CH3CN H2O Research Articles

Coordinative diversity of lanthanum(III), praseodymium(III), yttrium(III) and zinc(II) complexes based cyclen-tetraphenolate

The coordination properties of the macrocycle 1,4,7,10-tetrakis(2,4-dimethyl-1-hydroxy-6-methyl-benzyl)-1,4,7,10-tetraazacyclododecane, H4LMe,Me have been investigated with lanthanides La(III) and Pr(III) and 3/4d metal ions Zn(II) and Y(III). Two Pr(III) complexes [Pr(HLMe,Me)]‧MeOH (2a) and [Pr(HLMe,Me)]‧2H2O (2b) with coordination numbers (C.N.) 7 and 8, respectively as well as the [La(HLMe,Me)]‧2H2O (1) complex, which was isomorphic with 2b were isolated. In addition, [Y(HLMe,Me)]‧CH3CN‧H2O (3) and [Zn(H3LMe,Me)](NO3) (4) with C.N. 7 and 5, respectively were synthesized too. All complexes were spectroscopically and structurally characterized as well as luminescence emission of 2a and 2b.

Three Gd-based magnetic refrigerant materials with high magnetic entropy: From di-nuclearity to hexa-nuclearity to octa-nuclearity.

Magnetocaloric effect (MCE) is one of the most promising features of molecular-based magnetic materials. We reported three Gd-based magnetic refrigerant materials, namely, Gd2(L)(NO3)(H2O)‧CH3CN‧H2O (1, H2L = (Z)-N-[(1E)-(2-hydroxy-3-methphenyl)methylidene]pyrazine-2-carbohydrazonic acid), {Gd6(L)6(CO3)2(CH3OH)2(H2O)3Cl}Cl‧4CH3CN (2), and Gd8(L)8(CO3)4(H2O)8‧2H2O (3). Complex 1 contains two GdIII ions linked by two η 2:η 1:η 1:η 1:μ 2-L2- ligands, which are seven-coordinated in a capped trigonal prism, and complex 2 possesses six GdIII ions, contributing to a triangular prism configuration. For complex 3, eight GdIII ions form a distorted cube arrangement. Moreover, the large values of magnetic entropy in the three complexes prove to be excellent candidates as cryogenic magnetic coolants.

Stability of Detonation Nanodiamond Colloid with Respect to Inorganic Electrolytes and Anionic Surfactants and Solvation of the Particles Surface in DMSO–H2O Organo-Hydrosols

In this article, the stability of sols of detonated nanodiamonds, DND, with positively charged colloidal particles, is studied in different salt solutions in water–dimethyl sulfoxide (DMSO) binary systems containing 95 vol.% organic solvent. Additionally, several CCC values are determined in 95 vol.% acetonitrile for comparison. The critical coagulation concentrations (CCC) are determined using the dynamic light scattering technique and the Fuchs function. As coagulators, NaCl, NaBr, NaNO3, NaClO4, Nan-C8H17SO3, and Nan-C12H25OSO3 are used. Comparison of the CCC values in DMSO–H2O and CH3CN–H2O with those obtained in water allows us to make some conclusions. The variations of these values in different solvents are explained in terms of good and poor interfacial solvation of colloidal particles, “structural” contribution to the interparticle interaction energy, lyotropic series for anions, and more or less pronounced adsorption of surfactants. The study of the stability of DND hydrosol in solutions of anionic surfactants with different hydrocarbon tail length demonstrated the crucial role of adsorption in the coagulation process.

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH3CN and H2O:CH3CN ices

Context. Many C-, O-, and H-containing complex organic molecules (COMs) have been observed in the interstellar medium (ISM) and their formation has been investigated in laboratory experiments. An increasing number of recent detections of large N-bearing COMs motivates our experimental investigation of their chemical origin. Aims. We investigate the potential role of acetonitrile (CH3CN) as a parent molecule to N-bearing COMs, motivated by its omnipresence in the ISM and structural similarity to another well-known precursor species, CH3OH. The aim of the present work is to characterize the chemical complexity that can result from vacuum UV photolysis of a pure CH3CN ice and a more realistic mixture of H2O:CH3CN. Methods. The CH3CN ice and H2O:CH3CN ice mixtures were UV irradiated at 20 K. Laser desorption post ionization time-of-flight mass spectrometry was used to detect the newly formed COMs in situ. We examined the role of water in the chemistry of interstellar ices through an analysis of two different ratios of H2O:CH3CN (1:1 and 20:1). Results. We find that CH3CN is an excellent precursor to the formation of larger nitrogen-containing COMs, including CH3CH2CN, NCCN/CNCN, and NCCH2CH2CN. During the UV photolysis of H2O:CH3CN ice, the water derivatives play a key role in the formation of molecules with functional groups of: imines, amines, amides, large nitriles, carboxylic acids, and alcohols. We discuss possible formation pathways for molecules recently detected in the ISM.

Molecular switches and dual channel detection of Cd2+ and Fe3+ ions based on a multipodand system.

Multipodand conjugates were designed and synthesized and incorporated 5-chloro-8-hydroxyquinoline for efficient performance and fine tuning to behave as molecular switches by the addition of metals ions, protonation, and their combination in CH3 CN and CH3 CN-H2 O. Dipodand 3 and tetrapodand 4 showed a switching 'ON' of fluorescence (λem = 435-445) with Zn2+ and Cd2+ (OR logic) and switching 'OFF' of fluorescence (λem = 402) in the presence of Cu2+ , Co2+ and Ni2+ (NOR logic). 4 showed switching 'OFF' of fluorescence at 402 nm at low concentrations of Ag+ , Pb2+ , Hg2+ and Fe3+ and, on further accumulation of these metal ions, excimer bands at 432 nm (Ag+ ) and 510 nm (Pb2+ , Hg2+ and Fe3+ ) provided the opportunity for 'ON-OFF-ON' switching. In contrast, 3 showed no change with Ag+ , while Pb2+ caused only 'ON-OFF' switching and Hg2+ and Fe3+ ions caused similar 'ON-OFF-ON' switching. The H+ -induced 'ON-OFF-ON' molecular switch was combined with Cu2+ that persuaded NOR logic to mimic inhibit (INH) logic. The compound also exhibited a H+ /Cu2+ -induced 'OFF-ON-OFF' type of signalling pattern. These proton-induced multiple outputs provide opportunities for YES, NOT logic gates. 3 showed selective 'ON-OFF' behaviour with Fe3+ ions and 'OFF-ON' behaviour with Cd2+ ions in 20% HEPES buffer-CH3 CN.

A novel chemosensor for the distinguishable detections of Cu2+ and Hg2+ by off–on fluorescence and ratiometric UV–visible absorption

A novel dual-functional chemosensor, derived from the conjugation of rhodamine B with a quinoline derivative (RHQ), was firstly synthesized with high efficiency and cost-effectiveness for the distinguishable detections of Cu2+ and Hg2+ via ring-opening and ring-forming mechanism. The chemosensor exhibits highly selective and distinguishable responses for Cu2+ and Hg2+ in CH3CN–H2O (4:1, v/v) with off–on fluorescence and ratiometric ultraviolet–visible (UV–Vis) absorption changes. Additionally, Cu2+ is identified by opening a rhodamine spirocycle with a UV–Vis absorption band, at around 560 nm and fluorescence turn-on. Interestingly, Hg2+ is discerned by opening the rhodamine spirocycle and by generating a new special cycle for the quinoline unit. Resultantly, there were two UV–Vis absorption bands at around 365 nm and 560 nm, which were accompanied by fluorescence turn-on. Moreover, the chemosensor can quantitatively detect Cu2+ and Hg2+ by off–on fluorescence and ratiometric UV–Vis absorption changes, respectively. Furthermore, the chemosensor with low cytotoxicity could be successfully administered to monitor Cu2+ and Hg2+ in living cells. This work may pay the way for the development of dual-functional chemosensor for quantificationally detecting metal ions in environmental and biological systems.

A new 1,2,3-triazole-decorated imino-phenol: selective sensing of Zn2+, Cu2+ and picric acid under different experimental conditions

A new 1,2,3-triazole-based imino-phenol 1 is synthesized. It selectively senses Zn2+ in CH3CN–H2O with a detection limit of 1.8 × 10−6 M. Further, the selective sensing of Cu2+ and picric acid is achieved by the ensemble 1.Zn2+ in CH3CN–H2O.

Binuclear and tetranuclear Zn(ii) complexes with thiosemicarbazones: synthesis, X-ray crystal structures, ATP-sensing, DNA-binding, phosphatase activity and theoretical calculations.

Two Zinc(ii) complexes [Zn4(L1)4]·2H2O (1) and [Zn2(L2)2]·2H2O (2) of pyruvaldehydethiosemicarbazone ligands are reported. The complexes were characterized by elemental analysis, IR, NMR, UV-vis spectroscopy and by single-crystal X-ray crystallography. X-ray crystal structure determinations of the complexes show that though Zn : ligand stoichiometry is 1 : 1 in both the complexes, the molecular unit is tetranuclear for 1 and binuclear for 2. Both the complexes show selective sensing of ATP at pH 7.4 (0.01 M HEPES) in CH3CN–H2O (9 : 1) medium in the presence of other anions like AcO−, NO3−, F−, Cl−, H2PO4−, HPO42− and P2O72−. The UV-titration experiments of complexes 1 and 2 with ATP results in binding constants of 2.0(±0.07) × 104 M−1 and 7.1(±0.05) × 103 M−1 respectively. The calculated detection limits of 6.7 μM and 1.7 μM for 1 and 2 respectively suggest that the complexes are sensitive detectors of ATP. High selectivity of the complexes is confirmed by the addition of ATP in presence of an excess of other anions. DFT studies confirm that the ATP complexes are more favorable than those with the other inorganic phosphate anions, in agreement with the experimental results. Phosphatase like activity of both complexes is investigated spectrophotometrically using 4-nitrophenylphosphate (NPP) as a substrate, indicating the complexes possess significant phosphate ester hydrolytic efficiency. The kinetics for the hydrolysis of the substrate NPP was studied by the initial rate method at 25 °C. Michaelis–Menten derived kinetic parameters indicate that rate of hydrolysis of the P–O bond by complex 1 is much greater than that of complex 2, the kcat values being 212(±5) and 38(±2) h−1 respectively. The DNA binding studies of the complexes were investigated using electronic absorption spectroscopy and fluorescence quenching. The absorption spectral titrations of the complexes with DNA indicate that the CT-DNA binding affinity (Kb) of complex 1 (2.10(±0.07) × 106 M−1) is slightly greater than that of 2 (1.11(±0.04) × 106 M−1). From fluorescence spectra the apparent binding constant (Kapp) values were calculated and they are found to be 5.41(±0.01) × 105 M−1 for 1 and 3.93(±0.02) × 105 M−1 for 2. The molecular dynamics simulation demonstrates that the Zn(ii) complex 1 is a good intercalator of DNA.

Selective rhodamine–based probe for detecting Hg2+ and its application as test strips and cell staining

A novel probe 1 for detection of Hg2+ based on rhodamine platform was developed. The probe showed a high selectivity and anti–interference capability toward Hg2+ even in the presence of other metal ions (except Cu2+) in CH3CN–H2O (7/3, v/v) solution, and the low detection limits of 0.12 μM and 0.38 μM by using absorbance and fluorescence methods, respectively. Moreover, the mechanism of detecting Hg2+ was demonstrated due to the probe hydrolyzed to rhodamine acid in the presence of Hg2+ and exhibited a characteristic absorption band at 554 nm, which was recognized via the “naked–eye”. Noticeably, the probe was successfully applied to cell staining and the colorimetric detection for Hg2+ could realize by the test strips.

Bithiophene triarylborane dyad: An efficient material for the selective detection of CN− and F− ions

A new fluorescent chemosensor based on bithiophene coupled dimesitylborane (BMB‐1) was synthesized and characterized. BMB‐1 was used for colorimetric and turn‐on fluorescent sensing of cyanide (CN−) and fluoride (F−) ions, in the presence of other competitive anions in an aqueous (CH3CN–H2O) medium. BMB‐1 showed a hypsochromic shift (blue shift) with addition of CN− and F− ions in absorption studies. The lower detection level of CN− and F− ions is 1.37 × 10−9 and 1.75 × 10−9 M, respectively. The BMB‐1 binding mechanism is based on the nucleophilic addition of CN− and F− ions in the internal charge transfer transition of bithio moiety to the boranylmesitylene unit, and the color changes were observed under UV light. This result is further confirmed by Fourier transform infrared spectroscopy, mass spectrometry and density functional theory calculations. Also, the BMB‐1 probe is found to be a good adsorbent for the removal of F− ions in real water samples using the adsorption technique.

A dual‐function chemosensor based on coumarin for fluorescent turn‐on recognition of Hg2+ and colorimetric detection of Cu2+ in aqueous media

A novel coumarin derivative CTT was synthesized via the condensation of 7‐(N,N‐diethylamino) coumarin‐3‐aldehyde with 5‐amino‐1,3,4‐thiadiazole‐2‐thiol and its structure was characterized using infrared spectroscopy (IR), 1H NMR, mass spectrometry (MS) techniques, and elemental analysis. The recognition properties of CTT with metal ions were investigated in CH3CN–H2O (v/v = 1/1) solution using UV–vis absorption and fluorescence emission spectrum method. The results showed that CTT could monitor Cu2+ and Hg2+ simultaneously as a dual‐function chemosensor in CH3CN–H2O (v/v = 1/1). CTT could be used to detect Cu2+ colorimetrically; when using CTT, a color change from yellowish‐brown to yellowish‐green could be readily observed by the naked eye. CTT showed turn‐on fluorescent recognition of Hg2+, the fluorescence enhancement was attributed to the inhibited C=N isomerization and the obstructed excited state intramolecular proton transfer (ESIPT) of CTT. The recognition mechanism of CTT for Cu2+ and Hg2+ was studied by experiments and theoretical calculations, respectively. Therefore, CTT has the ability to be a “single chemosensor for dual targets.”

Fluorescent imidazole-based chemosensors for the reversible detection of cyanide and mercury ions.

We report 4-(2-(5-(tert-butyl)-3-formyl-2-hydroxyphenyl)-1H-phenanthro[9,10-d]imidazol-1-yl)benzoic acid 1 and 4-(2-(5-(tert-butyl)-3-formyl-2-hydroxyphenyl)-4,5-diphenyl-1H-imidazol-1-yl)benzoic acid 2 as reversible luminescent sensors for the detection of cyanide and mercury ions. These imidazole derivatives were characterized using spectroscopic techniques and single crystal X-ray crystallography. The compounds showed sensing exclusively towards CN- ions, which resulted in the quenching of fluorescence and a decreased singlet state life time. The detection limit of imidazole derivatives 1 and 2 were found to be 0.8 μM and 1.2 μM respectively, in a CH3CN/H2O system. Job's plot analysis, 1H NMR spectra and LC-MS studies supported the formation of the respective cyanohydrin. This cyanohydrin was further used as a reversible sensor for the detection of Hg2+ ions through metal-assisted elimination. The reversibility and reusability of sensors for the detection of CN- and Hg2+ ions were tested for four consecutive cycles.

The Mechanism and Kinetic Models of the Catalytic Oxidation of Ethylene by p-Benzoquinone in Aqueous–Acetonitrile Solutions of Pd(II) Cationic Complexes

A kinetic study of ethylene oxidation to acetaldehyde by p-benzoquinone in the Pd(OAc)2–HClO4−LiClO4–CH3CN–H2O system has been carried out under conditions when palladium(II) cationic complexes exist at a molar fraction of water of 0.67 and 30°С. For a reaction that mostly lead to the formation ofPd(CH3CN)(H2O) 3 2+ two-route mechanism and a kinetic model have been proposed that describe adequately the experimental dependence of the reaction initial rate on the concentration of p-benzoquinone, HClO4, and palladium. The model takes into account previous findings on the H2O/D2O and C2H4/C2D4 kinetic isotope effects and the important role of Pd(0) quinone complexes.

Hydrogen-Bond Directed Cyanide-Bridged Supramolecular 2D and 1D Bimetallic Coordination Polymers: Synthesis, Crystal Structure, and Magnetic Properties

By using K2[Ni(CN)4] as a building block and two Mn(III) compounds containing bicompartimental Schiff-base ligands as assembling segments, two new cyanide-bridged Ni–Mn complexes of the formula {[Mn(L1)(H2O)]4[Ni(CN)4]}[ClO4]2·2CH3CN (1) and {[Mn(L2)(H2O)]2[Ni(CN)4]}·CH3CN H2O (2) (L1 = N,N’-1,2-propylene-bis(3-methoxysalicylideneiminate; L2 = N,N’-1,2-propylene-bis(3-ethoxysalicylideneiminate) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray analysis. Single Xray diffraction analysis revealed the cationic pentanuclear and neutral trinuclear structures for complexes 1 and 2, respectively, and indicated that the structure of the Schiff-base ligand had obvious influence on the structural types of the target cyanide-bridged complexes. Both cyanide-bridged complexes are self-complementary via coordinated aqua ligand from one complex and the free O4 compartment from the neighboring complex, therefore giving supramolecular two-dimensional network and one-dimensional zig-zag chain structure. Study of magnetic properties revealed weak antiferromagnetic coupling within the Mn2 dimer formed by the intermolecular hydrogen bond.

A dipodal molecular probe for naked eye detection of trivalent cations (Al3+, Fe3+and Cr3+) in aqueous medium and its applications in real sample analysis and molecular logic gates.

A simple and low cost multifunctional colorimetric receptor L has been designed, synthesized and characterized by 1H-NMR, IR spectroscopy, ESI-MS spectrometry and elemental analysis. The chemosensor L can selectively detect three biologically and environmentally important trivalent metal ions (Al3+, Fe3+and Cr3+) both visually and spectrophotometrically in CH3CN–H2O (1 : 1, v/v) solution in the presence of other biologically relevant metal ions. The Job's plot analyses indicate the 2 : 2 binding stereochemistry for Al3+, Fe3+ and Cr3+ ions with L, which was further confirmed by 1H-NMR and ESI-MS studies. The binding constant values were found to be 2.9 × 104 M−1 for Al3+, 1.079 × 105 M−1 for Fe3+ and 1.366 × 105 M−1 for Cr3+ respectively. The detections limits of the sensor for Al3+ (2.8 × 10−7 M), Fe3+ (1.9 × 10−7 M) and Cr3+ (2.5 × 10−7 M) are far below than the limit set by the World Health Organization (WHO) for drinking water. Moreover, colorimetric test kits for rapid detection of Al3+, Fe3+, and Cr3+ could be successively applied for all practical purposes, indicating its potential use in environmental samples. It has also been used in building molecular logic gates.

Kinetic isotope effects in oxidation reaction of C2H4 and C2D4 by p-benzoquinone in the Pd2+—HClO4—CH3CN—H2O system

Kinetic isotope effects (KIE) have been measured for oxidation reactions of ethylene by p-benzoquinone in Pd2+—MeCN—H2O—HClO4 system. Under the conditions of preferred formation of complex Pd(MeCN)(H2O)3 2+ the ratio between the initial reaction rates $$R_{{C_2}{H_4}} 0/R_{{C_2}{D_4}} 0$$ is equal to 1.14±0.06 and is close to the KIE for classical chloride systems. Based on the obtained results and previous data for C2H4—C2D4 and H2O—D2O (0.97±0.12) systems, the slow step was proposed in the reaction mechanism–a trans-addition of water molecule to the cationic p-complex LPd(H2O)2(CH2CH2)2+ with formation of metalcarben-ium ion solvated by water molecule (LPd(H2O)2(CH2CH2O+H2)+).

Structure of bis(citrato)germanates with different types of cations: (Hphen)2[Ge(HCit)2·3H2O], [CuCl(phen)2]2[Ge(HCit)2·6H2O], where H4Cit is citric acid, phen IS 1,10-phenanthroline

The procedures are developed and the complexation products are preparatively isolated from GeO2–H4Cit-phen–CH3CN–H2O (I) and GeO2–H4Cit–CuCl2-phen–C2H5OH–H2O (II) systems (phen is 1,10-phenanthroline, H4Cit is citric acid). The (Hphen)2[Ge(HCit)2]·3H2O (I) and [Cu(phen)2Cl]2[Ge(HCit)2]·6H2O (II) complexes are characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction. The compounds are formed from centrosymmetric octahedral [Ge(HCit)2]2– anions, Hphen+ (I) and [Cu(phen)2Cl]+ (II) cations, and crystallization water molecules. The structural units in the crystals are linked via a system of hydrogen bonds.

Naphthalene and pyrrole substituted guanidine in selective sensing of Cu2+, Hg2+, Pb2+ and CN− ions under different conditions

Naphthalene and pyrrole substituted guanidine 1 has been designed and synthesised. Compound 1 efficiently distinguishes Cu2+, Hg2+ and Pb2+ ions by exhibiting different responses in fluorescence. While compound 1 exhibited turn-on emission selectively in the presence of Hg2+ and Pb2+ ions in CH3CN and CH3CN–H2O (1:1, v/v), respectively, it showed decrease in emission upon interaction with Cu2+ ion in CH3CN. Furthermore, the Cu-1 ensemble has been established as a potential probe for selective detection of CN− ion over a series of other anions involving colour change (in ordinary light: colourless to light yellow and under UV light: colourless to sky blue). Theoretical insight has been invoked to understand the mode of metal–ligand interaction.

Complexation study of Schiff base ligand: pyridin-2-ylimino methyl naphthanol with Co+2, Mn+2 and Ni+2 ions in solid and solution phase

Schiff base pyridin-2-ylimino methyl naphthanol (HL) was synthesized and characterized by spectroscopic (FTIR, ESIMS, and NMR) techniques. The ligand was reacted with perchlorate salts of Mn+2, Co+2, and Ni+2. ESIMS mass spectra indicate the formation of mononuclear complex ML2 for all three complexes. CoL2 crystallizes in P21/n space group, adopting a distorted tetrahedral geometry where Co is in a N2O2 donor environment. Structure of the Co complex was optimized by DFT calculation. Solution-phase complexation between the ligand and the three metals ions: Mn+2, Co+2, and Ni+2 (pH 7.2 in tris buffer), in CH3CN–H2O was performed spectrophotometrically by UV–vis spectral study. Job’s plot from each titration suggests a 1 : 2 metal to ligand combination. The association constants for the formation of ML2 are as follows: Mn (19.80 × 103 M−1), Co (14.54 × 103 M−1) and Ni (19.04 × 103 M−1).

3-Butenyloxycarbonyl as a new hydroxyl protecting group in carbohydrate synthesis

3-Butenyloxycarbonyl (Bloc) has been identified as a new hydroxyl protecting group, which can be introduced under mild conditions in high yields and selectively removed by OsO4/NaIO4/2,6-lutidine in CH3CN–H2O without affecting most commonly-used protecting groups. Moreover, this new protecting group is inert under glycosylation conditions.