Absorption spectrometric study of charge transfer complex formation between 4-acetamidophenol (paracetamol) and a series of quinones including vitamin K3

The formation of charge transfer (CT) complexes of 4-acetamidophenol (commonly called 'paracetamol') and a series of quinones (including Vitamin K3) has been studied spectrophotometrically in ethanol medium. The vertical ionisation potential of paracetamol and the degrees of charge transfer of the complexes in their ground state has been estimated from the trends in the charge transfer bands. The oscillator and transition dipole strengths of the complexes have been determined from the CT absorption spectra at 298 K. The complexes have been found by Job's method of continuous variation to have the uncommon 2:1 (paracetamol:quinone) stoichiometry in each case. The enthalpies and entropies of formation of the complexes have been obtained by determining their formation constants at five different temperatures.     

Thorium(IV) and uranium(VI) complexes with some heterocyclic azo dyes in absolute ethanol

Thorium(IV) and uranium(VI) chelate complexes with PAN, PAR, TAN and TAR have been studied in absolute ethanol. The uranyl ion forms complexes with PAN, PAR, TAN and TAR in the metal to ligand molar ratio of 1:1. Thorium(IV) forms complexes with PAR, TAR and TAN in the molar ratio of 1:2. In case of Th(IV)-PAN complexes the molar ratio is 1:2.4. The stability constants for all the above complexes have been worked out using the mole ratio method. The kinetics of aquation of Th(IV)-PAN complexes indicate that PAN acts as a tridentate ligand.     

Semi-empirical molecular orbital calculations of the properties of 2:1 hydrogen bonded complexes of water with some ketones and ethers

The properties (molecular geometries and hydrogen bond energies) of a number of 2:1 complexes formed between water and some ketones and ethers have been calculated using both the CNDO/2 and the MINDO/3 semi-empirical molecular orbital methods. The CNDO/2 results have been compared with those obtained using the MINDO/3 method, and have been correlated with the i.r. spectroscopic properties of the complexes. The results for the 2:1 complexes have also been compared with those of 1:1 complexes formed with the same solvents.     

Competition and interplay between σ-hole and π-hole interactions: a computational study of 1:1 and 1:2 complexes of nitryl halides (O2NX) with ammonia

Quantum calculations at the MP2/cc-pVTZ, MP2/aug-cc-pVTZ, and CCSD(T)/cc-pVTZ levels have been used to examine 1:1 and 1:2 complexes between O(2)NX (X = Cl, Br, and I) with NH(3). The interaction of the lone pair of the ammonia with the σ-hole and π-hole of O(2)NX molecules have been considered. The 1:1 complexes can easily be differentiated using the stretching frequency of the N-X bond. Thus, those complexes with σ-hole interaction show a blue shift of the N-X bond stretching whereas a red shift is observed in the complexes along the π-hole. The SAPT-DFT methodology has been used to gain insight on the source of the interaction energy. In the 1:2 complexes, the cooperative and diminutive energetic effects have been analyzed using the many-body interaction energies. The nature of the interactions has been characterized with the atoms in molecules (AIM) and natural bond orbital (NBO) methodologies. Stabilization energies of 1:1 and 1:2 complexes including the variation of the zero point vibrational energy (ΔZPVE) are in the ranges 7-26 and 14-46 kJ mol(-1), respectively.     

Chemistry of substituted sulphuric acids—XVII. Complexes of V(III), Cr(III), Mn(II) and Fe(II) methylsulphates

V(III), Cr(III), Mn(II) and Fe(II) methylsulphates form stable donor-acceptor complexes with nitrogen donors. 1:1 and 1:2 complexes with bipyridyl have been prepared in respect of trivalent salts and 1:2 and 1:4 metal:base complexes have been obtained in respect of divalent metal salts with bipyridyl and pyridine respectively. Electronic spectra suggest an octahedral geometry around metal ions. IR spectra of the anhydrous metal methylsulphates have been studied and assigned. The changes in the IR spectra of the methylsulphate group in different stereochemical situations have been observed.     

Titanium(IV) Complexes of Unsymmetrical Schiff Bases Derived from Ethylenediamine and o‐Hydroxyaldehyde/Ketone and Their Anti‐microbial Evaluation

The titanium(IV) complexes of the unsymmetrical Schiff base ligands (L) of ethylenediamine and salicylaldehyde, o‐hydroxyacetophenone, o‐hydroxynapthaldehyde have been prepared and characterized when unsymmetrical ligands are synthesized through in situ partial displacement of the symmetrical bis‐Schiff bases. Compounds have been characterized by elemental analysis, electronic, (Infra‐red) IR, 1H NMR spectral data, magnetic susceptibility measurement and molar conductance and eight coordinated geometry of the complexes was proposed. The complexes have been found to posses 1:2:1 (M:L:B) stoichiometry (B is the secondary ligand). The bio‐efficacy of the prepared complexes has been examined against the growth of bacteria and fungi in vitro to evaluate their anti‐microbial potential.     

Synthesis, spectral and thermal studies of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complex dyes based on hydroxyquinoline moiety

A series of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of azo-compounds containing hydroxyl quinoline moiety have been synthesized and characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic and ESR spectral studies. The results revealed the formation of 1:1 and 1:2 (L:M) complexes. The molar conductance data reveal that the chelates are nonelectrolyte. IR spectra indicate that the azodyes behave as monobasic bidentate or dibasic tetradentate ligands through phenolate or carboxy oxygen, azo N for 1:1 (L:M) complexes beside phenolate oxygen and quinoline N atoms for 1:2 (L:M) complexes. The thermal analyses (TG and DTA) as well as the solid electrical conductivity measurements are also studied. The molecular parameters of the ligands and their metal complexes have been calculated.     

Synthesis,Spectral, Characterization,and Anticancer Activity of Some Binary and Mixed Ligand Complexes of 4-Methyl-2-Pentanone Thiosemicarbazone and Some Amino Acids

The Schiff base ligand 4-methyl-2-pentanone thiosemicarbazone (MPTSC) (HL) has been synthesized by the interaction of 4-methyl-2-pentanone (MP) and thiosemicarbazone (TSC). The Ni(II), Cu(II), and Fe(III) binary complexes of this ligand have been prepared. The ternary complexes of VO(IV) and Mn(II) ions with HL and glutamine (Glu) as a secondary ligand, in addition to VO(IV), Mn(II), and La(III) with HL and glycine (Gly) as a secondary ligand, have also been synthesized. The binary and ternary complexes have been characterized based on elemental analysis, IR, UV-VIS, molar conductance, mass spectra, magnetic moment, and ESR measurements. The magnetic moment, UV, and ESR studies suggest that Ni(II) and Cu(II) complexes are square planar, whereas Fe(III), Mn(II), and La(III) complexes have octahedral geometry, but VO(IV) ternary complexes have square pyramidal geometry. The analytical data indicate that the metal-to-ligand ratio in binary complexes is 1:1, except HL-Cu(II) chloride complex where the metal-to-ligand to secondary ligand ratio in ternary complexes is 1:1:1. The anticancer studies showed that the anticancer activity is in the decreasing order: ternary complexes > binary complexes > free ligand (HL).

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Formation constants of alkaline-earth metal complexes with xylenol orange and methylthymol blue

The complexes of the alkaline-earth metals with Xylenol Orange and Methythymol Blue have been studied. Three 1:1 and two 2:1 (metal:ligand) complex species for each indicator and each element have been found to be formed in aqueous solutions, and the formation constants and the arrangements of these complexes have been determined.     

Thermal studies and vibrational analyses of m-methylaniline complexes of Zn(II), Cd(II) and Hg(II) bromides

The complexes having the MBr(2)L(2) (M: Zn, Cd and Hg; L: m-methylaniline) formulae have been prepared and characterized by their elemental analyses, thermogravimetric analyses, IR and Raman spectral studies. IR and Raman bands of the complexes have been assigned as compared with the free ligand. Coordination effects on the internal modes of m-methylaniline have been discussed. Vibrational spectra propose that the [ZnBr(2)(mMA)(2)] complex is in a tetrahedral environment around Zn(II) ion with C(2v) symmetry whereas Cd(II) and Hg(II) complexes have 5-coordinate polymeric bromide bridged structures.     

Potentiometric and conductometric studies of malonyl bis(salicyloylhydrazone) and divalent metal complexes

A series of complexes of divalent transition metal ions with malonyl bis(salicyloylhydrazone) (H₄MSH) have been prepared and characterized with the help of conductometric, potentiometric methods. The proton–ligand and metal–ligand stability constants were obtained pH-metrically. The electrical conductivity of solid complexes was measured at 289 K. The low molar conductance values observed for these complexes indicate that, they are non-electrolytes. They are soluble to a limited extent in DMF and DMSO. The elemental analyses of the complexes indicate that the complexes have 1:1 and 2:1 (M:L) stoichiometry with the existence of water, chloride, acetone molecules inside the coordination sphere as evidence from the IR spectral studies. Further, the complexes have been formulated by comparing C, H, N & metal analysis data, and UV–visible spectra of the complexes have been discussed. The protonation constants of the ligand and the stability constants of their metal complexes will be evaluated potentiometrically. The stoichiometric ratios of the complexes formed in solution will be evaluated applying the molar ratio (spectrophotometric) method and confirmed conductometrically.     

Antimicrobial,antifertility, and antiradiation studies of Ga(III) and Tl(I) complexes with N∩S and N ∩ O donor systems

New complexes of gallium(III) and thallium(I) derived from 5,6-dimethyl-1H-indol-2,3-dione hydrazinecarbothioamide (L¹H) and 5,6-dimethyl-1H-indol-2,3-dione hydrazinecarboxamide (L²H) have been prepared and investigated using a combination of microanalytical analysis, melting point, molar conductance measurement, electronic, IR, ¹H NMR, and ¹³C NMR spectral studies. Gallium isopropoxide interacts with the ligands in 1 : 1, 1 : 2, and 1 : 3 molar ratios resulting in the formation of colored products, whereas TlCl forms only unimolar products. The mono- and bis-alkoxy derivatives are dimeric, while the tris ligand metal complexes are monomeric. On the basis of conductance and spectral evidences, a pentacoordinate structure for gallium(III) 1 : 1 complexes, hexacoordinate structure for 1 : 2 and 1 : 3 complexes, and a bicoordinate geometry for thallium(I) complexes have been assigned. The ligands are coordinated to gallium(III) and thallium(I) via the azomethine nitrogen and the thiolic sulfur/enolic oxygen. The antimicrobial activities of the ligands and complexes have been screened in vitro against bacteria Pseudomonas cepacicola and Bacillus subtilis and fungi Collectatrichum capsici and Fusarium oxysporum. The complexes have higher activities than the free bases. In vivo studies of the ligands and their corresponding complexes have also been carried out to assess their antifertility and antiradiation activities. The results of these activities indicate the antiandrogenic and radiation protective nature of these complexes.     

Mixed ligand complexes of benzimidazole and pyrimidine hydroxy azo dyes with some transition metals and glycine, dl-alanine or dl-leucine

The overall formation constants of 1:1:1 ternary complexes of Cu(II), Zn(II), Cd(11) with glycine, dl-alanine or dl-leucine as primary ligands and o-hydroxyphenylyazo derivatives of 2-cyanomethyl benzimidazole (ABI) and barbituric acid (ABA) as secondary ligands have been investigated potentiometrically in 40% (v/v) EtOH. Formation constants of binary systems were also determined under the same experimental conditions (37 degrees C and mu=0.15 mol dm(-3)). The stability of ternary complexes have been quantitatively compared with those of the corresponding binary complexes in terms of the parameters DeltalogK, logX and logX'. The data were interpreted on the basis of statistical considerations and the nature of complexes. The concentration distribution of various species formed in solution was evaluated. The Cu(II) complexes have been synthesized and the coordination sites of the ligands were characterized by means of IR spectroscopy.     

Complexes of Erbium and Lutetium of Different Compositions with 4-R-5-Nitro-substituted Phthalocyanines

Metal complexes (metal: ligand = 1 : 1) have been obtained via the reaction of 4-R-5-nitrophthalonitriles with erbium and lutetium acetates and chlorides. 1 : 2 heteroleptic complexes have been synthesized based on them, containing unsubstituted and octasubstituted phthalocyanine ligands at the metal atom. The products have been characterized by a set of physico-chemical methods.     

Spectroscopic,spectrophotometric and potentiometric studies on 3-(naphthylazo)-5-phenylpyrazole dye and its metal chelates

The electronic absorption spectra of 3-(naphthylazo)-5-phenylpyrazole dye (L) are studied in some organic solvents of different polarities. The spectra comprise three absorption bands, which are assigned to the corresponding electronic transitions. The pKa value of (L) in ethanol-water mixtures have been determined pH-metrically at different temperatures. The thermodynamic parameters delta G zero, delta H zero and delta S zero have also been evaluated. The successive stability constants of some d-transition elements have been determined pH-metrically at 25 degrees C and mu = 0.1 in 60% (v/v) ethanol-water mixture. A 1:1 and 1:2 (M: L) complexes are formed and evidenced by conductometric studies. The solid complexes of Cu(II) have been isolated and characterized on the basis of elemental analysis, TGA and IR data. The complexes formed between (L) and Cu(II) were studied spectrophotometrically in solutions.     

Theoretical study of the 1:1 and 2:1 (homo- and heterochiral) complexes of XOOX' (X, X' = H, CH3) with lithium cation

A theoretical study of the 1:1 and 2:1 complexes of XOOX' (X, X' = H, CH(3)) with the lithium cation has been carried out by means of ab initio computational methods up to the MP2/aug-cc-pVTZ level. The optical rotatory power and NMR parameters (absolute chemical shielding and indirect coupling constants) have been calculated. In addition, the racemization barriers within the complexes formed have been evaluated. Special attention has been paid concerning the differences between the 2:1 homo- and heterochiral complexes.     

Infrared spectra of the (H2O)n-SO2 complexes in argon matrices

The infrared spectra of the (H(2)O)n-SO(2) complexes trapped in argon matrices have been investigated using Fourier transform infrared spectroscopy. In addition to the 1:1 and 2:1 complexes, the first spectroscopic evidence for the 3:1 complex has been obtained from the spectra of the SO stretching and the OH stretching modes. The observed frequency shifts in the bonded OH stretching region indicate that the hydrogen bonds of the 2:1 and 3:1 complexes are strengthened compared to that of the 1:1 complex, which suggests the cyclic structure of the complexes.     

Spectroscopic and biological studies on newly synthesized nickel(II) complexes of semicarbazones and thiosemicarbazones

Nickel(II) complexes, having the general composition Ni(L)2X2, have been synthesized [where L: isopropyl methyl ketone semicarbazone (LLA), isopropyl methyl ketone thiosemicarbazone (LLB), 4-aminoacetophenone semicarbazone (LLC) and 4-aminoacetophenone thiosemicarbazone (LLD) and X=Cl-, 1/2SO(4)2-]. All the Ni(II) complexes reported here have been characterized by elemental analyses, magnetic moments, IR, electronic and mass spectral studies. All the complexes were found to have magnetic moments corresponding to two unpaired electrons. The possible geometries of the complexes were assigned on the basis of electronic and infrared spectral studies. Newly synthesized ligand and its nickel(II) complexes have been screened against different bacterial and fungal growth.     

Complexation of quercetin with three kinds of cyclodextrins: an antioxidant study

The slightly water-soluble flavonoid quercetin (QUE) and its inclusion with either beta-cyclodextrin (betaCD), hydroxypropyl-beta-cyclodextrin (HP-betaCD) or sulfobutyl ether-beta-cyclodextrin (SBE-betaCD) were investigated. The stoichiometric ratios and stability constants describing the extent of formation of the complexes have been determined by phase-solubility measurements; in all cases type-A(L) diagrams have been obtained (soluble 1:1 complexes). The results showed that the inclusion ability of betaCD and its derivatives was the order: SBE-betaCD>HP-betaCD>betaCD. Kinetic studies of DPPH with QUE and CDs complexes were done. The results obtained indicated that the QUE-SBE-betaCD complex was the most reactive form. The scavenging capability of QUE and CDs complexes with DPPH and galvinoxyl was studied using ESR spectroscopy. All complexes showed a higher scavenging capability with both radicals, compare quercetin in water. Beside, these results indicated that the complexes formed maintained the quercetin antioxidant activity.     

Acid equilibria of methylthymol blue and formation constants of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with methylthymol blue

Potentiometric and spectrophotometric studies on acid equilibria and reactions with Co(II), Ni(II), Cu(II) and Zn(II) for Methylthymol Blue (MTB) are described. The equilibrium constants have been calculated. MTB has been found to form 1:1 and 2:1 (mole ratio of metal to ligand) complexes, including protonated ones. The probable configuration of the complexes and the effects on the stabilities have been discussed.