Theoretical studies and antibacterial activity for Schiff base complexes

New ligand 4‐((2‐Hydroxy1‐naphthyl) methylene amino)‐1.5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one (HL) was synthesized from the reaction of 2‐hydroxy‐1‐naphthaldehyde and 4‐aminophenaz one. A complexes of this ligand [VO(II)(HL)(SO₄)], [Pt(IV)(L)Cl₃], [Re(V)(L)Cl₃]Cl, and [M(II)(L)Cl] (M═Pd(II), Ni(II), Cu(II)) were synthesized. The resulted compounds were characterized by IR, NMR (¹H and ¹³C), mass spectrometry, element analysis, and UV‐Vis spectroscopy. Additionally, the spectroscopic studies revealed octahedral geometries for the Re(V), Pt(IV) complexes, and square pyramidal for VO(II), square planar for Pd(II) complex, and tetrahedral for the Ni(II) and Cu(II) complexes. Thermodynamic parameters (ΔE^*, ΔH^*, ΔS^*, ΔG^*, and K) were calculated using from the TGA curve Coats‐Red fern method. Therefore, hyper Chem‐8 program has been used to predict structural geometries of compounds in the gas phase. Finally, the synthesized Schiff base and its metal complexes were screened for their biological activity against bacterial species, 2 Gram‐positive bacteria (Bacillus subtilis and Staphylococcus aureus) and 2 Gram‐negative bacteria (Escherichia coli and Pseudomonas aeruginosa).     

Spectroscopic determination of binding between human serum albumin and a platinum(II) dimethylsulfoxide complex

We have used electronic absorption and fluorescence spectroscopy to study binding between a platinum(II) dimethylsulfoxide complex (cis-[Pt(DMSO)₂Cl₂]) and human serum albumin (HSA), and the effect of complexation on the structure of the protein. We have calculated the binding parameters for binding between cis-[Pt(DMSO)₂Cl₂] and HSA. We have determined the binding constant K_B = (1.2 ± 0.1)·10³ M⁻¹ and the Hill coefficient h = 1.03 ± 0.1. We have determined that binding between cis-[Pt(DMSO)₂Cl₂] and the protein leads to a change in the internal packing of the macromolecule. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 573–576, July–August, 2008.     

Far Infrared and Raman Spectra of Some Crystalline Iodomercurate Complexes

Abstract

Vibrational spectra of crystalline powders of [Nien₂] [HgI₃]₂ and [Men₂] [HgI₄] (where en = ethylene-diamine chelated to M = Ni(II), Pd(II) or Pt(II)) have been measured at room and liquid-nitrogen temperatures. The bands observed in the low frequency region 200–10 cm^?1 are interpreted in terms of mainly internal vibrations of the anions and external lattice modes. Raman and far infrared spectra are compared in order to make structural deductions. In comparison with present knowledge of the stereochemistry and vibrational spectroscopy of other iodomercurates, the triiodo-mercurate salt seems to contain nearly planar trigonal anions, while the tetraiodomercurates contain discrete tetrahedra. Probable site symmetries of the anions which may explain the spectra are discussed.     

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.     

A193Ir Mössbauer study of Pt−Ir catalysts prepared by impregnantion of silica with H2MCl6

The state of iridium on Pt?Ir catalysts prepared by impregnation of amorphous silica with H₂IrCl₆ and H₂PtCl₆ was studied by¹⁹³Ir Mössbauer spectroscopy after different steps of preparation. The Ir is adsorbed in its trivalent state, presumably as [IrCl₆]^3?. Calcination in air at 450°C converts this to IrO₂. The metallic clusters formed by subsequent reduction in H₂ at 200°C show a strong tendency towards segregation of Ir and Pt and re-oxidize partially when exposed to air at ambient temperature. In both respects the behaviour is similar to that of samples prepared by co-exchange from [Ir(NH₃)₅Cl]Cl₂ and Pt(NH₃)₄Cl₂. H₂O.     

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.     

Preparation,Chemical Characterization and Electronic Spectra of 6-(2-Pyridylazo)-3-Acetamidophenol and Its Metal Complexes

The stereochemistry of new iron (III), cobalt (II), nickel (II), copper (II), zinc (II) and cadmium (II) complexes of 6-(2-pyridylazo)-3-acetamidophenol (H2L) was studied on the basis of their analytical, spectroscopic, magnetic and conductance data. the dissociation constant of the ligand, as well as the stability constants of its metal complexes had been determined by spectrophotometric method. on the basis of infrared spectra, the coordination behaviour of the ligand to the metal ions was investigated. Magnetic susceptibility and solid reflectance spectra measurements were used to infer the structure. the isolated complexes were found to have the general formulae [M (HL). xH₂O] (A).yH₂O, M = Cu (II), Zn (II), Cd (II) and Fe (HI); HL = 6-(2-pyridylazo)-3-acetamido-phenol; a = acetate in the case of Cu (II) and Zn (II) or chloride in the case of Cd (II) and Fe (Ill), x = 1-3 and y=0-5. for [M (H₂L).xH₂O]Cl₂.yH₂O, M = Ni (II) and Co (II); HL = 6-(2-pyridyl-azo)-3-acetamidophenol, x=3 and y=5-6).     

Formation of gold nanoparticles in gold ruby glass: The influence of tin

A ¹¹⁹Sn Mössbauer study was carried out of tin(IV) complexes with 2-benzoylpyridine thiosemicarbazone (H2Bz4DH) and its N(4)-methyl (H2Bz4M) and N(4)-phenyl (H2Bz4Ph) derivatives: [Sn(2Bz4DH)Cl₃] (1), [Sn(2Bz4DH)PhCl₂] (2), [Sn(2Bz4M)Cl₃] (3), [H₂2Bz4M]₂[Ph₂SnCl₄] (4), [Sn(2Bz4Ph)PhCl₂] (5), [Sn(2Bz4Ph)Ph₂Cl] (6), in which H2Bz4R stands for the neutral ligand and 2Bz4R stands for the anionic thiosemicarbazone. In addition, ¹¹⁹Sn Mössbauer studies of the tin(IV) complexes [Sn(H4Bz4DH)₂Cl₄H₂O] (7), [Sn(H4BzPS)₂Cl₄H₂O] (8) with 4-benzoylpyridine thiosemicarbazone (H4Bz4DH) and the correspondent semicarbazone (H4BzPS) were performed. The isomer shifts decrease upon coordination due to the variation in the percentage of s character as tin changes from approximately sp³ hybridization in the tin salts to sp³d² in the octahedral or sp³d³ in the heptahedral complexes. The Mössbauer parameters of compound (4) showed the existence of two tin(IV) sites, which have been attributed to the presence of the cis and trans isomers.     

A Double Isotopic Labelling Study of the Infrared Spectra of the Linkage Isomers [Pd(bipy)(SCN)2], [Pd(bipy)(NCS)2] and Related Complexes

Abstract

The IR spectra of the linkage isomers [Pd(bipy)(SCN)₂] and [Pd(bipy)(NCS)₂] have been determined in the C≡N stretching region (2200–2000 cm^?1) and below 500 cm^?1. The band shifts resulting from deuteration of the 2,2′-bipyridine (bipy) ring and ¹⁵NCS-labelling are shown to provide a ready means for distinguishing between the internal ligand modes, the μPd-N(bipy) and μPd-SCN/μPd-NCS vibrations. The assignment technique has been further extended to the complexes [Pt(bipy)(SCN)₂] and [Pd(phen)(SCN)₂] (phen = 1,10-phenanthroline). Finally, a comparison between the IR spectra of [Pd(bipy)(NCO)₂], [Pd(bipy)(NCS)₂] and [Pd(bipy)(SCN)₂] reveals that the frequencies μM-NCO, μM-NCS and μM-SCN decrease in the sequence NCO > NCS > SCN.     

Interaction of dimethylsulfoxide and diethylsulfoxide complexes of platinum(II) with bovine serum albumin

We have used electronic absorption spectroscopy in the UV region to study the interaction of a dimethylsulfoxide complex of platinum(II) (cis-[Pt(DMSO)₂Cl₂]) and a diethylsulfoxide complex of platinum (II) (cis-[Pt(DESO)₂Cl₂]) with bovine serum albumin (BSA). We have calculated the physicochemical binding parameters for binding with BSA (the binding constants and the Hill coefficient). We found that sulfoxide ligands promote an increase in the rate of binding of the complexes with BSA. Binding of cis-[Pt(DMSO)₂Cl₂] and cis-[Pt(DESO)₂Cl₂] with BSA leads to a decrease in the thermal stability of the protein. The leaving groups in the complexes for binding with BSA are the sulfoxide molecules, and the mechanism for binding between the dialkylsulfoxide complexes and the protein remains unchanged.     

Chemical tuning of high-spin complexes based on 3- and 4-hydroxy-pentadentate-Fe (III) complex-units investigated by Mössbauer spectroscopy

The pentadentate ligands 3-OH-⁵L?=?[N,N′-Bis(1,3-dihydroxy-2-benzylidene)-1,7-diamino-4-azaheptane] and 4-OH-⁵L?=?[N,N′-Bis(1,4-dihydroxy-2-benzylidene)-1,7-diamino-4-azaheptane] has been prepared by a Schiff base condensation between 1,7-diamino-4-azaheptane and the dihydroxybenzaldehyde. Complexation with Fe(III) yields high-spin (S?=?5/2) complexes of [Fe^III(3-OH-⁵L)Cl] and [Fe^III(4-OH-⁵L)Cl]. These precursors were combined with [M(CN) _x ] ^y? (M?=?W(IV), Mo(IV), Ru(II), Co(III)) and heptanuclear and nonanuclear clusters of [M{(CN-Fe^III(3-OH-⁵L)} _x ]Cl _y and [M{(CN-Fe^III(4-OH-⁵L)} _x ]Cl _y resulted. Such starshaped hepta- and nonanuclear compounds are high-spin systems at room temperature. On cooling to 10 K some of the iron(III) centers switch to a second high-spin state as proven by Mössbauer spectra, i.e. multiple electronic transitions. Parts of the compounds perform a high-spin to high-spin transition.     

Synthesis, characterization, DNA binding and cleavage studies of mixed-ligand Cu(II) complexes of 2,6-bis(benzimidazol-2-yl)pyridine

Four novel copper(II) complexes of the composition [CuLX] where L = 2,6-bis(benzimidazole-2yl)pyridine, X = dipyridophenazine (L₁), 1,10-phenanthroline (L₂), hydroxyproline (L₃) and 2,6-pyridine dicarboxylic acid (L₄) were synthesized and characterized by using elemental analysis, FT-IR, UV–vis, ESI-MS, molar conductance and magnetic susceptibility measurements. The complexes [CuLL₁](NO₃)₂ [1], [CuLL₂](NO₃)₂ [2], [CuLL₃](NO₃) [3] and [CuLL₄] (NO₃) [4] are stable at room temperature. In DMSO the complexes [1] and [2] are 1:2 electrolytes, [3] and [4] are 1:1 electrolytes. Based on elemental and spectral studies five coordinated geometry is assigned to all the four complexes. The interaction of four copper ion complexes with calf thymus DNA were carried out by UV–vis titrations, fluorescence spectroscopy, thermal melting and viscosity measurements .The binding constant (K_b) of the above four metal complexes were determined as 5.43 × 10⁴ M_,⁻¹ 2.56 × 10⁴ M⁻¹, 1.21 × 10⁴ M⁻¹ and 1.57 × 10⁴ M⁻¹ respectively. Quenching studies of the four complexes indicates that these complexes strongly bind to DNA, out of all complex 1 is binding more strongly. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. Thermal melting studies also support intercalative binding. The nuclease activity of the above metal complexes shows that 1, 2 and 3 complexes cleave DNA through redox chemistry.     

The influence of the lattice on the spin transition in solids. Investigations of the high spin ag low spin transition in mixed crystals of [FexM1−x(2−pic)3]C12·MeOH

The spin transition behaviour in the iron(II) complex [Fe(2−pic)₃]Cl₂·MeOH (2−pic = 2−aminomethylpyridine) is discussed within a previously developed model which describes the High Spin (HS) ag Low Spin (LS) transition on the grounds of the elasticity theory. For this purpose, the relative HS fraction γ as a function of temperature was determined for mixed crystals of [Fe_xM_1-x(2-pic)₃]Cl₂·MeOH (M = Co, Zn, 0 < x ⩽ 1) employing ⁵⁷Fe Mössbauer spectroscopy. In addition, the temperature dependence of the lattice constants of the pure iron compound was derived from X-ray diffraction measurements and the Lamb Mössbauer factors for [Fe(2-pic)₃]Cl₂·Sol (Sol = EtOH, MeOH) were determined at room temperature. It is shown that essential features of the spin transition behaviour of the title system can be explained within the λ model. The quantitative agreement of the predicted elastic interaction energy with the experimental data, however, is not yet satisfactory.     

Complexes based on ethylene- and propylene-bridged-pentadentate-Fe(III)-units allow interplay between magnetic centers and multistability investigated by Mössbauer spectroscopy

The propylene-based ⁵3,3-L?=?[N,N′-Bis(1-hydroxy-2-benzylidene)-1,7-diamino-4-azaheptane] and ethylene-based pentadentate ligand ⁵2,2-L?=?[N,N′-Bis(1-hydroxy-2-benzylidene)-1,5-diamino-3-azapentane] has been prepared. Complexation with Fe(III) yields high-spin (S?=?5/2) complexes of [Fe^III(⁵2,2-L)Cl] and [Fe^III(⁵3,3-L)Cl]. Such precursors were combined with [M(CN) _x ] ^y? (M?=?W(IV), Mo(IV), Ru(II), Co(III)) and heptanuclear and nonanuclear clusters of [M{(CN-Fe^III(⁵2,2-L)} _x ]Cl _y and [M{(CN-Fe^III(⁵3,3-L)} _x ]Cl _y resulted. Such starshaped hepta- and nonanuclear compounds are high-spin systems at room temperature. On cooling to 20 K in all presented ethylene compounds the iron(III) centers switch to a second high-spin state as proven by Mössbauer spectra with a yield of about 30%, i.e., multiple electronic transitions. The propylene compounds, however, perform a high-spin to low-spin transition. Mössbauer spectra taken during green light irradiation indicate changes in the population of the different electronic states, i.e. concerted inorganic reaction.     

Structural Information from the Infrared Spectra of Metal(II) Complexes of Tropolone and 2-Thiotropone

Evidence for polynuclear octahedral coordination in the complexes [MT²]_n (M = Ni, Zn; T = tropolonate anion; n > 1) is adduced by observing the effect of base adduct formation on their infrared spectra. The spectra of the complexes [M(ST)₂] (M = Co, Ni, Cu, Zn; ST = 2-thiotroponate anion) are discussed in relation to their known or probable structures.     

Peculiarities of crystal structures and magnetic properties of Cu(II) and Ni(II) mixed-ligand complexes on the 1,3-dithiole-2-thione-4,5-dithiolate basis

Mixed-ligand Cu(II) and Ni(II) complexes, [Cu(dmit)(bpy)]₂ (I), [Ni(dmit)(phen)₂] (II) and [Ni(dmit)(phen)₂]·CH₂Cl₂ (III) (dmit=1.3-dithiole-2-thione-4.5-dithiolate, phen=1.10-phenantroline, bpy=2.2′-bipyridine) have been prepared by ligand exchange between phen or bpy and (Bu₄N)₂[M(dmit)₂] (M=Ni, Cu) and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray analysis and by investigation of magnetic and resonance properties. In complex I, the monomeric units form dimers in a head-to-tail arrangement by weak coordination bonds between copper and dithiolate sulfur atoms and π–π interactions between dmit and bpy from neighboring monomers. Dimers in I are further extended into chains by weak Cu–S(thione) contacts. In crystal packing of complex II and III, there exists a weak π–π interaction between two parallel phen molecules of the adjacent complexes. As a consequence, the magnetic and resonance characteristics of copper complex may be described in approximation of exchange-coupled pairs of Cu²⁺ ions with ion spin S=1/2. The nickel complexes are described by isotropic exchange model for single-site spin S=1.     

Low-frequency vibrational spectra of crystals of tutton salts

IR absorption spectra and polarized Raman spectra of crystals of Tutton salts K₂M(SO₄)₂6H₂O and (NH₄)₂M(SO₄)₂·6H₂O, where M=Co, Ni, Zn, have been obtained by experiment at 93 K and at room temperature. The frequencies and forms of normal modes of the [Zn(H₂O)₆]²⁺ octahedral complex have been calculated. The observed lines are assigned to the internal modes of the [M(H₂O)₆]²⁺ complex and external modes of the crystal lattice in accordance with the results of the calculations and factor-group analysis. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 445–449, July–August, 2000.     

Proton magnetic resonance study of the phase transitions of [N(CH3)4]2BCl4 (B=Co, Cu, Zn, and Cd) single crystals

The proton spin-lattice relaxation rates in [N(CH₃)₄]₂BCl₄ (B=⁵⁹Co, ⁶³Cu, ⁶⁷Zn, and ¹¹³Cd) single crystals grown using the slow evaporation method were investigated over the temperature range 120-400 K. It was found that the relaxation processes of ¹H for all the [N(CH₃)₄]₂BCl₄ crystals can be described with single exponential functions. The changes in the ¹H relaxation behavior in the neighborhood of the phase transition temperatures are used to detect changes in the state of internal motion. From the ¹H spin-lattice relaxation rate measurements for [N(CH₃)₄]₂BCl₄ crystals, the activation energies were calculated for each phase. The large values of the activation energies indicate that the N(CH₃)₄ groups are significantly affected during the transitions. Although these [N(CH₃)₄]₂BCl₄ crystals all belong to the group of A₂BX₄-type crystals, their ¹H spin-lattice relaxation rates have different temperature dependences and indicate the occurrence of different molecular motions within the crystals. We additionally show for the first time that the differences in ¹H spin-lattice relaxation rates among the [N(CH₃)₄]₂BCl₄ (B=⁵⁹Co, ⁶³Cu, ⁶⁷Zn, and ¹¹³Cd) single crystals arise from differences in the electron structures of the metal ions within the series.     

Spectroscopic Studies on Some Aminobenzoic Acid Hydrazide - Iron Complexes

Abstract

o ^?, m ^? and p ^? aminobenzoic acid hydrazide (ABAH) complexes with (NH₄)₂ Fe (So₄)₂ and Fe Cl₃ were prepared with the type [ML₂.2H₂O] X. where X = Cl₃ or SO₄. The prepared complexes were investigated using IR, electronic and Mossbauer spectroscopes. The obtained results indicated that the iron ions are present in octahedrally coordinated Fe²⁺, and Fe³⁺ states.

Also the results reveal that all the complexes contain keto form, except m ^? ABAH Fe (II) complex which contains enol form in addition to the keto form.