Schiff Base Coordination Research Articles

Evaluation of anti-inflammatory and antioxidant activities of Copper (II) Schiff mono-base and Copper(II) Schiff base coordination compounds of dien with heterocyclic aldehydes and 2-amino-5-methyl-thiazole

Highly reactive radicals are implicated in many pathological conditions. The quest for radical scavengers or antioxidants, spans the previous decades. A new series of complexes of the type [Cu (dien) (2a-2tzn) Y2] and [Cu (dienXXY2) (2a-5mt)] and of the type [Cu (dptaS) Cl2] and [Cu (dptaS) Br2] (dptaS = 1, 3-propanediamine) or Schiff mono-base of dipropylenetriamine with 2-thiophene-carboxaldehyde, has been tested for anti-inflammatory and antioxidant activity. The tested compounds inhibit the carrageenin-induced rat paw edema (52.0–82.6%) and present important scavenging activity. Compound 6 is the most potent (82.6%) in the in vivo experiment. Lipophilicity-as RM values – has been determined. The results support that in general, adducts of the type [Cu (dienXXY2) (2a-5mt)] exhibit increased activity compared to the starting material of type [Cu (dienXXY2)]. An attempt to correlate the biological results with their structural characteristics and physicochemical parameters has been made

Dinuclear and Tetranuclear Copper(II) Complexes with a Ligand Bearing Phthalocyanine and Schiff-Base Coordination Sites

Abstract Dinuclear and tetranuclear copper(II) complexes with a ligand bearing phthalocyanine and Schiff-base coordination sites were prepared and characterized. The dinuclear complex has two copper(II) phthalocyanine units linked by 2,6-diiminomethyl-4-methylphenol. The imino nitrogen (Schiff-base) coordinates to two more copper(II) ions to give a tetranuclear copper(II) complex composed of a hydroxo- and phenoxo-bridged copper(II) dinuclear unit and two copper(II) phthalocyanine units. Magnetic, spectroscopic, and electrochemical studies showed that there is no significant interaction among the two copper(II) phthalocyanine units and the hydroxo- and phenoxo-bridged dinuclear unit.

Synthesis, Magnetic Properties and X‐ray Structure Analysis of a 1‐D Chain Iron(II) Spin Crossover Complex with wide Hysteresis

AbstractThe reaction of [FeL(MeOH)2] (L being a tetradentate [N2O2]2− coordinating Schiff base like ligand [([3,3′]‐[1,2‐phenylenebis(iminomethylidyne)]bis(2,4‐pentane‐dionato)(2‐)N,N′,O2,O2′], MeOH = methanol) with 4,4′‐bipyridine (bipy) results in the formation of a new iron(II) spin crossover coordination polymer of the formula [FeL(bipy)] (1). T‐dependent susceptibility measurements revealed an abrupt HS ↔ LS spin transition with an approximately 18 K‐wide thermal hysteresis loop (T1/2↑ = 237 K and T1/2↓ = 219 K). The isolation of crystals suitable for X‐ray structure analysis allowed the determination of the motive of the molecule structure of the first 1‐D chain compound with hysteresis in the HS form at 250 K. Despite the low qualtity of the data, we were able to obtain some insight into the interplay of covalent and elastic interactions that are both responsible for the high cooperative interactions during the spin transition in this compound.

Dioxovanadium(V) Complexes Incorporating Tridentate ONO Donor Hydrazone Ligands Derived from Acetylhydrazide and 2-hydroxybenzaldehyde/2-hydroxyacetophenone. Synthesis, Characterization and Reactivity

Reaction of VOSO4 with the tridentate ONO donor ligand derived from the condensation of acetylhydrazide with either 2-hydroxybenzaldehyde (H2L1) or 2-hydroxyacetophenone (H2L2) (general abbreviation H2L) in an equimolar ratio in the presence of two equivalents of sodium acetate in aqueous-methanolic medium in air produces yellow dioxovanadium(V) complexes of the type, [VvO2(H+-L)], (1) and (2) in good yield. Aerial oxygen is most likely the oxidant (for the oxidation of VIV→VV) assisted by the ligand basicity. Complexes are characterized by elemental analyses and by i.r., n.m.r. and u.v.–vis. spectroscopies. I.r. spectra of the complexes indicate the tridentate dinegative forms of the ligands. The 1H-n.m.r. spectrum of (2) in CD3CN solvent indicates the presence of a strongly deshielded N–H proton. Conductivity measurements in DMF solution indicate that the complexes are non-electrolytic and so the H+ ion is strongly bonded probably with the uncoordinated imine-N nitrogen of the coordinated Schiff base moiety. Both complexes exhibit only the LMCT band in the u.v. region in MeOH and they are electroactive, displaying an irreversible reduction peak near −0.35 V versus s.c.e. in methanol solution. Methanol solutions of the complexes are reversibly reduced by ascorbic acid to the corresponding VIV analogue as is evident from their u.v.–vis. spectra. The CH2Cl2 suspension of these complexes (1) and (2) reacts separately with 8-hydroxyquinoline (Hhq) in air to produce the mixed-ligand complexes of the type [VvO(L)(hq)].

The one-dimensional chain compound n-butyldichloro[2-oxido-1-naphthaldehyde (4-pyridylcarbonyl)hydrazonato]tin(IV) methanol disolvate

In the title complex, [Sn(C4H9)(C17H11N3O2)Cl2]·2CH4O, the Sn atom is in a distorted octahedral geometry, with Sn—O distances of 2.093 (3) and 2.125 (3) Å. The tridentate Schiff base coordinates to the Sn via the azomethine N atom, the hydroxyl O atom and the carbonyl O atom. The complex is stabilized by intramolecular O—H...O hydrogen bonds, forming a one-dimensional chain.

Self-Assembly, Reorganization, and Photophysical Properties of Silver(I)−Schiff-Base Molecular Rectangle and Polymeric Array Species

A self-assembly of AgClO(4) with a Schiff-base ligand N,N'-bis(pyridin-2-ylmethylene)benzene-1,4-diamine (1) gave a 1D zigzag polymeric array [[Ag(2)(C(18)H(14)N(4))(2)](ClO(4))(2)(CH(3)CN)](n) (3), while the self-assembly of AgClO(4) with 3,3'-dimethyl-N,N'-bis(pyridin-2-ylmethylene)biphenyl-4,4'-diamine (2) afforded the molecular rectangle [[Ag(2)(C(26)H(22)N(4))(2)](ClO(4))(2)] (4). The structures of 3 and 4 were characterized by single-crystal X-ray diffraction analysis. Structural data for 3 indicate that the Ag(I) ion is coordinated by two ligands of 1 in a distorted tetrahedral fashion thereby leading to a 1D zigzag polymeric array. The zigzag chains are interdigitated with weak pi-pi stacking interactions. The structure of 4 consists of a discrete molecular rectangle where the silver atom has a distorted square-planar coordination with the pyridyl ligands and azomethine nitrogen atoms of 2. An intramolecular pi-pi interaction between the phenyl rings of adjacent Schiff-base 2 functions to stabilize the rectangular architecture. The Ag(I)-Schiff-base coordination polymer 3 is not stable in solution. The degradation and reorganization of 3 to form a [2 x 2] grid architecture [[Ag(4)(C(26)H(22)N(4))(4)](ClO(4))(4)] (3g) was supported in a FAB-MS study. The rectangular structure of 4 remains intact in solution at ambient temperature. The complexes 3g and 4 exhibit unusual luminescence behavior in solution at room temperature with significantly red-shifted emission in the visible region.

Selectivity of Asymmetric Macrocyclic Compartmental Lanthanide(III) Complexes towards Alkali and Alkaline‐Earth Metal Ions

AbstractThe asymmetric macrocyclic compartmental ligand H2L, derived from the [1+1] condensation of 3,3'‐(3‐oxapentane‐1,5‐diyldioxy)bis(2‐hydroxybenzaldehyde) with 1,5‐diamine‐3‐azamethylpentane, forms the complexes [LnNa(L)(Cl)2(CH3OH)] (Ln = La–Nd, Sm–Lu) where the lanthanide(III) ion resides in the N3O2 Schiff base coordination site and thesodium ion is located in the O3O2 crown‐like cavity. The new heterodinuclear complexes [LnCa(L)(Cl)2(CH3OH)(H2O)]Cl (Ln = Tb, Dy, Tm, Yb) were prepared and characterised by single‐crystal X‐ray diffraction, IR, 1H and 13C NMR spectroscopy and their homogeneity and stoichiometry (Ln:Ca:Cl = 1:1:3 molar ratio) were ascertained by SEM‐EDS analysis. The single‐crystal X‐ray structure of [YbCa(L)(Cl2)(EtOH)(H2O)]·Cl·2H2O has been determined. The complex is monoclinic, space group P21/c, with a = 10.033(2), b = 11.702(2), c = 27.796(6) Å and β = 105.51(3)°. The ytterbium ion is seven‐coordinate within the N3O2 site and is in a pentagonal bipyramidal environment and bonded, in the axial positions, to two chloride ions. The calcium ion is seven‐coordinate within the O3O2 site and is bonded to the ethyl alcohol oxygen and to one water molecule. The significant contact between the calcium ion and the chloride ions increases the coordination number of the metal ion to eight in a square antiprismatic environment. The selectivity of the etheric site towards alkali and alkaline‐earth metal ions has been quantitatively assessed by evaluating, with 23Na NMR spectroscopy, the transmetallation reaction involving the coordinated Na+ ion in the complexes [LnNa(L)(Cl)2 (CH3OH)] (Ln = Tb, Dy, Tm and Yb) and Li+, K+ and Ca2+. The affinity constants follow the general order KCa >> KLi ≥ KK. Quantitative kinetic analyses were performed on the complex [TmNa(L)(Cl)2(CH3OH)] using variable temperature 23Na NMR spectroscopy in CD3OD. It was ascertained that the exchange rate Nabound/Nafree is independent of the presence of increasing amounts of water in the methanolic solution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Synthesis, characterization and bioactivity of mixed-ligand Cu(II) complexes containing S-methyldithiocarbazate derivatives and saccharinate ligands and the X-ray crystal structure of the copper–saccharinate complex containing S-methyl-β-N-(6-methylpyrid-2-yl)methylenedithiocarbazate

Mixed-ligand complexes of general empirical formula, [Cu(NNS)(sac)(H 2 O)](NNS′ = S -methyl-β- N -(6-methylpyrid-2-yl)-methylenedithiocarbazate, NNS″ = S -methyl-β- N -(2-acetylpyrid-2-yl)-methylene-dithiocarbazate and NNS‴ = S -methyl-β- N -(2-benzoylpyrid-2-yl) methylenedithio-carbazate, sac = saccharinate anion) are reported. The complexes were characterized by elemental analyses and various physico-chemical techniques. X-ray structure analysis of [Cu(NNS′)-(sac)(H 2 O)] indicates a distorted square-pyramidal structure where the Schiff base coordinates as a uninegative tridentate NNS ligand, the fourth and fifth coordination positions of the five-co-ordinate copper(II) ion being occupied by the imino nitrogen of the saccharinate anion and oxygen atom of the aqua ligand. The bioactivity of these complexes has been investigated. New mixed-ligand complexes of general empirical formula, [Cu(NNS)(sac)(H 2 O)] (NNS′ = S -methyl-β- N -(6-methylpyrid-2-yl)methylenedithiocarbazate, NNS″ = S -methyl-β- N -(2-acetylpyrid-2-yl)methylenedithiocarbazate and NNS‴ = S -methyl-β- N -(2-benzoylpyrid-2-yl) methylenedithiocarbazate, sac = the saccharinate anion) have been synthesized by reacting [Cu(sac) 2 (H 2 O) 4 ] · 2H 2 O with the appropriate ligands in water–ethanol mixtures and characterized by elemental analysis and conductance, magnetic, IR and electronic spectroscopic measurements. Magnetic and spectral evidence support a five-coordinate geometry for the complexes in which the Schiff bases coordinate as NNS tridentate ligands and the saccharinate anion coordinates as a unidentate N-donor ligand. An X-ray crystallographic structural analysis of [Cu(NNS′)(sac)(H 2 O)] shows that the complex has a distorted square-pyramidal structure in which the Schiff base is coordinated to the copper ion as a tridentate NNS chelating agent via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulfur atom, the fourth and fifth coordination positions of the five-coordinate Cu(II) ion being occupied by the imino nitrogen of the saccharinate anion and oxygen atom of the aqua ligand. The complexes have been evaluated for their biological activities against eight pathogenic microbials and human T-lymphoblastic leukemia cell lines. The complexes exhibit marked cytotoxicity against leukemic cell lines and display moderate activity against pathogenic bacteria and fungi.

Copper(II) Schiff base coordination compounds of dien with heterocyclic aldehydes and 2-amino-5-methyl-thiazole: synthesis, characterization, antiproliferative and antibacterial studies. Crystal structure of CudienOOCl 2

A new series of coordination compounds of the starting materials [Cu(dienX 2Y 2)] and their adducts [Cu(dienXXY 2)(2a-5mt)] (where dien=diethylenetriamine, dienXX=Schiff bases of diethylenetriamine with 2-furaldehyde or 2-thiophene-carboxaldehyde, X=O, S, Y=Cl, Br, NO 3 and 2a-5mt=2-amino-5-methylthiazole) were synthesized by stepwise reactions and their structures were established by C, H, N, Cu analysis, spectroscopic, magnetic and molar conductivity measurements. The isolated compounds are monomers, paramagnetic and electrolytic compounds of the type 1:1. In all cases, the pentadentate Schiff base (dienXX) is bonded in a tridentate fashion through the 3 N atoms. In the CudienXXY 2 compounds the coordination sphere is completed by two Cl or Br or NO 3 groups in a square pyramidal arrangement. The proposed structure for this type of compound was further supported by X-ray diffraction analysis of the compound [Cu(dienOO)Cl 2]. Its basal plane consists of three Cu–N contacts [2.017(2), 2.025(2) and 2.012(2) Å] from dienOO, and the Cl(1) atom, while the Cl(2) atom possesses the apical position, the relevant distances being 2.2732(7) Å for Cu–Cl(1) and 2.6051(7) Å Cu–Cl(2). In the CudienX 2Y 2 · 2a-5mt adducts the coordination sphere of copper is further completed by the nitrogen ring atom of the 2a-5mt, forming an octahedral configuration. The study of the biological activity of the compounds synthesized against a panel of different normal and cancer cell lines (MRC5, HeLa, MCF7, HT-29, OAW42, T47D) and bacteria ( E. coli, B. cereus, B. subtilis) showed that the adducts of the type [Cu(dienXXY 2)(2a-5mt)] exhibit increased activity both in cancer cells and in bacteria, compared to the starting material of type [Cu(dienXXY 2)].

First structurally characterized complex of an acyclic tellurated Schiff base [4-MeOC6H4TeCH2CH2N[dbnd]C(CH3)C6H4-2-OH (L1H)] having metal–tellurium bond; synthesis and crystal structure of [PdCl(L1)

Acyclic tellurated Schiff base [4-MeOC6H4TeCH2CH2NC(CH3)C6H4-2-OH (L1H)] has been synthesized by reacting 2-(4-methoxyphenyltelluro)ethylamine with o-hydroxyacetophenone. The L1H on reaction with Na2PdCl4 forms a complex [PdCl(L1)] in which the tellurated Schiff base coordinates in a tridentate mode. The proton and carbon-13 NMR spectra of L1H and the complex are characteristic. The single crystal structure of the complex is solved. The Pd–Te, Pd–Cl, Pd–O and Pd–N bond distances are 2.504(1), 2.290(4), 2.03(1) and 2.01(1) Å, respectively.

The preparation of zinc(II) and cadmium(II) complexes of the pentadentate N 3S 2 ligand formed from 2,6-diacetylpyridine and S-benzyldithiocarbazate (H 2SNNNS) and the X-ray crystal structure of the novel dimeric [Zn 2(SNNNS) 2] complex

The pentadentate chelating agent, 2,6-diacetylpyridinebis( S-benzyldithiocarbazate) (H 2SNNNS) reacts with zinc(II) and cadmium(II) ions forming stable complexes of empirical formula, [M(SNNNS)] (M=Zn 2+, Cd 2+; SNNNS 2=doubly deprotonated anionic form of the Schiff base). These complexes have been characterized by a variety of physico-chemical techniques. IR and 1H NMR spectral evidence indicate that the Schiff base coordinates to the zinc(II) and cadmium(II) ions via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the mercaptide sulfur atoms. The crystal and molecular structure of the zinc(II) complex has been determined by X-ray diffraction. The complex is a dimer in which the pyridine nitrogen atom,the azomethine nitrogen atom and the thiolate sulfur atom from one ligand coordinate to one of the zinc(II) ions whereas the azomethine and thiolate sulfur atoms from another ligand complete pentacoordination around the zinc(II) ion, the ligands being coordinated in their deprotonated forms. The coordination geometry about each zinc(II) can be considered as intermediate between a square-pyramid and trigonal-bipyramid. The cadmium(II) complex is also assigned with a dimeric structure.

Uranyl(VI) complexes with [1+1] asymmetric compartmental ligands containing a Schiff base and a crown ether-like chamber

The [1+1] asymmetric compartmental ligands H 2L A and H 2L B, containing a N 3O 2 Schiff base coordination chamber and an adjacent O 2O n ( n=3, 4) crown-like coordination chamber, have been prepared by reaction of equimolar amount of 3,3′-(3-oxapentane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde (H 2L I) or 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)bis(2-hydroxybenzaldehyde) (H 2L II) and 1,5-diamino-3-azamethylpentane. These macrocycles react with UO 2 2+ to form the mononuclear complexes [UO 2(L A)] and [UO 2(L B)]; the same complexes have been obtained by condensation of the above formyl- and amine-precursors in the presence of UO 2 2+ as templating agent. The uranyl(VI) ion invariantly prefers the N 3O 2 site as evidenced by IR and NMR spectroscopy and confirmed by an X-ray diffractometric investigation for the complex [UO 2(L A)]. [UO 2(L A)] crystallizes in the monoclinic space group P2 1/ c with four formula units in a cell of dimensions a=10.412(2), b=12.973(3), c=19.743(4) Å and β=100.22(3)°. The structure was solved by standard methods and refined by full-matrix least-squares to the conventional R index of 6.9%. The uranyl(VI) atom presents a classic pentagonal bipyramidal coordination polyhedron with the base formed by three nitrogen and two phenolic oxygen atoms of the cyclic ligand. A detailed 1H and 13C NMR study was carried out in order to compare the structure in solution with that found in the solid state.

Nitrosyliron complexes of macrocyclic [N4 2−] and open-chain [N2O2 2−] chelate ligands: influence of the equatorial ligand on the NO binding mode

Several new nitrosyliron complexes FeLNO (L2−: macrocyclic [N4] coordinated or open-chain [N2O2] coordinated Schiff base ligand) were synthesised and compared with respect to their chemical behaviour (reactivity with dioxygen; redox potentials), their T-dependent magnetic susceptibility and their molecule structure. These properties reflect clearly the electronic influence of the equatorial chelate ligand (if present, also of an additional axial ligand) on the electron density at the central atom and, as a consequence, on the NO-binding mode. The macrocyclic complexes with the strongest equatorial donor ligands give pentacoordinated low spin (S=1/2) derivatives, best to interpret as [FeIIIL+NO−]—similar as the halides or pseudo-halides FeLX. These complexes show no tendency to add additional axial ligands and are insensitive to air in non-coordinating solvents. In presence of a donor ligand D (pyridine, MeOH) the reaction with dioxygen results in an octahedral nitro derivative FeL(NO2)×D that can also be prepared by reaction of the iron(III) complex [FeL×2D]+ with sodium nitrite. This could be proved especially for the most electron-rich complex Fe1NO which can also be oxidised electrochemically in MeCN to give [Fe1NO]+ and [Fe1NO]2+ in two reversible steps. The [N2O2] coordinated complexes with weaker donor ligands in the equatorial plane show a more differentiated behaviour depending on electronic effects of the peripheral ligand substituents. Octahedral adducts FeLNO×D could be isolated from several of such complexes under anaerobic conditions. Their reaction with dioxygen gives the μ-oxo derivative (FeL)2O as the main product. Decreasing electron density at the central atom results in a trend towards decreasing transition temperature between a low-temperature S=1/2 and a high-temperature S=3/2 state. The atom distances within the first coordination sphere of the complex Fe5NO×MeOH with the most electron withdrawing substitution of the equatorial ligand are significantly longer than those of the other complexes and show a surprising similarity to those of octahedral high-spin di-adducts FeL×2D of the iron(II) complexes. This fact suggests an interpretation as [FeIILNO×MeOH] with a coupling of the iron(II) S=4/2 state with the unpaired electron of the NO radical. The electronic influence of the equatorial ligands is also reflected in a significant correlation between the angle FeNO (varying from 140 to 167°) and the NO stretching frequencies (varying from 1629 to 1812 cm−1).

Stereochemistry of new nitrogen containing heterocyclic aldehyde. IX. Spectroscopic studies on novel mixed-ligand complexes of Rh(III)

Mono, bis and tris complexes of rhodium(III) oxine (systematic name 8-hydroxy-7-quinolinecarboxaldehyde) and mixed ligand have been prepared. The amine exchange reaction of coordinated Schiff base in these complexes has also been carried out, which gives symmetrical tetradentate Schiff base complexes. The complexes are characterized by elemental and thermal analysis, IR, magnetic and electronic spectral analysis methods were also employed as well as conductivity measurements. An octahedral structure is proposed for all the new complexes in which chloride is attached to the metal ion in 1:1; 1:2 (metal:ligand) ratio. The spectral data were utilized to compute the important ligand field parameter B, β and Dq. The B-values suggest a strong covalency in the metal-ligand σ-bond and the Dq-values indicate a medium strong ligand field. 1H NMR spectra show that the tris (ligand) complex is cis isomer. IR spectra show that the ligand is mono-basic bidentate.

Reversible fixation of carbon dioxide at nickel(0) centers: a route for large organometallic rings, dimers, and tetramers.

The reaction between bis(cycloocta-1,5-diene)nickel(0), carbon dioxide and benzaldehyde-N-furfurylideneimine (A) in 1,4-dioxane or THF results in the formation of the 24-membered organometallic macrocycles of the type [(A)Ni(-CH(R1)-N(R2)-COO-)]6(solv)n (R1: phenyl, R2: furfurylidene, solv: 1,4-dioxane in 1a, THF in 1b). According to the X-ray analyses, six monomeric nickelacyclic units are connected through six Ni-mu2-OCO-Ni bridges in these macrocycles. The cavities of the metallomacrocycles (diameter: 9.410(1) A in 1a, 9.250(1) A in 1b) each contain one solvent molecule. Reaction of 1b with Me3P results in the displacement of the peripheral ligands A by the phosphine to form the 24-membered organometallic macrocycle 1c. Both 1a and 1b isomerize in benzene to form the dimeric complex [(A)Ni(-CH(R1)-N(R2)-COO-)]2(solv)n (2). The X-ray crystal structure reveals that 2 consists of the same monomeric units as found in 1a and 1b. However two Ni-mu2-O-Ni bonds link the carboxylato groups. The solvent-dependent isomerization of 1b yielding 2 is a reversible reaction. Furthermore, the macrocycle 1b partially eliminates carbon dioxide above 20 degrees C, followed by elimination of half of the monodentately coordinated Schiff base ligands to form the planar tetrameric complex 6. This is also a reversible process.

Preparation and characterisation of new oxovanadium(IV) Schiff base complexes derived from salicylaldehyde and simple dipeptides

A range of mostly new oxovanadium(IV) complexes is described. They contain coordinated Schiff bases, made from simple dipeptides (glycylglycine, glycylsarcosine, l-alanylglycine, l-alanyl- l-alanine, d, l-alanyl- d, l-alanine and l-serylglycine), and salicylaldehyde. The compounds are characterised and the nature of their coordination spheres shown by analysis, TLC, by appropriate spectroscopy (EPR, IR, electronic and circular dichroism of solution and solids) and by magnetic susceptibility measurements. Serylglycine and threonylglycine are formed by reaction of VO(salGlyGly) with formaldehyde and acetaldehyde, respectively.

Encapsulation of copper(II) complexes with pentadentate N 3O 2 Schiff base ligands derived from acetylacetone in NaX zeolite

Copper(II) complexes with two five co-ordinate Schiff base ligands derived from acetylacetone and which provide a N 3O 2 co-ordination sphere, bis(acetylacetonate)-3-amino-bis(propyldiimine) and bis(acetylacetonate)-3-methylamino-bis(propyldiimine), were entrapped in the supercages of zeolite NaX by a two-step process in the liquid phase: (i) adsorption of copper(II) acetylacetonate in the supercages of the zeolite, and (ii) in situ Schiff condensation of the copper(II) precursor complex with the corresponding triamines. The new materials were characterised by several techniques: chemical analysis, morphological and surface analysis, spectroscopic methods (FTIR, UV/VIS) and electron paramagnetic resonance. Analysis of the data indicates that the Cu(II) complexes are encapsulated in the NaX zeolite supercages and exhibit structural and electronic properties that are different from those of the free complexes, which can arise from distortions caused by steric effects due to the presence of sodium cations, or from interactions with the zeolite matrix.

An unsymmetrical tripodal ligand with an N2OS donor set: coordination chemistry with nickel(II)ions and aerial oxidation to the sulfinate complex

The synthesis of the previously unknown tripodal ligand H4-1 is reported. The tetradentate ligand is equipped with a completely unsymmetrical N2OS donor set. It reacts with Ni(OAc)2. 4H2O or Ni(ClO4)2.6H2O to give the multinuclear nickel(II) complexes [Ni(H-1-Imin)(OAc)]2 (2) (which contains a coordinated Schiff base obtained by reation of the primary amine with the acetone solvent) and [Ni3(H3-1)(H2-1)2]-ClO4.H2O.3 MeCN (3), respectively. A solution of 3 in DMF is readily oxidized upon exposure to air or by aqueous H2O2 to yield [Ni(H2-1-sulfinate)]2. 2MeOH (4). The molecular structures of 2-4 have been determined by X-ray diffraction. Complex 2 exhibits a strongly distorted, octahedral coordination geometry around each nickel(II)ion. The primary amino group of the ligand in this case reacted with the solvent acetone to yield a Schiff base which is coordinated to the metal center. The molecular structure of the trinuclear complex cation in 3 consists of two subunits: a nickel atom with a square-planar N2S2 coordination geometry and two other nickel atoms with a trigonal-bipyramidal N2O2S coordination environment. The dinuclear complex 4 shows distorted octahedral geometry around each nickel(II) ion. The thiolato groups of the ligands are oxidized to sulfinato groups which are O,O-bound to the nickel center. This coordination mode is unusual for nickel sulfinate complexes.

Preparation and characterization of technetium complexes with Schiff base and phosphine coordination. 1. complexes of technetium-99g and -99m with substituted acac 2en and trialkyl phosphines (where acac 2en = N,N′-ethylenebis[acetylacetone iminato

A series of 23 technetium(III) complexes of the type [TcL(PR 3) 2]+, where L represents a tetradentate Schiff base ligand in the equatorial plane and PR 3 represents the axial phosphine ligands, are reported. Full ligand syntheses and characterizations are included. The technetium complexes were prepared with 99mTc to study the organ distribution in guinea pigs at 5 and 60 min postinjection. Four prototypical complexes of the series were also prepared with either 99gTc or 99gTc/99mTc (designated as carrier-added) to allow macroscopic characterization. Equivalence of the 99gTc and 99mTc complexes was demonstrated by dual detection high performance liquid chromatography (HPLC) techniques. The development of a one-step preparation from the standard two-step method is discussed for some complexes. Biodistribution data are related to structure and lipophilicity. None of the complexes in the series exhibited a tendency for in vivo reduction. Myocardial uptake was favorable for a number of complexes. The optimal agent from this series for further imaging development was chosen based on myocardial uptake, rapid blood and liver clearance, and ability to be formulated as a one-step kit.

Preparation and characterisation of new oxovanadium(IV) Schiff base complexes derived from amino acids and aromatic o-hydroxyaldehydes

A range of mostly new oxovanadium(IV) complexes is described. They contain coordinated Schiff bases, made from natural amino acids (glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, threonine, aspartic acid, and histidine) and salicylaldehyde or such derivatives as 3-, 4-, or 5-methoxy-salicylaldehyde. The coordination sphere is completed by simple ligands like water, 2,2′-bipyridyl or pyridine. The compounds are characterised and the nature of their coordination spheres shown by analysis, TLC, and by appropriate spectroscopy (EPR, IR, electronic and circular dichroism of solution and solids). In a few cases, magnetic properties are described to establish oxidation state. In several cases, the solubility of the compounds from racemic amino acids differs markedly from those containing the single enantiomer. The crystal and molecular structure of the related (and novel) compound with N-pyridoxylidene- d, l-isoleucinate, [VO(pyr- d, l-Ile)(bipy)]·H 2O is described. It contains two diastereomers. Denoting the chiral vanadium centres as A or C, these are and [ A(pyr- l-Ile)(bipy)] [ C(pyr- d-Ile)(bipy)].