Synthesis, magnetic properties and crystal structures of two compounds: [Cu(en)(H2O)]2[Fe(CN)6]·4H2O and [Cu(en)2][KFe(CN)6] (en=ethylenediamine)

Two new heterometallic complexes, [Cu(en)(H₂O)]₂[Fe(CN)₆]·4H₂O (1) and [Cu(en)₂][KFe(CN)₆] (2), have been isolated from the reactions of CuCl₂ and en with K₃[Fe(CN)₆] in different molar ratios. Both complexes have been characterized by X-ray analyses, IR spectra and elemental analyses. Complex 1 is a cyanide bridged bimetallic assembly, its crystal structure consists of a two-dimensional polymeric sheet with two different rings, one a four-membered square ring and another a 12-membered hexagonal ring. The Fe(II) ion of 1 has two terminal, two linear bridging and two 1,1 en-on bridging cyanide groups. In the crystal structure of 2, the neighboring [Fe(CN)₆]³⁻ units are bridged by the K⁺ and the [K[Fe(CN)₆]]²⁻ units forming a three-dimensional network structure. The [Cu(en)₂]²⁺ units fill in the holes of the network acting as counter cations and charge compensations. Variable temperature magnetic susceptibility studies of 1 indicate that the complex exhibits ferromagnetic interaction between the Cu(II) ions.     

Cu loading alters expression of non-IRE regulated, but not IRE regulated, Fe dependent proteins in HepG2 cells

This paper investigates the extent to which Cu loading influences Fe levels in HepG2 cells and the effect on proteins regulated by Fe status. Cu supplementation increased Cu content 3-fold, concomitant with a decrease in cellular Fe levels. Intracellular levels of both transferrin (Tf) and ceruloplasmin (Cp) protein rose in parallel with increased secretion into the culture media. There was no increase in mRNA levels for either protein. Rather, our data suggested increased translation of the mRNA. The increase was not reflected in total protein synthesis, which actually decreased. The effect was not a generalised stress or cell damage response, since heat shock protein 70 levels and lactate dehydrogenase secretion were not significantly altered. To test whether the Cu effect could be acting though the decrease in Fe levels, we measured transferrin receptor (TfR) levels using ¹²⁵I labeled Tf and mRNA analysis. Neither protein nor mRNA levels were changed. Neither was the level of ferroportin mRNA. As a positive control, Fe chelation increased Tf and Cp secretion significantly, and TfR mRNA levels rose 2-fold. We excluded the possibility that the increased Cp or Tf could provide the required substrate to stimulate Fe efflux, and instead demonstrate that Cu can substitute for Fe in the iron regulatory protein - iron responsive element regulation mechanism.     

Elucidation of the Mechanism by Which Catecholamine Stress Hormones Liberate Iron from the Innate Immune Defense Proteins Transferrin and Lactoferrin

The ability of catecholamine stress hormones and inotropes to stimulate the growth of infectious bacteria is now well established. A major element of the growth induction process has been shown to involve the catecholamines binding to the high-affinity ferric-iron-binding proteins transferrin (Tf) and lactoferrin, which then enables bacterial acquisition of normally inaccessible sequestered host iron. The nature of the mechanism(s) by which the stress hormones perturb iron binding of these key innate immune defense proteins has not been fully elucidated. The present study employed electron paramagnetic resonance spectroscopy and chemical iron-binding analyses to demonstrate that catecholamine stress hormones form direct complexes with the ferric iron within transferrin and lactoferrin. Moreover, these complexes were shown to result in the reduction of Fe(III) to Fe(II) and the loss of protein-complexed iron. The use of bacterial ferric iron uptake mutants further showed that both the Fe(II) and Fe(III) released from the Tf could be directly used as bacterial nutrient sources. We also analyzed the transferrin-catecholamine interactions in human serum and found that therapeutically relevant concentrations of stress hormones and inotropes could directly affect the iron binding of serum-transferrin so that the normally highly bacteriostatic tissue fluid became significantly more supportive of the growth of bacteria. The relevance of these catecholamine-transferrin/lactoferrin interactions to the infectious disease process is considered.Iron is a key nutritional element required for the growth of almost all bacteria (15, 22); therefore, its sequestration by the mammalian ferric-iron-binding proteins (principally transferrin [Tf] in serum and lactoferrin [Lf] in mucosal secretions) represents a primary nonspecific host defense mechanism against microbial infection. Tf has one of the highest metal binding affinities recorded, with a binding constant for ferric iron of 10⁻²³ M (16). The principal physiological role of serum Tf is Fe transport through the circulating blood and its release to Fe-dependent cells; its concentration in serum is usually about 35 μM (16). Importantly, serum Tf is not iron replete, with about 70% of it existing in the apo form (16). Work in our laboratories has shown that the “fight or flight” catecholamine stress hormones epinephrine (Epi), norepinephrine (NE), and dopamine (Dop) and the widely used structurally similar inotropes (heart and kidney therapeutic drugs) isoprenaline and dobutamine are all able to form complexes with Tf and Lf (7, 8, 10, 21). This complex formation is important microbiologically, as it reduces the Fe-binding capability of these key innate immune defense proteins to an almost insignificant level and renders them vulnerable to Fe theft by bacterial pathogens that would be unable to access this normally highly secure iron. We and others have shown that these catecholamines are all able to support greater-than-millionfold increases in bacterial growth by providing iron from Tf (1, 7, 8, 10, 11, 21). Significantly, in terms of their ability to deliver Tf/Lf-complexed iron to bacteria, certain pharmacologically inactive catechol-containing metabolites were also found to be similar in potency and effect to the parent catecholamine molecule (8).The interaction between catecholamines, Tf, and Lf can reduce the bacteriostatic nature of blood and serum and mucosal secretions to the extent that they become a highly supportive bacterial culture medium (7, 8, 10, 11, 21). This ability of stress hormones to mediate bacterial acquisition of Tf/Lf-iron has been shown to have important clinical implications; for example, they have been proposed to have roles in sepsis due to the formation of staphylococcal biofilms in intravenous lines (18) and in the development of stress-related intra-abdominal sepsis by Gram-negative bacteria (8). Although we and others have identified some of the molecular components that bacteria use to acquire iron from these stress hormone-Tf/Lf complexes (1, 4, 7, 9, 25), the precise mechanism(s) by which the catecholamines themselves modulate Tf and Lf iron binding remain to be determined. Elucidation of the mechanism by which stress-elaborated hormones enable bacterial-pathogen access to host-sequestered iron is therefore important both scientifically and clinically. Because the iron within Tf and Lf is in a high-spin Fe(III) oxidation state (16) and therefore paramagnetic, electron paramagnetic resonance (EPR) spectrometry is an ideal tool to study the dynamics of the interaction between the catecholamines and Tf and Lf. The present study utilized EPR spectrometry, biochemical, and microbiological approaches to elucidate the mechanism by which catecholamine stress hormones and inotropes liberate Tf- and Lf-complexed Fe.     

Interactions of arene-Ru(II)-chloroquine complexes of known antimalarial and antitumor activity with human serum albumin (HSA) and transferrin

The interactions of π-arene-Ru(II)-chloroquine complexes with human serum albumin (HSA), apotransferrin and holotransferrin have been studied by circular dichroism (CD) and UV-Visible spectroscopies, together with isothermal titration calorimetry (ITC). The data for [Ru(η⁶-p-cymene)(CQ)(H₂O)Cl]PF₆ (1), [Ru(η⁶-benzene)(CQ)(H₂O)Cl]PF₆ (2), [Ru(η⁶-p-cymene)(CQ)(H₂O)₂][PF₆]₂ (3), [Ru(η⁶-p-cymene)(CQ)(en)][PF₆]₂ (4), [Ru(η⁶-p-cymene)(η⁶-CQDP)][BF₄]₂ (5) (CQ: chloroquine; DP: diphosphate; en: ethylenediamine), in comparison with CQDP and [Ru(η⁶-p-cymene)(en)Cl][PF₆] (6) as controls demonstrate that 1, 2, 3, and 5, which contain exchangeable ligands, bind to HSA and to apotransferrin in a covalent manner. The interaction did not affect the α-helical content in apotransferrin but resulted in a loss of this type of structure in HSA. The binding was reversed in both cases by a decrease in pH and in the case of the Ru-HSA adducts, also by addition of chelating agents. A weaker interaction between complexes 4 and 6 and HSA was measured by ITC but was not detectable spectroscopically. No interactions were observed for complexes 4 and 6 with apotransferrin or for CQDP with either protein. The combined results suggest that the arene-Ru(II)-chloroquine complexes, known to be active against resistant malaria and several lines of cancer cells, also display a good transport behavior that makes them good candidates for drug development.     

Arene-Ru(II)-chloroquine complexes interact with DNA, induce apoptosis on human lymphoid cell lines and display low toxicity to normal mammalian cells

The complexes [Ru(η⁶-p-cymene)(CQ)Cl₂] (1), [Ru(η⁶-benzene)(CQ)Cl₂] (2), [Ru(η⁶-p-cymene)(CQ)(H₂O)₂][BF₄]₂ (3), [Ru(η⁶-p-cymene)(en)(CQ)][PF₆]₂ (4), [Ru(η⁶-p-cymene)(η⁶-CQDP)][BF₄]₂ (5) (CQ = chloroquine base; CQDP = chloroquine diphosphate; en = ethylenediamine) interact with DNA to a comparable extent to that of CQ and in analogous intercalative manner with no evidence for any direct contribution of the metal, as shown by spectrophotometric and fluorimetric titrations, thermal denaturation measurements, circular dichroism spectroscopy and electrophoresis mobility shift assays. Complexes 1-5 induced cytotoxicity in Jurkat and SUP-T1 cancer cells primarily via apoptosis. Despite the similarities in the DNA binding behavior of complexes 1-5 with those of CQ the antitumor properties of the metal drugs do not correlate with those of CQ, indicating that DNA is not the principal target in the mechanism of cytotoxicity of these compounds. Importantly, the Ru-CQ complexes are generally less toxic toward normal mouse splenocytes and human foreskin fibroblast cells than the standard antimalarial drug CQDP and therefore this type of compound shows promise for drug development.     

Metal–drug synergy: new ruthenium(II) complexes of ketoconazole are highly active against Leishmania major and Trypanosoma cruzi and nontoxic to human or murine normal cells

In our ongoing search for new metal-based chemotherapeutic agents against leishmaniasis and Chagas disease, six new ruthenium–ketoconazole (KTZ) complexes have been synthesized and characterized, including two octahedral coordination complexes—cis,fac-[Ru^IICl₂(DMSO)₃(KTZ)] (1) and cis-[Ru^IICl₂(bipy)(DMSO)(KTZ)] (2) (where DMSO is dimethyl sulfoxide and bipy is 2,2′-bipyridine)—and four organometallic compounds—[Ru^II(η⁶-p-cymene)Cl₂(KTZ)] (3), [Ru^II(η⁶-p-cymene)(en)(KTZ)][BF₄]₂ (4), [Ru^II(η⁶-p-cymene)(bipy)(KTZ)][BF₄]₂ (5), and [Ru^II(η⁶-p-cymene)(acac)(KTZ)][BF₄] (6) (where en is ethylenediamine and acac is acetylacetonate); the crystal structure of 3 is described. The central hypothesis of our work is that combining a bioactive compound such as KTZ and a metal in a single molecule results in a synergy that can translate into improved activity and/or selectivity against parasites. In agreement with this hypothesis, complexation of KTZ with Ru^II in compounds 3–5 produces a marked enhancement of the activity toward promastigotes and intracellular amastigotes of Leishmania major, when compared with uncomplexed KTZ, or with similar ruthenium compounds not containing KTZ. Importantly, the selective toxicity of compounds 3–5 toward the leishmania parasites, in relation to human fibroblasts and osteoblasts or murine macrophages, is also superior to the selective toxicities of the individual constituents of the drug. When tested against Trypanosoma cruzi epimastigotes, some of the organometallic complexes displayed activity and selectivity comparable to those of free KTZ. A dual-target mechanism is suggested to account for the antiparasitic properties of these complexes.     

Crystal structure, magnetic and electrochemical properties of five-coordinate copper (II) complexes with 1,10-phenanthroline-5,6-dione

Three new five-coordinate Cu^II complexes, [Cu(tpy)(phen-dione)](PF₆)₂, [Cu(phen)(phen-dione)Cl]PF₆ and [Cu(bpy)(phen-dione)Cl]PF₆ (tpy = 2,2′;6′,2″-terpyridine, phen = 1,10-phenanthroline and phen-dione = 1,10-phenanthroline-5,6-dione) have been prepared and characterized by elemental analysis, IR and UV-Vis spectroscopies and cyclic voltammetry.The complex of [Cu(tpy)(phen-dione)](PF₆)₂ crystallized with one molecule of acetonitrile. The ortep drawing of [Cu(tpy)(phen-dione)](PF₆)₂ · CH₃CN shows that the coordination geometry around Cu^II is a distorted trigonal- bipyramid. Due to the steric hindrance of in the unit cell, the tpy ligands in each complex cation cannot interact in a π-π fashion. The effective magnetic moment (μ_eff) of the complexes was measured by the Evans method. The cyclic voltammograms at Pt disk electrode for these complexes display only one reversible Cu(II)/Cu(I) redox couple.     

Intramolecular π-π stacking interactions in aqueous solution in mixed-ligand copper(II) complexes formed by heteroaromatic amines and the nucleotide analogue 9-[2-(phosphonomethoxy)ethyl]-2-aminopurine (PME2AP), an isomer of the antivirally active 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA)

The stability constants of the mixed-ligand complexes formed between Cu(Arm)²⁺, where Arm = 2,2′-bipyridine (Bpy) or 1,10-phenanthroline (Phen), and the monoanion or the dianion of 9-[2-(phosphonomethoxy)ethyl]-2-aminopurine (PME2AP), a structural isomer of the antivirally active 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA), were determined by potentiometric pH titrations in aqueous solution at 25 °C and I = 0.1 M (NaNO₃). Detailed stability constant comparisons reveal that in the monoprotonated ternary Cu(Arm)(H;PME2AP)⁺ complexes the proton is at the phosphonate group and that stacking between Cu(Arm)²⁺ and H(PME2AP)⁻ plays a significant role. The ternary Cu(Arm)(PME2AP) complexes are considerably more stable than the corresponding Cu(Arm)(R-PO₃) species, where represents a phosph(on)ate ligand with a group R that is unable to participate in any kind of interaction within the complexes. The increased stability is attributed to intramolecular stack formation in the Cu(Arm)(PME2AP) complexes and also, to a smaller extent, to the formation of 5-membered chelates involving the ether-oxygen present in the residue of PME2AP²⁻. This latter interaction was previously quantified by studying ternary Cu(Arm)(PME) complexes (PME²⁻ = dianion of (phosphonomethoxy)ethane), which can form the 5-membered chelates but where no intramolecular ligand-ligand stacking is possible. Application of these results allows a quantitative analysis of the intramolecular equilibria involving three structurally different Cu(Arm)(PME2AP) species; e.g., about 5% of the Cu(Bpy)(PME2AP) system exist with the metal ion solely coordinated to the phosphonate group, 15% as a 5-membered chelate involving the ether-oxygen atom of the residue, and 80% with an intramolecular π-π stack between the purine moiety of PME2AP²⁻ and the aromatic rings of Bpy. Finally, comparison of the stacking properties of PME2AP²⁻ and PMEA²⁻ in their ternary complexes reveals that stacking is somewhat more pronounced in the Cu(Arm)(PMEA) than in the Cu(Arm)(PME2AP) species. Speculatively, this reduced stacking intensity, together with a different hydrogen-bonding pattern, could well lead to a different positioning of the 2-aminopurine moiety (compared to the adenine residue) in the active site cavity of nucleic acid polymerases and thus be responsible for the reduced antiviral activity of PME2AP compared with that of PMEA.     

Brefeldin a down-regulates the transferrin receptor in K562 cells

The fungal metabolite brefeldin A (BFA) induces profound alterations in the morphology of intracellular organelles. Although BFA promotes the formation of extensive tubular endosomal domains, our understanding of the effects of the antibiotic on vesicle traffic events associated with endocytosis is limited. Thus, alterations in the transferrin (Tf) receptor's endocytic/recycling pathway upon treatment of human erythroleukemia K562 cells with BFA were studied as a pharmacological response. Treatment of K562 cells with BFA caused a down-regulation in the number of cell surface Tf receptors. This effect is highly reminiscent of the well-known action of phorbol 12-myristate 13-acetate (PMA) on Tf receptor traffic in K562 cells. However, our results demonstrate that these two agents down-regulate the Tf receptor via different mechanisms. The effects of BFA and PMA were additive when K562 cells were incubated with both together. Using the In/Sur method, the endocytic rate constant for Tf internalization was determined and PMA was found to greatly enhance k_e, from 0.28 min^–1 to 0.43 min^–1, while BFA had little effect (K_e=0.20 min^–1). In contrast, BFA-treatment alters the exocytic rate constant for return of internalized receptors to the cell surface, with the largest effect exerted on a slow-release, monensin-sensitive, compartment. The sum of the endocytic and exocytic kinetic data support a model in which BFA and PMA down-regulate the Tf receptor in K562 cells by mechanistically distinct actions, with BFA targeting exocytic monensin-sensitive intracellular compartments and PMA acting to exert a profound influence on elements of receptor internalization.Abbreviations BFA brefeldin A - ARF ADP-ribosylation factor - HRP horseradish peroxidase - Tf transferrin - PMA phorbol 12-myristate 13-acetate - DMSO dimethyl sulfoxide - PBS phosphate-buffered saline - HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - BSA bovine serum albumin - FITC-Tf fluorescein isothiocyanate-labelled transferrin     

Synthesis, spectral and magnetic properties and crystal structures of copper(II) pyridinecarboxylates as potential antimicrobial agents

Synthesis and characterization of six new complexes [Cu{2,6-(MeO)₂nic}₂(H₂O)]₂ (1), [Cu{2,6-(MeO)₂nic}₂(H₂O)]₂ · 3DMF (2), where 2,6-(MeO)₂nic is 2,6-dimethoxynicotinate and DMF is N,N-dimethylformamide, [Cu(3-pyacr)₂(H₂O)₂]_n (3), where 3-pyacr is trans-3-(3-pyridyl)acrylate, [Cu(en)₂(H₂O)₂]X₂, where X is 2,6-(MeO)₂nic (4) or 3-pyacr (5) and en is ethylenediamine, and [Cu(3-pyacr)₂(dien)(μ-H₂O)_0.5]₂ · 7H₂O (6), where dien is diethylenetriamine are reported. The characterizations were based on elemental analysis, infrared, electronic and EPR spectra, and magnetic measurements over a temperature range of 1.8-300 K. Crystal structures of complexes 2, 4 and 6 have been determined by X-ray single crystal structure analysis. The available evidence supports dimeric structure of the acetate type for 1 and 2. Crystal structure of polymeric complex 3 has been determined from X-ray powder diffraction data. The 3-pyacr anions in pairs form bridges between two octahedrally surrounded copper(II) atoms in such a way that one 3-pyacr is coordinated to the first Cu^II by an oxygen atom of its carboxyl group and to the second Cu^II by the nitrogen atom of its pyridine ring, while the other is coordinated to the same two Cu^II atoms in a similar way, but the other way round. Environment about the copper(II) atom for 4 and 5 is a square bipyramid (4+2).In complex 6 both Cu^II central atoms are bridged only by an axial water molecule forming a dimeric structure with the considerably long separation of Cu^II atoms of 5.194 Å and the angle Cu1-O3-Cu1a of 150.79°. Moreover, results of the quantitative determination of antimicrobial activity of the complexes as well as above organic ligands alone are discussed.     

Dicyanamido-metal(II) complexes. Part 4: Synthesis, structure and magnetic characterization of polynuclear Cu(II) and Ni(II) complexes bridged by μ-1,5-dicyanamide

The one pot aqueous reaction of M(ClO₄)₂ (M = Cu²⁺ or Ni²⁺) with N-methylbis[2-(2-pyridylethyl)]amine (MeDEPA) and N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethylenediamine (bpmen) and 1,4,7,10-tetraazacyclododecane (cyclen) in presence of sodium dicyanamide (Nadca) yielded dicyanamido-bridged polynuclear complex {[Cu(MeDEPA)(μ-1,5-dca)]ClO₄}_n (1), and two dinuclear complexes [Cu₂(bpmen)₂(μ-1,5-dca)]₂(ClO₄)₅dca (2) and [Ni(cyclen)(μ-1,5-dca)]₂(ClO₄)₂ (3). These complexes were characterized by IR and UV-Vis spectroscopy. Room temperature single-crystal X-ray studies have confirmed that the Cu(II) centers in 1 and 2 adopt geometries that are more close to trigonal bipyramidal (TBP) in 1 and close to square pyramidal (SP) in 2, whereas in 3, the Ni(II) centers are located in octahedral environment with doubly bridged μ-1,5-dca bonding mode. The intermolecular M···M distances in these complexes are in the range of 7.3-8.6 Å. Variable temperature magnetic susceptibility studies have confirmed that the dca-bridges mediate very weak antiferromagnetic interaction between the M(II) centers with J values of −0.35, −0.18 and −0.43 cm⁻¹ for 1, 2 and 3, respectively. The results are compared and discussed in the light of other related bridged μ-1,5-dca Cu(II) and Ni(II) complexes.     

Abnormal iron delivery to the bone marrow in neonatal hypotransferrinemic mice

Hypotransferrinemic (HP) mice have a splicing defect inthe transferrin gene, resulting in <1% of the normal plasma levels of transferrin. They have severe anemia, suggesting that transferrin is essential for iron uptake by erythroid cells in the bone barrow. To clarify the significance of transferrin on iron delivery to the bone marrow, iron concentration and ⁵⁹Fe distribution were determined in 7-day-old HP mice. Iron concentration in the femur, bone containing the bone marrow, of HP mice was approximately twice higher than in wild type mice. Twenty-four h after injection of ⁵⁹FeCl₃, ⁵⁹Fe concentration in the bone and bone marrow of HP mice was also twice higher than in wild type mice. The present findings indicate that iron is abnormally delivered to the bone marrow of HP mice. However, the iron seems to be unavailable for the production of hemoglobin. These results suggest that transferrin-dependent iron uptake by erythroid cells in the bone marrow is essential for the development of erythrocytes.     

Role of transferrin in iron uptake by the brain: a comparative study

Summary The role of specific transferrin (Tf) and Tf receptor interaction on brain capillary endothelial cells in iron transport from the plasma to the brain was investigated by using Tf from several species of animals labeled with ⁵⁹Fe and ¹²⁵I, and 15-day and adult rats. The rate of iron transfer was much greater in the 15-day rats. It was greatest with Tf from the mammals, rat, rabbit and human, but much lower with chicken ovotransferrin and quokka (a marsupial), toad, lizard, crocodile, and fish Tf. The uptake of Tf by the brain showed a similar pattern, except for a very high uptake of ovotransferrin (ovo Tf). Iron uptake by the femurs (a source of bone marrow) was also high with Tf from the mammalian species and low with the other types of Tf, but showed little change with aging of the animals. It is concluded that iron transport into the brain is dependent on the function of Tf receptors, probably on capillary endothelial cells, and that these receptors show the same type of species specificity as the receptors on immature erythroid cells. Also, the decrease in iron uptake by the brain as rats age from 15 days to adulthood is specific for the brain and is not a general effect of the aging process.Abbreviations Tf transferrin - ovo Tf ovotransferrin     

Synthesis and characterization of alkynes β-diketonate copper(I) complexes

The reactions of 1,3,5-tris-(trimethylsilylethynyl)benzene (1) with Cu₂O and 1,1,1,5,5,5,-hexafluoroacetylacetone in alkyne to Cu ratios 1:0.5, 1:1 and 1:3 in CH₂Cl₂ at room temperature give copper complexes (η²-1,3,5-tris(trimethylsilylethynyl)benzene)(Cu(hfac)) (2), (η²:η²-1,3,5-tris(trimethylsilylethynyl)benzene)(Cu(hfac))₂ (3) and (η²:η²:η²-(1,3,5- tris(trimethylsilylethynyl)benzene))₂(Cu(hfac))₃(4), respectively. In the same conditions, 2,5-bis-(trimethylsilylethynyl)thiophene (5) reacts with 0.5 or 1 equiv. of Cu₂O to give (η²:η²-2,5-bis(trimethylsilylethynyl)thiophene)(Cu(hfac)) (6) and (η²:η²-2,5-bis(trimethylsilylethynyl)thiophene)(Cu(hfac))₂ (7), respectively, and 1,4-bis(trimethylsilyl)-1,3-butadiyne (8) with 0.5 equiv. of Cu₂O give (η²:η²-1,4-bis(trimethylsilyl)-1,3-butadiyne)(Cu(hfac))₂(9). All the new compounds have been characterized by analytical and spectroscopic methods and their thermal properties were examined by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Bimetallic sheet and 3D threefold interpenetrating diamond-like network constructed by chelate Cu cations and Mn dicyanamide polymeric chains. Synthesis, crystal structure, and magnetism of [Cu(L)2][Mn(dca)4] (L=ethylenediamine or 1,3-diaminopropane; dca=dicyanamide N(CN)2)

Two novel bimetallic coordination polymers, [Cu(en)₂][Mn(dca)₄] (1) and [Cu(pn)₂][Mn(dca)₄] (2) (en, ethylenediamine; pn, 1,3-diaminopropane; dca, dicyanamide N(CN)₂⁻), have been synthesized and characterized. Both of them consist of Mndca anionic chains and chelate cations of copper. 1 has a sheet like architecture built by the [Cu(en)₂]²⁺ cations and the homoleptic trans-[Mn(dca)₄ ²⁻]_n chains. 2 shows unusual 3-D threefold interpenetrating diamond-like structure constructed by [Cu(pn)₂]²⁺ cations and the homoleptic cis-[Mn(dca)₄ ²⁻]_n chains. The magnetic susceptibilities obey the Curie-Weiss law with weak antiferromagnetic interactions.     

Cd(II)-ethylenediamine mono- and bimetallic complexes - Synthesis and characterization by Cd NMR spectroscopy and single crystal X-ray diffraction

Formation of three Cd(II)-ethylenediamine (en) complexes ([Cd(en)_n]²⁺, n = 1-3) in aqueous solution and in DMSO solvent has been established by means of ¹¹³Cd NMR spectroscopy. It is clearly shown that Cd(II)-en complexes form primarily in basic solutions. A correlation between the ¹¹³Cd NMR chemical shifts and the ethylenediamine (en) coordination number has been observed and discussed. Two single crystals with the composition [Cd₂(en)₅](ClO₄)₄ (1) and [Cd(en)₃](ClO₄)₂ (2) were prepared from aqueous solution, and their structures were determined by single crystal X-ray diffraction. Cd(II) ions are coordinated by six atoms in both compounds, 1 and 2: via five N-donor atoms and one O-donor atom forming a bimetallic complex 1, and via six N-donor atoms forming a distorted octahedral monometallic complex 2. Raman spectra of complexes 1 and 2 also provide additional evidence that the cis-form of the bridging en is present in complex 1.     

Synthesis,spectroscopic characterization,electrochemical behavior and computational analysis of mixed diamine ligand gold(III) complexes: antiproliferative and in vitro cytotoxic evaluations against human cancer cell lines

The gold(III) complexes of the type [(DACH)Au(en)]Cl₃, 1,2-Diaminocyclohexane ethylenediamine gold(III) chloride [where 1,2-DACH = cis-, trans-1,2- and S,S-1,2diaminocyclohexane and en = ethylenediamine] have been synthesized and characterized using various analytical and spectroscopic techniques including elemental analysis, UV–Vis and FTIR spectra; and solution as well as solid-state NMR measurements. The solid-state ¹³C NMR shows that 1,2-diaminocyclohexane (1,2-DACH) and ethylenediamine (en) are strongly bound to the gold(III) center via N donor atoms. The stability of the mixed diamine ligand gold(III) was determined by ¹H and ¹³C NMR spectra. Their electrochemical behavior was studied by cyclic voltammetry. The structural details and relative stabilities of the four possible isomers of the complexes were also reported at the B3LYP/LANL2DZ level of theory. The coordination sphere of these complexes around gold(III) center adopts distorted square planar geometry. The computational study also demonstrates that trans- conformations is slightly more stable than the cis-conformations. The antiproliferative effects and cytotoxic properties of the mixed diamine ligand gold(III) complexes were evaluated in vitro on human gastric SGC7901 and prostate PC3 cancer cells using MTT assay. The antiproliferative study of the gold(III) complexes on PC3 and SGC7901 cells indicate that complex 1 is the most effective antiproliferative agent among mixed ligand based gold(III) complexes 1–3. The IC₅₀ data reveal that the in vitro cytotoxicity of complexes 1 and 3 against SGC7901 cancer cells are fairly better than that of cisplatin.     

Spin-spin interactions in iron(III) porphyrin radical cations with ruffled and saddled structure

Oxidation of essentially pure intermediate-spin iron(III) porphyrinates such as ruffled Fe(TⁱPrP)ClO₄ and saddled Fe(OETPP)ClO₄ produces the corresponding six-coordinate iron(III) porphyrin(por) radical cations [Fe(Por)(ClO₄)₂], where TⁱPrP and OETPP are dianions of 5,10,15,20-tetraisopropylporphyrin and 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin, respectively.Spin-spin interactions in these complexes are very much different; while ruffled [Fe(TⁱPrP)(ClO₄)₂] exhibits no antiferromagnetic coupling, saddled [Fe(OETPP)(ClO₄)₂] does exhibit it. The difference in magnetic behaviors has been explained in terms of the deformation mode and electron configuration of these complexes.     

Heteroleptic Cu(I) complexes containing phenanthroline-type and 1,1′-bis(diphenylphosphino)ferrocene ligands: Structure and electronic properties

Three new heteroleptic Cu(I) complexes containing one phenanthroline and one diphosphine type ligand ([Cu(N-N)(P-P)]⁺) have been prepared. In particular, one ligand is constituted by 1,10-phenanthroline (1), 2,9-dimethyl-1,10-phenanthroline (2) and 2,9-diphenethyl-1,10-phenanthroline (3) and the other ligand is in all cases 1,1′-bis(diphenylphosphino)ferrocene (dppf). Therefore, copper and iron metal centres are quite close one another, as evidenced by X-ray crystal diffraction. The structure together with the electrochemical and photophysical properties of these complexes have been compared to that of the corresponding complexes where dppf has been replaced by bis[2-(diphenylphosphino)-phenyl]ether (POP). Cyclic voltammetric experiments evidenced that the first oxidation process is located on the ferrocene moiety and that oxidation of Cu(I) is moved to more positive potential values and a chemical reaction is coupled to the electron transfer process. The absorption spectra show a metal-to-ligand charge transfer (MLCT) band, typical of Cu(I) phenanthroline complexes, at a higher energy compared to the homoleptic [Cu(N-N)₂]⁺ species. No emission at either room temperature or 77 K has been observed for compounds 2 and 3, contrary to the high luminescence observed for the corresponding POP complexes. This result is consistent with a photoinduced energy transfer from the Cu(I) complex to the ferrocene moiety.