Synthesis, structural, spectral, thermal and antimicrobial studies of palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes derived from N,N,N,N-tetradentate macrocyclic ligand

Palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes of general stoichiometry [PdL]Cl(2), [PtL]Cl(2), [Ru(L)Cl(2)]Cl and [Ir(L)Cl(2)]Cl are synthesized with a tetradentate macrocyclic ligand, derived from 2,6-diaminopyridine with 3-ethyl 2,4-pentanedione. Ligand was characterized on the basis of elemental analyses, IR, mass, and (1)H NMR and (13)C NMR spectral studies. All the complexes were characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, mass, electronic spectral techniques and thermal studies. The value of magnetic moments indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moments corresponding its one unpaired electron. The macrocyclic ligand and all its metal complexes were also evaluated in vitro against some plant pathogenic fungi and bacteria to assess their biocidal properties.     

Interaction of Co(II), Ni(II) and Cu(II) with dibenzo-substituted macrocyclic ligands incorporating both symmetrically and unsymmetrically arranged N, O and S donors

The synthesis and characterisation of four 17-membered, dibenzo-substituted macrocyclic ligands incorporating unsymmetrical arrangements of their N(3)S(2), N(3)O(2) and N(3)OS (two ligands) donor atoms are described; these rings complete the matrix of related macrocyclic systems incorporating both symmetric and unsymmetric donor sets reported previously. The X-ray structures of three of the new macrocycles are reported. In two of the Cu(II) structures only three of the possible five donor atoms present in the corresponding macrocyclic ligand bind to the Cu(II) site, whereas all five donors are coordinated in each of the remaining complexes. The interaction of Co(II), Ni(II) and Cu(II) with the unsymmetric macrocycle series has been investigated by potentiometric (pH) titration in 95% methanol; X-ray structures of two nickel and three copper complexes of these ligands, each exhibiting 1:1 (M:L) ratios, have been obtained. The results are discussed in the context of previous results for these metals with the analogous 17-membered ring systems incorporating symmetrical arrangements of their donor atoms, with emphasis being given to both the influence of the donor atom set, as well as the donor atom sequence, on the nature of the resulting complexes.     

Synthesis and spectral studies on mononuclear complexes of chromium(III) and manganese(II) with 12-membered tetradentate N2O2, N2S2 and N4 donor macrocyclic ligands

Complexes of Cr^III and Mn^II of general formula [Cr(L)X₂] X and [Mn(L)X₂] respectively were prepared from N₂O₂, N₂S₂ and N₄ donor macrocyclic ligands. The complexes have been characterized by elemental analysis, molar conductance measurements, spectral methods (i.r, mass, ¹H-n.m.r, electronic spectra and e.p.r.) and magnetic measurements. The macrocyclic ligands have three different donating atom cavities, one with two unsaturated nitrogens and the other two have saturated nitrogen, oxygen and sulphur atoms. The effect of different donor atoms on the spectra and ligand field parameters is discussed. All the complexes show magnetic moments corresponding to a high-spin configuration. On the basis of spectral studies a six coordinated octahedral geometry may be assigned to these complexes.     

Syntheses,crystal structures,and spectroscopic properties of copper(II) complexes with 3,14-diethyl-2,6,13,17-tetraazatricyclo(16.4.0.07,12)docosane

[Cu(L)(NO₃)₂] (1) and [Cu(L)(H₂O)₂](SCN)₂ (2) [L?=?3,14-diethyl-2,6,13,17-tetraazatricyclo(16.4.0.0^7,12)docosane] have been prepared and structurally characterized by single-crystal X-ray diffraction at 100?K. For these constrained macrocycle complexes, copper(II) exists in a tetragonally distorted octahedral environment with the four nitrogen atoms of the macrocyclic ligands and two oxygen atoms from either nitrate or water in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans-III conformation. The Cu–N distances are 2.021(2)–2.047(2)?Å and typical but the axial ligands are weakly coordinating, with Cu–O bond lengths, 2.506(2)?Å for 1 and 2.569(2)?Å for 2, due to the pseudo Jahn–Teller effect. The crystals are stabilized by a 3-D network by intra and intermolecular hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms and nitrate in 1, and intermolecular hydrogen bonds are formed by water and thiocyanates in 2. The electronic absorption and IR spectral properties are also discussed.     

Synthesis, structure and spectral and redox properties of new mixed ligand monomeric and dimeric Ru(II) complexes: predominant formation of the "cis-alpha" diastereoisomer and unusual 3MC emission by dimeric complexes

The tetradentate ligands 1,8-bis(pyrid-2-yl)-3,6-dithiaoctane (pdto) and 1,8-bis(benzimidazol-2-yl)-3,6-dithiaoctane (bbdo) form the complexes [Ru(pdto)(mu-Cl)](2)(ClO(4))(2) 1 and [Ru(bbdo)(mu-Cl)](2)(ClO(4))(2) 2 respectively. The new di-mu-chloro dimers 1 and 2 undergo facile symmetrical bridge cleavage reactions with the diimine ligands 2,2'-bipyridine (bpy) and dipyridylamine (dpa) to form the six-coordinate complexes [Ru(pdto)(bpy)](ClO(4))(2) 3, [Ru(bbdo)(bpy)](ClO(4))(2) 4, [Ru(pdto)(dpa)](ClO(4))(2) 5 and [Ru(bbdo)(dpa)](ClO(4))(2) 6 and with the triimine ligand 2,2':6,2'-terpyridine (terpy) to form the unusual seven-coordinate complexes [Ru(pdto)(terpy)](ClO(4))(2) 7 and [Ru(bbdo)(terpy)](ClO(4))(2) 8. In 1 the dimeric cation [Ru(pdto)(mu-Cl)](2)(2+) is made up of two approximately octahedrally coordinated Ru(II) centers bridged by two chloride ions, which constitute a common edge between the two Ru(II) octahedra. Each ruthenium is coordinated also to two pyridine nitrogen and two thioether sulfur atoms of the tetradentate ligand. The ligand pdto is folded around Ru(II) as a result of the cis-dichloro coordination, which corresponds to a "cis-alpha" configuration [DeltaDelta/LambdaLambda(rac) diastereoisomer] supporting the possibility of some attractive pi-stacking interactions between the parallel py rings at each ruthenium atom. The ruthenium atom in the complex cations 3a and 4 exhibit a distorted octahedral coordination geometry composed of two nitrogen atoms of the bpy and the two thioether sulfur and two py/bzim nitrogen atoms of the pdto/bbdo ligand, which is actually folded around Ru(II) to give a "cis-alpha" isomer. The molecule of complex 5 contains a six-coordinated ruthenium atom chelated by pdto and dpa ligands in the expected distorted octahedral fashion. The (1)H and (13)C NMR spectral data of the complexes throw light on the nature of metal-ligand bonding and the conformations of the chelate rings, which indicates that the dithioether ligands maintain their tendency to fold themselves even in solution. The bis-mu-chloro dimers 1 and 2 show a spin-allowed but Laporte-forbidden t(2g)(6)((1)A(1g))--> t(2g)(5) e(g)(1)((1)T(1g), (1)T(2g)) d-d transition. They also display an intense Ru(II) dpi--> py/bzim (pi*) metal-to-ligand charge transfer (MLCT) transition. The mononuclear complexes 3-8 exhibit dpi-->pi* MLCT transitions in the range 340-450 nm. The binuclear complexes 1 and 2 exhibit a ligand field ((3)MC) luminescence even at room temperature, whereas the mononuclear complexes 3 and 4 show a ligand based radical anion ((3)MLCT) luminescence. The binuclear complexes 1 and 2 undergo two successive oxidation processes corresponding to successive Ru(II)/Ru(III) couples, affording a stable mixed-valence Ru(II)Ru(III) state (K(c): 1, 3.97 x 10(6); 2, 1.10 x 10(6)). The mononuclear complexes 3-7 exhibit only one while 8 shows two quasi-reversible metal-based oxidative processes. The coordinated 'soft' thioether raises the redox potentials significantly by stabilising the 'soft' Ru(II) oxidation state. One or two ligand-based reduction processes were also observed for the mononuclear complexes.     

Substituents effect on the spectral studies on rutheninum(III) complexes of 5(-4'-derivatives phenyldiazo)-3-phenyl-2-thioxo-4-thiazolidinone

A novel series of Ru(III) complexes with 5(-4'-derivatives phenyldiazo)-3-phenyl-2-thioxo-4-thiazolidinone (HLn) have been prepared. The ligands and structural composition of complexes were confirmed and characterized by various physico-chemical techniques. The spectral data were utilized to compute the important ligand field parameters B, beta and Dq. The effect of Hamett's constant on the ligand field parameters is also discussed. The spectral and magnetic results commensurate an octahedral environment around the Ru(III) ion. The B-values suggest a strong covalency in the metal-ligand sigma-bond and the Dq-values indicate a medium-strong ligand-field. IR spectra show that the ligand is neutral bidentate forming thereby a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The ligands are present in associated form in solution via intermolecular hydrogen bond and act as neutral bidentate coordinated to ruthenium(III).     

Spectroscopic characterization of chromium(III), manganese(II) and nickel(II) complexes with a nitrogen donor tetradentate, 12-membered azamacrocyclic ligand

The complexes of Cr(III), Mn(II) and Ni(II) were synthesized with macrocyclic ligand i.e. 5,11-dimethyl-6,12-diethyl-dione-1,2,4,7,9,10-hexazacyclododeca -1,4,6,10-tetraene. The ligand (L) was prepared by [2+2] condensation reaction of 2,3-pentanedione and semicarbazide hydrochloride. These complexes were found to have the general composition [Cr(L)X(2)]X and [M(L)X(2)] (where M=Mn(II) and Ni(II); X=Cl(-), NO(3)(-), (1/2)SO(4)(2-), NCS(-) and L=ligand [N(6)]). The ligand and its transition metal complexes were characterized by the elemental analysis, molar conductance, magnetic susceptibility, mass, IR, electronic and EPR spectral studies. On the basis of IR, electronic and EPR spectral studies, an octahedral geometry has been assigned for these complexes except sulphato complexes which are of five coordinated geometry.     

Synthesis and structural characterization of manganese(III,IV) and ruthenium(III) complexes derived from 2-hydroxy-1-naphthaldehydebenzoylhydrazone

Reaction of 2-hydroxy-1-naphthaldehydebenzoylhydrazone(napbhH₂) with manganese(II) acetate tetrahydrate and manganese(III) acetate dihydrate in methanol followed by addition of methanolic KOH in molar ratio (2 : 1 : 10) results in [Mn(IV)(napbh)₂] and [Mn(III)(napbh)(OH)(H₂O)], respectively. Activated ruthenium(III) chloride reacts with napbhH₂ in methanolic medium yielding [Ru(III)(napbhH)Cl(H₂O)]Cl. Replacement of aquo ligand by heterocyclic nitrogen donor in this complex has been observed when the reaction is carried out in presence of pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF (N,N-dimethyl formamide) of these complexes suggest non-electrolytic and 1 : 1 electrolytic nature for manganese and ruthenium complexes, respectively. Magnetic moment values of manganese complexes suggest Mn(III) and Mn(IV), however, ruthenium complexes are paramagnetic with one unpaired electron suggesting Ru(III). Electronic spectral studies suggest six coordinate metal ions in these complexes. IR spectra reveal that napbhH₂ coordinates in enol-form and keto-form to manganese and ruthenium metal ions in its complexes, respectively. ESR studies of the complexes are also reported.     

Synthesis, stability, and complexation behavior of isolable salen-type N2S2 and N2SO ligands based on thiol and oxime functionalities

The new salen-type N(2)S(2) tetradentate ligands, H(2)L(1) and H(2)L(2), which have a donor set comprising oxime and thiol groups, were synthesized. These ligands are obtained as isolable colorless crystals, whereas the imine analogues are too unstable to be isolated. The unsymmetrical N(2)SO ligands, H(2)L(3) and H(2)L(4), were also obtained as stable compounds. When ligands H(2)L(1)-H(2)L(4) are heated above the melting points, they mainly decompose via cleavage of the N-O bonds of a thiosalicylaldoxime moiety to give 1,2-benzisothiazole derivatives. The complexation of the N(2)S(2) ligands (H(2)L(1) and H(2)L(2)) with nickel(II) acetate afforded square-planar mononuclear complexes [Ni(L(1))] and [Ni(L(2))], respectively. In contrast, the complexation of the N(2)SO ligand H(2)L(3) with nickel(II) acetate resulted in cleavage of the N-O bond, giving a tetranuclear complex having a cubane-type Ni(4)O(4) core. The N-O bonds of H(2)L(1)-H(2)L(4) are more readily cleaved when the ligands are allowed to react with copper(II) acetate. In these cases, the alkoxo-bridged dinuclear complexes having a Cu-O-Cu-O four-membered ring are obtained. On the other hand, mononuclear complexes can be obtained by complexation of the ligands (H(2)L(1) or H(2)L(3)) with palladium(II) acetate without N-O bond cleavage.     

Spectral studies with coordination behaviour of (NO3) and (NCS) anions and EPR parameters of chromium(III) complexes which have different chromospheres macrocyclic ligands: synthesis and electronic spectroscopy

New macrocyclic ligands were prepared and chromium(III) stability in the marcrocyclic cavities are reported. Two of them have four-coordinate [N2O2]:[N4], third one has five-coordinate [N2O2S] and the last one has six-coordinate [N4O2] donor macrocyclic cavities. These macrocyclic ligands have been synthesized with their chromium(III) complexes which have mononuclear nature and their structural features have been discussed on the basis of: elemental analysis, magnetic moment, electronic, IR, 1H NMR, and EPR spectral studies. All the chromium(III) complexes show magnetic moments in the range of 3.74-3.80 B.M. corresponding to high-spin configuration. However, the interaction of oxygen to the chromium ion in complexes is much weaker than that of other donor atoms. The spin-orbit coupling parameter, z, gives no significance because the splitting of doublet transition lines are too large to be explained by spin-orbit coupling. The beta values (0.75-0.79) indicate the covalent character, which is due to the presence of sigma bond between the metal/ligand. lambda values indicate that the complexes under study have substantial covalent character and their g-values have also been calculated by using spin-orbital coupling constant (lambda).     

Structural studies and anticancer activity of a novel (N6O4) macrocyclic ligand and its Cu(II) complexes

A novel (N6O4) macrocyclic ligand (L) and its Cu(II) complexes have been prepared and characterized by elemental analysis, spectral, thermal (TG/DTG), magnetic, and conductivity measurements. Quantum chemical calculations have also been carried out at B3LYP/6-31+G(d,p) to study the structure of the ligand and one of its complexes. The results show a novel macrocyclic ligand with potential amide oxygen atom, amide and amine nitrogen atoms available for coordination. Distorted square pyramidal ([Cu(L)Cl]Cl·2.5H2O (1), [Cu(L)NO3]NO(3)·3.5H2O (2), and [Cu(L)Br]Br·3H2O (4) and octahedral ([Cu(L)(OAc)2]·5H2O (3)) geometries were proposed. The EPR data of 1, 2, and 4 indicate d1x2(-y)2 ground state of Cu(II) ion with a considerable exchange interaction. The measured cytotoxicity for L and its complexes (1, 2) against three tumor cell lines showed that coordination improves the antitumor activity of the ligand; IC50 for breast cancer cells are ≈8.5, 3, and 4 μg/mL for L and complexes (1) and (2), respectively.     

Preparation and spectroscopic characterization of novel cyclodiphosph(V)azane of N(1)-2-pyrimidinylsulfanilamide complexes. Magnetic, thermal and biological activity studies

Hexachlorocyclophosph(V)azane of sulfadiazine, (sulfupyrimidine) [N(1)-2-pyrimidinylsulfanilamide] (H2L1), was prepared and reacted with sulfur and glycine to give (H2L2) and (H2L3) ligands, respectively. The prepared ligands; H2L1, H2L2 and H2L3, react in 1:2 [ligands]:[metal ions] molar ratio with transition metals to give coloured complexes in a relatively good yields. The complexes were characterized using different physicochemical techniques, namely elemental analyses, IR, UV-vis, mass, 1H NMR, molar conductance, magnetic, solid reflectance and thermal analysis. The spectral data reveal that all the ligands behave as neutral bidentate ligands and coordinated to the metal ions via pyrimidine-N and enolic sulfonamide OH. The molar conductance data reveal that the complexes are non-electrolytes while UV-vis, solid reflectance and magnetic moment data have been shown that the complexes have octahedral geometry. The thermal behaviour of the complexes is studied and the thermodynamic activation parameters are calculated. The ligands and their complexes show high to moderate bactericidal activity.     

Spectroscopic approach in characterization of chromium(III), manganese(II), iron(III) and copper(II) complexes with a nitrogen donor tetradentate, 14-membered azamacrocyclic ligand

The complexes of Cr(III), Mn(II), Fe(III) and Cu(II) were synthesized with the macrocyclic ligand i.e. 2,3,9,10-tetraketo-1,4,8,11-tetraazacyclotetradecane. The ligand was prepared by the [2 + 2] condensation reaction of diethyloxalate and 1,3-diamino propane. These complexes were found to have the general composition M(L)X3 and M'(L)X2 [where M = Mn(II) and Cu(II), M' = Cr(III) and Fe(III), L = ligand (N4) and X = Cl-, NO3-, 1/2SO4(2-) and [CH3COO-]. The ligand and its transition metal complexes were characterized by the elemental analyses, molar conductance, magnetic susceptibility, mass, IR, electronic, and EPR spectral studies. On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Cr(III), Mn(II) and Fe(III) and a tetragonal geometry for Cu(II) complexes.     

Light-induced geometrical changes in acyclic ruthenium(II) complexes and their ruthena-macrocyclic analogues

The two ligands 1 (4'-(3-anisylphenyl)-2,2';6',2' '-terpyridine) and 2 (2-mesityl-8-anisyl-1,10-phenanthroline) (Scheme 2) were synthesized and coordinated to ruthenium. The corresponding complexes Ru(1)(2)(L)n+, where L = Cl-, CH3CN, or C5H5N, have been fully characterized. Notably, the hindering mesityl group of the phenanthroline ligand was shown to lie opposite to the monodentate ligand L both in solution and in the solid state. Upon irradiation in acetonitrile or pyridine, quantitative isomerization of the complex occurred, which consisted of a 90 degrees rotation of the bidentate chelate. In the new isomers the mesityl group was shown to pi stack to the coordinated monodentate ligand with the anisyl group of the phen (1,10-phenanthroline) lying on the other side of the ruthenium atom. The back reaction was performed by heating the photochemical isomers of the complexes in DMSO and exchanging the DMSO with chloride anion, acetonitrile, or pyridine. The stability of the ruthenium(II)-pyridine bond was used in order to inscribe the Ru(terpy)(phen) motif in a molecular ring. Functionalization of the ligands and subsequent cyclization reaction on the complex were performed on the two isomers of Ru(1)(2)(C5H5N)2+. Four macrocyclic complexes including the Ru(terpy)(phen)(py)n+ moiety were obtained and characterized. A (CH2)18 alkane chain or polyethylene glycol chain formed the flexible part of the ruthena-macrocycles. Upon visible light irradiation a dramatic geometrical changeover of the cyclic complex took place, which could be reversed thermally.     

EPR, IR and electronic spectral studies on Ni(II) and Cu(II) complexes with N-donor tetradentate [N4] macrocyclic ligand

Nickel(II) and copper(II) complexes are synthesized with a novel tetradentate macrocyclic ligand, i.e. 2,6,12,16,21,22-hexaaza;3,5,13,15-tetraphenyltricyclo[15,3,1,1(7-11)] docosa;1(21),2,5,7,9,11(22),12,15,17,19-decaene (L) and characterized by the elemental analysis, magnetic susceptibility measurements, mass, (1)H NMR, IR, electronic and EPR spectral studies. All the complexes are non-electrolytic in nature. Thus, these may be formulated as [M(L)X(2)] [M=Ni(II), Cu(II) and X=Cl(-), NO(3)(-) and (1/2)SO(4)(2-)]. Ni(II) and Cu(II) complexes show magnetic moments corresponding to two and one unpaired electron, respectively. On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Ni(II) and tetragonal geometry for Cu(II) complexes.     

Synthesis, structure, catalytic transfer hydrogenation and biological activity of cyclometallated ruthenium(III)2-(arylazo)phenolate complexes

A series of mononuclear organoruthenium complexes of the type [RuX(PPh₃)₂(L)] (X = Cl or Br; L = 2-(arylazo)phenolate ligand) have been synthesized from the reaction of five 2-(arylazo)phenol ligands with ruthenium(III) precursors, viz. [RuCl₃(PPh₃)₃] and [RuBr₃(PPh₃)₂(CH₃OH)] in benzene under reflux. In all these reactions, the 2-(arylazo)phenolate ligand replaces one triphenylphosphine molecule, two chlorides or bromides and one methanol from the precursors leading to five-membered cyclometallated species. The 2-(arylazo)phenol ligands behave as dianionic tridentate C, N, O donors and coordinated to ruthenium by dissociation of the phenolic proton and the phenyl proton at the ortho position of the phenyl ring. The compositions of the complexes have been established by elemental analysis, magnetic susceptibility measurement, FT-IR, UV-Vis and EPR spectral data. These complexes are paramagnetic and shows intense d-d and charge transfer transitions in chloroform. The solution EPR spectrum of the complex 7 in dichloromethane at 77 K shows rhombic distortion around the ruthenium ion. The structural conformation of the complex 1 has been carried out by X-ray crystallography. The redox behavior of the complexes has been investigated by cyclic voltammetry and the potentials are observed with respect to the electronic nature of substituents (R) in the 2-(arylazo) phenolate ligands. These complexes catalyze transfer hydrogenation of benzophenone to benzhydrol with up to 99.5% in the presence of i-prOH/KOH. Further, these complexes have shown great promise in inhibiting the growth of both Gram +ve and Gram −ve bacteria, viz. Staphylococcus aureus NCIM 2079 and Escherichia coli NCIM 2065 and fungus Candida albicans NCIM 3102.     

Nickel(II) complexes with different chromospheres containing macrocyclic ligands: spectroscopic and electrochemical studies

The mixed donor tetradentate (L(1)=N(2)O(2)) and pentadentate (L(2)=N(2)O(2)S) ligands have been prepared by the interaction of 1,3-diaminopropane and thiodiglycolic acid with diamine. These ligands possess two dissimilar coordination sites. Different types of complexes were obtained which have different stoichiometry depending upon the type of ligands. Their structural investigation have been based on elemental analysis, magnetic moment and spectral (ultraviolet, infrared, (1)H NMR, (13)C NMR and mass spectroscopy methods). The Ni(II) complexes show magnetic moments corresponding to two unpaired electrons except [Ni(L(1))](NO(3))(2) which is diamagnetic. Ligand field parameters of these complexes were compared. N(2)O(2)S donor ligand complexes show higher values of ligand field parameters, which are used to detect their geometries. The redox properties and stability of the complexes toward oxidation waves explored by cyclic voltammetry are related to the electron-withdrawing or releasing ability of the substituents of macrocyclic ligands moiety. The Ni(II) complexes displayed Ni(II)/Ni(I) couples irreversible waves associated with Ni(III)/Ni(II) process.     

Spectroscopic, redox and biological activities of transition metal complexes with ons donor macrocyclic ligand derived from semicarbazide and thiodiglycolic acid

A novel macrocyclic Schiff base ligand (2,5,9,12,14,18-hexaoxo-7,16-dithia-1,3,4,10,11,13-hexaazacycloocta-decane (H6L) with N4S2 coordinating sites was prepared by the reaction of the semicarbazide and thiodiglycolic acid. The transition metal complexes with macrocyclic ligand were synthesized and characterized by elemental analyses, magnetic susceptibility measurements, molar conductance, IR, electronic, and EPR spectral studies. Mass, 1H NMR and IR spectral techniques suggest the structural features of macrocyclic ligand. Magnetic and electronic spectral studies suggest an octahedral geometry of complexes. Electrochemical behaviour of cobalt, nickel and copper complexes were determined by cyclic voltammetry. The cyclic voltammogram of the copper complex at room temperature shows a quasi-reversible peaks for Cu(III)-->Cu(II) and Cu(II)-->Cu(I) couples. The macrocyclic ligand and its complexes show growth inhibitory activity against pathogenic bacteria and plant pathogenic fungi A. niger, A. alternata and P. variotii. Most of the complexes have higher activities than that of free ligand.     

Complexes of Ag(I), Hg(I) and Hg(II) with multidentate pyrazolyl-pyridine ligands: From mononuclear complexes to coordination polymers via helicates, a mesocate, a cage and a catenate

The coordination chemistry of a series of di- and tri-nucleating ligands with Ag(I), Hg(I) and Hg(II) has been investigated. Most of the ligands contain two or three N,N'-bidentate chelating pyrazolyl-pyridine units pendant from a central aromatic spacer; one contains three binding sites (2 + 3 + 2-dentate) in a linear sequence. A series of thirteen complexes has been structurally characterised displaying a wide range of structural types. Bis-bidentate bridging ligands react with Ag(I) to give complexes in which Ag(I) is four-coordinate from two bidentate donors, but the complexes can take the form of one-dimensional coordination polymers, or dinuclear complexes (mesocate or helicate). A tris-bidentate triangular ligand forms a complicated two-dimensional coordination network with Ag(I) in which Ag...Ag contacts, as well as metal-ligand coordination bonds, play a significant role. Three dinuclear Hg(I) complexes were isolated which contain an {Hg2}2+ metal-metal bonded core bound to a single bis-bidentate ligand which can span both metal ions. Also characterised were a series of Hg(II) complexes comprising a simple mononuclear four-coordinate Hg(II) complex, a tetrahedral Hg(II)4 cage which incorporates a counter-ion in its central cavity, a trinuclear double helicate, and a trinuclear catenated structure in which two long ligands have spontaneously formed interlocked metallomacrocyclic rings thanks to cyclometallation of two of the Hg(II) centres.     

Mössbauer and electronic spectral characterization of homo-bimetallic Fe(III) complexes of unsymmetrical [N10] and [N12] macrocyclic ligands

The homo-bimetallic complexes of stoichiometry Fe2(L)ClO4(ClO4)2 where L are novel unsymmetrical [N10] (L1.2HClO4) and [N12] (L2.2HClO4) macrocyclic ligands, have been prepared. The ligands were obtained from an in situ capping reaction of the reactive substrate, N,N'-bis(N-ethylaniline)hydrazine-1,2-diimine with a mixture of aniline or 1,3-diaminopropane and HCHO in presence of HClO4. The compounds have been characterized by elemental analyses, conductometric, IR, FAB-mass and electronic spectral studies. IR data of complexes suggest coordination from unsymmetrical aza sites as a tridentate (N,N,N) or tetradentate (N,N,N,N) ligand. mu(eff) values of the complexes suggest presence of antiferromagnetically coupled (Fe3+-Fe3+=S5/2-S5/2) spin exchange. M?ssbauer parameters of the complexes support (+/-3/2)-->(+/-1/2) nuclear transition in high-spin configurations of Fe(III) nuclei of the homo-bimetallic complexes with the presence of Kramer's double degeneracy.