The Vibrational Spectra of Complexes with Planar Monothiooxamides. IV. The Copper(II) and Copper(I) Complexes of Neutral Monothiooxamides

The new complexes CuX₂(LH₂), CuX₂ (SH₃) (X = Cl, Br), CuX(LH₂), CuX(SH₃) (X = Cl, Br, I), CuX(H₄MTO)₂ (X = Cl, Br), Cul(H₄MTO) and CuX(H₃MMTO)₂ (X = Cl, Br, I), where LH₂ = N.N′-dimethyl-monothiooxamide, SH₃ = N(s)-methylmonothiooxamide, H₄MTO = monothiooxamide and H₃MMTO = N_(o)-methylmonothiooxamide, have been prepared. The complexes were characterized by elemental analyses, conductivity measurements, magnetic moments and spectroscopic (UV/VIS, FT-IR, Laser-Raman) studies. The vibrational analysis of the complexes has been given using NH/ND, CH₃/CD₃ and ⁶³cu/⁶⁵cu isotopic substitutions. The neutral monothiooxamides behave as monodentate ligands in the Cu(I) complexes coordinating through their thioamide sulfur atom. The ligands LH2 and SH₃ act as bidentate chelating agents in the Cu(II) complexes with ligated atoms being the thioamide sulfur and the amide oxygen.     

The Synthesis,Vibrational Spectra,Electronic Spectra,and Thermal Analysis of Some Mixed Complexes with Planar Dithiooxamides

Planar Pd(LH)₂ complexes (LH₂ = H₂N C S C S N H₂, CH₃HNCSCSNHCH₃) form mixed polymeric complexes with Ni(II), Cu(II), Zn(II) and Cd(II) in alcalic media, where the planar Pd(LH)₂ complexes act as tetradentates with N-coordination. The electronic spectra and thermal behaviour are discussed, a thorough investigation of the i.r. spectra is presented and special attention has been given to the H/D, CH₃/CD₃ and ⁵⁸Ni/⁶²Ni, ⁶³Cu/⁶⁵Cu and ⁶⁴Zn/⁶⁸Zn isotopic shifts.     

The Vibrational Spectra of Complexes with Planar Monothiooxamides. III. The Palladium(II) Complexes of Neutral Monothiooxamides

The new complexes trans-[PdX₂(H₄MTO)2] (X = Cl, Br, I), trans-[PdX₂(H₃MMTO)2] (X = Cl, Br, I), trans-[PdX₂(SH₃)2] (X = Cl, Br), [Pd(H₄MTO)₄]CI₂ and [Pd(H₃MMTO)₄]CI₂, where H₄MTO = monothiooxamide, H₃MMTO = N(o)-methylmonothiooxamide and SH₃ = N(s)-methylmonothiooxamide, have been prepared. The complexes were characterized by elemental analyses, conductivity measurements, X-ray powder patterns, thermal methods and spectroscopic (UV/VIS, FT-IR, Laser-Raman) studies. The vibrational analysis of the complexes is given using NH/ND and CH₃/CD₃ isotopic substitutions. Monomeric square planar structures are assigned for the complexes in the solid state. The neutral monothiooxamides behave as monodentate ligands coordinating through their thioamide sulfur atom. The complex [Pd(SH2)2] was isolated during the thermal decomposition of trans-[PdCl₂(SH₃)₂].     

Synthesis and Characterization of New Cationic Fe(III),Co(II) and Ni(II) Complexes Containing Isatin/Triphenylphosphine Mixed Ligands

New cationic Fe(III),Co(II) and Ni(II) mixed ligand complexes containing both triphenylphosphine and isatin ligands were prepared and characterized using conventional physical and chemical methods of analysis

(I.R., UV-Vis., and ¹H NMR). Microanalytical data of the investigated complexes are consistent with the formulations. [Fe(Isa)₂ {P(Ph)₃}₂]³⁺, [Co(Isa)₂ {P(Ph)₃}₂]²⁺ and [Ni(Isa)₂ {P(Ph)₃}₂]²⁺, (Where Isa = Isatin and P(Ph)₃ = Triphenylphosphine).

The prepared complexes are soluble in polar solvents and could be of potential use in bio-inorganic applications.     

Synthesis,Characterization, DNA Binding Properties,Fluorescence Studies and Toxic Activity of Cobalt(III) and Ruthenium(II) Polypyridyl Complexes

The new ligand 4-(isopropylbenzaldehyde)imidazo[4,5-f ][1,10]phenanthroline (ippip) and its complexes [Ru(phen)₂(ippip)]²⁺(1),[Co(phen)₂(ippip)]³⁺(2),[Ru(bpy)₂(ippip)]²⁺(3),[Co(bpy)₂(ippip)]³⁺(4)(bpy=2,2-bipyridine) and (phen=1,10-phenanthroline) were synthesized and characterized by ES⁺-MS, ¹H and ¹³C NMR. The DNA binding properties of the four complexes were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that complexes bind to calf thymus DNA (CT-DNA) through intercalation. When irradiated at 365 nm, the complexes promote the photocleavage of pBR322 DNA, and complex 1 cleaves DNA more effectively than 2, 3, 4 complexes under comparable experimental conditions. Furthermore, photocleavage studies reveal that singlet oxygen (¹O₂) plays a significant role in the photocleavage.     

A Pulsed EPR and DFT Investigation of the Stabilization of Coordinated Phenoxyl Radicals in a Series of Cobalt Schiff-Base Complexes

We recently demonstrated how the aerobic addition of acetic acid to N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamino Co^II, [Co(1)], leads to the formation of an unusual coordinated Co^III-phenoxyl radical. In this work, some of the structural aspects associated with the Schiff-base-derived ligand (1) that are crucial for the acid-mediated formation of the phenoxyl radical are investigated. For comparison with [Co(1)], we therefore studied the influence of acetic acid on two complexes: (1) the N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-ethane-diamino Co^II complex, [Co(2)], that lacks the cyclohexyl group of [Co(1)], and (2) the N′-disalicylidene-ethylenediamine Co^II salen complex, [Co(3)], that lacks both the tertiary butyl groups and the cyclohexyl groups. It is shown that the cyclohexyl group of [Co(1)] is not involved in the formation or stabilization of the phenoxyl radical, whereas the tertiary butyl groups of [Co(1)] play a crucial role. In addition, the characteristics of the phenoxyl radical, formed after aerobic addition of acetic acid to [Co(2)], are analyzed in detail by pulsed electron paramagnetic resonance, in combination with isotopic labeling. The experimental data are compared to density functional theory computations and to previous data on the acid-mediated phenoxyl radical of [Co(1)].     

Chemical tuning by 5-Methyl and N-Methyl-substitution in heptanuclear complexes effects multistability investigated by Mössbauer spectroscopy

The precursors [Fe^(III)(^N???R???L)Cl] (^N???R???LH₂=N,N′-bis(2′-hydroxy- 5′-methyl-benzyliden)-1,7-diamino-4-R-4-azaheptane, R ?=? H, methyl(Me)) are high-spin (S?=?5/2) complexes. The Lewis-acidic precursors are combined with Lewis- Base-bridging-units [M(CN) _x ] ^y??? (M = Fe^(II), Ru^(II), Co^(III)) to form heptanuclear star-shaped [M{CN-Fe^(III)(^N???R???L)} _x ]Cl _y molecular switches. The star-shaped compounds are high-spin systems at room temperature. On cooling to 20 K some of the compounds exhibit multistability, i.e. several iron(III) centers within a molecule switch to the low-spin state as shown by Mössbauer spectroscopy.     

Magnetic properties of some gadolinium—Cobalt intermetallic compounds

Crystallographic and magnetic properties of the single crystals having the compositions of GdCo₃, Gd₂Co₇, GdCo₅, Gd_2.2Co_16.6 and Gd₂Co₁₇ were studied in order to contribute to the investigation of the magnetic anisotropy in the Gd–Co system. The single crystal used were prepared by means of the Bridgman method using BN-coated alumina crucibles.The room-temperature magnetocrystalline anisotropy constants K₁ of GdCo₃, Gd₂Co₇, GdCo₅, Gd_2.2Co_16.6 and Gd₂Co₁₇ are determined as 8.1 × 10⁶, 1.3 × 10⁷, 4.1 × 10⁷, 3.0 × 10⁶ and -2.7 × 10⁶ erg/cm³, respectively. it is also found that the magnetocrystalline anisotropy of Gd–Co phases in the stable region of the Th₂Zn₁₇-type structure changes very sensitively from negative to positive as the ratio Gd/Co increases above the stoichiometric ratio of 2/17.     

Mononuclear Co(III) and Ni(II) Complexes with Polypyridyl Ligands, [Co(phen)2(taptp)]3+ and [Ni(phen)2(taptp)]2+: Synthesis, Photocleavage and DNA-binding

Two novel, mixed ligand complexes of cobalt(III) and nickel(II), [Co(phen)₂(taptp)]³⁺ (1) and [Ni(phen)₂(taptp)]²⁺ (2) (phen = 1,10-phenanthroline and taptp = 4,5,9,18-tetraazaphenanthreno [9,10-b]triphenylene), were synthesized and characterized by elemental analyses, UV-visible and NMR spectroscopies. The binding interactions of the two complexes with DNA have been investigated using absorption and emission spectroscopy methods and electrophoresis measurement mode. The intrinsic binding constants for these complexes to DNA are in the order of 10⁵. In Tris buffer, the Co(III) complex shows a moderate luminescence which was enhanced after binding to DNA. However for complex Ni(II), no emission was observed in Tris buffer. The [Co(phen)₂(taptp)]³⁺ and [Ni(phen)₂(taptp)]²⁺ can cause the photocleavage of DNA supercoiled pBR322 upon irradiation by 360 nm light. Based on the data, an intercalative mode of DNA binding is suggested for the two complexes.     

3-Methyl and N-Methyl-substitution in heptanuclear complexes effects multistability investigated by Mössbauer spectroscopy

The precursors [Fe^(III)(^N???R???L)Cl] (^N???R???LH₂ = N,N ^′ -bis(2’-hydroxy-3’- methyl-benzyliden)-1,7-diamino-4-R-4-azaheptane, R = H, methyl(Me)) are high-spin (S?=?5/2) complexes. The Lewis-acidic precursors are combined with Lewis-Base-bridging-units [M(CN) _x ] ^y??? (M = Fe^(II), Ru^(II), Co^(III)) to form heptanuclear star-shaped [M{CN–Fe^(III)(^N???R???L)} _x ]Cl _y molecular switches. The starshaped compounds are high-spin systems at room temperature. On cooling to 20 K some of the compounds exhibit multistability, i.e. several iron(III) centers within a molecule switch the spin state as shown by Mössbauer spectroscopy.     

Probing the structural,bonding, electronic and magnetic properties of transition–metal borazine systems: Co m (borazine) n (m = 1, 2; n = 1–3)

ABSTRACT

The geometrical structures of neutral and anionic Co _m (borazine) _n (m?=?1, 2; n?=?1–3) complexes have been determined by using density functional theory. The results indicate that most of the ground state structures for the complexes are similar to those of Co _m (benzene) _n , which might because borazine is isoelectronic and isostructural to benzene. The frontier molecular orbitals (FMOs) analyses show that their FMOs mainly arise from the 3d/4s electrons of cobalt atoms and the weak π-cloud of borazine molecule. Furthermore, the magnetic moments of complexes were studied and the results revealed that the Co atoms carry most of the magnetic moments. Comparing with the magnetic moment of a free Co atom (3.0μ_B), the magnetic moments of Co atom in most of Co _m (borazine) _n ^0/- complexes are significantly reduced and even quenched except that the Co(borazine) remains unchanged. More importantly, there is a transition FM-to-AFM between neutral and anionic Co₂(borazine)₂. Finally, natural population analyses were performed to insightfully explore the reliable electronic structure properties.     

Reactive sputtering of (Co,Fe) nitride thin films on TiN-bufferd Si

Epitaxial (Co,Fe) nitride films were prepared on TiN buffered Si(001) substrates by dual-target reactive co-sputtering method. With lower Co content, thin films mainly consist of (Co _x Fe_1?x )₄N phase. With higher Co content, STEM EELS found no N signal in the thin film, and, combined with XRD results, shows that fcc Co is the main phase of the thin films instead of Co₄N. The N₂ atmosphere is helpful to induce the fcc Co phase formation during dual-target reactive co-sputtering deposition. For the films with less Co content, the RT magnetization measurements show similar magnetic properties as epitaxial Fe₄N(001) films, while increasing the Co content, the resulting fcc Co thin films show biaxial anisotropy with the [110] in-plane easy axis.     

DFT/TDDFT study on the electronic structures and optoelectronic properties of a series of iridium(III) complexes based on quinoline derivatives in OLEDs

The electronic structures and photophysical properties of several heteroleptic iridium(III) complexes Ir(C^∧N)₂(acac) with acetylacetonate (acac) ligand, including 1 [C^∧N = 2‐phenylisoquinoline], 2 [C^∧N = 2‐biphenyl‐4‐yl‐quinoline], 3 [C^∧N = 2‐(fluoren‐2‐yl)‐quinoline], 4 [C^∧N = 2‐dibenzofuran‐3‐yl‐quinoline], 5 [C^∧N = 2‐dibenzothiophen‐3‐yl‐quinoline], and 6 [C^∧N = 2‐phenanthren‐2‐yl‐quinoline], have been investigated by density functional theory (DFT) and time‐dependent DFT. They show a wide color tuning of photoluminescence from orange–red (λ = 601 nm) to saturated red (λ = 685 nm). The calculated absorption and emission properties of complexes 1 and 2 are in good agreement with the available experimental data. Complex 6 has the smallest ionization potentials (IP) value, which is consistent with its highest occupied molecular orbital energy level, and thus its hole injection is easiest. Corresponding to its lowest unoccupied molecular orbital energy level, the assumed complex 5 has the large electron affinities value and enhanced electron injection ability compared to the others. These calculated results show that the assumed complex 3 may possess better charge transfer abilities than others and is the potential candidate for an efficient electrophosphorescent polymer‐based red‐emitting material. Copyright © 2013 John Wiley & Sons, Ltd.     

Ab initio study of the electronic structure of the molecule-based ferromagnet Co[N(CN)2]2

We have investigated the electronic and magnetic properties of the molecule-based magnet Co[N(CN)₂]₂ using the full potential linearized augmented plane wave (FP-LAPW) method. The relative stability of the ground state, density of states and charge distributions were examined. Total energy calculations reveals that the ferromagnetic phase is a stable ground state for Co[N(CN)₂]₂ in agreement with the previous experimental findings. It is noteworthy that we predict the Co[N(CN)₂]₂ is a ferromagnetic semiconductor with a small band gap of 0.027 eV, and the semiconductor property can be connected to the strong crystal field splitting of Co²⁺ 3d states for Co[N(CN)₂]₂. Such a molecule-based ferromagnetic semiconductor would offer a potential for semiconductor applications, therefore, an experimental confirmation of our theoretical predictions is encouraged.     

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.

     

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.     

Synthesis and Vibrational Studies of Oxovanadium (IV) - Tetradentate Schiff Base Complexes

The two new Schiff base complexes of oxovanadium (IV) [VO(acac-en)] (acac-en = bisacetylactone-ethylenediimino) and [VO(sal-o-phdn)] (sal-o-phdn = N,N′-o-phenylenebis (salicylideneiminato) have been prepared. The infrared spectra of the solid complexes have been obtained and assigned on the bases of C_s symmetry. A polymeric chain structure with V-O-V bridge has been adopted for the both complexes.     

熔体快淬Pr(Fe1-xCox)2合金的结构和磁性

通过熔体快淬方法获得Pr(Fe_1-xCo_x)₂合金条带,经过X射线衍射、差示扫描量热计和磁性测量对其结构、磁性和热稳定性进行了研究.发现当Co的含量x大于0.2时才可能获得Pr(Fe,Co)₂立方Laves相化合物.对Pr(Fe_0.6Co_0.4)₂合金,在快淬速度为30m/s时,条带由Pr₂(Fe,Co)₁₇,Pr(Fe,Co)₂和富稀土相组成;在速度为40m/s时,获得了几乎单相的Pr(Fe_0.6Co_0.4)₂化合物,其居里温度为305℃;在速度为45m/s时,除了Pr(Fe_0.6Co_0.4)₂化合物外,还存在少量的非晶相.Pr(Fe_0.6Co_0.4)₂化合物在770℃以上发生分解.用40m/s快淬纳米晶粉胶粘磁体有大的磁致伸缩系数（λ_∥-λ_⊥=140×10^-6)和高的硬磁性能（_iH_c=398kA/m). 关键词：     

Study of DNA Light Switch Ru(II) Complexes : Synthesis,Characterization, Photocleavage and Antimicrobial Activity

The three Ru(II) complexes of [Ru(phen)₂dppca]²⁺ (1) [Ru(bpy)₂dppca]²⁺ (2) and [Ru(dmb)₂dppca]²⁺ (3) (where phen = 1,10 phenanthroline, bpy = 2,2-bipyridine, dmb = 2 ,2-dimethyl 2′,2′-bipyridine and polypyridyl ligand containing a single carboxylate functionality dppca ligand (dipyridophenazine-11-carboxylic acid) have been synthesized and characterized. These complexes have been shown to act as promising calf thymus DNA intercalators and a new class of DNA light switches, as evidenced by UV-visible and luminescence titrations with Co²⁺ and EDTA, steady-state emission quenching by [Fe(CN)₆]⁴⁻ and KI, DNA competitive binding with ethidium bromide, viscosity measurements, and DNA melting experiments. The results suggest that 1, 2, and 3 complexes bind to CT-DNA through intercalation and follows the order 1 > 2 > 3. Under irradiation at 365 nm, the three complexes have also been found to promote the photocleavage of plasmid pBR322 DNA.     

Infrared Spectra of trans-nitrobis (2, 4-pentanediono) Aniline-Cobalt(III) Complexes

The infrared spectra of eighteen complexes of general formula trans-[Co(NO₂) (acac)₂ (R-C₆H₄NH₂)] (acac = acetylacetonate anion, R = 3- or 4-aniline substituent) are discussed. ¹⁵N-Labelling of the complexes containing aniline and p-toluidine yields assignments of the N-H, C-N and Co-N stretching frequencies and the N-H bending frequencies. These assignments receive support from the observed frequency shifts induced by varying the substituent R which also permits the assignment of the Co-o stretching frequencies.