Bidentate Schiff Base Ligand Research Articles

(E,E)-N1,N4-Bis(2,6-difluorobenzylidene)butane-1,4-diamine

The asymmetric unit of the title compound, C18H16F4N2, comprises two half crystallographically independent potentially bidentate Schiff base ligands, with an inversion centre located at the mid-point of the central C—C bond. The crystal packing is stabilized by inter­molecular C—H⋯F and π–π inter­actions [centroid–centroid distance = 3.8283 (11) Å].

(E,E)-N1,N2-Bis(2,6-difluorobenzylidene)ethane-1,2-diamine

The asymmetric unit of the title compound, C16H12F4N2, 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 inter­molecular C—H⋯N and π–π inter­actions [centroid–centroid distance = 3.6793 (12) Å and inter­planar spacing = 3.4999 (7) Å].

The reaction of salicylhydrazide with [ReOX3(PPh3)2]. Influence of X on product formation

Abstract The reactions of 2-hydroxybenzhydrazide (salicylhydrazide; Hshz) with trans-[ReOX3L2] (X = Cl (a), Br (b); L = PPh3] in acetonitrile and acetone were studied. With a in acetonitrile, the rhenium(III) complex [ReCl2(shz)(NCCH3)L2] (1), with shz coordinated as a monodentate diazenide, was isolated. However, with b in acetonitrile, the oxorhenium(V) dimer (μ-shd) [ReOBr(OPPh3)]2 (2) was formed. The bridging ligand shd4− was formed by the condensation of two shz ligands, with the elimination of hydrazine. In acetone, the reaction of Hshz with a produced [ReOCl2(sha)L] (3), in which the bidentate Schiff base ligand sha− was formed by the condensation of shz with acetone. The spectral and X-ray crystallographic characterization of complexes 1–3 are reported.

Synthesis, characterization and crystal structures of new bidentate Schiff base ligand and its vanadium(IV) complex: The catalytic activity of vanadyl complex in epoxidation of alkenes

The Schiff base ligand N-salicylidin-2-bromoethylimine ( L) and its vanadium(IV) complex, VOL 2 ( 1), were synthesized and characterized by using X-ray, CHN, 1H NMR and FT-IR methods. X-ray analysis shows the Schiff base ligand L acts as a bidentate (O, N) chelating ligand and coordinates via imine nitrogen and phenolato oxygen atoms to the V(IV) center. The coordination geometry around the V(IV) center in 1 is approximately square pyramidal, as indicated by the unequal metal–ligand bond distances and angles, with the basal plane formed by the N 2O 2 donors of the two bidentate Schiff base ligands, the two phenolato O atoms and the two imine N atoms are in the trans position. The coordination sphere of the V(IV) is completed by one oxygen atom in apical position. In the Schiff base ligand, L, there are some classical intramolecular O1–H1⋯N1 and non-classical intermolecular C9–H9b⋯O1 hydrogen bonds, while in 1, there are two non-classical intermolecular C7–H7⋯O3 and C8–H8b⋯O3 hydrogen bonds. The catalytic activity of 1 in epoxidation of cyclooctene was investigated in different conditions to obtain optimum conditions. The effects of solvent, oxidant, catalyst concentration and alkene/oxidant ratio were studied and the results showed that in CCl 4 in the presence of tert-butylhydroperoxide in 1:3 alkene/oxidant ratio, high epoxide yield was obtained. The epoxidation of alkenes was also carried out in optimized conditions that high catalytic activity and selectivity were obtained.

Two one-dimension copper(II) coordination polymers based on imine-based bidentate Schiff-base ligand: Synthesis, crystal structure and luminescent properties

Two new one-dimension copper(II) coordination polymers [CuL 2(NCS) 2] n ( 1) and [CuL 2(NO 3) 2] n ( 2) (L = (C 5H 4N)C(CH 3) N–N (CH 3)C(C 5H 4N)) have been synthesized and characterized by IR, elemental analysis, TG technique and X-ray crystallography. Each Cu(II) atom has a distorted octahedral N 6 ( 1) or N 4O 2 ( 2) environment with four pyridyl N atoms from four ligands and two N atoms from two NCS − anions for polymer 1 or two O atoms from two NO 3 − anions for polymer 2, respectively. A pair of bis-monodentate bridging ligands links two Cu(II) centers to form one dimension chain structure containing bimetallic 22-membered macrometallacyclic rings. 1D chain is held together with its neighboring ones via C–H⋯S hydrogen bonds for 1 and C–H⋯O hydrogen bonds, C–H⋯π interactions for 2 to form a 3D supramolecular structure, respectively. The luminescent properties of the polymers 1 and 2 were investigated in the solid state at room temperature.

Cobalt(III) Complex [CoL3] Derived from an Asymmetric Bidentate Schiff Base Ligand L (L=(5‐Bromo‐2‐hydroxybenzyl‐2‐furylmethyl)‐imine): Synthesis, Characterization and Crystal Structure

AbstractCobalt(III) complex [CoL3], where L=(5‐bromo‐2‐hydroxybenzyl‐2‐furylmethyl)imine, has been synthesized by reacting cobalt(II) nitrate with L. The complex has been characterized by elemental analysis and FT‐IR spectroscopy. The crystal structure of [CoL3] was determined by X‐ray crystallography from single crystal data. It crystallizes in the triclinic space group$ P {\bar 1} $with unit cell parameters:a=9.6644(10) Å,b=11.5657(11) Å,c=16.5809(17) Å,α=102.833(4)°,β=102.999(3)°,γ=105.480(3)°,V=1659.9(3) Å3andZ=2. Thermal decomposition of [CoL3] was studied by thermogravimetry in order to evaluate its thermal stability and thermal decomposition pathways.

Synthesis, spectral and thermal studies of zinc(II) and mercury(II) complexes with bidentate Schiff-base ligand (234-MeO-Ba)2En: the crystal structure of Zn(234-MeO-Ba)2En)I2

New Symmetric bidentate Schiff-base ligands N,N′-bis(2,3,4-trimethoxybenzylidene)-1,2-di-aminoethane, (234-MeO-Ba)2En, and its corresponding zinc(II) and mercury(II) complexes, Zn((234-MeO-Ba)2En)I2 (I), Hg((234-MeO-Ba)2En)Cl2 (II) have been synthesized and characterized by elemental analyses (CHN), FT-IR and 1H NMR spectroscopy. The thermal behaviors of complexes were study using thermogravimetry in order to evaluate their thermal stability and thermal decomposition pathways. The crystal structure of I was determined from single-crystal X-ray diffraction. The coordination polyhedron about the zinc(II) center in complex I is best described as a distorted tetrahedron.

Structural and Electronic Modulation of Magnetic Properties in a Family of Chiral Iron Coordination Polymers

The complexes FeL(2) [L = bidentate Schiff base ligands obtained from (R)-(+)-α-phenylethanamine and 4-substituted salicylaldehydes, substituent R = H, (t)Bu, NO(2), OMe, CN, OH] react with ditopic proligands 1,4-pyrazine (pz) or 4,4'-bipyridine (bpy), to give a family of optically pure Fe(II) polymeric chain complexes of formula {FeL(2)(μ-pz)}(∞) and {FeL(2)(μ-bpy)}(∞). Crystallographic studies show that a range of structures are formed including unidirectional and bidirectional linear polymers and canted zigzag chains. Interchain interactions via π-contacts and hydrogen bonding are also observed. SQuID magnetometry studies on all of the complexes reveal antiferromagnetic interactions, the magnitudes of which are rationalized on the basis of substituent electronic properties and bridging ligand identity. For complexes with bridging pz, the antiferromangnetic interaction is enhanced by electron-releasing substituents on the Fe units, and this is accompanied by a contraction in the intrachain distance. For complexes bridged with the longer bpy the intrachain antiferromagnetic couplings are much weaker as a result of the longer intrachain distance. The magnetic data for this series of chain complexes follow a Bonner-Fisher 1D chain model, alongside a zero field splitting (ZFS) model for Fe(II) (S = 2) as appropriate. The intrachain antiferromagnetic coupling J values, g-factors, and the axial ZFS parameter D were obtained.

Bis{2-[(2-furylmethyl)iminomethyl]-5-methoxyphenolato-κ2N,O}zinc(II)

In the title complex, [Zn(C13H12NO3)2], the ZnII ion is located on a twofold rotation axis and is coordinated by two bidentate Schiff base ligands in a distorted tetra­hedral environment. The complex mol­ecules are stacked in columns along the b axis through C—H⋯O hydrogen bonds.

Synthesis, characterization and antimicrobial studies of CoII, NiII, CuII and ZnII complexes involving a bidentate Schiff base ligand

Synthesis, characterization and antimicrobial studies of CoII, NiII, CuII and ZnII complexes involving a bidentate Schiff base ligand

Synthesis, characterization, antimicrobial and diuretic study of Mg(II), Mn(II), Fe(II) and VO(II) complexes of chemotherapeutic importance

The synthesis, characterization and diuretic activity of four new biologically active complexes of Mg(II) and VO(II) with bidentate Schiff base ligand acetazolamide–salicylaldimine (L) obtained from the inserted condensation of 5-acetamido-1,3,4-thiadiazole-2-sulphonamide (acetazolamide) with salicylaldehyde in a 1:1 molar ratio have been reported. Using this bidentate ligand complexes of Mg(II), Mn(II), Fe(II) and VO(II) with general formula ML2 have been synthesized. The synthesized complexes were characterized by several techniques using elemental analysis, FT-IR, electronic spectra, TGA, mass, particle size analysis and molar conductance measurements. The elemental analysis data suggest the stoichiometry to be 1:2 [M:L]. The molar conductance measurements suggest non-electrolytic nature of the complexes. Infrared spectral data agreed with the coordination to the central metal ion through deprotonated phenolic oxygen and azomethine nitrogen atoms. On the basis of spectral studies, octahedral geometry is suggested for Mg(II), Mn(II), Fe(II) and square pyramidal geometry is suggested for VO(II) complexes. The pure drug, synthesized ligand and metal(II) complexes were screened for their antimicrobial activities against Eschericia coli, Bacillus subtilis, Aspergillus niger and Aspergillus flavous. The results show that the metal complexes were more active than the ligand and pure drug against these microbial species as expected. The ligand and its Mg(II) complexes was screened for their diuretic activity also.

Unprecedented π⋯π interaction between an aromatic ring and a pseudo-aromatic ring formed through intramolecular H-bonding in a bidentate Schiff base ligand: crystal structure and DFT calculations

A combination of a single crystal X-ray diffraction study and density functional theory calculations has been applied to a bidentate Schiff base compound to elucidate different cooperative non-covalent interactions involved in the stabilization of the keto form over the enol one in the solid state. The single crystal X-ray structure reveals a remarkable supramolecular assembly of the keto form through a cyclic hydrogen bonded dimeric motif. The most interesting feature in the supramolecular assembly is the formation of a 'dimer of dimer' motif by π···π, CH···π and N···O/O···O interactions in which the π···π interaction involving the aromatic phenyl ring and the intramolecularly hydrogen bonded pseudo-aromatic ring of the keto form lying just above or below the phenyl ring of the other dimer seems to be unprecedented. The optimized geometry of the hydrogen bonded dimeric motif of the keto form of the organic molecule has been obtained by DFT calculations and agrees very well with that found within the crystalline state. The X-ray crystallographic geometry of the 'dimer of dimer' has also been computed, which shows that in the HOMO, the π electrons are localized in the phenyl rings away from each other, while in the LUMO, there is a strong π-π interaction between the phenyl ring of one dimer with the pseudo-aromatic ring of another dimer with an energy estimated to be 7.95 kJ mol(-1). Therefore, on HOMO → LUMO excitation there is localization of π electrons in the central part of the complex moiety which plays a stabilizing role of the dimer of dimer motif in the solid state.

Aerobic epoxidation of olefins over the composite catalysts of Co-ZSM-5(L) with bi-/tridentate Schiff-base ligands

Three tridentate or bidentate Schiff-base ligands inclusive of salicylaldehyde benzoylhydrazone (L1), vanillic aldehyde benzoylhydrazone (L2) and 4-methyl benzaldehyde benzoylhydrazone (L3), have been designed, synthesized and employed to coordinate with Co2+ ions and ion-exchanged Co-ZSM-5 forming several Co-L complexes and Co-ZSM-5(L) composite catalysts. The catalytic epoxidation of several alkenes with dry air has been carried out at 90°C under atmospheric pressure using Co-L complexes and Co-ZSM-5(L) catalysts (using TBHP in small amounts as the initiator). In contrast, the catalysts Co-ZSM-5(L) shows higher catalytic activity than Co-ZSM-5 itself and Co-L complexes. Among three Co-ZSM-5(L) catalysts, Co-ZSM-5(L1) exhibits the highest activity for the selective epoxidation of alkenes. Recycling studies show the recyclability of Co-ZSM-5(L1) as a heterogeneous catalyst, which does not lose the catalytic activity after even eight reuses appreciably. Based on the experiments, one possible reaction mechanism is proposed.

Nickel(II) and copper(II) complexes with an asymmetric bidentate Schiff-base ligand derived from furfurylamine

New asymmetric bidentate Schiff-base ligand (5-bromo-2-hydroxybenzyl-2-furylmethyl)imine, (HL), and its nickel(II) and copper(II) complexes with the general composition ML2 (M = Ni (1 )a nd Cu (2)), were prepared. The ligand and the metal complexes were characterized by elemental analysis, FT-IR, and UV-Vis spectroscopy. In addition, 1 H-NMR and X-ray powder diffraction (XRD) were employed for characterization of ligand and metal complexes, respectively. Thermogravimetric analysis (TGA) of the ligand and metal complexes revealed the thermal stability and decomposition pattern of the species.

Dioxidobis{2-[(E)-p-tolyliminomethyl]phenolato}molybdenum(VI)

The asymmetric unit of the title compound, [Mo(C14H12NO)2O2], comprises half of the complex with the full mol­ecule generated by the application of twofold symmetry. The MoVI atom is surrounded by two oxide O atoms and the two sets of N,O-donor atoms of the bidentate Schiff base ligands. The resulting N2O4 donor set defines a distorted octa­hedral coordination geometry. Inter­molecular C—H⋯O contacts link mol­ecules into chains along the b axis. The crystal structure is further stabilized by inter­molecular π–π inter­actions [ring centroid–centroid distance = 3.724 (6) Å].

Dibromido{2-[1-(cyclopropylimino)ethyl]pyridine}zinc(II)

In the title compound, [ZnBr2(C10H12N2)], the Zn2+ ion is coordinated by the N,N′-bidentate Schiff base ligand and two bromode ions in a distorted tetra­hedral arrangement. The dihedral angle between the pyridine and the cyclo­propyl rings is 95.4 (8)°.

Synthesis, Crystal Structures, and Antibacterial Activity of Cobalt(III) Complexes with Bidentate Schiff Base Ligands

Two cobalt(III) complexes with the Schiff bases 4-X-2-(cyclopentyliminomethyl)phenol (X = chloro and bromo) were synthesized and structural characterized by elemental analysis (C, H, N), FT-IR spectra, and single crystal X-ray diffraction. The Co atom in each complex is six-coordinated in an octahedral geometry by three O atoms and three N atoms from three Schiff base ligands. The antibacterial activity of the complexes and the Schiff bases against the bacteria Staphylococcus aureus, Bacillus anthracis, Pseudomonas aeruginosa, and Streptococcus agalactiae were investigated.

Synthesis, characterization, and crystal structure of two zinc(II) halide complexes with the symmetrical bidentate Schiff-base ligand (3,4-MeO-ba)2en

In this study two zinc(II) halide complexes with the Schiff-base ligand (3,4-MeO-ba)2en [N,N′-bis(3,4-dimethoxybenzylidene)ethane-1,2-diamine] have been synthesized and characterized by elemental analyses (CHN), single-crystal X-ray diffraction, Fourier-transform infrared (FT-IR), and 1H nuclear magnetic resonance (NMR) spectroscopy. The metal-to-ligand ratio was found to be 1:1 within the formula ZnX2((3,4-MeO-ba)2en) (X = Br, I). Crystal structure analysis reveals that the coordination geometry around the zinc(II) ions in the two isotypic complexes is distorted tetrahedral. The Schiff-base ligand (3,4-MeO-ba)2en acts as a chelating ligand and coordinates via two N atoms to the metal center and adopts an (E,E) conformation. The coordination spheres of the metal atoms are completed by the two halide atoms, which are also involved in weak non-classical hydrogen-bonding interactions of the type C–H···X–Zn.

Synthesis, Crystal Structure, and Luminescent Properties of One Cadmium(II) Coordination Polymer with Mixed Imine-based Bidentate Schiff-Base and Thiocyanate Ligands

A new one-dimension Cd(II) coordination polymer [CdL2(NCS)2] n (L = (C5H4N)C(CH3) = N−N = C(CH3)(C5H4N)) has been synthesized and characterized by IR, UV, elemental analysis, TG technique and X-ray crystallography. Cd(II) atom has an distorted octahedral environment with a N6 donor set from four ligands and two NCS− anions, respectively. A pair of ligands bridge two adjacent Cd(II) centers to form one dimension chain structure containing bimetallic 22-membered macrometallacyclic rings. A 1D structure is held together with its neighboring ones via multiform hydrogen bonds to form a 3D supramolecular structure. The luminescent properties of the complex at room temperature were investigated.

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.