₄ aggregates is selective recognition of QUATSs, possessing trimethylammonium group, detected by NMR relaxation method.     

Simple bis-thiocarbono-hydrazones as sensitive, selective, colorimetric, and switch-on fluorescent chemosensors for fluoride anions

Bis-thiocarbono-hydrazones are found to be a class of sensitive, selective, ratiometric, and colorimetric chemosensors for anions such as fluoride (F(-)) or acetate (Ac(-)). The sensitivities, or the binding constants of the sensors with anions, were found to be strongly dependent on the substituents appended on the pi-conjugation framework, the delocalization bridge CH==N, the aromatic moiety, and the hetero atom in the C==X group (X=O, S) of the sensors. Single-crystal structures and (1)H NMR titration analysis shows that the --CH==N-- moiety is a hydrogen-bond donor, and it is proposed that an additional CHF hydrogen bond is formed for the sensors in the presence F(-). A sensor bearing anthracenyl groups is demonstrated as a switch-on fluorescent chemosensor for F(-) and Ac(-). The recognition of F(-) in acetonitrile (MeCN) by a sensor with nitrophenyl substituents is tolerant to MeOH (MeCN/MeOH=10:1, v/v) and water (MeCN/H(2)O=30:1, v/v); at these solvent ratios the absorption intensity of the sensor-F(-) complex solution at maximal absorption wavelength was attenuated to half of the original value in pure MeCN.     

Transition metal binding properties of the redox-active 1,4,7,10,13,16-hexa(ferrocenylmethyl)-1,4,7,10,13,16-hexaazacyclooctadecane and its electrochemical behaviour in a non-aqueous solvent

Solution studies to elucidate the coordination behaviour and the electrochemical response of the ferrocene-functionalized polyazamacrocycle 1,4,7,10,13,16-hexa(ferrocenylmethyl)-1,4,7,10,13,16-hexaazacyclooctadecane (L¹) by potentiometric methods and electrochemical techniques have been carried out. Potentiometric methods in the presence of Cd²⁺, Hg²⁺, Pb²⁺ and Zn²⁺ were carried out in 1,4-dioxane/water (70:30 v/v, 25°C, 0.1 mol dm⁻³ KNO₃). Electrochemical studies were carried out in acetonitrile/dichloromethane (50:50 v/v, 25°C, 0.1 mol dm⁻³ TBAClO₄) in the presence of transition metal ions and anions.     

Heterocyclic columnar pyrimidines: synthesis, characterization and mesomorphic properties

The synthesis, characterization, and mesomorphic properties of two series of heterocyclic compounds derived from a pyrimidine core are reported. These series, 1a and 1b, are substituted with a variety of functional groups (X=NHSO₂CF₃, F, Cl, Br, I, OCH₃, CH₃, C₂H₅) at the C^3' (meta)- or C^4' (para)-position of the terminal phenyl ring, and the substituent effect on mesophase formation was studied. The compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analysis, and the mesomorphic behavior of the compounds was characterized and studied by differential scanning calorimetry, polarizing optical microscopy and powder X-ray diffraction. Most of the compounds were mesogenic at room temperature, and the mesophases were assigned as lamellar columnar (Col_L) phases, as expected for disk-like molecules. The results also revealed that compounds with a para-substituent (1a; except for -OCH₃) at the C^4'-position, exhibited higher clearing temperatures and wider temperature mesophase ranges than those of compounds with a meta-substituent (1b) at the C^3'-position. The higher clearing temperatures may be attributed to stronger dipolar interactions resulting from a greater resonance effect with the central core for para-substitution than for meta-substitution. The results also indicated that the columnar mesophases observed show a correlation with the electronic properties of the substituents; compounds containing electron-withdrawing substituents (X=F, Cl, Br, I, NHSO₂CF₃) also have higher clearing temperatures than compounds containing electron-donating substituents (X=Me, Et, OMe).     

Liquid crystalline properties of salicylaldimine-based dimers: influence of terminal alkyl chain length and central part

The synthesis and thermotropic properties of four homologous series of salicylaldimine-based dimer liquid crystals are reported. Two 4-(4-alkoxy-2-hydroxybenzylideneamino)benzoyloxy groups are connected to a central part consisting of a 1,3-phenylene, 1,5-pentylene, 2,2-dimethyl-1,5-pentylene or 3,3-dimethyl-1,5-pentylene unit. The terminal alkoxy chains have been varied from 4 to 16 carbon atoms in length. All the compounds exhibit liquid crystalline phases whose behaviour depends on the nature of the central part and the length of the alkoxy terminal chains. All compounds of the series with the central phenyl part exhibit enantiotropic B-phases, and the sequence B₆-B₁-B₂ on increasing terminal chain length was observed. Replacement of the phenyl group with a pentyl central group partly suppresses the formation of B-phases. The longer homologues of this series show the B₁ phase, while the shorter exhibit an intercalated SmC_c mesophase. The introduction of methyl substituents to the pentyl spacer causes the melting points to fall dramatically and the formation of B-phases is totally suppressed. The compounds with the long tails show intercalated SmA_c phases and those with short tails show intercalated SmC_c phases.     

Synthesis and thermal properties of dimeric alkoxy-substituted tolans

Four homologous series of dimeric tolans of the general formula RC₆H₄C≏C₆H₄O(CH₂)_m OC₆H₄C'CC₆H₄R (m'6-10; R'H, OC₆H₁₃, OC₁₀H₂₁ and OC₁₄H₂₉), denoted further as TOmOT or nOTOmOTOn, according to the number of aliphatic carbon atoms, have been synthesized. Dimers with terminal chains exhibited liquid crystalline behaviour. Crystal-crystal transitions were also observed. Resulting from the optical, thermal and miscibility studies, the following mesophases have been identified: nematic, smectics A and B, and the tilted smectics C and (probably) F or I. In the 6OTOmOTO6 series, a phase with a strong tendency to self-alignment occurred between the nematic and smectic A phases. This phase resembled the nematic in its viscoelastic properties, but also showed focal-conic textures. A transition between this 'intermediate phase' and the nematic was detected only from microscopic observations. On the contrary, the 'intermediate phase'-smectic A transition was also detected by DSC (δH ∼ 1kJ mol^-1). Both tilted (S_c and S_F/I) and non-tilted (S_A and S_B) smectics were observed in the 10OTOmOTO10 series, while only tilted smectic phases were identified in the dimers with longer terminal substituents (14OTOmOTO14). Double melting behaviour was found in 14OTO8OTO14 and 14OTO10OTO14. An alternation of the transition temperatures and enthalpies with the odd-even alternation of the lengths of bridging groups was clearly observed. A correlation between total enthalpies of transition and solubilities of the dimeric tolans is stated.     

基于SiO_(2)@Fe_(3)O_(4)的磁性纳米材料分离富集谷物中痕量黄曲霉毒素B_(1)北大核心CSCD

将SiO_(2)包覆的Fe_(3)O_(4)磁性纳米材料(SiO_(2)@Fe_(3)O_(4))表面偶联识别黄曲霉毒素B_(1)(AFB_(1))的抗体(Ab),用于特异性分离富集谷物中的AFB_(1),进而与高效液相色谱-串联质谱法(HPLC-MS/MS)结合,用于大米、玉米和小麦中AFB_(1)的高效准确检测。采用微波辅助水热合成法制备得到Fe_(3)O_(4)磁性纳米颗粒,并用100μL正硅酸乙酯(TEOS)对其进行SiO_(2)的包覆,得到SiO_(2)@Fe_(3)O_(4)磁性纳米材料,随后进行抗体的偶联得到Ab-SiO_(2)@Fe_(3)O_(4);以pH=7.4的磷酸盐缓冲液(PBS)作为富集缓冲液,加入8 mg Ab-SiO_(2)@Fe_(3)O_(4),在37℃下反应10 min进行AFB_(1)的分离富集,随后采用甘氨酸-盐酸(Gly-HCl)缓冲液对Ab-SiO_(2)@Fe_(3)O_(4)分离富集的AFB_(1)进行洗涤,将洗涤液氮吹后复溶,采用高效液相色谱-串联质谱法检测。在最佳条件下,方法检测AFB_(1)的线性范围为2~50μg/L,相关系数(R^(2))>0.99,检出限为0.04μg/kg,定量限为0.13μg/kg。在4个不同加标水平下,AFB_(1)在3种谷物基质中的加标回收率为76.21%~92.85%,RSD≤5.29%。大米、玉米和小麦等实际谷物样品中AFB_(1)的测定结果显示,在1个小麦样品和2个玉米样品中检出AFB1,其含量分别为0.38、0.13和0.47μg/kg,其他样品中并未发现AFB_(1)。方法将磁性纳米材料与HPLC-MS/MS相结合,实现了AFB_(1)的高效分离富集,富集材料成本低廉,储存性能好,在30 min内即可完成前处理过程,可在较短的时间内实现大批量样品的实际分析,在谷物中真菌毒素的检测方面具有良好的应用前景。     

Structures and luminescence properties of two copper(I) halide complexes featuring 2-(2-benzimidazolyl)-6-methylpyridine

Two new copper（I） halide complexes bearing 2-（2-benzimidazolyl）-6-methylpyridine（Hbmp） and PPh₃ ligands, Cu（Hbmp）（PPh₃）X（X = Br（1）;I（2））,have been synthesized and characterized.Single-crystal X-ray structure analysis reveals that the halide ligand has a significant impact on the Cu-N_pyridyl bond lengths.Complexes 1 and 2 show the solid-state emissions at ambient temperature,varying with the halide bound to the {Cu（Hbmp）（PPh₃）} motif,which are perhaps best attributed to the metal-to-ligand charge-transfer（Cu（I）→Hbmp） transition mixed with some ligand-to-ligand charge-transfer（X and PPh₃→Hbmp） character.     

Anion binding by bambus[6]uril probed in the gas phase and in solution

Electrospray ionization mass spectrometry (ESI-MS) is used to probe the binding of small anions to the macrocycle of bambus[6]uril. For the halide ions, the experimental patterns suggest F(-) < Cl(-) < Br(-) < I(-), which is consistent with the order of anion binding found in the condensed phase. Parallel equilibrium studies in the condensed phase establish the association constants of halide anions and bambus[6]uril in mixed solvents. A detailed analysis of the mass spectrometric data is used to shed light on the correlations between the binding constants in the condensed phase and the ion abundances observed using ESI-MS. From the analysis it becomes apparent that ESI-MS can indeed represent the situation in solution to some extent, but the sampling in the gas-phase experiment is not 1:1 compared to that in solution.     

Electrospray mass spectrometry of zinc dithiophosphate derivatives and its application to the analysis of engine oil antiwear additives

Electrospray mass spectrometry (ES-MS) has been applied to a variety of zinc O,O′-dialkyldithiophosphate (DTP) derivatives. The neutral Zn(DTP)₂ compounds were converted to the [Zn(DTP)₃]⁻ anions by reaction with excess DTP⁻ and these principal anions are readily observed by ES-MS. Exchange reactions between two different zinc tris(DTP) anions leads to the simultaneous observation of zinc anions containing all possible combinations of ligands even though the species in solution are exchanging rapidly on the NMR timescale. Similar mass spectra are observed upon mixing Zn(DTP)₂ with a different DTP⁻ anion. Reaction of Zn(DTP)₂ with dimethylsulfoxide (DMSO) in methanol solution gives [Zn(DTP)(DMSO)_1,2]⁺ and free DTP⁻ ions which are observed in the positive ion and negative ion ES mass spectra respectively. This latter reaction provides a convenient method for the characterisation and qualitative analysis of engine oil inhibitor and antiwear additives, which contain zinc dithiophosphates with alkyl and aryl substituents.     

Synthesis of dendritic oligo(aryl sulfone)s as supports for synthesis

A short, divergent route to G₁ oligo(aryl sulfone)s and a G₂ oligo(aryl sulfone) dendrimer using nucleophilic aromatic substitution reactions is described. A range of tetrasubstituted pentasulfones are proposed for applications as homogeneous supports for synthesis. Key to achieving selectivity in the syntheses is the activation of leaving groups by sulfide to sulfone oxidation. Preparation of the G₂ oligo(aryl sulfone) is low-yielding due to competition from SET processes that are interesting from a mechanistic point of view. The utility of the supports is exemplified with a four step synthesis of a dipeptide and by ‘react and release’ synthesis of amides.     

Highly selective olefin epoxidation with manganese triazacyclononane complexes: Impact of ligand substitution

Manganese complexes of 1,4,7-triazacyclononane with different substituents catalyze the selective epoxidation of a large number of olefins to epoxides with H₂O₂. The activities of complexes with methyl (L₁), 2-hydroxybutyl (L₂) and acetato (L₃) substituents are compared. The effects of solvent and temperature on the epoxide yield are very different for the three complexes. It is proposed that these differences are related to the binding of the pendant arms in Mn---L₂ and Mn---L₃ complexes. In general, acetone or methanol are preferred solvents. Variations of stereoretention are also observed: with Mn---L₁ in acetone, isomer scrambling occurs, while with Mn---L₁ in methanol, the epoxidation is almost stereospecific. UV-visible and electron spin resonance spectroscopy are used to characterize the state of manganese under oxidizing conditions.     

一种长链烷氧基苯腙衍生物对氟离子的高选择性识别

设计并合成了一种新型长链烷氧基酰腙衍生物1-(2,4-二硝基苯基)-2-(4-(十四烷氧基)亚苄基)肼R,系统研究了受体R对9种阴离子(F^-、Cl^-、Br^-、I^-、HSO^-₄、NO^-₃、ClO^-₄、H₂PO^-₄、Ac^-)的紫外-可见吸收光谱(UV-Vis)及裸眼识别性能。 结果表明,该受体在二甲基亚砜(DMSO)体系中对F^-、Ac^-和H₂PO^-₄表现出良好的UV-Vis及裸眼识别能力。 此外,在H₂O/DMSO(体积比1∶9)体系中可对F^-实现单一UV-Vis及裸眼识别,且检出限可达7.02×10^-7 mol/L,同时制备了受体R对阴离子的检测试纸,Job曲线表明受体与阴离子形成1∶1型配合物。 F^-离子的识别机理为“氢键型”响应识别现象。     

Synthesis, structural and spectroscopic characterisation of three di-μ-fluoro-bis[dioxouranyl] complexes

Three novel uranyl complexes with organic phosphine oxide ligands and bridging fluorides have been synthesised and structurally characterised. In [ UO₂(μ-F)(TPPO)_{3 2}][BF₄]₂ · ⁿC₆H₁₄, 1, and [ UO₂(-μF)(TBPO)_{3 2}][BF₄]₂ 2, (where TPPO and TBPO are triphenylphosphine oxide and tri-n-butylphosphine oxide, respectively) two UO₂ ²⁺ moieties are bridged by two fluorides with three additional terminal PO donor ligands coordinated to each uranium centre. The dicationic complexes are both charge balanced by two uncoordinated tetrafluoroborate anions. In the related structure, [UO₂(μ-F)(F)(DPPMO₂)]₂ · 2MeOH (3), terminal fluoride is also coordinated to both uranyl centres (where DPPMO₂ = bis(diphenylphosphine oxide)methane). All three complexes were prepared during attempted syntheses of complexes with tetrafluoroborate directly coordinated to uranium. It is clear from these results that the fluorophilicity of UO₂ ²⁺ causes the abstraction of fluoride from [BF₄]⁻, with the weakly coordinating anion only present as a counter cation in 1 and 2, and absent completely in 3.     

Syntheses of complexes containing substituted 4-ethynylquinolines or 1-azabuta-1,3-dienes by addition of imines to a cationic butatrienylidene-ruthenium complex

Reactions of [Ru(=C=C=C=CH₂)(PR₃)₂Cp]⁺ (R=Ph or OMe) with arylimines ArN=CH(C₆H₄R) afford either substituted quinolines, Ru{CCC₉H₄RN(Ar)}(PR₃)₂Cp, by attack of the terminal carbon of the butatrienylidene ligand at the imine carbon, followed by C---C bond formation between the ortho carbon of the N-aryl group and C_γ of the unsaturated carbene, or 1-azabuta-1,3-dienyl complexes, formed by cycloaddition of the N=CH group to C_γ=C_δ of the carbene, followed by opening of the resulting four-membered ring. Some product dependence on the nature of the substituents in the N- and C-aryl groups is found. The N atoms in the products are strongly basic, being readily protonated, methylated or aurated. The molecular structures of nine complexes are reported, together with that of a new modification of RuCl{P(OMe)₃}₂Cp.     

Kinetische und mechanistische untersuchungen von Übergangsmetall-komplex-reaktionen : III. Abhängigkeit des gleichgewichts der addition von tributylphosphan an pentacarbonyl(arylmethoxycarben)wolfram vom substituenten am ring

The reaction of pentacarbonyl(arylmethoxycarbene)tungsten, (CO)₅W[C(OCH₃(p-C₆H₄R)] [R = OCH₃ (a), CH₃ (b), H (c), Br (d), CF₃ (e)], with tributylphosphane at low temperatures results in a reversible addition of the phosphane to the carbene carbon atom. The addition—dissoziation equilibrium is not only dependent on the temperature but also to a strong degree on the nature of the substituent R. ΔG, ΔH and the equilibrium constant K increase in the series from R = OCH₃ to R = CF₃. With the exception of R = OCH₃ the substituents b to e form an isentropic class. For all substituents (a to e) a linear dependency from Jaffés σ-constants was observed for ΔH. Good linear correlation for the substituents b to e was also found for log K and σ as well as for log K and the CO-force constants k_cis and k_trans.     

Absolute control of helicity at the C-termini in quinoline oligoamide foldamers by chiral oxazolylaniline moieties

Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H NMR.X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring.CPL investigations demonstrated that S-CQn-a-d are CPL active and its g(lum)values are dependent on its length.Interestingly,the sizes of the substituents in the chiral centers are different,howeve r,they exert no effect on the dissymmetric factors g(abs)and g(lum)of quinoline oligoamide foldamers.