An Efficient Probe for Rapid Detection of Cyanide in Water at Parts per Billion Levels and Naked‐Eye Detection of Endogenous Cyanide

A new molecular probe based on an oxidized bis‐indolyl skeleton has been developed for rapid and sensitive visual detection of cyanide ions in water and also for the detection of endogenously bound cyanide. The probe allows the “naked‐eye” detection of cyanide ions in water with a visual color change from red to yellow (Δλ_max=80 nm) with the immediate addition of the probe. It shows high selectivity towards the cyanide ion without any interference from other anions. The detection of cyanide by the probe is ratiometric, thus making the detection quantitative. A Michael‐type addition reaction of the probe with the cyanide ion takes place during this chemodosimetric process. In water, the detection limit was found to be at the parts per million level, which improved drastically when a neutral micellar medium was employed, and it showed a parts‐per‐billion‐level detection, which is even 25‐fold lower than the permitted limits of cyanide in water. The probe could also efficiently detect the endogenously bound cyanide in cassava (a staple food) with a clear visual color change without requiring any sample pretreatment and/or any special reaction conditions such as pH or temperature. Thus the probe could serve as a practical naked‐eye probe for “in‐field” experiments without requiring any sophisticated instruments.     

Synthesis of Novel 4‐((Substituted bis‐indolyl)methyl)‐benzo‐15‐crown‐5 for the Colorimetric Detection of Hg2+ Ions in an Aqueous Medium

A practical, two‐step synthesis of novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 has been reported. The strategy employed for the synthesis of the desired molecules involved Duff formylation of benzo‐15‐crown‐5 to get 4‐formyl benzo‐15‐crown‐5 followed by subsequent reactions with substituted indoles in trifluoroacetic acid to yield novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 in moderate to good yield. One of the reported novel molecule tested for the complexation behavior with various metal cations, such as Li⁺, Na⁺, K⁺, Mg²⁺ Ca²⁺, Al³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Sn²⁺, Ba²⁺, Hg²⁺, and Pb²⁺, showed a visual colorimetric probe for the detection of mercury cations (Hg²⁺) in an aqueous medium.     

Wasserstoffbrückenbindungen mit Cyanidionen? Die Strukturen von 1,3‐Diisopropyl‐4,5‐dimethylimidazoliumcyanid und 1‐Isopropyl‐3,4,5‐trimethylimidazoliumcyanid

Hydrogen Bonds with Cyanide Ions? The Structures of 1,3‐Diisopropyl‐4,5‐dimethylimidazolium Cyanide and 1‐Isopropyl‐3,4,5‐trimethylimidazolium Cyanide 1,3‐Diisopropyl‐4,5‐dimethylimidazolium cyanide ( 2a ) and 1‐isopropyl‐3,4,5‐trimethylimidazolium cyanide ( 2b ) are obtained from the reaction of the corresponding 2,3‐dihydrodimethylimidazol‐2‐ylidenes ( 1 ) and hydrogen cyanide in excellent yield. Their crystal structure analyses reveal the presence of ion pairs linked by hydrogen bonds. The crystal structure analysis of 2a reveals a near colinear orientation of the C(1)‐H bond axis and the cyanide ion while in 2b this orientation is perpendicular. In both cases, the interionic distances are in the expected range for hydrogen bonds. Ab‐initio calculations of the total energy of the salts 2 indicate small differences in energy between the colinear and perpendicular orientation of the ions as well as between the colinear C‐H···C‐N and C‐H···N‐C orientations. The comparison of calculated and measured ¹³C and ¹⁵N NMR chemical shifts does not allow the distinction between the possible orientations.     

Manganese(I)‐Catalyzed C−H (2‐Indolyl)methylation: Expedient Access to Diheteroarylmethanes

An unprecedented Mn^I‐catalyzed (2‐indolyl)methylation of heteroarenes is reported. This method makes use of an aromatizing cascade strategy to install a (2‐indolyl)methyl group into target molecules, thereby leading to the expedient synthesis of previously challenging and important unsymmetrical diheteroarylmethanes, in particular bis(2‐indolyl)methanes. The proposed cascade process comprises the reorganization of multiple bonds with controlled regioselectivity and high atom economy and can be performed on a gram‐scale. Furthermore, a metal‐free C?H propargylation is observed. The diverse application of this method is also demonstrated.     

Synthese und Reaktivität von 2‐Brom‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol Molekülstruktur von Bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐yl)

Synthesis and Reactivity of 2‐Bromo‐1,3‐diethyl‐2,3‐dihydro‐1 H ‐1,3,2‐benzodiazaborole Molecular Structure of Bis(1,3‐diethyl‐2,3‐dihydro‐1 H ‐1,3,2‐benzodiazaborol‐2‐yl The reaction of a slurry of calcium hydride in toluene with N,N′‐diethyl‐o‐phenylenediamine ( 1 ) and boron tribromide affords 2‐bromo‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol ( 2 ) as a colorless oil. Compound 2 is converted into 2‐cyano‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborole ( 3 ) by treatment with silver cyanide in acetonitrile. Reaction of 2 with an equimolar amount of methyllithium affords 1,3‐diethyl‐2‐methyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborole ( 4 ). 1,3,2‐Benzodiazaborole is smoothly reduced by a potassium‐sodium alloy to yield bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐yl] ( 7 ), which crystallizes from n‐pentane as colorless needles. Compound 7 is also obtained from the reaction of 2 and LiSnMe₃ instead of the expected 2‐trimethylstannyl‐1,3,2‐benzodiazaborole. N,N′‐Bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐ yl)‐1,2‐diamino‐ethane ( 6 ) results from the reaction of 2 with Li(en)C≡CH as the only boron containing product. Compounds 2 – 4 , 6 and 7 are characterized by means of elemental analyses and spectroscopy (IR, ¹H‐, ¹¹B{¹H}‐, ¹³C{¹H}‐NMR, MS). The molecular structure of 7 was elucidated by X‐ray diffraction analysis.     

Solid‐phase extraction using bis(indolyl)methane‐modified silica reinforced with multiwalled carbon nanotubes for the simultaneous determination of flavonoids and aromatic organic acid preservatives

A novel bis(indolyl)methane‐modified silica reinforced with multiwalled carbon nanotubes sorbent for solid‐phase extraction was designed and synthesized by chemical immobilization of nitro‐substituted 3,3′‐bis(indolyl)methane on silica modified with multiwalled carbon nanotubes. Coupled with high‐performance liquid chromatography analysis, the extraction properties of the sorbent were evaluated for flavonoids and aromatic organic acid compounds. Under optimum conditions, the sorbent can simultaneously extract five flavonoids and two aromatic organic acid preservatives in aqueous solutions in a single‐step solid‐phase extraction procedure. Wide linear ranges were obtained with correlation coefficients (R²) ranging from 0.9843 to 0.9976, and the limits of detection were in the range of 0.5–5 μg/L for the compounds tested. Compared with the silica modified with multiwalled carbon nanotubes sorbent and the nitro‐substituted 3,3′‐bis(indolyl)methane‐modified silica sorbent, the developed sorbent exhibited higher extraction efficiency toward the selected analytes. The synergistic effect of nitro‐substituted 3,3′‐bis(indolyl)methane and multiwalled carbon nanotubes not only improved the surface‐to‐volume ratio but also enhanced multiple intermolecular interactions, such as hydrogen bonds, π–π, and hydrophobic interactions, between the new sorbent and the selected analytes. The as‐established solid‐phase extraction with high‐performance liquid chromatography and diode array detection method was successfully applied to the simultaneous determination of flavonoids and aromatic organic acid preservatives in grape juices with recoveries ranging from 83.9 to 112% for all the selected analytes.     

Controlled Synthesis of Heterotrimetallic Single‐Chain Magnets from Anisotropic High‐Spin 3 d–4 f Nodes and Paramagnetic Spacers

By using the node‐and‐spacer approach in suitable solvents, four new heterotrimetallic 1D chain‐like compounds (that is, containing 3d–3d′–4f metal ions), {[Ni(L)Ln(NO₃)₂(H₂O)Fe(Tp*)(CN)₃] ? 2 CH₃CN ? CH₃OH}_n (H₂L=N,N′‐bis(3‐methoxysalicylidene)‐1,3‐diaminopropane, Tp*=hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate; Ln=Gd ( 1 ), Dy ( 2 ), Tb ( 3 ), Nd ( 4 )), have been synthesized and structurally characterized. All of these compounds are made up of a neutral cyanide‐ and phenolate‐bridged heterotrimetallic chain, with a {? Fe? C?N? Ni(? O? Ln)? N?C? }_n repeat unit. Within these chains, each [(Tp*)Fe(CN)₃]^? entity binds to the Ni^II ion of the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ motif through two of its three cyanide groups in a cis mode, whereas each [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit is linked to two [(Tp*)Fe(CN)₃]^? ions through the Ni^II ion in a trans mode. In the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit, the Ni^II and Ln^III ions are bridged to one other through two phenolic oxygen atoms of the ligand (L). Compounds 1 – 4 are rare examples of 1D cyanide‐ and phenolate‐bridged 3d–3d′–4f helical chain compounds. As expected, strong ferromagnetic interactions are observed between neighboring Fe^III and Ni^II ions through a cyanide bridge and between neighboring Ni^II and Ln^III (except for Nd^III) ions through two phenolate bridges. Further magnetic studies show that all of these compounds exhibit single‐chain magnetic behavior. Compound 2 exhibits the highest effective energy barrier (58.2 K) for the reversal of magnetization in 3d/4d/5d–4f heterotrimetallic single‐chain magnets.     

Highly Efficient Synthesis of Unsymmetrical 3,3′‐Bis(1H‐indol‐3‐yl)methanes in Water

A simple and practical approach for the preparation of unsymmetric bis(indolyl)methanes (BIMs) was realized by Lewis acid InBr₃‐catalyzed Friedel‐Crafts reaction of indoles with 3‐indolyl‐substituted phthalides in water.     

A Multifunctional Bimetallic Molecular Device for Ultrasensitive Detection,Naked‐Eye Recognition,and Elimination of Cyanide Ions

A new bimetallic Fe^II–Cu^II complex was synthesized, characterized, and applied as a selective and sensitive sensor for cyanide detection in water. This complex is the first multifunctional device that can simultaneously detect cyanide ions in real water samples, amplify the colorimetric signal upon detection for naked‐eye recognition at the parts‐per‐million (ppb) level, and convert the toxic cyanide ion into the much safer cyanate ion in situ. The mechanism of the bimetallic complex for high‐selectivity recognition and signaling toward cyanide ions was investigated through a series of binding kinetics of the complex with different analytes, including CN^?, SO₄^2?, HCO₃^?, HPO₄^2?, N₃^?, CH₃COO^?, NCS^?, NO₃^?, and Cl^? ions. In addition, the use of the indicator/catalyst displacement assay (ICDA) is demonstrated in the present system in which one metal center acts as a receptor and inhibitor and is bridged to another metal center that is responsible for signal transduction and catalysis, thus showing a versatile approach to the design of new multifunctional devices.     

Selective Lanthanides Sequestration Based on a Self‐Assembled Organosilica

In this paper, we investigate the cation‐exchange properties of a self‐assembled hybrid material towards trivalent ions, lanthanides (La³⁺, Eu³⁺, Gd³⁺, Yb³⁺) and Fe³⁺. The bis‐zwitterionic lamellar material was prepared by sol–gel process from only 3‐aminopropyltriethoxysilane (APTES), succinic anhydride, and ethylenediamine. In ethanol heated under reflux, the exchange ethylenediammonium versus Ln³⁺ proved to be complete by complexometry measurements and elemental analyses, one Cl^? ion per one Ln^III remaining as expected for charge balance. In aqueous solution at 20 °C, the material was found to be selective towards lanthanide in spite of the similarity of their ionic radii. The cation uptake depends on the nature of the salt, the difference between two lanthanides reaching up to 20 % in some cases. Finally, ion‐exchange reaction with FeCl₃ was chosen as a probe to get more information on the material after incorporation of trivalent ions. Based on Mössbauer spectroscopic investigations on the resulting material in conjunction with the XRD analysis of materials containing trivalent ions, a structural model was proposed to describe the incorporation of trivalent ions by exchange reaction within the original zwitterionic material.     

Development of a Simple and Inexpensive Optical Absorption One‐Shot Sensor Membrane for Detection and Determination of Cyanide Ions in Water Samples

A new one‐shot optical cyanide ion sensor is proposed for determination of cyanide ions. The sensor was constructed by immobilizing crystal violet (CV) on triacetylcellulose membrane. The sensing mechanism involves reaction between cyanide ions and the immobilized CV at pH = 5.4, which results in a decrease in absorbance of the membrane at 600 nm. The sensor shows sufficient repeatability, reproducibility, operational lifetime of 3 weeks, and a response of less then 10 min under the optimum conditions and response time of 8 min. Cyanide can be determined in the concentration range of 50.0‐800 μg mL^‐1 with a detection limit of 5.0 μg mL^‐1. Most ions do not interfere with the determination of cyanide ions. The proposed sensor was successfully applied to the determination of cyanide in spiked water samples.     

Synthesis,Characterization, and Antimicrobial Screening of Ethylene‐Spaced Bis‐heterocycles

A new class of ethylene‐spaced bis‐heterocycles that was synthesized in a simple and efficient method from the one‐pot, three‐component reaction of amine 2 , propargyl halide 3 , and indolyl azide 1 in water is described. The identities of these compounds were confirmed following elemental analysis, IR, ¹H, ¹³C NMR, and mass spectral studies. All the title compounds exhibited pronounced in vitro antibacterial and antifungal activities.     

Iron‐containing ionic liquid as an efficient and recyclable catalyst for the synthesis of C3‐substituted indole derivatives

A facile and efficient protocol for the synthesis of C3‐substituted indole derivatives has been developed under mild condition. The iron‐containing ionic liquid, 1‐(2‐hydroxyethyl)‐1,4‐diazabicyclo[2.2.2] octanylium tetrachloroferrate ([Dabco‐C₂OH][FeCl₄]) as a recyclable catalyst has been successfully used in the synthesis of trisindolines, bis(3‐indolyl) methanes and β‐indolyl alcohols for the first time. The products of trisindolines and bis(3‐indolyl) methanes are easily separated and purified without chromatographic technique. The catalyst was recycled six times without significant activity loss.     

A Post‐Synthetically Modified MOF for Selective and Sensitive Aqueous‐Phase Detection of Highly Toxic Cyanide Ions

Selective and sensitive detection of toxic cyanide (CN^?) by a post‐synthetically altered metal–organic framework (MOF) has been achieved. A post‐synthetic modification was employed in the MOF to incorporate the specific recognition site with the CN^? ion over all other anions, such as Cl^?, Br^?, and SCN^?. The aqueous‐phase sensing and very low detection limit, the essential prerequisites for an effective sensory material, have been fulfilled by the MOF. Moreover, the present detection level meets the standard set by the World Health Organization (WHO) for the permissible limit of cyanide concentration in drinking water. The utilization of MOF‐based materials as the fluorometric probes for selective and sensitive detection of CN^? ions has not been explored till now.     

A Schiff base‐grafted nanoporous silica material as a reversible optical probe for Hg2+ ion in water

A novel organic–inorganic silica‐based fluorescent probe was designed, synthesized and characterized by different techniques such as XRD, BET, TGA, and FT‐IR. The fluorescence properties of the probe were studied in the presence of a variety of metal‐ions in water. The results revealed that various metal‐ions negligibly vary the emission intensity of the probe except for Hg²⁺, which quenched the intensity dramatically. The selectivity of the probe toward Hg²⁺ ion was further investigated in the presence of common competing metal‐ions and the results demonstrated the high selectivity of the probe toward Hg²⁺ ion. The fluorescence emission of the probe was also studied as a function of the concentration of Hg²⁺ ion. A nanomolar limit of detection was estimated for Hg²⁺, indicating a high sensitivity. Furthermore, the probe showed INHIBIT‐type logic behavior with Hg²⁺ and H⁺ as inputs. Also, the optimum pH range was studied in addition to reversibility and real world applicability of the probe.     

Investigation of ionic liquids under Bi‐ion and Bi‐cluster ions bombardment by ToF‐SIMS

A systematic study of five different imidazolium‐based room temperature ionic liquids, 1‐butyl‐3‐methylimidazolium acetate, 1‐butyl‐3‐methylimidazolium nitrate, 1‐butyl‐3‐methylimidazolium iodide, 1‐butyl‐3‐methylimidazolium hexafluorophosphate and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide were carried out by means of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) in positive and negative ion mode. The compounds were measured under Bi‐ion and Bi‐cluster ions (Bi_2–7⁺, Bi_{3, 5}²⁺) bombardment, and spectral information and general rules for the fragmentation pattern are presented. Evidence for hydrogen bonding, due to high molecular secondary cluster ions, could be found. Hydrogen bonding strength could be estimated by ToF‐SIMS via correlation of the anionic yield enhancement with solvent parameters. Copyright © 2010 John Wiley & Sons, Ltd.     

An Imidazoline–Aminophenol (IAP) Nickel Catalyst: Structure and Catalytic Activity in the Enantioselective 1,4‐Addition of 3′‐Indolyl‐3‐Oxindoles to Nitroethylene

The structure of a nickel complex of imidazoline–aminophenol (IAP) prepared from IAP with Ni(OAc)₂ was elucidated as cis‐bis(imidazolineaminophenoxide) [Ni(IAP)₂]. The [Ni(IAP)₂] complex smoothly promoted catalytic asymmetric 1,4‐addition of 3′‐indolyl‐3‐oxindole to nitroethylene to provide chiral mixed 3,3′‐bisindoles with high enantioselectivities. Mechanistic studies using ESI‐MS analyses suggest that one IAP ligand dissociated from [Ni(IAP)₂] to generate the Ni–enolate of 3′‐indolyl‐3‐oxindole. From the optically active 3,3′‐mixed indole adduct, biologically important 3′‐indolyl‐3‐pyrrolidinoindoline was successfully synthesized in a three‐step reaction sequence.     

Development of Polymeric Resin Ion‐exchanger Based Chloride Ion‐selective Electrode for Monitoring Chloride Ion in Environmental Water

A chloride ion‐selective electrode (ISE) membrane was developed by using a copolymeric ion‐exchanger resin (trimethyl ethenyl quaternary ammonium chloride polystyrene‐divinylbenzene copolymer resin, TMEQAC PSDVB), the ionophore ({μ‐[4,5‐Dimethyl‐3,6‐bis(dodecyloxy)‐1,2‐phenylene]}bis(mercury chloride), ETH9033), the plasticizer (bis(2‐ethylhexyl) sebacate, DOS), and the membrane substrate (polyvinylchloride, PVC). At 25 °C, the electrode exhibited an ideal Nernstian response of 59.2 mV/decade with the linear calibration concentration range from 1.0 × 10^?4‐1.0 × 10^?2 M (r² = 0.9930). The limit of detection was 2.45 ppm (6.9 × 10^?2 mM) and the measurement response time was less than 10 seconds. The working temperature range of electrode was 10‐45 °C. The working pH range for chloride ion measurement was 2.0‐11.0. Among the various anions examined in this work, only I^?, SCN^?, and MnO₄^? ions show significant interference to the electrode measurement. The chloride ISE can be used at least 72 days. The determination of chloride ion content in three kinds of environmental water sample with the electrode method was accurate (92‐95%) and precise (RSD < 4.4%) and did not show significance difference from the high‐performance liquid chromatography method.     

Rare‐Earth Metal Alkyl Complexes with 3‐Arylamido‐Functionalized Indolyl Ligands: Synthesis,Characterization and Reactivity†

A series of dinuclear rare‐earth metal alkyl complexes {[μ‐η²:η¹:η¹‐3‐( L NCH)(CH₂SiMe₃)Ind]RE(CH₂SiMe₃)(THF)}₂ ( L ¹ = 2‐^tBuC₆H₄, RE = Y, Gd, Dy, Er, Yb; L ² = 2,4,6‐Me₃C₆H₂, RE = Dy, Er; Ind = indolyl) and {[μ‐η²:η¹:η¹‐3‐( L NCH₂)Ind]RE(CH₂SiMe₃)(THF)}₂ ( L ¹, RE = Y, Dy, Er, Yb; L ², RE = Er, Yb) bearing 3‐arylamido functionalized indolyl ligands having diverse bonding modes with metal ions were synthesized either by the insertion reaction of the imino group to the RE—C bond or by the alkane elimination reaction. In the preparation of above complexes, rare‐earth metal alkyl complexes [μ‐η⁵:η¹:η¹‐3‐( L ²NCH)(CH₂SiMe₃)Ind]Gd(CH₂SiMe₃)(THF)}₂ with a μ‐η⁵:η¹:η¹ coordination mode to the gadolinium ion and {[μ‐η³:η¹:η¹‐3‐( L ²NCH₂)Ind]Dy(CH₂SiMe₃)(THF)}₂ with a μ‐η³:η¹:η¹ coordination mode to the dysprosium ion were unexpectedly isolated. The reactions of 3‐( L ²N=CH)Ind with Er(CH₂SiMe₃)₃(THF)₂ at room temperature, generated a tetranuclear imino‐indolyl erbium intermediate {[μ‐η¹:η¹‐3‐( L ²N=CH)Ind]Er(CH₂SiMe₃)₂(THF)}₄, which can transform into the amido functionalized indolyl erbium complex in hot toluene. Moreover, the reactivities of the newly synthesized ytterbium complex with N‐heterocyclic compounds were investigated, affording the corresponding products of the mixed pyridyl‐indolyl, imidazolyl‐indolyl, and ortho‐metalated complexes. The yttrium complexes showed a high regioselectivity and steroselectivity for the isoprene polymerization with 1,4‐trans selectivity up to 91.7% and 1,4‐cis selectivity up to 96.1% in the presence of cocatalysts, respectively.     

Selective and Sensitive Fluorescent Chemosensors for Cu2+ Ion Based upon Bis‐1,8‐naphthalimide Dyads

A series of new fluorescent chemosensors 5a – 5e , composed of two aminonaphthalimide fluorophores and 2,6‐bis((N‐aminoalkyl)aminocarboxy)pyridines, were prepared, characterized, and their fluorescent properties towards heavy and transition metal (HTM) ions were investigated. Chemosensors 5c – 5e exhibited high selectivity and sensitivity for Cu²⁺ ion over other HTM ions with fluorescent quenching (green to colourless). It clearly demonstrated that the length of the linkers (diamines) between the aminonaphthalimides and 2,6‐dicarboxypyridine of 5a – 5e was very important for their sensitivity and selectivity for Cu²⁺ ion over other HTM ions.