Solvent and metal ion effects in condensation reactions between semicarbazides and pyridine derivatives and study of the complexes with metal chlorides

Co, Ni, Cu, Zn, Cd and Hg chloride complexes of 3-acetylpyridinesemicarbazone, 3-acetylpyridinethiosemicarbazone 4-pyridinesemicarbazone and 4-pyridinethiosemicarbazone have been obtained, and have the general formulae [MLCl₂], [ML₂Cl₂], [MLCl₂]H₂O, [ML₂Cl₂]-H₂O, [ML_xCl₂] (L=3-apsc, 3-aptsc, 4-psc or 4-ptsc). The reaction product of 4-pyridinecarbaldehyde with semicarbazide has properties consistent with 4-pyridinecarbaldehyde·semicarbazide, without condensation, but this condensation may be obtained by solvent or metal template effects using Cd or Hg. The products have been characterized by physicochemical and spectroscopic methods.     

Synthesis of copper and zinc chloride complexes with tri- and tetranitrofluorenones. Crystal and molecular structure of 2,4,5,7-tetranitrofluorenone

The complexes MLCl₂ · nH₂O and ML₂Cl₂ · nH₂O, where M = Cu(II), Zn and n = 1–4, were isolated and identified due to the reactions of Cu(II) and Zn(II) chlorides with 2,4,7-trinitrofluorene (L¹), 2,4,7-trinitrofluorenone (L^1a), and 2,4,5,7-tetranitrofluorene (L²). It was shown that, during complex formation, L¹ and L² were oxidized to fluorenones (L^1a, L^2a) and as neutral ligands formed 1: 1 and 2: 1 complexes with metal cations. A single crystal of tetranitrofluorenone (L^2a) was isolated, and its crystal and molecular structure was determined. The complexes were studied by X-ray powder diffraction analysis, their spectral (IR and UV) characteristics were determined, and the structures for the complexes were proposed.     

Synthesis of binuclear complexes of PdCl2 with chiral ethylenediamine dioxime (H2L1), piperazine dioxime (H2L2), and propylenediamine dioxime (H2L3), the derivatives of the natural monoterpenoid (R)-(+)-limonene. The crystal structures of [Pd2(H2L1)Cl4] and [Pd2(H2L2)Cl4]

The diamagnetic complexes [Pd₂(H₂L¹)Cl₄] (I), [Pd₂(H₂L²)Cl₄] (II), and Pd₂(H₂L³)Cl₄(III) with chiral ligands derived from the natural monoterpenoid (R)-(+)-limonene are obtained (H₂ L¹ is ethylenediamine dioxime, H₂L² is piperazine dioxime, and H₂L³ is propylenediamine dioxime). According to X-ray diffraction data, the crystal structures of complexes I and II are composed of binuclear acentric molecules. The coordination polyhedra PdN₂Cl₂ are trapeziums (squares distorted in a tetrahedral manner) made up of two N atoms of the tetradentate bridging cyclic ligands H₂L¹ and H₂L² and two Cl atoms. The fragments PdCl₂ are trans in the complexes. The ¹³C and ¹H NMR spectra of complexes I and II in CDCl₃ also suggest their binuclear structures.     

Systematische Studie zu den Koordinationseigenschaften des Guanidin‐Liganden Bis(tetramethylguanidino)propan mit den Metallen Mangan,Cobalt, Nickel,Zink, Cadmium,Quecksilber und Silber

The transition metal complexes with the ligand 1,3‐bis(N,N,N′,N′‐tetramethylguanidino)propane (btmgp), [Mn(btmgp)Br₂] ( 1 ), [Co(btmgp)Cl₂] ( 2 ), [Ni(btmgp)I₂] ( 3 ), [Zn(btmgp)Cl₂] ( 4 ), [Zn(btmgp)(O₂CCH₃)₂] ( 5 ), [Cd(btmgp)Cl₂] ( 6 ), [Hg(btmgp)Cl₂] ( 7 ) and [Ag₂(btmgp)₂][ClO₄]₂·2MeCN ( 8 ), were prepared and characterised for the first time. The stoichiometric reaction of the corresponding water‐free metal salts with the ligand btmgp in dry MeCN or THF resulted in the straightforward formation of the mononuclear complexes 1 – 7 and the binuclear complex 8 . In complexes with M^II the metal ion shows a distorted tetrahedral coordination whereas in 8 , the coordination of the M^I ion is almost linear. The coordination behavior of btmgp and resulting structural parameters of the corresponding complexes were discussed in an comparative approach together with already described complexes of btmgp and the bisguanidine ligand N¹,N²‐bis(1,3‐dimethylimidazolidin‐2‐ylidene)‐ethane‐1,2‐diamine (DMEG₂e), respectively.     

NMR and Raman spectroscopic study of complex formation between 2-methyl-2-azabicyclo-[2,2,2] -octa-3-one and TiCl4

From analysis of ¹H and ¹³C NMR and Raman spectroscopic data, in CDCl₃ and 1,1,2,2-tetrachloroethane-d₂ solution, the lactam 2-methyl-2-azabicyclo-[2,2,2]-octa-3-one (L) was found to form complexes with TiCl₄ (M) of overall composition M₂L, ML and ML₂. Two forms of the ML₂ complex were observed by NMR. In all these complexes, Ti coordinates to the carbonyl oxygen, and the metal—carbonyl bond is of the same type. The complexes ML and ML₂ contain hexacoordinated Ti; in M₂L the coordination number is probably five. The dynamics of exchange of the lactam between the ML₂ complexes and the uncomplexed form have been characterized and structures are proposed for the four complexes.     

Synthesis,spectroscopic, thermal,and antimicrobial studies of tetradentate 12 and 14 member Schiff bases and their complexes with Fe(III), Co(II), and Cu(II)

Two Schiff bases, L¹ (5,6;11,12-dibenzophenone-2,3,8,9-tetramethyl-1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene) and L² (6,7;13,14-dibenzophenone-2,4,9,11-tetramethyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene), bearing functionalized pendant arms have been synthesized by cyclocondensation of 3,4-diaminobenzophenone with 2,3-butanedione and 2,4-pentanedione, respectively. Mononuclear macrocyclic complexes [FeL¹Cl₂]Cl, [FeL²Cl₂]Cl, [ML¹Cl₂], and [ML²Cl₂] (where M?=?Co(II) and Cu(II)) have been prepared by reacting iron(III), cobalt(II), and copper(II) with the preformed Schiff base. The ligands and their corresponding metal complexes were characterized by elemental analyses, ESI-mass spectra, conductivity, magnetic moments, UV-Vis, EPR, IR, ¹H-, and ¹³C-NMR spectral studies, and TGA-DTA/DSC data. The TGA profiles exhibit a two-step pyrolysis, although the iron complexes decompose in three steps, leaving behind metal oxides as the final product. The ligands and complexes were screened in vitro against Gram-positive bacteria, Gram-negative bacteria, and fungi.     

Synthesis,Structures and Spectroscopic Properties of Platinum(II), Palladium(II) and Copper(I) Halide Complexes with Pyrimidine‐phosphine Ligand

The reactions of pyrimidine‐phosphine ligand N‐[(diphenylphosphino)methyl]‐2‐pyrimidinamine ( L ) with various metal salts of Pt^II, Pd^II and Cu^I provide three new halide metal complexes, Pt₂Cl₄(μ‐L)₂·2CH₂Cl₂ ( 1 ), Pd₂Cl₄(μ‐L)₂ ( 2 ), and [Cu₂(μ‐I)₂L₂]_n ( 3 ). Single crystal X‐ray diffraction studies show that complexes 1 and 2 display a similar bimetallic twelve‐membered ring structure, while complex 3 consists of one‐dimensional polymeric chains, which are further connected into a 2‐D supramolecular framework through hydrogen bonds. In the binuclear complexes 1 and 2 , the ligand L serves as a bridge with the N and P as coordination atoms, but in the polymeric complex 3 , both bridging and chelating modes are adopted by the ligand. The spectroscopic properties of complexes 1 ‐ 3 as well as L have been investigated, in which complex 3 exhibits intense photoluminescence originating from intraligand charge transfer (ILCT) π→π* and metal‐to‐ligand charge‐transfer (MLCT) excited states both in acetonitrile solution and solid state, respectively.     

Transition metal complexes of 2-Carbethoxypyridine (Ethyl picolinate)

Summary A variety of metal(II) complexes of 2-carbethoxypyridine (L) have been prepared and characterised. With metal(II) chlorides the bis complexes can be formulated [ML₂Cl₂]^o (M=Cu^II, Ni^II, Co^II, Fe^II or Mn^II). The complexes are six-coordinate with 2-carbethoxypyridine acting as a bidentate ligandvia the pyridine nitrogen and the carbonyl group of the ester. The chloro complexes are nonelectrolytes in nitroethane; magnetic susceptibility measurements, i.r. and d-d electronic spectra are reported. With metal(II) perchlorate salts the complexes can be formulated as six-coordinate [ML₂ (OH₂)₂] [ClO₄]₂ species containing ionic perchlorate. The ester exchanges of some of these complexes with a variety of primary alcohols have been investigated.     

Synthesis and electrochemical study of 3- and 4-(2-pyridyl)-1,3-benzothiazole complexes with transition metals (CoII, NiII, and CuII). Molecular structure of bis{(4-(2-pyridyl)-1,3-benzothiazole)copper(ii)} tetraacetate

A series of the M(L)Cl₂ · nH₂O and {M(L)}₂(OAc)₄ complexes (M = Ni^II, Co^II, and Cu^II; L is 3- and 4-(2-pyridyl)-1,3-benzothiazole) were synthesized by the reaction of L with MX₂ · nH₂O (X = Cl, OAc) in ethanol. The molecular and crystal structures of the CuL₂(OAc)₄ binuclear complex (L is 4-(2-pyridyl)benzothiazole) were determined by X-ray diffraction analysis. The copper atoms have a distorted tetragonal bipyramidal environment and are coordinated to the nitrogen atom of the pyridine moiety of the ligand and to two oxygen atoms of the bridging acetate ligands. The Cu-Cu distance is 2.6129(9) Å. The electrochemical behavior of the synthesized ligands and complexes was studied using the cyclic voltammetry and rotating disk electrode techniques in DMF solutions (0.1 M Bu₄NClO₄). The primary reduction of all the complexes under study is directed to the metal.     

Intramolecular stacking interaction in mixed-ligand complexes containing ATP4- and aromatic N-heterocyclic ligands

The stability constants of the binary ML2+ and ternary M(ATP)L2- complexes,where L=Iq (isoquinoline) or BIm (benzimidazole) and M=Zn2+ or Cd2+,have been determined by poten-tiometric pH titration in aqueous solution at I=0.1 mol/L (NaClO4),T=25℃.The stability of the ternary complexes characterized by corresponding to the equilibrium M(ATP)2-+ML2+=M(ATP)L2-+M2+ is higher than what would be expected on statistical grounds.The increase may be related to the stacking interaction between the aromatic ring of the ligands L and the purine moiety of ATP4- 1H NMR studies of Zn2+/ATP4-/L confirm the presence of stacking in the ternary complexes.It is concluded that the strength of the intramolecular stacking interaction is dependent on the structure of the aromatic ring of the ligand L and the formation of a metal ion bridge.Possible implications are discussed briefly.     

Spectroscopic,theoretical, and antibacterial approach in the characterization of 5-methyl-5-(3-pyridyl)-2,4-imidazolidenedione ligand and of its platinum and palladium complexes

A series of Pt(IV), Pt(II), and Pd(II) complexes (PtCl₄L₂ (1), PtCl₂L₂ (2), PdCl₂L₂ (3), and Pd₂Cl₄L₂ (4)) with 5-methyl-5-(3-pyridyl)-2,4-imidazolidenedione ligand (L) have been synthesized by the reaction of metal chlorides (K₂[PtCl₆], K₂[PtCl₄], K₂[PdCl₄], and PdCl₂) with L in 1:2 (1-3) and 1:1 (4) molar ratios. The binding manner of L, and the composition and geometry of the metal complexes were examined by elemental analysis, IR, ¹H, and ¹³C NMR spectroscopies. Theoretical calculations invoking geometry optimization of different isomers, performed using density functional theory, suggested that in both gas and solution phases the trans isomers are more stable than the cis ones. The experimental results and calculated molecular parameters, bond distances and angles, revealed slightly distorted octahedral (1) and square-planar (2–4) geometry around the metallic center through the pyridine-type nitrogen (N_py) and chlorine atoms. In 4, the binuclear complex, each palladium atom is coordinated by one nitrogen and three chlorine atoms (one as terminal and two as bridging ligands). Antibacterial activity of L and the corresponding complexes was investigated against six species of microorganisms. Testing was performed by disk diffusion method and minimum inhibitory concentrations (MIC) have been determined. The results showed that the title compounds have the capacity of inhibiting the metabolic growth of bacteria to different extents. In general, the binuclear palladium(II) complex was the most active one.     

Thermogravimetric and spectroscopic studies on La(III) and Ce(III) complexes with some thio-schiff bases

Solid complexes of five derivatives of thio-Schiff bases with La(III) and Ce(III) ions were prepared and characterized by elemental and thermogravimetric analyses. The suggested general formula of the solid complexes is [ML₂(H₂O)X]·2H₂O, whereM=trivalent lanthanide ion,L=Schiff base andX=Cl^? or ClO ₄ ^? . Information about the water of hydration, the coordinated water molecules, the coordination chemistry and the thermal stability of these complexes was obtained and is discussed. Additionally, a general scheme of thermal decomposition of the lanthanide-Schiff base complexes is proposed.     

Interaction of Co(II), Ni(II), Cu(II), and Zn(II) with 12- and 14-membered macrocycles containing O2N2 donors

The 12- and 14-membered diazadioxo macrocyclic ligands, 1,2?:?7,8-diphenyl-6,9-diaza-3,12-dioxocyclododecane (L¹) and 1,2?:?8,9-diphenyl-7,10-diaza-3,14-dioxocyclotetradecane (L²), were synthesized by condensation between o-phenylenediamine, 1,2-dibromoethane/1,3-dibromopropane, and catechol. Metal complexes [ML¹Cl₂] and [ML²Cl₂] [M?=?Co(II), Ni(II), Cu(II), and Zn(II)] were prepared by interaction of L¹ or L² with metal(II) chlorides. The ligands and their complexes were characterized by elemental analyses, IR, ¹H, and ¹³C NMR, EPR, UV-Vis spectroscopy, magnetic susceptibility, conductivity measurements, and Electrospray ionization-mass spectral (ESI-MS) studies. The results of elemental analyses, ESI-MS, Job's method, and conductivity measurements confirmed the stoichiometry of ligands and their complexes while absorption bands and resonance peaks in IR and NMR spectra confirmed the formation of ligand framework around the metal ions. Stereochemistry was inferred from the UV-Vis, EPR, and magnetic moment studies.     

1,3-Bis(2-alkyltetrazol-5-yl)triazenes and their Fe(II), Co(II) and Ni(II) complexes: Synthesis,spectroscopy, and thermal properties. Crystal structure of Fe(II) and Co(II) 1,3-bis(2-methyltetrazol-5-yl)triazenide complexes

Complexes ML¹₂ and ML²₂, with M = Fe^II, Co^II, Ni^II, and 1,3-bis(2-R-tetrazol-5-yl)triazenide ligands L¹ (R = Me) and L² (R = ^tBu), have been synthesized by the reaction of corresponding 1,3-bis(2-R-tetrazol-5-yl)triazenes with metal(II) salts in basic media and characterized by IR, UV–Vis spectroscopy, thermal and X-ray diffraction analyses. Both 1,3-bis(2-R-tetrazol-5-yl)triazenes were found to deprotonate on coordination and act as tridentate chelating ligands forming distorted MN₆ octahedra around metal(II) cations.     

Synthesis of binuclear complexes of PdCl2 with chiral α,α′-diamino-meta-xylene dioximes H2L1, H2L2, and H2L3, the derivatives of the terpenes (+)-3-carene, (R)-(+)-limonene, and (S)-(−)-α-pinene. Crystal structure of [Pd2(H2L1)Cl4]

Chiral α,α′-diamino-meta-xylene dioximes H₂L¹, H₂L², and H₂L³ were obtained from the naturally occurring terpenoids (+)-3-carene, (R)-(+)-limonene, and (S)-(?)-α-pinene, respectively. Reactions of these ligands with PdCl₂ gave the diamagnetic complexes Pd₂(H₂L¹)Cl₄ (I), Pd₂(H₂L²)Cl₄ (II), and Pd₂(H₂L³)Cl₄ (III). According to X-ray diffraction data, the crystal structure of complex I consists of acentric binuclear molecules [Pd₂(H₂L¹)Cl₄]. The coordination polyhedron PdN₂Cl₂ is a square distorted in a tetrahedral manner (trapezium) made up of two N atoms of the tetradentate bridging cyclic ligand H₂L¹ and two Cl atoms. The fragments PdCl₂ in the complex are cis to each other. According to the ¹H NMR spectra of complexes I–III in CDCl₃, the organic ligands are coordinated through the N atoms; in solution, the complexes exist in several forms.     

Bivalent 3d-metal complexes of malonyl- and succinyldihydrazide based macrocyclic ligands. Synthesis and characterization

Summary The macrocycles 2,10-dimethyl-3,4,8,9,15-pentaazabicyclo-[9.3.1]-pentadeca-1 (15),2,9,11,13-penta-ene-5,7-dione (L) and 2,11-dimethyl-3,4,8,9,10,16-pentaazabicyclo[10.3.1]-hexadeca-1 (16),2,10,12,14-penta-ene-5,8-dione (L) were prepared and characterized by elemental, i.r. and mass spectral data. The macrocycles react with various metal(II) chlorides to yield complexes of the types [MLCl₂H₂O] (M = Mn, Co, Ni, Cu or Zn), [MLCl₂H₂O] (M = Mn, Ni, Cu or Zn) and [Co₃L₂Cl₄]Cl₂. The complexes were characterized by physico-chemical and spectroscopic methods.     

Studies on platinum(II) and palladium(II) complexes of some N,N′-disubstituted thiourea derivatives

Summary A series of new Pt^II and Pd^II complexes of N,N-disubstituted thiourea derivatives of general formulae [MLCl₂]₂, [ML₂Cl₂] and [ML₄]Cl₂ have been prepared and characterised by physicochemical and spectroscopic methods. The reaction of these ligands with [M(DMSO)₂Cl₂], M = Pt, cis- or Pd, trans-, in CHCl₃ and EtOH at ambient temperature or under reflux, is described.     

Synthesis and characterization of CuII and CoII complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPT) by chemical and tribochemical reactions

Four Cu^II and Co^II complexes–[Cu(L₁)Cl₂(H₂O)]3/2H₂O · 1/2EtOH, [Cu(L₁)₂Cl₂]6H₂O, [Co(L₁)Cl₂]3H₂O · EtOH, and [Co₂(L₁)(H₂O)Cl₄]1.5H₂O · EtOH (L₁ = 2,4,6-tri(2-pyridyl)-1,3,5-triazine; TPT)–were synthesized by conventional chemical method and used to synthesize another four metal complexes–[Cu(L₁)I₂(H₂O)]6H₂O, [Cu(L₁)₂I₂]6H₂O, [Co(L₁)I(H₂O)₂]I · 2H₂O, and [Co₂(L₁)I₄(H₂O)₃]–using tribochemical reaction, by grinding it with KI. Substitution of chloride by iodide occurred, but no reduction for Cu^II or oxidation of Co^II. Oxidation of Co^II to Co^III complexes was only observed on the dissolution of Co^II complexes in d₆-DMSO in air while warming. The isolated solid complexes (Cu^II and Co^II) have been characterized by elemental analyses, conductivities, spectral (IR, UV-Vis, ¹H-NMR), thermal measurements (TGA), and magnetic measurements. The values of molar conductivities suggest non-electrolytes in DMF. The metal complexes are paramagnetic. IR spectra indicate that TPT is tridentate coordinating via the two pyridyl nitrogens and one triazine nitrogen forming two five-membered rings around the metal in M : L complexes and bidentate via one triazine nitrogen and one pyridyl nitrogen in ML₂ complexes. In binuclear complexes, L is tridentate toward one Co^II and bidentate toward the second Co^II in [Co₂(L₁)Cl₄]2.5H₂O · EtOH and [Co₂(L₁)I₄(H₂O)₃]. Electronic spectra and magnetic measurements suggest a distorted-octahedral around Cu^II and high-spin octahedral and square-pyramidal geometry around Co^II.     

Preparation,characterization, reactivities and electrochemistry of some homo- and heterodinuclear complexes of 2-hydroxy-5- methylbenzene-1,3-dicarbaldehyde and 1,3-diacetyl- 2-hydroxy-5-methylbenzene

Homo- and heterodinuclear complexes of composition [M₂L₂](ClO₄)₂·4H₂O, [CuML₂](ClO₄)₂·nH₂O (M = Ni, Co or Mn; L = L¹ or L²) and [CuML²Cl₂]·2H₂O (M = Ni or Co) have been synthesized with the dinucleating ligands 2-hydroxy-5-methyl- benzene-1,3-dicarbaldehyde (HL¹) and 1,3-diacetyl-2-hydroxy-5-methylbenzene (HL₂). These compounds have been characterized and their chemical reactivities investigated. The electrochemical behaviour of [M₂L₂²](ClO₄)₂·4H₂O and [CuML₂²](ClO₄)₂·nH₂O complexes have been examined in acetonitrile and dimethyl sulfoxide using Hg and Pt electrodes. The cyclic voltammograms obtained with a Hg electrode show quasi-reversible electron transfers for both metal centres that often get complicated due to decomplexation of metal ions and adsorption phenomena. On a Pt electrode irreversible electron transfers occur at more negative potentials.