Synthesis,characterization and biological application of cyclometalated heteroleptic platinum(II) complexes

A series of square planar cyclometalated heteroleptic platinum(II) complexes of the type [(C^N)Pt(O^O)] [where, O^O is a β‐diketonato ligand of acetylacetone (acac), C^N = cyclometalating 7‐(4‐fluorophenyl)‐5‐phenylpyrazolo[1,5‐a]pyrimidine (L¹), 7‐(4‐chlorophenyl)‐5‐phenylpyrazolo[1,5‐a]pyrimidine (L²), 7‐(4‐bromophenyl)‐5‐phenylpyrazolo[1,5‐a]pyrimidine (L³), 7‐(4‐methoxyphenyl)‐5‐phenylpyrazolo[1,5‐a]pyrimidine (L⁴), 5‐phenyl‐7‐(p‐tolyl)pyrazolo[1,5‐a]pyrimidine (L⁵)] have been design, synthesized and characterized. All compounds have been screened for biological studies like in vitro antibacterial, in vitro cytotoxicity, cellular level cytotoxicity, absorption titration, viscosity measurements, fluorescence quenching analysis, molecular docking and DNA nuclease. The intrinsic binding constants (K_b) of compounds with HS‐DNA has been obtained in range of 2.892–0.242 × 10⁵ M^?1. All the compounds bound with HS DNA by partial intercalative mode of binding. MIC study has been carried out against Gram^(+ve) and Gram^(?ve) bacterial species. In vitro cytotoxicity against brine shrimp lethality bioassay has been also carried out. The LC₅₀ values of the ligands and complexes have been found in range of 56.49–120.22 μg/mL and 6.71–11.96 μg/mL, respectively.     

Synthesis and characterization of novel chiral diporphyrins and their dimetal complexes

Reaction of chiral 2,2'-biamino-1,1'-binaphthalene (R or 5) with monosubstituted porphyrin 1b and 2b-c afforded novel chiral diporphyrins 3a-c and 4a-c. Their dimetal complexes [(M)2DiPor] have also been prepared. Both structures have been identified by MS, IR, UV-visible, 1H NMR spectra and elemental analysis. These novel chiral compounds show very high optical activities.     

Synthesis, characterization and reactivity of heteroleptic rare earth metal bis(phenolate) complexes

The synthesis, characterization and reactivity of heteroleptic rare earth metal complexes supported by the carbon-bridged bis(phenolate) ligand 2,2'-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP(2-)) are described. Reaction of (C(5)H(5))(3)Ln(THF) with MBMPH(2) in a 1 : 1.5 molar ratio in THF at 50 degrees C produced the heteroleptic rare earth metal bis(phenolate) complexes (C(5)H(5))Ln(MBMP)(THF)(n) (Ln = La, n = 3 (); Ln = Yb (), Y (), n = 2) in nearly quantitative yields. The residual C(5)H(5)(-) groups in complexes to can be substituted by the bridged bis(phenolate) ligands at elevated temperature to give the neutral rare earth metal bis(phenolate) complexes, and the ionic radii have a profound effect on the structures of the final products. Complex reacted with MBMPH(2) in a 1 : 0.5 molar ratio in toluene at 80 degrees C to produce a dinuclear complex (MBMP)La(THF)(mu-MBMP)(2)La(THF)(2) () in good isolated yield; whereas complexes and reacted with MBMPH(2) under the same conditions to give (MBMP)Ln(MBMPH)(THF)(2) (Ln = Yb (), Y ()) as the final products, in which one hydroxyl group of the phenol is coordinated to the rare earth metal in a neutral fashion. The reactivity of complexes and with some metal alkyls was explored. Reaction of complex with 1 equiv. of AlEt(3) in toluene at room temperature afforded unexpected ligand redistributed products, and a discrete ion pair ytterbium complex [(MBMP)Yb(THF)(2)(DME)][(MBMP)(2)Yb(THF)(2)] () was isolated in moderate yield. Furthermore, reaction of complex with 1 equiv. of ZnEt(2) in toluene gave a ligand redistributed complex [(mu-MBMP)Zn(THF)](2) () in reasonable isolated yield. Similar reaction of complex with ZnEt(2) also afforded complex ; whereas the reaction of complex with 1 equiv. of n-BuLi in THF afforded the heterodimetallic complex [(THF)Yb(MBMP)(2)Li(THF)(2)] (). All of these complexes were well characterized by elemental analyses, IR spectra, and single-crystal structure determination, in the cases of complexes , and -.     

Synthesis,characterization, CT-DNA binding and docking studies of novel selenated ligands and their palladium complexes

A novel selenated Schiff base (S) -L ¹ H has been synthesized from (2S)-1-(benzylselanyl)-3-phenylpropan-2-amine which upon reduction formed a reduced Schiff base (S) -L ² H . Palladium (II) complexes (S) -1 and (S) -2 of ligands (S) -L ¹ H and (S) -L ² H respectively were successfully synthesized. The structures of all four compounds were thoroughly identified by analytical and various spectroscopic techniques. The absolute molecular structures of the above two complexes were further confirmed by single crystal X-ray diffraction. Both (S) -L ¹ H and (S) -L ² H coordinated as monobasic ((S) -L ^1–2 ), chelating, tridentate (Se,N,O⁻) ligands resulting in the complexes of composition (S) - [PdCl( L ^1/2 )] [(S) -1/2 ]. In the crystals of complexes (S) -1 and (S) -2 , there were moderate to strong Se⋯O, CH⋯Cl and CH⋯O types of intermolecular secondary interactions. CT-DNA binding activity of these selenium-containing ligands and their palladium complexes bearing a Pd–Se bond have been evaluated for the first time by performing electronic absorption titration and fluorescence emission quenching using CT-DNA-EB and viscometric experiments. These ligands and complexes exhibited remarkable DNA binding activity as shown by their intrinsic DNA binding constants (K_b) and Stern–Volmer constants (K_sv) in the ranges 5.2–9.9 × 10⁴ and 3.6–4.7 × 10⁴, respectively. The viscosity of CT-DNA decreases with increasing concentration of these compounds. The results of the DNA-binding studies revealed that all of the compounds interact with DNA at a minor groove which was further confirmed by molecular docking studies.     

新型稀土配合物的合成表征及EXAFS研究

合成了五种新的稀土配合物RE2(NO3)6L2.nH2O, 其中L为一新的含β-双酮和Schiff-base配体, 1, 5-双(1'-苯基-3'-甲基-5'-吡唑啉酮-4')-1-(4'-氨基丁烷-1'-亚胺基)-5-戊酮, RE=Sm, Eu, Gd, Dy, Ho。对配合物进行了质谱、FTIR、变温红外、EXAFS等研究。结果表明: 配合物为双核结构; 配合物中NO3^-以离子型、单齿及双齿同时存在; 配体L中的C=O, C=N及NH2均参与配位; 稀土离子的总配位数为8, 双配位层分别为2个氮和6个氧, RE-N距离在0.230~0.240nm, RE-O0.240~0.250nm。     

Synthesis, characterization, and crystal structures of novel intramolecularly base-stabilized borane derivatives with six- and seven-membered chelate rings

The reaction of (2-dimethylaminophenyl)alcohols 1-HOX-2-NMe(2)C(6)H(4) [X = CPh(2) (1), X = CCy(2) (2), X = CPh(2)CH(2) (4)] and 1-phenylaminoalkyl-2-dimethylaminobenzene 1-HN(Ph)X-2-NMe(2)C(6)H(4) [X = C(H)Ph (3), C(H)PhCH(2) (5)] with BH(3)(THF) yielded the BH(2) derivatives 1-H(2)BOX-2-NMe(2)C(6)H(4) [X = CPh(2) (6), CCy(2) (7), CPh(2)CH(2) (9)] and 1-H(2)BN(Ph)X-2-NMe(2)C(6)H(4) [X = C(H)Ph (8), C(H)PhCH(2) (10)]. Treatment of 1-H(2)BOCPh(2)-2-NMe(2)C(6)H(4) (6) with acetic acid gave 1-(CH(3)COO)HBOCPh(2)-2-NMe(2)C(6)H(4) (11). Compounds 6-11 were characterized spectroscopically (NMR, IR, MS). Crystal structure determinations were carried out on 6-11, which are novel examples of structurally characterized BH(2) derivatives containing six- or seven-membered chelate rings. For the chiral compounds 8, 10, and 11, both enantiomers are present in the unit cell.     

Synthesis and characterization of heteroleptic iron(II) thiolate complexes with weak iron-arene interactions

Selective preparation and characterization of a series of heteroleptic thiolate complexes of iron(II) are described. The compounds were synthesized by treatment of iron bis-amide Fe{N(SiMe₃)₂}₂ (1) with 1 equiv. of terphenyl thiols HS(2,6-(aryl)₂C₆H₃) followed by addition of another equivalent of different thiol. An amide-thiolate intermediate [{(Me₃Si)₂N}Fe]₂(μ-SDpp)₂ (2; Dpp = 2,6-Ph₂C₆H₃) was isolated from the 1:1 reaction of 1 and HSDpp. The X-ray crystal structures of all new thiolate complexes have been determined. The compounds crystallize as monomers or dimers, dependent on the substituents. They consist of distorted tetrahedral or trigonal-planar iron centers with weak interactions between the aromatic rings of thiolate ligands, where the Fe-C(arene) contact is 2.272(2) Å at shortest. The stronger iron-arene interaction appears to induce more pyramidalized geometry at the iron center.     

Synthesis,characterization, crystal structure,and antimicrobial studies of novel thiourea derivative ligands and their platinum complexes

N,N-Di-R-N′-(4-chlorobenzoyl)thiourea (Di-R: diethyl, di-n-propyl, di-n-butyl and diphenyl) ligands (HL^1–4) and their Pt(II) complexes (cis-[Pt(L^1–4-S,O)₂]) have been synthesized and structurally characterized by elemental analyses, FT-IR and NMR spectroscopy. HL² ligand and cis-[Pt(L⁴-S,O)₂] metal complex have been also characterized by a single-crystal X-ray diffraction study. HL², C₁₄H₁₉ClN₂OS, crystallizes in the monoclinic space group P2₁/n (no. 14), with Z = 4, and unit cell parameters, a = 11.1405(16) Å, b = 9.7015(12) Å, c = 14.790(2) Å, β = 106.547(7)°. The cis-[Pt(L⁴-S,O)₂], C₄₀H₂₈Cl₂N₄O₂PtS₂: triclinic, space group P-1 (no. 2), a = 8.9919(3) Å, b = 14.7159(6) Å, c = 15.7954(6) Å, α = 113.9317(18)°, β = 97.4490(18)°, and γ = 105.0492(16)°. Single crystal analysis of complex, cis-[Pt(L^1–4-S,O)₂], revealed that a square planar coordination geometry is formed around the platinum atom by two sulfur and two oxygen atoms of the related ligands, which are in a cis configuration. In addition, the thiourea derivative ligands and their complexes were evaluated for both their in-vitro antibacterial and antifungal activity. The results have been reported, explained, and compared with fluconazole and ampicillin, used as reference drugs.     

Synthesis and characterization of tris(heteroleptic) Ru(II) complexes bearing styryl subunits

We have developed and optimized a well-controlled and refined methodology for the synthesis of substituted π-conjugated 4,4'-styryl-2,2'-bipyridine ligands and also adapted the tris(heteroleptic) synthetic approach developed by Mann and co-workers to produce two new representative Ru(II)-based complexes bearing the metal oxide surface-anchoring precursor 4,4'-bis[E-(p-methylcarboxy-styryl)]-2,2'-bipyridine. The two targeted Ru(II) complexes, (4,4'-dimethyl-2,2'-bipyridine)(4,4'-di-tert-butyl-2,2'-bipyridine)(4,4'-bis[E-(p-methylcarboxy-styryl)]-2,2'-bipyridine) ruthenium(II) hexafluorophosphate, [Ru(dmbpy)(dtbbpy)(p-COOMe-styryl-bpy)](PF(6))(2) (1) and (4,4'-dimethyl-2,2'-bipyridine)(4,4'-dinonyl-2,2'-bipyridine)(4,4'-bis[E-(p-methylcarboxy-styryl)]-2,2'-bipyridine) ruthenium(II) hexafluorophosphate, [Ru(dmbpy)(dnbpy)(p-COOMe-styryl-bpy)](PF(6))(2) (2) were obtained as analytically pure compounds in high overall yields (>50% after 5 steps) and were isolated without significant purification effort. In these tris(heteroleptic) molecules, NMR-based structural characterization became nontrivial as the coordinated ligand sets each sense profoundly distinct magnetic environments greatly complicating traditional 1D spectra. However, rational two-dimensional approaches based on both homo- and heteronuclear couplings were readily applied to these structures producing quite definitive analytical characterization and the associated methodology is described in detail. Preliminary photoluminescence and photochemical characterization of 1 and 2 strongly suggests that both molecules are energetically and kinetically suitable to serve as sensitizers in energy-relevant applications.     

Synthesis,characterization and antileishmanial studies of some bioactive heteroleptic pentavalent antimonials

In pursuit of safe drug candidates for the treatment of parasitic diseases like leishmaniasis, a series of heteroleptic pentavalent antimonials of the type [R₃Sb(O₂CR′)₂] ( 1 – 9 ) have been synthesized and characterized using elemental analysis (CHN), Fourier transform infrared spectroscopy and multinuclear (¹H and ¹³C) NMR spectroscopy. The carboxylates studied are predominantly substituted benzoates with some complexes having acetato or nicotinato ligands. The crystal structures of [Sb(C₆H₅)₃(o ‐NH₂C₆H₄COO)₂] ( 1 ) and [Sb(C₆H₅)₃(3,5‐Cl₂C₆H₃COO)₂] ( 4 ) were determined as essentially monomeric with an Sb(V) centre and shown to adopt geometries intermediate between trigonal bipyramidal and square pyramidal. The antileishmanial activity was assessed against Leishmania tropica KWH23, and also human macrophages were used to measure the cytotoxicity of these complexes. The IC₅₀ of the antimonials 1 – 9 indicates their efficaciousness as compared with the standard antimonial drug used. The significant activity of complex 1 assumes that greater multitude of interactions is the cause of enhanced antileishmanial activity. Cytotoxicity results showed that these antimonials are highly active even at low concentrations and are biocompatible with human macrophages, making them promising drug candidates for further investigations in this field.     

Synthesis and characterization of novel oxime-imine ligands and their heteronuclear ruthenium(III) complexes

Vicinal carbonyl oxime (HL¹) and oxime-imine (H₂L²) ligands and their mononuclear Ru(III) and Cu(II), heterodinuclear Ru(III)-Mn(II), Ru(III)-Ni(II), Ru(III)-Cu(II), and heterotrinuclear Ru(III)-Cu(II)-Ru(III) chelates were synthesized and characterized by elemental analysis, molar conductivity, IR, ESR, ICP-OES, magnetic moment measurements, and thermal analyses studies. The free ligands were also characterized by ¹H NMR spectra. The carbonyl-oxime ligand coordinates through the oxygen of =N-OH to form a six-membered chelate ring. The quadridentate tetraaza ligand (H₂L²) obtained by condensing of the bidentate ligand 1-p-diphenylmethane-2-hydroxyimino-2-(1-naphthylamino)-1-ethanone (HL¹) with 1,2-phenylenediamine coordinates with Ru(III) through its nitrogen donors in the equatorial position with the loss of one of the oxime protons and concomitant formation of an intramolecular hydrogen bond. Stoichiometric and spectral results of the metal complexes indicated that the metal: ligand ratios in the mononuclear complexes of the ligand (HL¹) were found to be 1: 2, while these ratios were 1: 1 in the mononuclear complexes of the ligand (H₂L²). The metal: ligand ratios of the dinuclear complexes were found to be 2: 1, and this ratio was 3: 2 in the trinuclear complex. The article is published in the original.     

Synthesis and characterization of novel chiral NHC-palladium complexes and their application in copper-free Sonogashira reactions

A new series of chiral N-heterocyclic carbene (NHC) palladium complexes were synthesized from a relatively inexpensive amino acid, l-phenylalanine. All these compounds were fully characterized by (1)H-NMR, (13)C-NMR and elemental analysis. The X-ray molecular structures of two of the complexes were reported. The catalytic activity of the four palladium complexes was successfully tested in the Sonogashira reaction under copper free conditions in air. The palladium complex 3a provided good activity in the Sonogashira coupling reaction.     

Synthesis and characterization of rigid +2 and +3 heteroleptic dinuclear ruthenium(II) complexes

Synthesis and characterization of the dinuclear ruthenium coordination complexes with heteroleptic ligand sets, [Cl(terpy)Ru(tpphz)Ru(terpy)Cl](PF₆)₂(7) and [(phen)₂Ru(tpphz)Ru(terpy)Cl](PF₆)₃(8), are reported. Both structures contain a tetrapyrido[3,2-α:2′,3′-c:3′′,2′′-h:2′′,3′′-j]phenazine (tpphz) (6) ligand bridging the two metal centers. Complex 7 was obtained via ligand exchange between, RuCl₂(terpy)DMSO (5) and a tpphz bridge. Complex 8 was obtained via ligand exchange between, [Ru(phen)₂tpphz](PF₆)₂(4) and RuCl₂(terpy)DMSO (5). Metal-to-ligand-charge-transfer (MLCT) absorptions are sensitive to ligand set composition and are significantly red-shifted due to more electron donating ligands. Complexes 7–9 have been characterized by analytical, spectroscopic (IR, NMR, and UV–Vis), and mass spectrometric techniques. The electronic spectral properties of 7, 8, and [(phen)₂Ru(tpphz)Ru(phen)₂](PF₆)₄(9), a previously reported +4 analog, are presented together. The different terminal ligands of 7, 8, and 9 shift the energy of the MLCT and the π–π* transition of the bridging ligand. These shifts in the spectra are discussed in the context of density functional theory (DFT). A model is proposed suggesting that low-lying orbitals of the bridging ligand accept electron density from the metal center which can facilitate electron transfer to nanoparticles like single walled carbon nanotubes and colloidal gold.     

Synthesis and characterization of new ketooximes and their complexes

The starting point of the research was the reaction of chloroacetyl chloride with biphenyl in the presence of aluminum chloride. 4-Biphenylhydroximoyl chloride (HL) was obtained by reacting synthesized 4-(chloroacetyl)biphenyl with alkyl nitride. Four new substituted 4-(alkylaminoisonitrosoacetyl)biphenyles (ketooximes) were prepared by reacting 4-biphenylhydroximoyl chloride with corresponding amines in EtOH. The following amines were used for ligands: p-toluidine, p-chloroaniline, pyrrolidine, and 4-aminoacetophenone. Mononuclear complexes with a metal-ligand ratio of 1: 2 were prepared using cadmium(II), cobalt(II), copper(II), nickel(II), lead(II), and zinc(II) salts. These compounds have been characterized by elemental analyses, AAS, infrared spectra and magnetic susceptibility measurements. The ligands have been further characterized by ¹H NMR. The results suggest that the ketooximes act as bidentate ligands which bond metal ions through the oxime and carbonyl oxygen. The text was submitted by the authors in English.     

Salen-iron complexes: Synthesis,characterization and their reactivity with lactide

Schiff-base metal complexes as efficient catalysts are widely used in ring-opening polymerization of cycle esters.The salen Fe complexes were formed with their excellent biocompatibility and less toxicity.A series of salen Fe complexes were designed in this work in order to study the activity and control of polymerization of lactide.The salen Fe complexes' activities changed with the ligands configuration and substituent groups.     

Synthesis and characterization of manganese and rhenium tricarbonyl complexes with (O,O,O)-donor ligands

Complexes of the type [(C₅H₅)Co{P(O)R₂}₃]^?, R = OCH₃, OC₂H₅, react as tridentate oxygen ligands L^? with [MBr(CO)₅], M = Mn, Re, in hexane or tetrahydrofuran to give the tricarbonyl derivatives [LM(CO)₃]. The slightly volatile yellow crystalline compounds have been characterized by elemental analysis, ¹H NMR, IR and mass spectra. The low CO stretching frequencies indicate that the ligands L^? are good π-donor ligands.     

Molecular architecture and rheological characterization of novel intramolecularly crosslinked polystyrene nanoparticles

Novel polystyrene nanoparticles were synthesized by the controlled intramolecular crosslinking of linear polymer chains to produce well‐defined single‐molecule nanoparticles of varying molecular mass, corresponding directly to the original linear precursor chain. These nanoparticles are ideal to study the relaxation dynamics/processes of high molecular mass polymer melts, as the high degree of intramolecular crosslinking potentially inhibits entanglements. Both the nanoparticles and their linear analogs were characterized by measuring their intrinsic viscosity, hydrodynamic radius (R_h), and radius of gyration (R_g). The ratio R_g/R_h was computed to characterize the molecular architecture of the nanoparticles in solution, revealing a shift toward the constant density sphere limit with increasing crosslink density and molecular mass. Further, confirming particulate behavior, Kratky plots obtained from neutron scattering data show a shift toward particle‐like nature. The rheological behavior of the particles was found to be strongly dependent on both the extent of intramolecular crosslinking and molecular mass, with a minimal viscosity change at low crosslinking levels and a gel‐like behavior evident for a large degree of crosslinking. These and other results suggest the presence of a secondary mode of polymer relaxation/movement besides reptation, which in this case, is influenced by the total number of crosslinked loops present in the nanoparticle. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1930–1947, 2006     

Synthesis,characterization of Schiff base metal complexes and their biological investigation

A new Schiff base ligand named (E)‐2‐(((3‐aminophenyl)imino)methyl)phenol (HL) was prepared through condensation reaction of m‐phenylenediamine and 2‐hydroxybenzaldehyde in 1:1 molar ratio. The new ligand was characterized by elemental analysis and spectral techniques. The coordination behavior of a series of transition metal ions named Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) with the newly prepared Schiff base ligand (HL) is reported. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV–Vis, ¹H NMR, mass, electronic spectra, magnetic susceptibility and conductivity measurements and further their thermal stability was confirmed by thermogravimetric analysis (TG). From IR spectra, it was observed that the ligand is a neutral tridentate ligand coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH₂ group. The existence, the number and the position of the water molecules was studied by thermal analysis. The molecular structures of the Schiff base ligand (HL) and its metal complexes were optimized theoretically and the quantum chemical parameters were calculated. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species (Staphylococcus aureus and Bacillis subtilis, (gram positive bacteria)), (Salmonella SP., Escherichia coli and Pseudomonas aeruginosa, (gram negative bacteria)) and fungi (Aspergillus fumigatus and Candida albicans). The complexes were found to possess high biological activities against different organisms. Molecular docking was used to predict the efficiency of binding between Schiff base ligand (HL) and both receptors of Escherichia coli (3 T88) and Staphylococcus aureus (3Q8U). The receptor of Escherichia coli (3 T88) showed best interaction with Schiff base ligand (HL) compared to receptor of Staphylococcus aureu (3Q8U).     

Synthesis and characterization of heteroleptic Schiff base transition metal complexes: a study of anticancer,antimicrobial, DNA cleavage and anti-TB activity

In search of effective bioactive compounds, we have synthesized the new Co(II), Ni(II), and Cu(II) complexes of the Schiff base derived from 8-formyl-7-hydroxy-4-methylcoumarin and 2-hydrazino benzothiazole and characterized by analytical, spectroscopic (IR, NMR, UV–vis, Mass), magnetic, powder X-ray diffraction data (PXRD) and TGA studies. Elemental analysis suggests the stoichiometry of the synthesized complexes and the solution electronic spectral study revealed the octahedral geometry of the compounds. Thermal analysis shows the presence of water molecule outside the coordination sphere and powder-XRD patterns have been studied to test the degree of crystallinity of the complexes and unit cell calculations were made. All the synthesized compounds were tested against human ovarian cancer cell line (PA-1). The synthesized metal complexes exhibited enhanced activity against the tested bacterial (Staphylococcus aureus and Escherichia Coli) and fungal strains (Candida albicans and Aspergillus fumigatus) as compared to free ligand (LH). The results of the DNA-cleavage activity suggest that the ligand and its metal complexes can cleave CT-DNA at different degrees. Further, anti-tuberculosis activity was done using microplate almar blue assay. Among all these synthesized compounds, the Cu(II) complex exhibits good cleaving ability compared to other newly synthesized metal complexes.     

Synthesis and characterisation of four novel N x O y -Schiff-base macrocyclic ligands and their metal complexes

Macrocyclic Schiff-bases, L¹ and L², and bis-macrocyclic ligands, L³ and L⁴, have been prepared by [1 + 1] and [2 + 1] cyclocondensation of 1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane or 2,6-bis(2-formylphenoxymethyl)pyridine with 2,6-bis(o-aminophenoxymethyl)pyridine or 1,2,4,5-tetraaminebenzene · 4HCl, respectively. The related Y^III, M^II (M=Co, Ni, Zn, Cd or Pb) and Ln^III nitrate or perchlorate complexes have been synthesised following a template procedure, demonstrating the effectiveness of these metal ions to promote the assembly of these four symmetric Schiff-base macrocycles. The complexes were characterised by elemental analyses, molar conductivity, mass spectrometry, i.r., u.v.–vis, and ¹H-n.m.r spectroscopy.