Adsorption of Cu(II) and Co(II) complexes on a silica gel surface chemically modified with 2-mercaptoimidazole

The isotherms of adsorption of MeX₂ (Me = Cu²⁺, Co²⁺; X = Cl^–, Br^–, ClO ₄ ^– ) by silica gel chemically modified with 2-mercaptoimidazole (SiMI) were studied in acetone and ethanol solutions, at 25 °C. Covalently attached 2-mercaptoimidazole molecule to silica gel surface adsorbs MeX₂ from solvent by forming a surface complex. The metal is bonded to the surface through the nitrogen atom of attached 2-mercaptoimidazole. At low loading, the electronic and ESR spectral parameters indicated that the Cu²⁺ complexes are in a distorted-tetragonal symmetry field. The d-d electronic transition spectra showed that for Cu(ClO₄)₂ complex, the peak of absorption did not change for any degree of metal loading and for Cl^– and Br^– complexes, the peak maxima shifted to higher energy with lower metal loading. The CoX₂(X = Cl^–, Br^–, ClO ₄ ^– ) analogues possess a distorted-tetrahedral field.     

η1-Allyrhenium pentacarbonyl and η3-allylrhenium tetracarbonyl; preparations, 1H N.M.R., mass and vibrational spectra

η¹-C₃H₅)Re(CO)₅ has been prepared from [Re(CO)₅]^? and photo-decarbonylated to give η³-C₃H₅)Re(Co)₄. Both allyl complexes have been characterised by ¹H n.m.r., mass spectrometry and liquid-phase infrared and Raman spectra. The vibrations of the Re(CO)₅ unit in the η¹-allyl compound can be assigned in terms of local C_4v symmetry, but such an an approximation is not valid for the η³-allyl compound which must be discussed in terms of overall C_s symmetry. The η¹- and n³-allyl internal modes are discussed in terms of C_s symmetry.     

The mechanisms of substitution reactions in octahedral complexes from the point of view of ligand field theory

Two possible mechanisms for substitution reactions in octahedral complexes, ML₆, are discussed in terms of molecular orbital theory. Jorgensen's model with angular parameters is used to calculate the change in activation energy on forming complexes of the type ML₅ (D₃h symmetry), ML₅ (C_4v symmetry), and ML₇ D_5h symmetry). Analysis of the quantities obtained (Table 4) shows that high spin ML₆ octahedral complexes of metals with d³ or d⁸ electronic configurations, and low spin complexes with d⁶ electronic configurations are particularly stable. An S_N1 mechanism is, apparently, characteristic for complexes of metals with d¹ or d² electronic configurations. The formation of bonds facilitates the course of substitution reactions in octahedral complexes. The results we have obtained explain the available experimental material and permit us to make some predictions.     

Structures of Rydberg transitions in the absorption spectra of methyl-substituted derivatives of bis(η6-benzene)chromium

The effect of methylation of ligands in bis(η⁶-benzene)chromium (1) on the structure of Rydberg transitions in absorption spectra has been studied. A detailed analysis and interpretation of all Rydberg elements of the vapor-phase spectra of bis(η⁶-benzene)chromium (2), bis(η⁶-o-xylene)chromium (3), bis(η⁶-m-xylene)chromium (4), and bis(η⁶-mesitylene)chromium (5) was carried out. The vapor-phase electronic absorption spectrum of bis(η⁶-p-xylene)chromium (6) was measured, and the assignment of the Rydberg bands was made for the first time. The first ionization potentials of complexes 2–5 were refined. The energy of detachment of the 3d_z ² electron and the parameters of the Rydberg excitations for molecule 6 were determined. The vibronic components of the 3d_z ²→R4p _x,y transition in the spectra of complexes 2 and 6 were assigned. The differences in the Rydberg structure of the spectra of compounds 2–6 were analyzed in terms of the selection rules for optical transitions in the corresponding symmetry groups. The vapor-phase spectra correspond to conformers with the symmetry groupsC _2v andC ₂ for complexes 2–4, with the symmetry groupsD _3h andD ₃ for compound 5, and with the symmetry groupD _2d for complex 6. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 897–903, May, 1998.     

Darstellung und Charakterisierung der Pentammin-Komplexe [Os(NH3)5(NCS)]2+ und [Os(NH3)5(NCSe)]2+

Preparation and Characterization of the Pentammine Complexes [Os(NH₃)₅(NCS)]²⁺ and [Os(NH₃)₅(NCSe)]²⁺ The new pentammine complexes [Os(NH₃)₅(NCS)]²⁺ and [Os(NH₃)₅(NCSe)]²⁺ are prepared from the reaction of [Os(NH₃)₅(CF₃SO₃)](CF₃ SO₃)₂ with NH₄SCN and KSeCN, respectively, in acetone, and subsequent purification by ion exchange chromatography on carboxymethyl cellulose. Evidence of N-bonding in both cases is given by the vibrational spectra, indicating that Os³⁺ is in terms of Lewis acidity harder than Ru³⁺, Rh³⁺, and Ir³⁺. I.r. and Raman spectra are interpreted according to local C_4v symmetry around Os, and the presumed assignments are confirmed by comparison with the i.r. spectra of the perdeuterated compounds. In the electronic spectra of both complexes charge transfer bands at 412 nm (NCS) and 498 nm (NCSe) are observed, respectively. Further weak absorptions near 4500 and 5100 cm^?1, which are in correlation with electronic Raman bands, are assigned to intraconfigurational transitions within the ²T_2g (O_h) ground term, split into three Kramers doubletts by spin-orbit coupling and lowered symmetry. Electrochemical measurements demonstrate a stabilisation of +III and +II oxidation states by π-back donation to —NCS and —NCSe ligands.     

Synthesis,characterization, and spectroscopic studies of tetradentate Schiff base chromium(III) complexes

Eight chromium(III) complexes of tetradentate Schiff bases have been prepared in situ by condensing of a substituted salicylaldehyde compound with ethylenediamine. These were characterized by elemental analysis, m.p., IR, molar conductivity, magnetic moment measurements, and electronic spectra. The free ligands were also characterized by ¹H and ¹³C NMR spectra. The ¹³C NMR spectra are discussed in terms of possible substituent effects. The IR and electronic spectra of the free ligand and the complexes are compared and discussed. The electrospray ionization (ESI) mass spectra of four free ligands and their complexes were measured. The deconvolution of the visible spectra of the complexes, C_2v symmetry, in DMSO yields three peaks at ca. 15 600–17 600, 18 400–20 400 and 20 000–23 100, and are assigned to the three d–d transitions, ⁴B_1g → ⁴E_g(⁴T_2g); ⁴B_1g → ⁴B_2g(⁴T_2g); ⁴B_1g → ⁴E_g(⁴T_1g), respectively. The complexes showed magnetic moment in the range of 3.5–4.2 BM which corresponds to three unpaired electrons.     

Theoretical and experimental study on metal(II) halide complexes of 1,3-bis(4-pyridyl)propane

We report the results of detailed experimental and theoretical studies on the molecular structure and vibrational spectra of metal(II) halide complexes of 1,3-bis(4-pyridyl)propane [M(N₂C₁₃H₁₄)X₂, where M represents Zn or Hg, and X represents Cl, Br, or I]. The FT–infrared spectra (FT-IR) and FT-Raman spectra of the metal complexes of the 1,3-bis(4-pyridyl)propane molecule in the powder form were recorded between the 400–4000 and 5–3500 cm^?1 regions, respectively. The molecular geometry and vibrational frequencies of the metal complexes of 1,3-bis(4-pyridyl)propane in the ground state were calculated using density functional theory (B3LYP functional) with LANL2DZ and SDD as basis sets. The total energy distributions (TED) among the symmetry coordinates of the normal modes were computed for the low-energy structure of the molecules. Complete vibrational assignments based on the calculated TED values are given.     

Some mixed halogenozincate(II) complexes: Infrared and Raman spectra

Anionic complexes of the type ZnX₂Y⁻ where X and Y = Cl, Br or I have been prepared as salts of the tetrapropylammonium cation. The i.r. and Raman spectra have been interpreted in terms of halogen-bridged dimeric structures of C_2ν(A) symmetry.     

Vibrational spectra and structure of gaseous and solid dimethylboric anhydride

The Raman spectra of gaseous, liquid and solid dimethylboric anhydride (CH₃)₂BOB(CH₃)₂ have been recorded from 10–3500 cm^?1. The IR spectra from 4000–30 cm^?1 have also been recorded. The spectra of the gaseous phase have been interpreted in terms of C₂ symmetry implying a bent B-O-B skeleton with the B(CH₃)₂ groups twisted and consistent with a rather larger barrier to internal rotation about the B-O bonds. The spectra of the crystalline state, however, suggest that the molecular symmetry is altered upon solidification. Isotopic substitution of the oxygen atom by ¹⁸O confirmed that the B-O-B skeleton is linear in the solid state, and the spectra have been interpreted in terms of D_2h molecular symmetry.     

Electron spin resonance studies on some copper(II) complexes with a few nitrogen donors derived from pyridine

Electron spin resonance spectral studies have been made on copper(II) chloride, bromide, thiocyanate and sulphate complexes with some pyridine derivatives, viz. nicotinic acid (NA), nicotinamide (NICA) and isonicotinamide (INA) in solid and DMF-solution states to see the effect of different anions on the Spin-Hamiltonian parameters at the paramagnetic site for a particular ligand. The spectra of the complexes for a particular anion are almost comparable suggesting the same local symmetry for them. Analysis of the ESR data reveals axial symmetry for all the complexes, except Cu(NA)₂SO₄ for which a rhombic symmetry is suggested. The study shows the interaction of solvent (DMF) molecules with copper(II) ion in the axial plane as evident from the differences in 295 and 77 K g_| values. Moreover, the spectra are consistent with the complete absence or negligbly small copper(II)—copper(II) interactions (in few cases) in these complexes. The various Spin-Hamiltonian parameters calculated from ESR data indicate the presence of an unpaired electron in the d_x²−y² orbital of the copper(II) ion with the additional possibility of a d_xy ground state for Cu(NA)₂SO₄.     

The IR and Raman spectra of 2-amino pyrimidine complexes of some Zn(II), Cd(II) and Hg(II) halides

A series of complexes of the type HgX₂(2-AMP) and MX₂(2-AMP)₂ where M = Zn(II) or Cd(II), X = Cl, Br or I and 2-AMP = 2-amino pyrimidine have been prepared, characterized and their IR and Raman spectra recorded. The IR spectra show that the ligand coordinates through the amino group, and that the heterocyclic nitrogens do not play an important role in coordination. The above conclusion is also supported by the ¹H and ¹⁹C NMR spectra. The far-IR and Raman spectra show that the HGX₂(2-AMP) species possess a trans halogen-bridged structure of C_2h symmetry, whereas the Zn₂(2-AMP)₂ and CdI₂(2-AMP)₂ complexes are pseudotetrahedral of C_2υ symmetry.     

The infrared spectra of pyridine N-oxide complexes of transition metal perchlorates in relation to their structures

The infrared spectra of the complexes [M(pyO)₆](ClO₄)₂ (pyO = pyridine N-oxide; M = Mn, Fe, Co, Ni, Zn) are discussed. Assignments of v(M-O) and other significant vibrations are based on the band shifts induced by deuteration of the heterocyclic ring and the effects of metal ion substitution. Earlier spectroscopic evidence suggesting distortion from regular octahedral site symmetry is discounted by the far-infrared spectra. In agreement with recent crystallographic evidence for O_h site symmetry in these complexes, one infrared-active v(M-O) band is expected and observed. The effects on the spectra of structural distortion in the 6-coordinate Cu^II complex [Cu(pyO)₆](ClO₄)₂, reduced coordination number in the 4-coordinate complex [Cu(pyO)₄](C1O₄)₂, and increased cationic charge in the Ga^III complex [Ga(pyO)₆](C1O₄)₃are discussed.     

N-acetyl-DL-leucinate cobalt(II), nickel(II) and zinc(II) complexes

Summary Complexes of the type M(AcLeu)₂ · B₂ (M = Co^II, Ni^II or Zn^II; B = H₂O, py, 3-pic, 4-pic; AcLeu =N-acetyl-DL-leucinate ion) and M(AcLeu)₂ B (M = Co^II or Zn^II and B = o-phen) were prepared and investigated by means of magnetic and spectroscopic measurements. The i.r. spectra of all the complexes are consistent with bidentate coordination of the amino acid to the metal ion. The room temperature solid state electronic spectra indicate that the symmetry of this species is closer toD _4h and that MO₆ and MO₄N₂ chromophores are present in the M(AcLeu)₂ · 2 H₂O and M(AcLeu)₂B_n · x H₂O (B = py, 3-pic, 4-pic, n=2 and x=0 for M = Ni^II; B = o-phen, n=1 and x=0 for M = Co^II; B = py, 3-pic, 4-pic, n=1 and x=1 for M = Co^II) complexes, respectively. By comparing the Dq values of the amino acid and those of other N-substituted amino acids previously studied, a spectrochemical series of the the cobalt(II) and nickel(II) complexes is proposed. The¹ H n.m.r. spectra of the zinc(II) complexes confirm the proposed stereochemistry.     

Synthesis,characterization and biological activity of triaminoxime and its metal complexes

Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes of multifunctional triaminoxime have been synthesized and characterized by elemental analyses, IR, UV–Vis spectra, magnetic moments, ¹H- and ¹³C-NMR spectra for ligand and its Ni(II) complex, mass spectra, molar conductances, thermal analyses (DTA, DTG and TG) and ESR measurements. The IR spectral data show that the ligand is bi-basic or tri-basic tetradentate towards the metals. Molar conductances in DMF indicate that the complexes are non-electrolytes. The ESR spectra of solid copper(II) complexes [(HL)(Cu)₂(Cl)₂] · 2H₂O (2) and [(L)(Cu)₃(OH)₃(H₂O)₆] · 7H₂O (6) show axial symmetry of a d _{x²???y ²} ground state; however, [(HL)(Co)] (4) shows an axial type with d _Z ² ground state and manganese(II) complex [(L)(Mn)₃(OH)₃(H₂O)6] · 4H₂O (10) shows an isotropic type. The biological activity of the ligand and its metal complexes are discussed.     

A single crystal EPR study of VO ions doped in Cs2Co(SO4)2.6H2O Tutton salt

EPR spectra of VO²⁺ ions doped in single crystals of Cs₂Co(SO₄)₂.6H₂O single crystals have been studied at various temperatures (390–103 K) on X-band frequency. The detailed EPR analysis shows three vanadyl complexes with differing intensities. The g and A tensors are found to be axially symmetric. The intense vanadyl complexes in the lattice are found to occupy the Co²⁺ substitutional sites, whereas the weak vanadyl complex at the interstitial sites. The optical absorption spectrum at room temperature shows three absorption bands characteristic of VO²⁺ ions in tetragonal symmetry. By correlating the EPR and optical data, the molecular bonding coefficients and the Fermi contact interaction terms have been evaluated and discussed. The line broadening of VO²⁺ spectra on cooling the crystal is explained on the basis of spin-lattice relaxation narrowing. The spin-lattice relaxation time for the host Co²⁺ ions has been estimated at various temperatures.     

Synthesis,characterization and structural assessment of nitrato,chloro, bromo,perchlorato, thiocyanato and sulphato mono-(benzoin thiosemicarbazonato) copper(II) complexes

Summary Some copper(II) complexes of the type Cu(HL)X·nH₂O (where H₂L = benzoin thiosemicarbazone; X=NO₃; Cl, Br, SCN, ClO₄ or 1/2SO₄; n=O–2) have been prepared and characterized. All complexes have tetragonally distorted octahedral stereochemistry except the sulphatocomplex which is square pyramidal. The i.r. spectra reveal that HL acts as a monobasic tridentate ligand coordinating through the azine group nitrogen atom, thiocarbonyl sulphur atom and hydroxylic oxygen atom while NO₃, Cl, Br and ClO₄ act as terminal monodentate ligands and SCN and SO₄ act as bidentate bridging ligands. The polycrystalline e.s.r. spectra suggest tetragonal symmetry for the copper(II) ion, involving a dx ²–y² ground state.     

Vibrational and 119Sn Mössbauer Study of Tin Tetrahalide Complexes with Benzofuroxan Derivatives

The reactions of SnX₄ (X = Cl, Br) with benzofuroxan and some substituted derivatives are studied, and the hexacoordinated complexes SnCl₄(Y-C₆H₃N₂O₂)₂ (Y = H, Cl, Me, OMe), and SnBr₄ (Y-C₆H₃N₂O₂)₂ (Y = H, OMe) have been isolated. The adducts are studied by IR, Raman, and ¹¹⁹Sn Mössbauer spectroscopies, which suggest a cis structure (C_2v symmetry) for them. The good correlation between υ Sn? Cl (IR and Raman spectra) and the Mössbauer quadrupole splitting for the SnCl₄ complexes, supports the consistency of the structural assignments. The Mössbauer spectra show resolved quadrupole doublets, in spite of the cis structure of the adducts, which emphasizes the fact that the resolvable or unresolvable nature of the doublets cannot be used confidently to elucidate the structure of tin tetrahalide complexes.     

Spectroscopic studies on copper(II) halide complexes with isomeric benzoylpyridines: Electronic and electron spin resonance spectral evidence for five-coordinate copper(II) species in solution

Coordination compounds formed by copper(II) chloride and bromide with 2-, 3- and 4-benzoylpyridines (BOP)Cu(2-BOP)Cl₂, Cu(3-BOP)₂Cl₂, Cu(4-BOP)Cl₂, Cu(2-BOP)₂Br₂, Cu(3-BOP)₂Br₂ and Cu(4-BOP)₂Br₂—have been characterized by elemental analyses, molar conductance, magnetic moments, electronic, IR and ESR spectral studies. It is suggested that Cu(2-BOP)Cl₂ is monomeric tetrahedral, Cu(3-BOP)₂Cl₂ and Cu(4-BOP)Cl₂ are dimeric octahedral and tetrahedral structures, respectively, bridging through chlorines while all the bromo complexes are polymeric octahedral structures with bridging bromine atoms in the solid state. Powder ESR data reveal rhombic symmetry for all the chloro complexes. Cu(2-BOP)₂Br₂ is suggested to have an axial symmetry while the other bromo complexes are isotropic in nature. Electronic and ESR spectral studies in DMSO solution suggest the interaction of solvent molecules with copper(II) ions in the axial plane. The solution spectral data are almost comparable suggesting same local symmetry for all the compounds consistent with five-coordinate square pyramidal geometry in each case. ESR spectra also suggest considerable CuCu interactions in Cu(3-BOP)₂Cl₂. Various Spin—Hamiltonian parameters calculated from ESR data indicate the presence of an unpaired electron in the d_x²−y² orbital of the copper(II) ion in an axial symmetry.     

Structure of the tetrakis(benzoylacetonate) compound of europium used to obtain the laser effect

The spatial symmetry group of unit cells of diethylammonium and plperidinium europium tetrakis(benzoylactonate) B₄EuHD and B₄EuHP, and also the structure of the B₄Eu^– anion in B₄EuHD, which belongs to the C₂ symmetry group and exists as the cis, cis, cis isomer, have been determined. On the basis of an analysis of the luminescence spectra and structure of the B₄Eu^– anion it has been shown that the splitting of the levels of the ground state of the europium ion formally corresponds to C₂ symmetry, but may be determined by the C₄ symmetry of the immediate oxygen environment of europium EuO₈. Both complexes give a stable laser effect at a wavelength of 613 nm, corresponding to the transition from the ⁵D₀ level to the x- or y-component of the ⁷F₂ level, split by a crystal field with C₂ or C₄ symmetry.     

基于非手性邻苯酚胺衍生物的半醌Fe(III)络合物的镜面对称性破缺及其绝对构型关联

以2- 苯胺基-4,6- 二叔丁基苯酚(H₂L)和FeCl₂·4H₂O为原料制备了一对手性半醌Fe(III) 络合物Λ-mer-[Fe(L^ISQ)₃]和Δ-mer-[Fe(L^ISQ)₃] (L^ISQ: 2-苯亚胺基-4, 6-二叔丁基苯酚, mer: 经式构型), 通过单晶X射线衍射分析结合单晶压制片膜的固体圆二色(CD)光谱确定了该络合物的绝对构型, 在此基础上建立了此类半醌络合物[M(L^ISQ)₃] (M=Cr, Fe, Co)的惟手性金属中心绝对构型与固体CD光谱之间的关联. 此外, 还对10份合成的[Fe(L^ISQ)₃]的大宗产物粉末与单晶的固体CD谱进行了比对分析, 以及对1 份合成产物进行10 次重结晶的固体CD 光谱表征. 研究表明该化合物在结晶过程中发生了镜面对称性破缺(MSB), 对映体过量(ee) 值在15%-100%之间.