Two cobalt(II) complexes based on 2-propyl-4,5-imidazoledicarboxylic acid: syntheses,crystal structures,and properties

Two complexes, [Co(H₂pimdc)₂(H₂O)₂]?·?2DMF (1) and [Co(H₂pimca)₂(H₂O)₂]?·?4H₂O (2), have been designed, synthesized, and characterized (X-ray single crystal analysis, thermal analysis, electrochemical analysis, and infrared spectrum) based on the imidazole ligand [H₃pimdc?=?2-propyl-4,5-imidazoledicarboxylic acid]. Both compounds have 3-D hydrogen-bonding networks. Because of different coordination of water, 1 forms a layer-like geometry via hydrogen bonds, but 2 forms a fishingnet-like latticed geometry via hydrogen bonds.     

Synthesis,crystal structures,and characterization of copper(II) carboxylate complexes incorporating 1,10-phenanthroline and bipyridine

A series of Cu(II) carboxylate complexes (carboxylate?=?2-fluorobenzoic acid (2-HFBA) or 4-fluorobenzoic acid (4-HFBA)) containing either one chelating 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, and thermal analyses. In [Cu(bipy)(H₂O)(2-FBA)₂] (1), [Cu(bipy)(H₂O)(4-FBA)₂] (3), and [Cu(phen)(H₂O)(2-FBA)₂] (4), Cu is five-coordinate in a square pyramidal geometry and four-coordinate in [Cu(phen)(2-FBA)₂] (2). The four complexes are extended into 1-D chains through hydrogen-bonding and π?···?π interactions in 1 and 4, only hydrogen-bonding in 2, and π?···?π interactions in 3. These contacts lead to aggregation and supramolecular self-assembly.     

Hydrothermal syntheses and characterization of cobalt(II) and nickel(II) complexes of 1,3-adamantanedicarboxylic acid and 1,10-phenanthroline

Two coordination complexes, namely [Co(phen)(H₂O)L]·H₂O and [Ni₂(phen)₂(H₂O)₂L₂]·4H₂O (phen = 1,10-phenanthroline, H₂L = 1,3-adamantanedicarboxylic acid) have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. [Co(phen)(H₂O)L]·H₂O consists of 1D chains of the complex plus lattice H₂O molecules. Interchain hydrogen bonds and π–π stacking interactions assemble the 1D chains into 2D layers. [Ni₂(phen)₂(H₂O)₂L₂]·4H₂O is a binuclear complex which is assembled into a 3D supramolecular structure by strong hydrogen bonds and π–π stacking interactions. Both complexes were characterized by physico-chemical and spectroscopic methods.     

Iron(II) and nickel(II) mixed-ligand complexes containing 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline

Two types of mixed-ligand complexes, i.e. [M(phen)2 (dip)]2+ and [M(phen)(dip)2]2+ (M = iron(II) and nickel(II); phen = 1,10-phenanthroline and dip = 4,7-diphenyl-1,10-phenanthroline) have been prepared from their related tris-complexes, [M(phen)3]2+ by ligand substitution, and isolated by semi-preparative HPLC. Elemental and chromatographic analyses confirm the purity of the isolated complexes while u.v./vis and i.r. spectra were used to identify and characterize them. 1H-n.m.r. and room temperature Mössbauer spectra of the iron(III) complexes were also measured and the results are discussed. In addition, our preliminary results on hypochromicity in the MLCT band and circular dihroism (CD) emerging in the u.v./vis region upon addition of CT(calf thymus)-DNA to the racemic complexes indicated that the iron(II) mixed-ligand complexes interact with CT-DNA.     

Synthesis,characterization, and cytotoxicity of mixed-ligand complexes of palladium(II) with 1,10-phenanthroline and N-carbonyl-L-isoleucine dianion

Three novel palladium(II) complexes [Pd(Phen)(Bzile)] (I), [Pd(Phen)(p-mBzile)] (II), and [Pd(Phen)(p-NBzile)] · H₂O (III), where Bzile = N-benzoyl-L-isolecine), p-MBzile = N-(p-methylbenzoyl)-L-isolecine), p-NBzile = N-(p-nitrobenzoyl)-L-isolecine), have been synthesized and characterized by elemental analysis, ES-MS, and IR. The crystal and molecular structure of the complex II has been determined by single crystal X-ray diffraction. The cytotoxicity was tested against carcinoma cell lines: KB, BGC-823, Bel-7402 and HL-60 by MTT assay. The results indicated that these complexes exerted cytotoxicity, but none of them showed higher cytotoxicity than cisplatin. The cytotoxicity against HL-60, BGC-823, Bel-7402 and KB cell lines decreases in the sequence: p-MBzile > Bzile > p-NBzile. It suggests that the acylated groups have important impact on the cytotoxicity of complexes.     

Electron transfer reactions of tris(1,10-phenanthroline)cobalt(II) with copper(III) imine-oxime complexes

Summary The kinetics of oxidation of [Co^II(phen)₃]²⁺ (phen = 1,10-phenanthroline) by copper(III) imine-oxime complexes are first-order in each reactant. All reactions proceed via two parallel pathways; one pH independent, the other pH dependent. The second-order rate constant varies with [H⁺] as k₂ = k _inf2 ^supo + k _inf2 ^supH [H⁺]. The rapidity of the electron transfer step, coupled with the relative inertness of [Co^II(phen)₃]²⁺ over the pH range studied and the absence of a bridging atom on the phen ligand, supports an outer-sphere mechanism for this process. Reasonably good agreement between the experimental rate constants and those calculated using the Marcus equation has been obtained.     

Supramolecular cobalt(II) complexes: syntheses,crystal structures and solvent effects

Two Co^II complexes, namely {[CoL(MeOH)(μ-OAc)]₂Co}·2MeCN·2MeOH (1) and {[CoL(EtOH)(μ-OAc)]₂Co}·3EtOH (2) (H₂L=3,3′-dimethoxy-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol), have been synthesized and characterized by X-ray crystallography. Both complexes contain octahedral coordination geometries, comprising three Co^II atoms, two deprotonated bisoxime L²⁻ units in which four μ-phenoxo oxygen atoms form two [CoL(X)] (X = MeOH or EtOH) units, two acetate ligands coordinated to three Co^II centers through Co–O–C–O–Co bridges, and coordinated and non-coordinated solvent. Both complexes exhibit 2D supramolecular networks through different intermolecular hydrogen-bonding interactions.     

Synthesis, structures and properties of Cu(II) and Mn(II) complexes with 1,10-phenanthroline-2-carboxylic acid and 2,2'-bipyridine ligands

Four new 2,2'-bipyridine and 1,10-phenanthroline complexes, namely [Mn(phenca)(2)]·(H(2)O)(2) (1), [Cu(4)(phen)(4)(OH-)(4)(H(2)O)(2)](DMF)(4)(ClO(4)-)(4)(H(2)O) (2), [Cu(2)(2,2-bipy)(2)(C(2)O(4)2-)(H(2)O)(2)(NO(3))(2)] (3) and [Cu(2,2-bipy)(2)(ClO(4)-)](ClO(4)-) (4) (2,2'-bpy = 2,2'-bipyridine, Hphenca = 1,10-phenanthroline-2-carboxylic acid) have been synthesized by a hydrothermal reaction. The products were characterized by elemental analysis, infrared spectroscopy and X-ray crystal diffraction. While strong hydrogen bonds play central roles in the formation of the 3D structure, the combined influence of the weak interactions such as π···π interactions is also evident in the structures. A preliminary investigation on the ion exchange properties of the complexes is presented.     

Tetrakis(thione)platinum(II) complexes: synthesis,spectroscopic characterization,crystal structures,and in vitro cytotoxicity

A new series of platinum(II) complexes based on thione ligands with general formula [Pt(thione)₄]X₂ (X^??=?Cl^?, NO₃^?) has been synthesized and characterized using CHNS elemental analysis, infrared, ¹H and ¹³C solution-state NMR as well as ¹³C and ¹⁵N solid-state NMR spectroscopy, and X-ray crystallography. The spectroscopic methods confirm the coordination of Pt(II) with thiocarbonyl groups via sulfur of the thione ligands. The X-ray structures showed a distorted square planar geometry for 1, [Pt(MeImt)₄]Cl₂ (MeImt = N-Methylimidazolidine-2-thione) while the hydrogen bonding interactions in 7, [Pt(iPrImt)₄](NO₃)₂·0.6(H₂O) induce a bent see-saw distortion relative to the ideal square planar geometry. The in vitro cytotoxicity studies showed that 2, [Pt(EtImt)₄]Cl₂ is generally the most effective, a two-fold better cytotoxic agent than cisplatin and carboplatin against MCF7 (human breast cancer).     

Three 3-amino-1,2,4-triazole-based cobalt(II) complexes incorporating with different carboxylate coligands: synthesis,crystal structures,and magnetic behavior

Three 3-amino-1,2,4-triazole (Hatz)-based paramagnetic metal complexes, {[Co₂(Hatz)₂(nip)₂]·H₂O}_n (1), [Co(atz)(nb)]_n (2), and {[Co₃(H₂O)₄(Hatz)₆(btc)₂]·11.5H₂O} (3) (nip^2? = 5-nitroisophathalate, nb^– = p-nitrobenzolate, and btc^3– = 1,2,4-benzenetricarboxylate), were respectively prepared by introducing differently carboxylate-containing rigid coligands. All these complexes were structurally and magnetically characterized by single-crystal and powder X-ray diffractions, elemental analysis, FT-IR spectra, thermogravimetric and magnetic measurements. Complex 1 has a four-connected CdSO₄-type framework with binuclear subunits periodically extended by ditopic μ-N1, N3-Hatz and carboxylate-containing linkers. Tetrahedral Co^II ions in 2 are periodically interlinked into an undulated layer by anionic μ₃-N1,N2,N3-atz^? connectors with deprotonated nb^– spacers located on the both sides. By contrast, complex 3 is a centrosymmetric trinuclear molecule aggregated by six neutral μ-N1, N3-Hatz molecules. The structural difference of 1–3 is significantly due to the flexible binding modes adopted by triazolyl and carboxylate groups. Additionally, 1 exhibits a field-induced metamagnetic transition from an antiferromagnetic ordering to a weak ferromagnetic state resulting from the magnetic competition between triazolyl and carboxylate mediators. Instead, comparable antiferromagnetic couplings transmitted by cyclic triazolyl groups are observed in the nearest neighbors of 2 and 3.     

Reactions of platinum complexes with 4,7-phenanthroline: crystal structures of mono- and binuclear platinum(II) complexes containing 4,7-phenanthroline

The reaction of a mixture of cis and trans-[PtCl₂(SMe₂)₂] with 4,7-phen (4,7-phen = 4,7-phenanthroline) in a molar ratio of 1 : 1 or 2 : 1 resulted in the formation of mono and binuclear complexes trans-[PtCl₂(SMe₂)(4,7-phen)] (1) and trans-[Pt₂Cl₄(SMe₂)₂(μ-4,7-phen)] (2), respectively. The products have been fully characterized by elemental analysis, ¹H, ¹³C{¹H}, HHCOSY, HSQC, HMBC, and DEPT-135 NMR spectroscopy. The crystal structure of 1 reveals that platinum has a slightly distorted square planar geometry. Both chlorides are trans with a deviation from linearity 177.66(3)°, while the N–Pt–S angle is 175.53(6)°. Similarly, the reaction of a mixture of cis and trans-[PtBr₂(SMe₂)₂] with 4,7-phen in a 1 : 1 or 2 : 1 mole ratio afforded the mono or binuclear complexes trans-[PtBr₂(SMe₂)(4,7-phen)] (3) and trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)] (4), respectively. The crystal structure of trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)].C₆H₆ reveals that 4,7-phen bridges between two platinum centers in a slightly distorted square planar arrangement of the platinum. In this structure, both bromides are trans, while the PtBr₂(SMe₂) moieties are syn to each other. NMR data of mono and binuclear complexes of platinum 1–4 show that the binuclear complexes exist in solution as a minor product, while the mononuclear complexes are major products.     

Saccharin complexes of zinc(II) with phenanthroline and 2,9-dimethyl-1,10-phenanthroline: synthesis and characterization

The saccharinato complexes [Zn(phen)₂(sac)(H₂O)]sac (1) and [Zn(sac)(dmp)(H₂O)](sac) (2), where phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline, and sac =saccharinato ion/ligand, were synthesized by the reaction of [Zn(sac)₂(H₂O)₄] · 2H₂O with ligands and have been characterized by elemental analysis, IR, and ¹H NMR spectroscopies. Conductivity of complexes was measured in DMSO. Compound 1 is characterized by single crystal X-ray diffraction and compared with some isomorphous zinc-saccharinate complexes reported previously. Complex 1 crystallizes in the triclinic system, space group P 1 , with Z = 2, and consists of alternating slightly distorted octahedral [Zn(phen)₂(sac)(H₂O)]⁺ and noncoordinated saccharinate. The zinc bound aqua is hydrogen bonded to an oxygen of carbonyl in the saccharinate ligand and the SO₂ group in the saccharinate counter-ion from an adjacent molecule. Intermolecular and intramolecular hydrogen bonds and C–H ··· O and C–H ··· N short contacts lead to a 3-D network.     

Ruthenium(II) bipyridine complexes: from synthesis and crystal structures to electrochemical and cytotoxicity investigation

Complexes 1–4, [Ru(L)(bpy)₂]PF₆, where bpy = 2,2′-bipyridine; HL = 3-methylpyridine-2-carboxylic acid (HL1), 6-methylpyridine-2-carboxylic acid (HL2), 5-bromopyridine-2-carboxylic acid (HL3) and 6-bromopyridine-2-carboxylic acid (HL4), were synthesized and characterized. The electrochemical character of the complexes was investigated by cyclic voltammetry revealing two reversible reduction waves in the negative range of potentials, most likely due to a reduction of the bipyridine moiety. Cytotoxicity studies by MTT assay for 72 h of drug action revealed that 2–4 exhibited moderate activity in cervical human tumor cells (HeLa). Complex 2 exhibited low activity in colon cancer LS-174 cells (180 ± 10), while all complexes were devoid of activity in lung cancer A549 and non-tumor MRC-5 cells, up to 200 μM. Combinational studies of the most active complex 2, with pharmacological modulators of cell redox status, L-buthionine-sulfoximine (L-BSO) or N-acetyl-L-cysteine (NAC), showed that when L-BSO potentiated, 2 induced a sub-G1 peak of the cell cycle in the HeLa cell line. UV–vis and cyclic voltammetry were performed in order to investigate the binding mode of 2 to DNA and suggested intercalation for the complex–DNA interaction.     

Cobalt(II) complexes with thiosemicarbazone as potential antitumor agents: synthesis,crystal structures,DNA interactions,and cytotoxicity

Two cobalt(II) complexes [Co(QCT)₂]·Cl·1.5H₂O (1) (QCT = quinoline-2-carboxaldehyde thiosemicarbazone) and [Co(QCMT)(CH₃OH)Cl₂] (2) (QCMT = quinoline-2-carboxaldehyde N⁴-methyl-thiosemicarbazone) have been synthesized and structurally characterized. Complex 1 crystallizes in a triclinic system with space group P–1 and complex 2 crystallizes in a monoclinic system with space group P2(1)/n. In both complexes the cobalt(II) center is six coordinated with distorted octahedral geometry. The interactions of two complexes with CT-DNA were investigated by electronic absorption spectra, circular dichroism (CD) spectra and fluorescence spectra. Results suggest that the complexes bind to DNA via groove binding mode, and complex 2 has stronger binding ability than complex 1. The in vitro cytotoxicity has been tested against the human lung adenocarcinoma cell line A-549, cisplatin-resistant cell line A-549/CDDP, and human breast adenocarcinoma cell line MCF-7. Complex 2 is more cytotoxic than complex 1, and both of them show higher cytotoxicity than the parent ligands alone. Compared with cisplatin, the two cobalt(II) complexes are more active against A-549/CDDP and MCF-7 cell lines at most experimental concentrations. Notably, although complex 2 is found to be less effective than cisplatin against the parent cell line A-549, it is much more effective than cisplatin against the resistant cell A-549/CDDP.     

Thio-azo proligands based on 5,6-derivatives-1,10-phenanthroline and their use for iron(II) complexes: Synthesis,characterization and crystal structures

The preparation and characterization of 5,6-substituted-1,10-phenanthrolines, phdtos = 5,6-bistosyl-1,10-phenanthroline (1) and phdbt = 5,6-dibenzyltiol-1,10-phenanthroline (2) are described. The synthesis of (1) was achieved in good yield via the corresponding dihydroxide and 2 was obtained by cross-coupling reaction of 5,6-dibromo-1,10-phenanthroline and benzylthiol mediated by a palladium catalytic system in refluxing toluene (120 °C). These phenanthroline derivatives were used as ligands to afford [Fe^II(phdtos)₃](PF₆)₂ (5) and [Fe^II(phdbt)₃](PF₆)₂ (6) complexes.     

Low Valence States of Metal Chelates. V. Tris(1,10-phenanthroline)cobalt(II) and bis(2,9-dimethyl-1,10-phenanthroline)cobalt(II) perchlorates

D. C. polarography and cyclic voltammetry were used for investigating the reduction processes of the tris(1,10-phenanthroline)cobalt(II) and bis(2,9-dimethyl-1, 10-phenanthroline)-cobalt(II) perchlorates in 0.1 M solutions of tetraethylammonium perchlorate in acetonitrile. The first complex gave a four-step reduction wave; the first two steps were found to be diffusion controlled and reversible reductions from Co(phen)⁺ to Co(phen)₃⁺ to Co(phen) to Co(phen;) occured. The second complex gave a six-step reduction wave; the first three steps were found to be diffusion controlled and were to be considered as successive reversible reductions from Co(2, 9dm-phen)⁺ to Co(2, 9dmphen), from Co(2, 9dmphen) to Co(2, 9dmphen)₂ and from Co(2, 9dmphen)₂ to Co(2, 9dmphen).     

Synthesis,crystal structures and thermal decomposition kinetics of four new lanthanide complexes with 3,4-dimethylbenzoic acid and 1,10-phenanthroline

A new series of lanthanide complexes [Ln(3,4-DMBA)₃phen]₂ [Ln(III) = Nd(1), Sm(2), Tb(3) and Dy(4), 3,4-DMBA = 3,4-dimethylbenzoate, phen = 1,10-phenanthroline] have been synthesized and characterized by elemental analysis, infrared spectra and TG-DTG techniques. The single crystals of the complexes 3 and 4 have been obtained and their structures have been determined by single-crystal X-ray diffraction. In the complexes 3 and 4, each Ln(III) ion is coordinated by four bidentate-bridging 3,4-DMBA ligands, one bidentate-chelating 3,4-DMBA group and one bidentate-chelating phen ligand, giving a coordination number of eight. The complex 3 shows bright green luminescence under ultraviolet light in the solid state. Thermal analysis of the complexes 1–4 are discussed by TG-DTG and IR techniques. The non-isothermal kinetics of the complexes 1–4 are investigated by using double equal-double step method. The thermodynamic parameters (ΔH ^≠ , ΔG ^≠ and ΔS ^≠ ) and kinetic parameters (activation energy E and the pre-exponential factor A) of the four complexes are also calculated.     

Copper(II), nickel(II) and cobalt(II) complexes of 4-cyanobenzonic acid: syntheses, crystal structures and spectral properties

Three new metal complexes, Cu(4-Hcba)₂(4-cba)₂(Py)₂ (4-Hcba=4-cyanobenzoic acid) 1 and M[H(4-cba)₂]₂(Py)₂ (M=Ni 2, Co 3), have been prepared by the treatment of 4-Hcba with the respective metal nitrate M(NO₃)₂ (M=Cu, Ni, Co) in the presence of pyridine (Py). Single-crystal X-ray diffraction analyses (3 is isostructural to 2) show that the obtained complexes are of isolated mononuclear and the metal atoms have distorted octahedral coordination environment. Two different types of intramolecular hydrogen bonds exist: asymmetrical O–HO for 1 and symmetrical OHO for 2 and 3. The crystal packing between the molecular complexes is controlled mainly by T-shaped C–Hπ interactions between pyridine and phenyl rings. Preliminary discussions on IR, UV–VIS and fluorescent spectra have also been carried out.     

Nickel(II) complexes with Schiff bases derived from 2-acetylpyrazine and tryptophan: synthesis, crystal structures and DNA interactions

A pair of stereoisomers of nickel Schiff base complexes, namely [Ni(C₁₇H₁₅N₄O₂)₂·2CH₃OH]_n (1) (C₁₇H₁₅N₄O₂ = 2-acetylpyrazine-l-tryptophan) and [Ni(C₁₇H₁₅N₄O₂)₂·2CH₃OH]_n (2) (C₁₇H₁₅N₄O₂ = 2-acetylpyrazine-d-tryptophan), were synthesized and characterized by physico-chemical and spectroscopic methods. The X-ray diffraction single-crystal analyses indicate that the structure of 2 is essentially 0D monomeric, while a 2D layer structure is formed through N–H…O intermolecular hydrogen bonds for 1. The interactions between complex 1 and calf thymus DNA were investigated by spectroscopic and viscometric methods. The results indicate that complex 1 interacts with DNA very strongly (K _b = 1.01 × 10⁷ mol^?1 L and K _sq = 1.11). The nature of the binding seems to be mainly an electrostatic interaction between DNA and the complex. However, other binding modes, such as hydrogen bonding, may also be present in this system.