Ligand environment and the structure of schiff base adducts and tetracoordinated metal-chelates

(E,E)-N,N-Bis(2,6-difluoro-benzyl-idene)ethane-1,2-diamine

The asymmetric unit of the title compound, C(16)H(12)F(4)N(2), comprises half of the potentially bidentate Schiff base ligand, with an inversion centre located at the mid-point of the central C-C bond. The crystal packing is stabilized by inter-molecular C-H⋯N and π-π inter-actions [centroid-centroid distance = 3.6793 (12) Å and inter-planar spacing = 3.4999 (7) Å].

Probing the compound (E)-5-(diethylamino)-2-[(4-methylphenylimino)methyl]phenol mainly from the point of tautomerism in solvent media and the solid state by experimental and computational methods

In this study, the molecular structure and spectroscopic properties of (E)-5-(diethylamino)-2-[(4-methylphenylimino)methyl]phenol were characterized experimentally by X-ray diffraction, FT-IR and UV-vis spectroscopic techniques and computationally by DFT method. It is concluded on the basis of X-ray diffraction and FT-IR analyses that the title compound exists in enol form in the solid state. UV-vis spectra of the title compound were recorded in different organic solvents to investigate the dependence of tautomerism on solvent types. The tautomerism-solvent relation was also studied by computational methods to have more insight on structural properties. The geometry optimization of the title compound in gas phase was performed by using DFT (B3LYP) method with 6-311G(d,p) basis set. The geometry optimizations in solvent media were carried out at the same theory level by the polarizable continuum model (PCM). In the calculation of excitation energies, TD-DFT calculations were carried out in both gas and solution phases. The computational investigation of non-linear optical properties indicates that the title compound has a good second order nonlinear optical property. The thermodynamic properties were obtained in the range of 100-500 K.

{4,4'-Dichloro-2,2'-[2,2-dimethyl-propane-1,3-diylbis(nitrilo-methanyl-ylidene)]diphenolato-κO,N,N',O'}nickel(II)

In the title compound, [Ni(C(19)H(18)Cl(2)N(2)O(2))], the Ni(II) atom shows a slightly distorted square-planar geometry. The dihedral angle between the mean planes of the coordination rings is 9.15 (12)° while the dihedral angle between the mean planes of the two aromatic rings is 3.48 (16)°. In the crystal, pairs of inter-molecular C-H⋯O hydrogen bonds link neighboring mol-ecules into a chain along the a axis. The crystal structure is further stabilized by π-π inter-actions [centroid-centroid distance = 3.883 (2) Å].

(E)-1-[(2-Chloro-4-nitro-phenyl-imino)-meth-yl]naphthalen-2-ol

In the title compound, C₁₇H₁₁ClN₂O₃, an intra­molecular O—H⋯N hydrogen bond influences the mol­ecular conformation; the naphthol system and the substituted benzene ring form a dihedral angle of 3.5 (1)°. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds link mol­ecules into chains in the [010] direction The crystal packing exhibits π–π inter­actions between the aromatic rings from the neighbouring mol­ecules, with a centroid–centroid distance of 3.566 (7) Å.

Bis[4-(2-hydroxybenzylideneamino)benzoato-κO1]tetrakis(methanol-κO)cadmium

In the title mononuclear complex, [Cd(C₁₄H₁₀NO₃)₂(CH₃OH)₄], the Cd²⁺ cation is situated on an inversion centre. It exhibits a distorted octa­hedral coordination, defined by two carboxyl­ate O atoms from two monodentate anions and by four O atoms from four methanol mol­ecules. The crystal structure comprises intra­molecular O—H⋯O and O—H⋯N, and inter­molecular O—H⋯O hydrogen bonds. The latter help to construct a layered structure extending parallel to (100).

Triaqua-bis-{2-meth-oxy-6-[(phenyl-iminium-yl)meth-yl]phenolate-κO}manganese(II) dinitrate

The crystal structure of the title compound, [Mn(C(14)H(13)NO(2))(2)(H(2)O)(3)](NO(3))(2), is comprised of two Schiff base 2-meth-oxy-6-(N-phenyl-carboximido-yl)phenol (HL) ligands and three coordinated water mol-ecules. The Mn(II) ion lies on a twofold axis that bis-ects one water O atom. The coordination sphere of the five-coordinate Mn atom is completed by the two monodentate HL ligands and three coordinated water mol-ecules binding through their O atoms, affording a distorted tetra-gonal-pyramidal geometry. In the phenolate ligands, the hy-droxy H atom transfers to the imine N atom. This H atom is also involved in an intra-molecular N-H⋯O hydrogen bond that imposes a nearly planar conformation on each ligand, with dihedral angles of 2.78 (3) and 2.43 (5)° between the aromatic rings of each ligand. In the crystal, mol-ecules are linked by inter-molecular O-H⋯O hydrogen bonds.

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes

Two new mixed-ligand iron(III) complexes, [Fe(L(n))(acac)(C(2)H(5)OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac)(3)] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H(2)L(1)) or 2-aminobenzoic acid (H(2)L(2)). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L(n))(acac)X] (n=1, 2; X=Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, (1)H and (13)C NMR spectroscopy. Room temperature magnetic susceptibility measurements (μ(eff)∼5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (ΔE(p)>100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential (E(1/2)) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level.

catena-Poly[copper(II)-{μ(3)-4,4'-dibromo-2,2'-[butane-1,4-diylbis(nitrilo-methanyl-yl-idene)]diphenolato-κN,O:N',O':O'}]

The asymmetric unit of the title coordination polymer, [Cu(C(18)H(16)Br(2)N(2)O(2))](n), consists of a Schiff base complex in which a crystallographic twofold rotation axis bis-ects the central C-C bonds of the n-butyl spacers of the designated Schiff base ligands, making symmetry-related dimer units, which are twisted around Cu(II) atoms in a bis-bidentate coordination mode. In the crystal, these dimeric units are connected through Cu-O bonds, forming one-dimensional coordination polymers, which propagate along [001]. The Cu(II) atom adopts a square-based pyramidal coordination geometry, being coordinated by two N and two O atoms of symmetry-related ligands and by a third O atom of a neighboring complex. Furthermore, inter-molecular π-π inter-actions [centroid-centroid distance = 3.786 (2) Å] and C-H⋯O inter-actions stabilize the crystal packing.

catena-Poly[copper(II)-{μ(3)-4,4'-dichloro-2,2'-[butane-1,4-diylbis(nitrilo-methanyl-yl-idene)]diphenolato-κN,O:N',O':O'}]

The asymmetric unit of the title coordination polymer, [Cu(C(18)H(16)Cl(2)N(2)O(2))](n), consists of a Schiff base complex in which the Cu(II) atom adopts a square-pyramidal coordination geometry, being coordinated by two N and two O atoms of symmetry-related ligands and by a third O atom from a complex related by an inversion center. In the structure, a crystallographic twofold rotation axis bis-ects the central C-C bonds of the n-butyl spacers of the designated Schiff base ligands, making symmetry-related dimeric units, which are twisted around Cu(II) atoms in a bis-bidentate coordination mode. In the crystal, these dimeric units are connected through the third bridging Cu-O bonds [2.3951 (13) Å], forming one-dimensional coordination polymers, which propagate along [001]. Furthermore, inter-molecular π-π inter-actions [centroid-centroid distance = 3.811 (1) Å] stabilize the crystal packing.

{1,1′-[Butane-1,4-diylbis(nitrilomethylidyne)]di-2-naphtholato}copper(II) ethanol monosolvate

The asymmetric unit of the title compound, [Cu(C₂₆H₂₂N₂O₂)]·C₂H₅OH, comprises a Schiff base complex and an ethanol mol­ecule of crystallization. The Cu^II atom shows a distorted square-planar geometry. The dihedral angle between the two aromatic rings is 48.16 (13)°. The crystal structure is stabilized by inter­molecular O—H⋯O and C—H⋯O hydrogen bonds and inter­molecular π–π inter­actions with centroid–centroid distances in the range 3.485 (2)–3.845 (3) Å.

Concentration dependent tautomerism in green [Cu(HL¹)(L²)] and brown [Cu(L¹)(HL²)] with H₂L¹ = (E)-N'-(2-hydroxy-3-methoxybenzylidene)benzoylhydrazone and HL² = pyridine-4-carboxylic (isonicotinic) acid

The in situ formed hydrazone Schiff base ligand (E)-N'-(2-hydroxy-3-methoxybenzylidene)benzoylhydrazone (H₂L¹) reacts with copper(II) acetate in ethanol in the presence of pyridine-4-carboxylic acid (isonicotinic acid, HL²) to green-[Cu(HL¹)(L²)]·H₂O·C₂H₅OH (1) and brown-[Cu(L¹)(HL²)] (2) complexes which crystallize as concomitant tautomers where either the mono-anion (HL¹)⁻ or di-anion (L¹)²⁻ of the Schiff base and simultaneously the pyridine-carboxylate (L²)⁻ or the acid (HL²) (both through the pyridine nitrogen atom) function as ligands. The square-planar molecular copper(II) complexes differ in only a localized proton position either on the amide nitrogen of the hydrazone Schiff base in 1 or on the carboxyl group of the isonicotin ligand in 2. The proportion of the tautomeric forms in the crystalline solid-state can be controlled over a wide range from 1:2 = 95 : 5 to ∼2 : 98 by increasing the solution concentration. UV/Vis spectral studies show both tautomers to be kinetically stable (inert), that is, with no apparent tautomerization, in acetonitrile solution. The UB3LYP/6-31+G* level optimized structures of the two complexes are in close agreement with experimental findings. The solid-state structures feature 1D hydrogen-bonded chain from charge-assisted O((-))H-N and O-H((-))N hydrogen bonding in 1 and 2, respectively. In 1 pyridine-4-carboxylate also assumes a metal-bridging action by coordinating a weakly bound carboxylate group as a fifth ligand to a Cu axial site. Neighboring chains in 1 and 2 are connected by strong π-stacking interactions involving also the five- and six-membered, presumably metalloaromatic Cu-chelate rings.

Spectroscopic investigations and quantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenol

In this work the electronic structure of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenol has been characterized by the B3LYP/6-31G(d) level by using density functional theory. The experimental infrared and electronic absorption spectra have been obtained and compared with the theoretically obtained ones. Molecular electrostatic potential map has been evaluated; natural bond orbital and frontier molecular orbitals analysis have been performed from the optimized geometry. The energetic behavior of the title compound has been examined in solvent media using polarizable continuum model. The non-linear optical properties have been computed with the same level of theory. In addition, the changes of thermodynamic properties have been obtained in the range of 100-500 K.

Synthesis, Structural, and Insulin-Enhancing Studies of Oxovanadium(IV) Complexes

Oxovanadium(iv) complexes with Schiff bases derived from substituted salicylaldehyde and diamine have been prepared and characterized. 1H NMR and IR spectral data revealed that the symmetrical Schiff base was isolated, and elemental analysis confirmed the purity of all the compounds as formulated. The room-temperature magnetic moments of 1.6–1.8 Bohr magneton for the complexes confirmed that the complexes are VIV complexes, with d1 configuration. Cyclic voltammetry revealed only one quasi-reversible wave for each complex and they all showed redox couples with peak-to-peak separation values (ΔEp) ranging from 76 to 84 mV, indicating a single-step one-electron transfer process. An oral administration of these complexes supplied at a dose of 0.2 mmol kg–1 to streptozotocin-induced diabetic rats elicited a progressive reduction in plasma glucose over 6-h periods. Two of the complexes produced significant and consistent reduction in fasting blood glucose levels over a 6-h monitoring period.

{5,5'-Dimeth-oxy-2,2'-[4,5-dimethyl-o-phenyl-enebis(nitrilo-methyl-idyne)]diphenolato}nickel(II)

In the title Schiff base complex, [Ni(C(24)H(22)N(2)O(4))], the Ni(II) atom shows a square-planar geometry. The dihedral angles between the central benzene ring and the two outer rings are 4.79 (15) and 7.54 (15)°. In the crystal, mol-ecules are connected through inter-molecular C-H⋯O hydrogen bond, resulting in chains extending along the c axis. The crystal structure is further stabilized by inter-molecular π-π inter-actions, with centroid-centroid distances in the range 3.3760 (15)-3.7196 (17) Å.

N-Benzylpyridin-2-amine

In the title compound, C₁₂H₁₂N₂, the dihedral angle between the benzene and pyridine rings is 67.63 (8)°. Mol­ecules are linked into centrosymmetric dimers by a simple inter­molecular N—H⋯N hydrogen bond with graph-set motif R₂²(8).

Complexation properties and synthesis of a novel Schiff base with triphenylene nucleus

We presented the synthesis of a novel Schiff base and its complexation properties with some transition metal ions in this work. For this, the 2,3,4,6,7,10,11 hexahydroxytriphenylene (HHTP) as starting material was synthesized according to known procedure. Moreover, the 2-((2-chloroethylimino)methyl) phenol material was prepared with reaction of salicylaldehyde and 2-chloroethylamine hydrochloride. To give the 2,3,4,6,7,10,11-hexakis(salicyliminoethoxy)triphenylene (HSE-TP) as a novel Schiff base, the HHTP were treated with 2-((2-chloroethylimino)methyl)phenol in acetone media. Complexation properties of this Schiff base were investigated towards Ni(II), Cu(II), Co(II), Zn(II), Pd(II) and Cd(II) as transition metals. The structures of these new compounds (ligand and complexes) were characterized with FT-IR, magnetic susceptibility measurement, thermal methods (TGA), (1)H NMR and elemental analyses.

2-[(E)-(2-Chlorophenyl)iminomethyl]-6-methylphenol

The title compound, C₁₄H₁₂ClNO, a Schiff base derived from 3-methyl­salicyl­aldehyde, crystallizes in the phenol–imine tautomeric form with an E conformation for the imine functionality. The mol­ecule is not planar, the dihedral angle between the aromatic rings being 36.38 (5)°. The hy­droxy H atom is involved in a strong intra­molecular O—H⋯N hydrogen bond, generating an S(6) ring.

Synthesis, structural characterization, catalytic, thermal and electrochemical investigations of bidentate Schiff base ligand and its metal complexes

In this study, we prepared the Schiff base ligand (L) and its Cu(II), Co(II) and Ni(II) complexes. The compounds were characterized by the analytical and spectroscopic methods. The ligand (L) behaves as a bidentate ligand and coordinates to the metal ions via the nitrogen atoms. The complexes have the mononuclear structures. The analytical and spectroscopic results indicated that the chloride ions coordinate to the metal ions. The complexes have the general formulae [M(L)(Cl)(2)] (M: Cu(II), Co(II) and Ni(II) metal ions). Electrochemical properties were investigated as ligand and metal centres in the different solvents and at the scan rates, respectively. The thermal properties of the metal complexes were studied in the N(2) atmosphere. We investigated the improved catalytic activity of the Cu(II), Co(II) and Ni(II) complexes on the cyclohexane as a substrate. Obtained data showed that the best catalyst is the Cu(II) complex. The single crystal of the ligand (L) was obtained from CH(3)CN solution. There is a C-H...N H-bond linking the molecules into chains (C6)...N(2) 3.4415(18)A under symmetry operation (x+1,y,z) as well as pi-pi stacking on the outside of the "V" shape--nothing on the inside.