Multi-technique approach on the effect of surfactant concentrations on the thermal unfolding of rabbit serum albumin: Formation and solubilization of the protein aggregates

Effect of cationic surfactant, cetyltrimethylammonium bromide (CTAB) addition on the thermal denaturation of rabbit serum albumin (RSA) has been studied by employing small-angle neutron scattering (SANS), circular dichroism (CD), intrinsic fluorescence and ultra violet (UV) spectroscopy. The studies were performed at three different temperatures viz., 30, 50 and 70 °C and at two different concentrations of CTAB: the low concentration of CTAB used was 1 mM and the higher concentration was 80 mM (for SANS) and 20 mM (for CD, fluorescence and UV). A collective effect of high temperature and low concentration of CTAB led to the protein aggregation followed by solubilization of these aggregates at higher concentration of surfactant. At 1 mM CTAB and 30 °C, the protein–surfactant complex has a prolate ellipsoidal shape with semi-major axis of 88.9 Å and semi-minor axis of 19.6 Å which are slightly greater than the values of the native RSA. At 50 °C, the size of the semi-major axis increases while at 70 °C an increase in the size of both axes was found. The thermal outcome at higher concentration of CTAB (80 mM) was rather different. Higher concentration of CTAB unfolds the protein by the formation of micelle-like aggregates along the polypeptide chains of the protein and the complex was stabilized at higher temperatures, which was not found with lower concentration of CTAB. The CD results were found to be consistent with the SANS results, i.e., decrease in α-helicity of RSA was more when less amount of surfactant was present as compared to the system with higher surfactant concentration. In a similar fashion, results of relative fluorescence intensity (RFI) reveal that increase in temperature causes decrease in λ_max of native RSA as well as RSA + 1 mM CTAB, whereas the λ_max remains unchanged for RSA + 20 mM CTAB systems. That means the structure remains compact in presence of 20 mM CTAB while the structure becomes loose when low or zero amount of surfactant was present. The UV results indicate that the protein aggregation takes place in presence of low amount of CTAB and these aggregates become soluble at high concentration of CTAB.     

Phage Langmuir monolayers and Langmuir–Blodgett films

Stable, insoluble Langmuir monolayer films composed of Staphylococcus aureus-specific lytic bacteriophage were formed at an air–water interface and characterized. The phage monolayer was very strong, withstanding a surface pressure of ～40 mN/m at 20 °C. The surface pressure–area (Π–A) isotherm possessed a shoulder at ～7 × 10⁴ nm²/phage particle, attributed to a change in phage orientation at the air–water interface from horizontal to vertical capsid-down/tail-up orientation as surface pressure was increased. The Π–A-dependence was accurately described using the Volmer equation of state, assuming horizontal orientation to an air–water interface at low surface pressures with an excluded area per phage particle of 4.6 × 10⁴ nm². At high pressures phage particles followed the space-filling densely packed disks model with a specific area of 8.5 × 10³ nm²/phage particle. Lytic phage monolayers were transferred onto gold-coated silica substrates from the air–water interface at a constant surface pressure of 18 mN/m by Langmuir–Blodgett method, then dried and analyzed by scanning electron microscopy (SEM) and ellipsometry. Phage specific adsorption (Γ) in Langmuir–Blodgett (LB) films measured by SEM was consistent with that calculated independently from Π–A isotherms at the transfer surface pressure of 18 mN/m (Γ = 23 phage particles/μm²). The 50 nm-thickness of phage monolayer measured by ellipsometer agreed well with the horizontal phage average size estimated by SEM. Surface properties of phage Langmuir monolayer compare well with other monolayers formed from nano- and micro-particles at the air–water interface and similar to that of classic amphiphiles 1,2-diphytanoyl-sn-glycero-3-phosphocholine (phospholipid) and stearic acid.     

Effects of H3PO4 and KOH in carbonization of lignocellulosic material

Samples of lignocellulosic material, stem of date palm (Phoenix dactylifera), were carbonized at different temperatures (400–600 °C) to investigate the effects of their impregnation with aqueous solution of either phosphoric acid (85 wt%) or potassium hydroxide (3 wt%). The products were characterized using BET nitrogen adsorption, helium pycnometry, Scanning Electron Microscopy (SEM) and oil adsorption from oil–water emulsion (oil viscosity, 60 mPa s at 25 °C). True densities of the products generally increased with increase in carbonization temperature. Impregnated samples (acid/base) showed wider differences in densities at 400 (1.978/1.375 g/cm³) than at 600 °C (1.955/2.010 g/cm³). Without impregnation, the sample carbonized at 600 °C showed higher density of 2.190 g/cm³. This sample has impervious surface with BET surface area of 124 m²/g. Acid-impregnated sample carbonized at 500 °C has the highest surface area of 1100 m²/g and most regular pores as evidenced by SEM micrographs. The amounts of oil adsorbed decreased with increase in carbonization temperature. Without impregnation, sample carbonized at 400 °C exhibited equilibrium adsorption of 4 g/g which decreases to about a half for sample carbonized at 600 °C. Impregnation led to different adsorptive capacities. There are respective increase (48 wt%) and decrease (5 wt%) by the acid- or base-impregnated samples carbonized at 600 °C. This suggests higher occurrence of oil adsorption-enhancing surface functional groups such as carbonyl, carboxyl and phenolic in the former sample.     

Micro- and mesoscopic structure of poly(vinyl alcohol) gels determined by neutron and light scattering

We studied the structure of poly(vinyl alcohol) (PVA) gels formed in mixtures of dimethyl sulfoxide (DMSO) and water using several scattering techniques such as wide-angle neutron scattering (WANS), small-angle neutron scattering (SANS), ultra-small-angle neutron scattering (U-SANS) and light scattering (LS) to cover a very wide Q range from 10^-4 to 10 Å^-1. The WANS measurements have revealed that the cross-linking points of the gels are crystallites, and the size and its distribution have been evaluated by the SANS measurements. The SANS results have also shown that the structure observed in the low Q range below 10^-2 Å^-1 is dominated by a liquid–liquid-phase separation. The early stage of the phase separation has been studied in detail using the time-resolved LS technique, while the late stage has been investigated by the U-SANS technique because the LS measurements cannot access the opaque samples. On the basis of the results, we present a quantitative sketch of the structure of the PVA gel.     

Controlling the dimensionality of oxalate-based bimetallic complexes: The ferromagnetic chain {[K(18-crown-6)][Mn(bpy)Cr(ox)3]}∞(18-crown-6 = C12H24O6, ox=C2O42-, bpy = C10H8N2)

The bimetallic ferromagnetic chain {[K(18-crown-6)][Mn(bpy)Cr(ox)₃]}_∞ (1) has been synthesized and characterized. It crystallizes in the orthorhombic chiral space group P2₁2₁2₁ [a = 9.0510(2) Å, b = 14.4710(3) Å, c = 26.8660(8) Å, V = 3510.97(1) Å³, Z = 2]. Compound 1 is made up by anionic [Mn(bpy)Cr(ox)₃]⁻ 1D chains and cationic [K(18-crown-6)]⁺ complexes. The magnetic exchange within the chain is ferromagnetic [J = +7.8(7) cm⁻¹]. In the solid state, the ferromagnetic chains are well isolated magnetically and no long range magnetic ordering has been observed above 2 K.     

A simple method of electrochemical lithium intercalation within graphite from a propylene carbonate-based solution

Electrochemical lithium intercalation within graphite from 1 mol dm^− 3 solution of LiClO₄ in propylene carbonate (PC) was investigated at 25 and − 15 °C. Lithium ions were intercalated into and de-intercalated from graphite reversibly at − 15 °C despite the use of pure PC as the solvent. However, ceaseless solvent decomposition and intense exfoliation of graphene layers occurred at 25 °C. The results of the Raman spectroscopic analysis indicated that the interaction between PC molecules and lithium ions became weaker at − 15 °C by chemical exchange effects, which suggested that the thermodynamic stability of the solvated lithium ions was an important factor that determined the formation of a solid electrolyte interface (SEI) in PC-based solutions. Charge–discharge analysis revealed that the nature of the SEI formed at − 15 °C in 1 mol dm^− 3 of LiClO₄ in PC was significantly different from that formed at 25 °C in 1 mol dm^− 3 of LiClO₄ in PC containing vinylene carbonate, 3.27 mol kg^− 1 of LiClO₄ in PC, and 1 mol dm^− 3 of LiClO₄ in ethylene carbonate.     

Synthesis and structure of the novel anion [AsMo6O15(OH)3(SO4)3]6–, first example of a reduced molybdo-sulphate cluster

A novel anion derived from the Anderson structure has been obtained in aqueous acid solution by condensation of three pairs of edge-sharing molybdenum octahedra around a central arsenite. This association forms a hexanuclear ring of Mo(V) with three external sulphate groups bridging the binuclear molybdenum units. This compound crystallizes in the presence of alkaline ions and its orthorhombic structure was solved by single crystal X-ray diffraction [Cmca, a=24.3189(3) Å, b=12.4454(1) Å, c=26.9211(3) Å, V=8 147,9 ų] from 4 277 unique reflections [I≥2 σ(I)], R₁=0.0471 and _wR₂=0.1429. The solid is a three-dimensional network built up from cluster anions strongly connected to alkaline ions via ionic links. This soluble compound, presenting labile peripheral sulphates, is predisposed for exchanges to build new anions. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASpolyoxometalate / sulphate / reduced cluster / arsenite / molybdenum     

Copper and cadmium phosphonates based on 2-quinolinephosphonate

Hydrothermal reactions of 2-quinolinephosphonic acid (1) and CuSO₄ or CdSO₄ result in two new compounds with formula Cu(2-C₉H₆NPO₃) (2) and Cd(2-C₉H₆NPO₃)(H₂O) (3). Compound 2 has a layer structure in which dimers of edge-sharing {CuO₄N} square-pyramids are linked by {CPO₃} tetrahedra through corner sharing. Compound 3 shows a new type of layer structure where chains of corner sharing {CdO₅N} octahedra are connected by {CPO₃} tetrahedra into an inorganic layer. The quinoline groups fill in the inter-layer spaces in both cases. Crystal data for 1: monoclinic, space group P2₁/c, a = 10.270(2) Å, b = 13.566(3) Å, c = 6.9818(16) Å, β = 101.916(4)°, V = 951.8(4) Å³, Z = 4. For 2: monoclinic, space group P2₁/c, a = 13.976(3) Å, b = 7.9398(18) Å, c = 7.8687(18) Å, β = 101.150(5)°, V = 856.7(3) Å³, Z = 4. For 3: monoclinic, space group P2₁/c, a = 17.164(4) Å, b = 5.4870(12) Å, c = 10.850(2) Å, β = 101.557(4)°, V = 1001.1(4) Å³, Z = 4. The magnetic measurement on 2 reveals a dominant antiferromagnetic exchange coupling between the Cu(II) centers. A quasi-reversible electrochemical reaction is observed for complex 2 immobilized on the surface of GC electrode, corresponding to the redox couple Cu²⁺/Cu⁺. The fluorescent properties of 1–3 are also investigated.     

Crystal structures of Th(OH)PO4, U(OH)PO4 and Th2O(PO4)2. Condensation mechanism of MIV(OH)PO4 (M = Th,U) into M2O(PO4)2

Three new crystal structures, isotypic with β-Zr₂O(PO₄)₂, have been resolved by the Rietveld method. All crystallize with an orthorhombic cell (S.G.: Cmca) with a = 7.1393(2) Å, b = 9.2641(2) Å, c = 12.5262(4) Å, V = 828.46(4) Å³ and Z = 8 for Th(OH)PO₄; a = 7.0100(2) Å, b = 9.1200(2) Å, c = 12.3665(3) Å, V = 790.60(4) Å³ and Z = 8 for U(OH)PO₄; a = 7.1691(3) Å, b = 9.2388(4) Å, c = 12.8204(7) Å, V = 849.15(7) Å³ and Z = 4 for Th₂O(PO₄)₂. By heating, the M(OH)PO₄ (M = Th, U) compounds condense topotactically into M₂O(PO₄)₂, with a change of the environment of the tetravalent cation that lowers from 8 to 7 oxygen atoms. The lower stability of Th₂O(PO₄)₂ compared to that of U₂O(PO₄)₂ seems to result from this unusual environment for tetravalent thorium.     

Synthesis,structure, and characterization of a new two-dimensional lead(II) vanadate,Ba3PbV4O14

A new two-dimensional lead(II) vanadate, Ba₃PbV₄O₁₄ has been synthesized by standard solid state techniques using BaCO₃, PbO, and V₂O₅ as reagents. The structure of Ba₃PbV₄O₁₄ was determined by single-crystal X-ray diffraction. Ba₃PbV₄O₁₄ crystallizes in the triclinic space group P-1 (no. 2), with a = 7.2997(15) (Å), b = 7.2932(15) (Å), c = 13.379(3) (Å), α = 93.68(3)°, β = 99.68(3)°, γ = 91.49(3)°, V = 700.2(2) (ų) and Z = 2. Ba₃PbV₄O₁₄ exhibits a novel two-dimensional layered structure consisting of corner shared VO₄ tetrahedra that are linked by edge shared PbO₇ polyhedra, in which the Ba²⁺ cations occupy the interlayer region. The Pb²⁺ cations are in asymmetric coordination environments attributable to its lone pair. Infrared, Raman, and UV–vis diffuse reflectance spectroscopy, thermogravimetric analysis, and dipole moment calculations are also presented.     

Syntheses,structures and single-molecule magnetic behaviors of two dicubane Mn4 complexes

The reaction of MnX₂ · 4H₂O (X = Cl or Br) with 2,6-bis(hydroxymethyl)-4-methylphenol (H₃L) and NaOH in methanol solution yielded two tetranuclear manganese complexes, [Mn₄(HL)₄(MeOH)₄Cl₂] (1) and [Mn₄(HL)₄(MeOH)₄Br₂] (2). Both compounds crystallize in the monoclinic space group C₂/c with cell parameters: a = 26.0945(19) Å, b = 11.4999(8) Å, c = 21.2188(16) Å, β = 121.050(1)° and z = 4 for 1 · 2Et₂O; a = 25.8145(3) Å, b = 11.6734(2) Å, c = 21.3956(3) Å, β = 120.1277(6)° and z = 4 for 2 · 2Et₂O. Both complexes consist of a mixed-valence dicubane structure, which comprises two Mn^II and two Mn^III ions. Magnetic susceptibilities and magnetization of complexes 1 and 2 in the solid state indicate that two clusters have an S = 9 ground state. Frequency-dependent out-of-phase signals of alternating current magnetic susceptibilities were observed in the low temperature range (<3 K) for both complexes indicating a slow magnetic relaxation.     

Syntheses and crystal structures of new vanadium(IV) oxyphosphates M(VO)2(PO4)2 with M = Co,Ni

We have extended our research interest on titanium oxyphosphates (M^II(TiO)₂(PO₄)₂, with M^II = Mg, Fe, Co, Ni, Cu, Zn) to vanadium oxyphosphates M^II(V^IVO)₂(PO₄)₂ (M^II = Co, Ni). For each compound two phases, named α and β according to synthesis conditions, have been stabilized at room temperature, then characterized. The four crystal structures M(VO)₂(PO₄)₂ (α and β for M = Co, Ni) have been determined in monoclinic P2₁/c space group using X-ray single crystals diffraction data. Structure of the α phase is derived from the Li(TiO)(PO₄) (orthorhombic Pnma) and LiNi_0.50(TiO)₂(PO₄)₂ (monoclinic P2₁/c) types, with cell parameters: a = 6.310(1) Å, b = 7.273(1) Å, c = 7.432(1) Å, β = 90.43(1)° for M = Co, and a = 6.297(2) Å, b = 7.230(2) Å, c = 7.421(2) Å, β = 90.36(2)° for M = Ni. Structure of the β phase is derived from the Ni(TiO)₂(PO₄)₂-type (monoclinic P2₁/c) with cell parameters: a = 7.2742(2) Å, b = 7.2802(2) Å, c = 7.4550(2) Å, β = 120.171(2)° for M = Co, and a = 7.2691(2) Å, b = 7.2366(2) Å, c = 7.4453(2) Å, β = 120.231(2)° for M = Ni. All these structures consist of a three dimensional (3D) framework built up of infinite chains of tilted corner-sharing [VO₆] octahedra, cross-linked by corner-sharing [PO₄] tetrahedra. The M²⁺ ion (M = Co, Ni) is located in a triangular based antiprism which shares faces with two [VO₆] octahedra. Structural filiation is discussed based on a common structural unit, a sheet where divalent cations M²⁺ (M = Co, Ni) are inserted. A thermal study of the α ? β transition is also presented.     

Synthesis and crystal structure of the first chain-type nitridosilicates RE5Si3N9 (RE = La,Ce)

The novel branched chain-type nitridosilicates Ce₅Si₃N₉ and La₅Si₃N₉ have been synthesized in a radio-frequency furnace starting from the respective metals and silicon diimide Si(NH)₂ at 1625 °C for La₅Si₃N₉ and 1650 °C for Ce₅Si₃N₉, respectively. The structure of Ce₅Si₃N₉ has been determined by single-crystal X-ray diffraction (Ce₅Si₃N₉, Cmca (no. 64), a = 10.567(2) Å, b = 11.329(2) Å, c = 15.865(3) Å, V = 1899.3 Å³, Z = 8, R₁ = 0.0391, 1480 independent reflections, 90 refined parameters). The structure of isotypic La₅Si₃N₉ has been refined by the Rietveld method, starting from single-crystal data of Ce₅Si₃N₉ (La₅Si₃N₉, Cmca (no. 64), a = 10.647(4) Å, b = 11.414(4) Å, c = 16.030(5) Å, V = 1948.1 Å³, Z = 8, R_P = 0.0348, R_F² = 0.0533). Both compounds are built up of alternating Q²- and Q³-type corner sharing SiN₄ tetrahedra with additional corner sharing Q¹-units attached to the Q³-tetrahedra pointing alternately in opposing directions. These zipper-like chains are intertwined in both directions perpendicular to the chain itself to form a three-dimensionally interlocked structure with the rare-earth ions situated between the chains. Magnetic measurements resulted in a ferromagnetic ground state with a magnetic moment in agreement with Ce³⁺.     

Synthesis,structure and solid state NMR analysis of a new templated titanium(III/IV) fluorophosphate

The title compound MIL-131 (MIL stands for Material from Institut Lavoisier) was prepared hydrothermally (4 days, 473 K, autogenous pressure) in the presence of an organic base (N((CH₂)₂NH₂)₃). The structure of MIL-131 or Ti^IIITi^IV(OH)F₄(HPO₄)·(PO₄)·(N((CH₂)₂NH₃)₃) has been determined ab initio from X-Ray synchrotron powder diffraction data using simulated annealing methods and was refined in the triclinic space group P-1 (no. 2). MIL-131 exhibits a one-dimensional structure built up from inorganic chains of corner sharing TiO₅(OH) titanium(III) octahedra and PO₄ and HPO₄ phosphate tetrahedra, related to TiO₂F₄ titanium octahedra. Protonated triamine cations are located between the inorganic motifs, and interact strongly with the mineral network through hydrogen bondings both with terminal fluorine atoms and hydroxo or oxo groups. Multinuclear solid state NMR has allowed a clear attribution of the protons, fluoride, and phosphate groups environment within the framework of MIL-131. The large values of chemical shift anisotropy together with the absence of any ¹³C NMR response confirmed the presence of paramagnetic titanium(III) species deduced from the crystal structure. Finally, 2D MAS ¹H-³¹P CP-HETCOR NMR correlation experiment gives some insight on the nature of the intra-framework hydrogen bonding.Crystal data for MIL-131: a = 14.109(1) Å, b = 8.462(3) Å, c = 7.179(1) Å, α = 93.772(1)°, β = 96.566(2)°, γ = 98.004(1)°, V = 840.36(2) ų, z = 2.     

The experimental and DFT studies of 1,3-dimethyl-2-[4-chloro-styryl]-benzimidazolium iodide

1,3-Dimethyl-2-[4-chloro-styryl]-benzimidazolium iodide (1) was synthesized and characterized by X-ray diffraction, ¹H NMR, MS, IR, UV–vis spectra and elemental analysis. The crystals are monoclinic, space group P2₁/c, with a = 12.507(3) Å, b = 7.3259(19) Å, c = 36.705(9) Å, V = 3358.9(15) Å³, and Z = 4 (at 296(2) K). Crystal stacking scheme indicates the face-to-face π?π aromatic stacking interactions. Molecular geometries, frequencies, IR, ¹H NMR and UV–vis were calculated at DFT/TD-DFT level using two hybrid exchange–correlation functionals, B3LYP and PBE1PBE. The stability of the molecule arising from hyperconjugative interaction and charge delocalization had been analyzed using natural bond orbital (NBO) analysis. These calculations on (1) provide deep insight into its electronic structure and properties.     

Synthesis and structure of a new scorpionate-dithio carboxyl oxovanadium complex and an organic dithio carboxyl compound

A new complex of oxovanadium(IV), V₂O₂[(HB(pz)₃)₂(pyrro)₂ (1) and a dimer-dithio carboxyl compound (C₅H₈NS₂)₂ (2) have been synthesized by the reaction of VOSO₄·nH₂O with NaHB(pz)₃ and pyrrolidine dithio carboxylic acid ammonium salt. They were characterized by element analysis, IR spectra, UV–vis spectra and X-ray diffraction. Structural analyses of 1 and 2 gave the following parameters: 1, triclinic, P-1, a = 7.732(4) Å, b = 14.285(8) Å, c = 17.802(9) Å, α = 101.314(8)°, β = 92.682(9)°, γ = 92.228(9)°, V = 1923.6(18) Å³, and Z = 4; 2, monoclinic, C2/c, a = 13.857(2) Å, b = 10.4213(18) Å, c = 9.436(2) Å, β = 97.099(2), V = 1352.1(4) Å³, and Z = 4. In complex 1, vanadium atom adopts a distorted tetragonal bipyramid structure, which is typical for oxovanadium(IV) complexes. Compound 2 is a dimer-dithio carboxyl compound with S–S bond. In addition, thermal analysis was performed for analyzing the stabilization of the complexes.     

Phase transition and thermal decomposition of silver isocyanate (AgNCO)

The thermal behavior of AgNCO (silver isocyanate) has been studied via thermal analysis, optical spectroscopy, X-ray powder diffraction and transmission electron microscopy. Upon quenching the high temperature polymorph (HT-AgNCO) to room temperature, a new modification has been obtained (q-AgNCO). Its crystal structure was solved from X-ray powder diffraction data and refined by the Rietveld method (Pmmn (no. 59), a = 3.579(3) Å, b = 5.777(4) Å, c = 5.807(2) Å, V = 120.08(3) Å³, Z = 2, T = 295 K). The structure consists of chains of Ag⁺ ions bridged by isocyanate units. HT-AgNCO exists between T = 135 °C and the melting/decomposition point and exhibits virtually free rotation of the complex anions. According to preliminary single-crystal studies, HT-AgNCO (C2/m, a = 5.87 Å, b = 3.51 Å, c = 5.81 Å, ß = 105.953°, Z = 2, T = 373 K) is structurally related to α-NaN₃. The crystal structures of both, HT-AgNCO and q-AgNCO have been compared with that of the room temperature modification (RT-AgNCO). The thermal behavior and the ionic conductivity of AgNCO are discussed with respect to the related compounds AgN₃ and KSCN. Decomposition of AgNCO proceeds in distinct steps, as seen from TGA, and results in the formation of nanoparticles of elemental silver and an amorphous polymer consisting of C, N and O, only.     

Real structure of SrSi2O2N2

SrSi₂O₂N₂ is an important host lattice for Eu²⁺ doped phosphors. Its crystal structure (space group P1, a = 7.0802(2) Å, b = 7.2306(2) Å, c = 7.2554(2) Å, α = 88.767(3)°, β = 84.733(2)°, γ = 75.905(2)° and V = 358.73(2) Å³, Z = 4) is isotypic with EuSi₂O₂N₂: highly condensed silicate layers are separated by Sr²⁺. The samples are characterized by pronounced real structure effects owing to pseudosymmetry of partial structures. Polysynthetic twinning with domains of various sizes is ubiquitous and oriented intergrowth of domains with different orientations has also been observed and analysed in detail by means of electron diffraction and high-resolution electron microscopy. These effects also affect the X-ray powder pattern and were taken into account in a Rietveld refinement.     

Synthesis,spectroscopic studies and structures of square-planar nickel(II) and copper(II) complexes derived from 2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol

Two new nickel(II) [Ni(L)₂] and copper(II) [Cu(L)₂] complexes have been synthesized with bidentate NO donor Schiff base ligand (2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol) (HL) and both complexes Ni(L)₂ and Cu(L)₂ have been characterized by elemental analyses, IR, UV–vis, ¹H, ¹³C NMR, mass spectroscopy and room temperature magnetic susceptibility measurement. The tautomeric equilibria (phenol-imine, O–H?N and keto-amine, O?H–N forms) have been systemetically studied by using UV–vis absorption spectra for the ligand HL. The UV–vis spectra of this ligand HL were recorded and commented in polar, non-polar, acidic and basic media. The crystal structures of these complexes have also been determined by using X-ray crystallographic techniques. The complexes Ni(L)₂ and Cu(L)₂ crystallize in the monoclinic space group P2₁/n and P2₁/c with unit cell parameters: a = 10.4552(3) Å and 12.1667(4) Å, b = 8.0121(3) Å and 10.4792(3) Å, c = 13.9625(4) Å and 129.6616(3)Å, V = 1155.22(6) Å³ and 1155.22(6) Å³, D_x = 1.493 and 1.476 g cm^?3 and Z = 2 and 2, respectively. The crystal structures were solved by direct methods and refined by full-matrix least squares to a find R = 0.0377 and 0.0336 of for 2340 and 2402 observed reflections, respectively.