EPR investigation of the spin-spin interactions in a Cu(II)-Gd(III)-Fe(III) heterospin system

The spin-spin interactions in a system that contains three different spin carriers, [{LCu}Gd(H₂O)₃×{Fe(CN)₆}] _n ·4nH₂O (1) [L²⁻, N,N-propylenedi(3-methoxysalicylideneiminato)], were investigated by electron paramagnetic resonance spectroscopy. Additional information was obtained by analyzing the discrete heterobinuclear system [LCu(OH₂)Gd(O₂NO)₃] (2), which contains the Cu(II)-Gd(III) pair also existing in the structure of 1, and the compounds [{LCu}Gd(H₂O)₃{Co(CN)₆}] _n ·3.5nH₂O and [{LCu}La(H₂O)₃×{Fe(CN)₆}] _n ·4nH₂O, which are isostructural with 1 and in which the paramagnetic low-spin Fe(III) and Gd(III) ions were replaced by diamagnetic low-spin Co(III) and La(III), respectively. The investigations were carried out in the temperature range of 293–4 K in both X- and Q-bands and also using a dual-mode X-band. The experimental spectra of the Cu(II)-Gd(III) pairs in 2 were interpreted as the sum of spectra of the ground spin state with total S = 4 and the excited state with S = 3 appearing due to the ferromagnetic exchange interaction between Cu(II) and Gd(III) ions. By fitting the experimental and simulated spectra, the zero-field splitting parameters of the Gd(III) ion are estimated and it is shown that no influence of the anisotropic interaction is detected. The magnetic properties of 1 are discussed from the perspective of the interaction of the Cu(II)-Gd(III) binuclear fragments with the Fe(III) ions.     

Sonochemical synthesis and characterization of three nano zinc(II) coordination polymers; Precursors for preparation of zinc(II) oxide nanoparticles

Nanostructures of three Zinc(II) coordination polymers, [Zn(NNO)₂(H₂O)₄]_n (1), [Zn(PNNO)₂(H₂O)₂]_n (2) and [Zn(H₂O)₆]·(INNO)₂ (3) {NNO: Nicotinic acid N-oxide, PNNO: Picolinic acid N-oxide and INNO: Isonicotinic acid N-oxide}, have been synthesized by a sonochemical process and reaction of ligands with Zn(CH₃COO)₂. The Zinc(II) oxide nano-particles have been synthesized from thermolysis of [Zn(NNO)₂(H₂O)₄]_n (1), [Zn(PNNO)₂(H₂O)₂]_n (2) and [Zn(H₂O)₆]·(INNO)₂ (3) at two different methods (with surfactant and without surfactant) and two temperatures (200 and 600 °C). The ZnO nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Comparison of the SEM images of ZnO nano-particles at two different methods and temperatures shows that higher temperature results in an increasing of agglomeration and thus small and spherical ZnO particles with good separation were produced by thermolysis of compounds at 200 °C and by use of surfactant.     

The Infrared Spectra of the First Transition Series Metal(II) Bis(Aquo) Complexes Of 8-Hydroxyquinoline

Abstract

The infrared spectra (700–100 cm^?1) of the complexes [M(ox)₂(H₂O)₂] (ox = 8-hydroxyquinolinate anion, M = Mn, Fe, Co, Ni, Cu, Zn) are discussed. For the purposes of assignment of the metal ligand modes, deuterated 8-hydroxyquinoline-d ₇ was prepared by the Skraup synthesis and the spectra of the deuterated complexes were compared with those of the unlabelled species. Furthermore, [⁶⁴Zn(ox)₂(H₂O)₂] and [⁶⁸Zn(ox)₂(H₂O)₂] were prepared by reaction of ⁶⁴ZnSO₄ and ⁶⁸ZnSO₄ with 8-hydroxyquinoline and the effects of metal isotope labelling on the spectra were examined and compared with earlier isotopic data on the nickel and zinc complexes.     

Effect of (H2O)n (n = 1–3) clusters on H2O2 + HO → HO2 + H2O reaction in tropospheric conditions: competition between one-step and stepwise routes

ABSTRACT

Effects of (H₂O)_n (n?=?1–3) on the H₂O₂?+?HO?→?HO₂?+?H₂O reaction have been investigated by the reactions of H₂O₂L(H₂O)_n (n?=?1–3)?+?HO and H₂O₂?+?HOL(H₂O)_n (n?=?1–3) at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory, coupled with rate constant calculations by using canonical variational transition state theory. Interestingly, for the former reactions, one-step process and stepwise mechanism are involved, where one-step processes occurring though cage-like hydrogen bonding network complexes and the transition states are favourable. Due to larger effective rate constants, these favourable processes are also favourable than the corresponding latter reactions. Meanwhile, the catalytic effect of (H₂O)_n (n?=?1–3) is mainly taken from water monomer, because the effective rate constant (k'(R_WM2)) of H₂O₂···H₂O?+?HO reaction is, respectively, larger by 3, 6–10 orders of magnitude than that of H₂O₂···(H₂O)₂?+?HO (k'(R_WD1)) and H₂O₂···(H₂O)₃?+?HO (k'(R_WT1)) reactions. Furthermore, the enhancement factor of water molecular (k'(R_WM2)/k_tot) is only 0.28% at 240?K, while at high temperature (such as at 425?K), the positive water vapour effect enhances up to 27.13%. This shows that at high temperatures the positive water effect is obvious under atmospheric conditions.     

Acid‐base properties and supramolecular structure of N‐[(hydroxymethyl)triazolyl]triflamides: DFT,ab initio,and FTIR study

For N‐{[2‐(hydroxymethyl)‐2H‐1,2,3‐triazolyl‐4‐yl]methyl}triflamide 1 , N‐{[2‐(hydroxymethyl)‐2H‐1,2,3‐triazolyl‐4‐yl]methyl}‐N‐phenyltriflamide 2 , and N,N‐bis{[2‐(hydroxymethyl)‐2H‐1,2,3‐triazolyl‐4‐yl]methyl}triflamide 3 , the proton affinities of the triazole nitrogen atoms and the hydroxy and sulfonyl oxygen atoms as well as the energies of formation of the conformers with intramolecular H‐bonds and dimers with intermolecular NH?N, OH?N, OH?O═S, and NH?O═S H‐bonds were calculated by density functional theory and second‐order Møller‐Plesset perturbation methods. Quantum Theory of Atoms in Molecules analysis was performed to investigate the nature of H‐bonds. According to Fourier transform infrared spectroscopy, in CH₂Cl₂ solution, the monomeric molecules of 1 to 3 exist in the equilibrium with cyclic dimers having the OH?N hydrogen bonds.     

Infrared and Raman Spectra of Sulfur-Nitride Complexes of Nickel(II) and Palladium(II)

Abstract

The infrared and Raman spectra of trans-Ni(S₂N₂CH₃)₂ and Pd(S₃N)₂ were measured from 4000-200 cm^?1. The absorption bands were assigned by comparison to the sulfur nitride complexes of nickel(II), palladium(II) and platinum(II). Normal coordinate analyses on these complexes were carried on these data using molecular parameters taken from X-ray data. To aid in band assignments, isotope shift data on trans-⁶²Ni(S₂N₂CH₃)₂ have also been carried out.     

A luminescent Zn(II)-Containing Complex: Selective Sensing of Cr(VI) Anion and Application Values on Tuberculosis Care Through Increasing the Antibacterial Response of Macrophages

Journal of Fluorescence - A new Zn(II)-bearing metal-organic framework (MOF), namely, {[Zn2(L)2(H2O)]·8H2O·DMF}n (1) has been generated via applying...     

Preparation, Structure and Near-infrared Luminescent Property of Yb(III) Complex with 2,4,6-Pyridinetricarboxylic Acid

A rare earth ytterbium complex with 2,4,6-pyridinetricarboxylic acid (H₃pta) has been synthesized by hydrothermal method, the formula is {[Yb₂(pta)₂(H₂O)₃]·H₂O}_n. The complex crystallized in monoclinic system, P2₁/c space group with lattice parameters a?=?11.6556(19)Å, b?=?7.8364(12), c?=?22.020(4), α?=?γ?=?90º, β?=?92.120(3), Z?=?4, GOF?=?1.026, R1?=?0.0334, wR2?=?0.0660. The pta anions connect four rare earth Yb(III) ions with two different coordination modes. The complex exhibit intense characteristic near-infrared luminescence of Yb(III) ions at 990 nm with excitation of UV-rays.     

Ultrasound-assisted synthesis of metal organic framework for the photocatalytic reduction of 4-nitrophenol under direct sunlight

In this study, the metal organic framework MOF [Zn(BDC)(DMF)] crystal was synthesized via ultrasonic irradiation and solvothermal method. The synthesized MOF [Zn(BDC)(DMF)] crystal was characterized by PXRD, FTIR, FESEM-EDX, TGA, UV-DRS and BET. The catalytic activity of MOF [Zn(BDC)(DMF)] was investigated by 4-nitrophenol (4-NP) degradation under direct sunlight irradiation. The influence of various degradation parameters such as initial 4-NP concentration, dosage, pH and H₂O₂ concentration were investigated. The results indicated that the synthesized MOF [Zn(BDC)(DMF)] exhibited strong photocatalytic activity in the presence of NaBH₄ under sunlight irradiation and the reduction of 4-NP to 4-aminophenol (4-AP) completed within 10 min. The study provides the synthesized MOF [Zn(BDC)(DMF)] crystal can be used as a high performance catalyst for the treatment of dyes in wastewater.     

A Co-Crystallised Cobalt(II) Cluster of Pyridinedicarboxylic Acid (PDC) as a Luminescent Material for Selective Sensing of Methanol

A luminescent Cobalt(II) co-crystal [Co₁₃(PDC)₁₆(H₂O)₂₄.7H₂O] 1 (where H₂PDC?=?2,6-pyridinedicarboxylic acid) have been prepared by oven-heating and slow evaporation of solvent. Single crystal X-ray diffraction (SCXRD) analysis revealed that 1 is a mixture of complexes that crystallizes in the triclinic space group P-1 and the geometry around the Co(II) ions is octahedral. The structure is extensively imbued with hydrogen bonding that helps in stabilizing the complex. Thermogravimetric analysis indicates that 1 is thermally stable up to 364 ^οC. The luminescence properties of 1 revealed a strong emission centered at 437 nm (λex?=?345 nm) assigned to ligand to metal charge transfer (LMCT). The luminescence sensing of 1 towards volatile organic molecules were also examined. However, 1 displayed a turn off towards methanol compared to other molecules with high quenching efficiency and low limit of detection (3.5?×?10^?4 vol%). The results show excellent selectively and high sensitivity. Powder X-ray diffraction studies revealed that the structural integrity of the complex was maintained after exposure to methanol vapour. Theoretical studies also revealed small binding energy (?413.2 au) and low energy gap (1.19) for 1-CH₃OH adduct.

     

Vibrational spectroscopic investigation of the hydrates of manganese(II) oxalate

The three known hydrates of manganese(II) oxalate, α‐MnC₂O₄ · 2H₂O, γ‐MnC₂O₄ · 2H₂O and MnC₂O₄ · 3H₂O were synthesized by known procedures and characterized by X‐ray powder diffractometry. Their infrared (IR) and Raman spectra were recorded and discussed on the basis of its structural peculiarities allowing to establish some interesting relations between them and with other, previously investigated, oxalate complexes. The IR spectra of partially deuterated samples of α‐MnC₂O₄ · 2H₂O were also discussed, reinforcing some of the performed assignments. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectroscopic and E. P. R Studies of the Crystal and Molecular Structure of Cu(2-Benzoylpyridine)2(NO3)2.H2O

Abstract

Solid Cu(2-Benzoylpyridine)₂(NO₃)₂ has been studied by UV-Vis, IR, and EPR (X-band, Q-band) techniques. Monoclinic crystal symmetry was determined with two molecules per unit cell. Copper (II) is coordinated by two benzoylpyridine ligands and a single NO₃ group in the chromophore CuN₂O₃ of distorted trigonal bypiramidal stereochemistry. Exchange coupling values were determined from EPR spectra as |J| = 0.0026(2) cm^?1 between magnetically nonequivalent copper (II) sites, and |J| < O.3 cm^?1 between equivalent sites.

Results are discussed by a comparison with Cu(II)-benzoyl-pyridine complexes coordinated with azide N₃ ^? anions.     

Infrared Spectra of Some Metal (II) Complexes of 2-Aminomethylpyridine

Abstract

Band assignments in the IR spectra (700–150 cm^?1) of [M(amp)₃] (ClO₄)₂ (amp = 2-aminomethylpyridine; M = Mn(II), Fe(II), Co(II), Ni(II), Zn(II), [Zn(amp)₂Cl₂] and [Pt(amp)Cl₂] derived from amp-ND₂, their unlabelled analogues, [Zn(amp)₂X₂] (X = Br, I) and [Pt(amp)Br₂] are discussed.     

Syntheses, structures, fluorescence and thermal properties of three lanthanide coordination polymers built by N-benzoyl-N′-(4-benzoxy)thiourea

Three novel lanthanide 1-D chain coordination polymers, namely {[Tb(μ₂-L)₂(η²-NO₃)(CH₃OH)(H₂O)]·0.5CH₃OH·0.5H₂O}_n (1), {[Dy(μ₂-L)₂(η²-NO₃)(CH₃OH)(H₂O)]·H₂O}_n (2) and {[Ce(μ₂-L)₂(η²-NO₃)(H₂O)₃]·H₂O}_n (3) (HL=N-benzoyl-N′-(4-benzoxy)thiourea), have been prepared and characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. The luminescence properties and themostabilities of polymers 1-3 have been determined as well.     

Radiation chemistry of tris(acetylacetonato) cobalt(iii) in aqueous solutions

Abstract

On radiolysis tris(acetylacetonato) cobalt(III) in aqueous solutions is found to get reduced by reaction with (1) hydrated electrons, (2) H atoms, (3) OH radicals and (4) C₂H₂OH radicals. The bimolecular rate constants for the first three reactions, determined by competition kinetics are: 4 × 10¹⁰, 2.3 × 10⁹ and 4.7 × 10⁹ M^?1sec^?1 respectively. Absorption spectra of the irradiated solutions indicate the formation of bis(acetylacetonato) cobalt(II) from reaction (1), but not from (3). The total cobaltous yield in air-free solutions is given byG(Co⁺⁺) = 5.6 and 6.5 at pH 6.5 and 1 respectively. It appears that G_eaq- ∽ _H ⁺ G_oH ∽ 2.8 in neutral solutions. Considerations of material balance for the primary yields of radiolysis of water suggest the possibility that the so-called independent H-atoms in neutral solutions are probably excited water molecules or ion-pairs.     

ESR investigation of some copper(II)-dioxime-dichloride compounds

The following copper(II)-dioxime-dichloride compounds: [Cu(G)Cl₂]₂, [Cu(P)Cl₂]₂, [Cu(DMG)Cl₂]₂ and [Cu(O)Cl₂]₂ (where G=C₂H₄O₂N₂, P=C₃H₆O₂N₂, DMG=C₄H₈O₂N₂, O=C₈H₁₄O₂N₂) were investigated by ESR method. Spectra of powder samples obtained in the g?2 region suggest the presence of triplet ground state (S=1) realized by a weak ferromagnetic exchange coupling. In liquid and frozen solutions the monomeric species (S=1/2) prevail. Some delicate changes in the coordination polyhedra symmetry in terms of ligand molecules and solvents nature were evidence. A 4p-admixture degree of 2% in the d_xy ground state was estimated for pseudotetrahedral (Td) species in frozen solutions.     

EPR of Cu2+ in cadmium saccharin [Cd(sac)2(H2O)4]·2H2O and [Cd(sac)2(HydEt-en)2] complexes in single-crystal and powder forms

The electron paramagnetic resonance spectra of Cu²⁺ in [Cd(sac)₂(H₂O₄]·2H₂O and [Cd(sac)₂(HydEt-en)₂] (HydEt-en=N-(2-hydroxyethyl)-ethylenediamine) single crystals and powder were examined at room temperature. A detailed study of the spectra of the compounds indicates the replacement of Cd²⁺ in the host compounds with Cu²⁼. [Cd(sac)₂(H₂O)₄]·2H₂Oshows the presence of two sites for Cu²⁺ and [Cd(sac)₂(HydEt-en)₂] has a single site. The principal values for theg-tensor and the hyperfine tensor for Cu²⁺ in the two compounds were obtained. The Cu²⁺ ion was found to be mostly in the 3d_x ²−y ² orbital and the ground-state wavefunction of [Cd(sac)₂(HydEten]₂] was constructed.     

On the luminescence of manganese(II) phosphates

Luminescent properties of manganese(II) phosphates prepared by thermal dehydration of Mn(H₂PO₄)₂·2H₂O have been studied. The emission spectrum consists of two bands whose relative intensity and spectral position depend on the chemical and crystalline structure of phosphates. The different courses of temperature quenching of luminescence intensity and excitation spectra of each emission band of Mn(H₂PO₄)₂·2H₂O, Mn(H₂PO₄)₂, MnH₂P₂O₇ and c-Mn₂P₄O₁₂ are discussed.     

The HO4H → O3 + H2O reaction catalysed by acidic,neutral and basic catalysts in the troposphere

A detailed effects of catalyst X (X?=?H₂O, (H₂O)₂, NH₃, NH₃···H₂O, H₂O···NH₃, HCOOH and H₂SO₄) on the HO₄H → O₃?+?H₂O reaction have been investigated by using quantum chemical calculations and canonical vibrational transition state theory with small curvature tunnelling. The calculated results show that (H₂O)₂-catalysed reactions much faster than H₂O-catalysed one because of the former bimolecular rate constant larger by 2.6–25.9 times than that of the latter one. In addition, the basic H₂O···NH₃ catalyst was found to be a better than the neutral catalyst of (H₂O)₂. However it is marginally less efficient than the acidic catalysts of HCOOH, and H₂SO₄. The effective rate constant (k'_t) in the presence of catalyst X have been assessed. It was found from k'_t that H₂O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320?K at 0?km altitude. However, compared with the rate constant of HO₄H → H₂O?+?O₃ reaction, the k _eff values for H₂O catalysed reaction are smaller by 1–2 orders of magnitude, indicating that the catalytic effect of H₂O makes a negligible contribution to the gas phase reaction of HO₄H → O₃?+?H₂O.

Highlights

• A detailed effects of catalyst of H₂O, (H₂O)₂, NH₃, NH₃···H₂O, H₂O···NH₃, HCOOH and H₂SO₄ on the HO₄H → O₃?+?H₂O reaction has been performed.

• From energetic viewpoint, H₂SO₄ exerts the strongest catalytic role in HO₄H → O₃?+?H₂O reaction as compared with the other catalysts.

• At 0 km altitude H₂O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K.

• HO₄H → H₂O?+?O₃ reaction with H₂O cannot be compete with the reaction without catalyst, due to the fact that the effective rate constants in the presence of H₂O are smaller.

     

Structural, vibrational, thermal and magnetic investigation of novel Co(II), Cu(II), Zn(II) and Hg(II) crystalline metal complexes with 2-amino-5-benzylmercapto-1,3,4-thiadiazole: a low weight model of protonated copolymer resin

The 2-amino-5-benzylmercapto-1,3,4-thiadiazole (C₉H₉N₃S₂) is a low weight model of a protonated copolymer resin used as a metal uptake agent. New monomeric crystalline metal complexes of C₉H₉N₃S₂ with Co(II), Cu(II), Zn(II) and Hg(II) were synthesized and investigated in order to facilitate the interpretation of the metal/resin binding mode. These materials have been studied by single crystal X-ray Diffraction and FTIR Spectroscopy at room temperature. Crystal data for these triclinic phases are reported. All frameworks consist of discrete monomeric units that provide crystalline stability through a network of hydrogen bond interactions. The Co(II), Zn(II) and Hg(II) ions are surrounded by a tetrahedral arrangement of two thioether monodentate ligands (each one coordinating by a N(1)_thiadiazole atom) and two chlorine atoms. The Cu(II) ion is coordinated by four thioether monodentate ligands (each one coordinating by a N(1)_thiadiazole atom) and one chlorine atom as nearest neighbor in a distorted square pyramidal polyhedron. The spectroscopic data are consistent with the structural model. FTIR spectra evidence changes in the H-bonds in the crystal packing when coordination with these divalent ions is present. Magnetic susceptibility at room temperature for Cu(II) and Co(II) complexes, EPR spectrum at room temperature for Cu(II) complex and thermal properties for all complexes were measured. These results could be useful for the interpretation of the binding mode of M(II)/1,3,4-thiadiazole-2-amino-5-thiol in protonated copolymer resin which are used as uptake agents of toxic metallic ions.