Synthesis,Spectral and Magnetic Properties,and Crystal Structures of Copper(II) Pyridinecarboxylate Adducts with N‐Heterocyclic Ligands

Synthesis and characterization of seven new complexes [Cu(2‐MeSnic)₂(CH₃OH)]₂ (where 2‐MeSnic is 2‐methylthionicotinate), [Cu(2‐MeSnic)₂L₂]₂ (where L is pyridine — py, ethylnicotinate — Etnic and butylnicotinate — Bunic), [Cu(2‐MeSnic)₂L₂(H₂O)₂] (where L is py and nicotinamide — nia) and [Cu(2‐MeSnic)₂(N‐Menia)₂(H₂O)₂]·2H₂O (where N‐Menia is N‐methylnicotinamide) are reported. The characterization were based on elemental analysis, infrared, electronic and EPR spectra, and magnetic susceptibility measurements over a temperature range of 1.8 — 300 K or 70 — 300 K. Three complexes of different type were studied by X‐ray analysis. The molecule of [Cu(2‐MeSnic)₂(CH₃OH)]₂ has dimeric paddle‐wheel cage structure with a tetragonal pyramidal arrangement around Cu^II. The dimer results from the fact that carboxyl groups of four 2‐MeSnic anions function as bridging in a syn‐syn arrangement. On the other hand [Cu(2‐MeSnic)₂(py)₂]₂ forms dimers with hexacoordinated Cu^II atoms in highly distorted coordination octahedra, each with two oxygen atoms of bridging carboxyl groups in an anti‐anti arrangement of two 2‐MeSnic anions, with two oxygen atoms of one asymmetrically chelating 2‐MeSnic anion and with two nitrogen atoms of two pyridine ligands. The temperature independent EPR spectrum for this complex exhibits an axial signal which corresponds to almost isolated S = ¹/₂ magnetic ions. Magnetic data for the dimer show a weak antiferromagnetic interaction between the two metal ions with J = —0.65 cm^—1. The Cu^II atom in complex [Cu(2‐MeSnic)₂(py)₂(H₂O)₂] is hexacoordinated in an elongated centrosymmetrical tetragonal‐bipyramidal arrangement (4 + 2). Based on the molecular structure the electronic, infrared, electron paramagnetic resonance spectra and magnetic properties are discussed and stereochemistry as well as the mode of ligand coordination in new solid complexes under study have been determined.     

Sensitivity and specificity of the BAX for screening/Listeria monocytogenes assay: internal validation and independent laboratory study

In this study to certify the BAX for Screening/Listeria monocytogenes assay (DuPont Qualicon, Wilmington, DE), an internal evaluation was conducted on 16 food types that were simultaneously analyzed with the BAX system (BAX), and the ISO method for the detection of L. monocytogenes (ISO). No statistically significant difference in performance between the BAX and ISO methods was observed. Inclusivity/exclusivity testing showed that the BAX system was able to detect 97 of 97 (100%) of L. monocytogenes strains tested. None of 56 other Listeria species or non-Listeria tested gave a reproducible positive BAX result. Ruggedness testing demonstrated that performance of the assay was not affected by reasonable variability in the operating parameters. BAX was then submitted for independent laboratory validation. In this phase, BAX was compared with standard culture methods for the detection of L. monocytogenes in chicken (USDA-FSIS), crab meat (BAM), and milk (AOAC). This study validated product claims of sensitivity and specificity >98% in accordance with AOAC Performance Tested Method requirements.     

Tetrathiomolybdates of nickel

Summary The complexes [Ni(en)₃]MoS₄, [Ni(dien)₂]MoS₄ and [Ni(phen)₂(MoS₄)]·2H₂O (en = ethylenediamine, dien = diethylenetriamine, phen = 1,10-phenanthroline) were prepared. On the basis of their magnetochemical and spectral properties the compounds can be characterized as octahedral nickel(II) complexes. The complexes were also studied by c.v. Chemical oxidation of [Ni(en)₃]MoS₄ affords [Ni(en)MoS₄]₂SO₄; this complex has been characterized by i.r. and e.p.r. spectroscopy and by magnetic measurements.     

Diethylenetriammonium Aquapentachloroferrate(III) Chloride: Structure and Magnetic Properties

Diethylenetriamine (dien) and iron(III) chloride in aqueous HCl yield (dienH₃) [FeCl₅(H₂O)]Cl, in which the chloroferrate(III) anion is significantly distorted from octahedral symmetry due to the extensively hydrogen‐bonded lattice. On cooling, the high spin Fe^III material shows weak antiferromagnetic coupling that results in a Néel temperature of 2.70 K.     

Evaluation of the BAX system for detection of Listeria monocytogenes in foods: collaborative study

A multilaboratory study was conducted to compare the automated BAX system and the standard cultural methods for detection of Listeria monocytogenes in foods. Six food types (frankfurters, soft cheese, smoked salmon, raw, ground beef, fresh radishes, and frozen peas) were analyzed by each method. For each food type, 3 inoculation levels were tested: high (average of 2 CFU/g), low (average of 0.2 CFU/g) and uninoculated controls. A total of 25 laboratories representing government and industry participated. Of the 2335 samples analyzed, 1109 were positive by the BAX system and 1115 were positive by the standard method. A Chi square analysis of each of the 6 food types, at the 3 inoculation levels tested, was performed. For all foods, except radishes, the BAX system performed as well as or better than the standard reference methods based on the Chi square results.     

Sensitivity and specificity of the test kit BAX for screening/E. coli O157:H7 in ground beef: independent laboratory study

An independent laboratory study of the BAX for Screening/E. coli O157:H7 kit was conducted at the National Food Laboratory, Inc., Dublin, CA, to complete AOAC Performance Tested Method certification. The BAX system kit was compared with the BAM culture method and a modified BAM culture method for detection of E. coli O157:H7 in ground beef. The BAX system kit detected the target organism at levels approximately 10-fold lower than those that gave positive BAM results. This study validated product claims, and Performance Tested Method status was granted.     

[Fe19] “Super‐Lindqvist” Aggregate and Large 3D Interpenetrating Coordination Polymer from Solvothermal Reactions of [Fe2(OtBu)6] with Ethanol

The syntheses, crystal structures, and physical properties of [HFe₁₉O₁₄(OEt)₃₀] and {Fe₁₁(OEt)₂₄}_∞ are reported. [HFe₁₉O₁₄(OEt)₃₀] has an octahedral shape. Its core with a central Fe metal ion surrounded by six μ₆‐oxo ligands is arranged in the rock salt structure. {Fe₁₁(OEt)₂₄}_∞ is a mixed‐valence coordination polymer in which Fe^III metal ions form three 3D interpenetrating (10,3)‐b nets. The arrangement of the Fe^III ions can also be compared to that of Si ions in α‐ThSi₂. Thus, the described structures are at the interface between molecular and solid‐state chemistry.     

A mononuclear complex and a cubane cluster from the initial use of 2-(hydroxymethyl)pyridine in nickel(II) carboxylate chemistry

The reactions of 2-(hydromethyl)pyridine, hmpH, with Ni(O₂CMe)₂·4H₂O in H₂O, in the absence of counterions, have been investigated. The synthetic study has led to the two new complexes [Ni(O₂CMe)₂(hmpH)₂] (1) and [Ni₄(O₂CMe)₄(hmp)₄(H₂O)₂] (2). Complex 1 can also be transformed into 2 by reacting with an excess of NaOH in H₂O. The structures of 1 and 2·2.25H₂O·0.5(1,4-dioxane) have been solved by single-crystal, X-ray crystallography. The octahedral Ni^II center in centrosymmetric 1 is coordinated by two 1.10 (Harris notation) MeCO₂⁻ groups and two N,O-chelating (1.11) hpmH ligands. The tetranuclear cluster molecule of 2·2.25H₂O·0.5(1,4-dioxane) possesses a distorted cubane {Ni₄(μ₃-OR′)₄}⁴⁺ core [R′ = (2-pyridyl)CH₂–] with the Ni^II ions and the oxygen atoms from the 3.31 hmp⁻ ligands occupying alternate vertices of the cube. Two 2.11 MeCO₂⁻ groups cap two opposite faces of the cube, while two 1.10 MeCO₂⁻ ions and two aqua ligands complete the octahedral coordination sphere of the metal centers. Characteristic IR bands for the two complexes are discussed in terms of the nature of bonding and the structures of the two complexes. The variable-temperature magnetic properties of 2 have been modeled with two J values, and reveal antiferromagnetic exchange interactions between the four Ni^II ions to give a diamagnetic ground state.     

Preparation,Structure, Spectral,and Magnetic Properties of Copper(II) Halogenonicotinates: Crystal and Molecular Structure of Tetrakis(μ‐2‐chloronicotinato‐O,O′)‐diaquadicopper(II)

The characterization of the complexes [Cu₂(2‐Clnic)₄(H₂O)₂] ( 1 ), [Cu(2,6‐Cl₂nic)₂(H₂O)₂] ( 2 ) and [Cu(5‐Brnic)₂(H₂O)₂]_n ( 3 ) (where 2‐Clnic = 2‐chloronicotinate, 2,6‐Cl₂nic = 2,6‐dichloronicotinate or 5‐Brnic = 5‐bromonicotinate) was based on elemental analysis, IR, electronic and EPR spectra, and magnetic susceptibility. Complex 1 was also studied by X‐ray analysis at 298 1a and 80 K 1b . The complex 1 contains a dinuclear Cu‐acetate molecular structure in which the carboxyl groups of the 2‐chloronicotinate ligands act as bridges and water molecules are at apical positions. The stereochemistry about Cu atom at both temperatures is typical for square pyramidal geometry with CuO₄O chromophore. The Cu‐Cu distance is 2.6513(8) and 2.6382(6) Å for 1a and 1b , respectively. The Cu atoms are displaced by 0.2069(9) and 0.1973(7) Å, respectively, from the plane containing four oxygen atoms bonded to the Cu atom toward the apical water molecules. Strong and weak hydrogen bonds as well as C–Cl···π interactions in the crystal structure are discussed as well. Both complexes, monomeric [Cu(2,6‐Cl₂nic)₂(H₂O)₂] ( 2 ) and polymeric [Cu(5‐Brnic)₂(H₂O)₂]_n ( 3 ), possess octahedral copper(II) stereochemistry with differing tetragonal distortions.