Carboxylato Ligands Research Articles

Linear, Planar, Orbicular, and Macrocyclic Multinuclear Zinc (Meth)acrylate Complexes.

Zinc carboxylate complexes are widely utilized as artificial models of metalloenzymes and as secondary building units of PCPs/MOFs. However, the relationship between the structure of the monodentate carboxylato ligand and the molecular arrangement of multinuclear zinc carboxylate complexes is not fully understood because of the coordination flexibility of the Zn ion and carboxylato ligands. Herein, we report the structural analysis of a series of complexes derived from zinc (meth)acrylate which has a linear infinite chain structure. The molecular structure of μ4-oxido-bridged tetranuclear complexes [Zn4(μ4-O)(OCOR)6] revealed a distorted Zn4O core. Crystallization of zinc acrylate under aqueous conditions afforded a μ3-hydroxido-containing pentanuclear complex [Zn5(μ3-OH)2(OCOR)8] as the repeating unit of an infinite sheet-like structure in the solid state. It was also obtained by the hydrolysis of the μ4-oxido-bridged tetranuclear complex. In sharp contrast, the methacrylate analog retained the methacrylato ligands under aqueous crystallization conditions to form a macrocyclic dodecanuclear complex with methacrylato as the sole ligand.

Novel diphenyltin(IV) complexes with carboxylato N-functionalized 2-quinolone ligands: Synthesis, characterization and in vitro anticancer studies

Three new diphenyltin(IV) complexes, bis(3-(4-methyl-2-oxoquinolinyl-1(2H)-yl)propanoato)diphenyltin(IV) (1), bis(2-(4-methyl-2-oxoquinolin-1(2H)-yl)ethanoato)diphenyltin(IV) (2), and bis(2-(4-hydroxy-2-oxoquinolin-1(2H)-yl)ethanoato)diphenyltin(IV) (3), were synthesized and characterized by elemental microanalysis, FT-IR spectroscopy, and multinuclear (1H, 13C and 119Sn) NMR spectroscopy. Crystal structure of ligand precursor, 2-(4-methyl-2-oxoquinolinyl-1-(2H)-yl)acetic acid (HL2), has been determined by X-ray diffraction studies. Asymmetric bidentate coordination of the carboxylato ligands and skew trapezoidal structures are assumed for the synthesized complexes. In vitro anticancer activity of the synthesized diphenyltin(IV) complexes was evaluated against three human: MCF-7 (breast adenocarcinoma), A375 (melanoma), HCT116 (colorectal carcinoma), and three mouse tumor cell lines: 4T1 (breast carcinoma), B16 (melanoma), CT26 (colon carcinoma) using MTT and CV assays. The IC50 values fall in the range from 0.1 to 3.7 μM. Flow cytometric analysis and fluorescent microscopy suggest that complex 1 induces caspase-dependent apoptosis followed with strong blockade of cell division in HCT116 cells. Since complex 1 showed ROS/RNS scavenging potential mentioned cytotoxicity was not connected with oxidative stress.

Pentacoordinate Mixed-Ligand Zn(II) Complexes with Flufenamato and Niflumato Ligands: Crystal Structure, Spectral Characterization and Biological Properties

Mixed-ligand complexes featuring a carboxylato ligand and bidentate chelate N,N′-donor ligands along with a single halogenido ligand are rarely subjected to studies despite their interesting physical, chemical and biological properties. A direct synthesis involving non-steroidal anti-inflammatory drugs flufenamic acid and niflumic acid and sterically hindering N,N′-donor ligands (neocuproine and 2,2′-biquinoline) has been used to prepare mononuclear mixed-ligand zinc complexes with a composition of [ZnCl(flu)(neo)] (1A and 1B) and [ZnCl(nif)(biq)] (2). Single-crystal X-ray diffraction data have shown that the carboxylate binding mode differs in the two polymorphs 1A and 1B, which form molecules of same composition, and the deviations in molecular geometry are further reflected in their supramolecular structures. The inter- and intramolecular interactions and their contributions to the stability of the crystal structures has been investigated by Hirshfeld surface analysis. The spectral properties of the prepared complexes in solid-state and solution have been analyzed. Additionally, the interaction with the biomacromolecules (fish sperm DNA, human and bovine serum albumins), studied by fluorescence assays, showed a stronger binding of 1A and 1B in comparison with 2.

Triphenyltin(IV) Carboxylates with Exceptionally High Cytotoxicity against Different Breast Cancer Cell Lines.

Organotin(IV) carboxylates are a class of compounds explored as alternatives to platinum-containing chemotherapeutics due to propitious in vitro and in vivo results, and distinct mechanisms of action. In this study, triphenyltin(IV) derivatives of non-steroidal anti-inflammatory drugs (indomethacin (HIND) and flurbiprofen (HFBP)) are synthesized and characterized, namely [Ph3Sn(IND)] and [Ph3Sn(FBP)]. The crystal structure of [Ph3Sn(IND)] reveals penta-coordination of the central tin atom with almost perfect trigonal bipyramidal geometry with phenyl groups in the equatorial positions and two axially located oxygen atoms belonging to two distinct carboxylato (IND) ligands leading to formation of a coordination polymer with bridging carboxylato ligands. Employing MTT and CV probes, the antiproliferative effects of both organotin(IV) complexes, indomethacin, and flurbiprofen were evaluated on different breast carcinoma cells (BT-474, MDA-MB-468, MCF-7 and HCC1937). [Ph3Sn(IND)] and [Ph3Sn(FBP)], unlike the inactive ligand precursors, were found extremely active towards all examined cell lines, demonstrating IC50 concentrations in the range of 0.076-0.200 µM. Flow cytometry was employed to examine the mode of action showing that neither apoptotic nor autophagic mechanisms were triggered within the first 48 h of treatment. However, both tin(IV) complexes inhibited cell proliferation potentially related to the dramatic reduction in NO production, resulting from downregulation of nitric oxide synthase (iNOS) enzyme expression.

Mixed crystal of bis-(ammonium/oxonium) tetra-aqua-μ3-fluorido-dodeca-kis-(μ2-tri-fluoro-acetato)octa-hedro-hexa-ytterbiate(III) tetra-hydrate, [(NH4)1-x (H3O) x ]2[Yb6F8(O2CCF3)12(H2O)4]·4H2O (x = 1/4), containing a hexa-nuclear ytterbium(III) carboxyl-ate complex with face-capping fluoride ligands and comprising an unusual kind of substitutional disorder.

The reaction of ytterbium metal with ammonium tri-fluoro-acetate in liquid ammonia resulted in a green substance comprising a substantial amount of ytterbium(II) tri-fluoro-acetate that is a useful precursor for the oxidative synthesis of the new ytterbium(III) compound, [(NH4)1-x (H3O) x ]2[Yb6F8(O2CCF3)12(H2O)4]·4H2O (x = 1/4), in aqueous tri-fluoro-acetic acid. This mixed ammonium/oxonium crystalline solid is the first example of a substance containing an octa-hedro-hexa-nuclear ytterbium(III) complex with μ3-face-capping fluorido ligands. The main structural features of its [Yb6F8] core are non-bonding Yb⋯Yb distances and Yb-F bond lengths of 3.7576 (3)-3.9413 (5) and 2.2375 (17)-2.3509 (17) Å, respectively. Yb-O bond lengths involving the O atoms of O,O'-bridging carboxyl-ato ligands and vertex-substituting aqua ligands are in the ranges 2.23 (4)-2.329 (2) and 2.448 (2)-2.544 (3) Å, respectively. These bond lengths are in accordance with expectations, taking into account lanthanoid contraction. Inter-estingly, there is a significant ammonium versus oxonium ion site dependence, not only of the hydrate water mol-ecule positions within the solid's hydrogen-bonding framework, but also of the coordination sites of one carboxyl-ato and one aqua ligand in the hexa-nuclear complex.

Zwitterion coordination to configurationally flexibled10cations: synthesis and characterization of tetrakis(betaine) complexes of divalent Zn, Cd, and Hg

AbstractThed10ions MII(M = Zn, Cd, Hg) and four equivalents of the neutral zwitterion trimethylglycine (betaine, bet) aggregate to discrete six-coordinated cationic complexes. With nitrate as counter anions, solids of the composition [M(bet)4](NO3)2·H2O are obtained. Their structural characterization reveals close relationship: they crystallize in metrically similar unit cells adopting three different subgroups of a hypothetical aristotype. In all cases, the divalent cations exhibit a strongly distorted coordination sphere in which two betaine ligands bind with both carboxylato O atoms and the other two with only one oxygen to the cation. Non-coordinating O atoms of different betaine ligands act as hydrogen bond acceptors towards co-crystallized water molecules. At least for the Pearson-soft HgIIcations, this coordination is unexpected: to the best of our knowledge, HgIIcomplexes with four carboxylato ligands have not yet been characterized. Without the necessity for charge balancing, the composition of zwitterion complexes is dominated by steric requirements and possibly by competition with alternative dipole molecules such as solvent water.

Structures and Properties of 4-phpy, pyz, and 4,4′-bpy Adducts of Lantern-Type Dirhodium Complexes with µ-Formamidinato and µ-Carboxylato Bridges

Dinuclear and polymer complexes of 4-phenylpyridine (4-phpy), pyazine (pyz), and 4,4′-bipyridine (4,4′-bpy) were prepared by using cis-[Rh2(4-Me-pf)2(O2CR)2] (4-Me-pf- =N,N’-bis(4-methylphenyl)formamidinate anion; R = CF3 and CMe3) as precursor dinuclear units. The dinuclear structures of cis-[Rh2II,II(4-Me-pf)2(O2CR)2(4-phpy)2] and cis-[Rh2II,III(4-Me-pf)2(O2CCMe3)2(4-phpy)2]BF4 and polymer structures of [Rh2II,II(4-Me-pf)2(O2CR)2(L)]n (L = pyz and 4,4′-bpy) were confirmed by X-ray crystal structure analyses. In these complexes, the lantern-type dinuclear core structures with cis-(2:2) arrangement of formamidinato (4-Me-pf-) and carboxylato ligands are preserved with Rh–Rh distances of 2.44–2.47 Å, regardless of the difference in the axial ligand and oxidation state Rh2II,II or Rh2II,III. In the cyclic voltammograms (CVs) in CH2Cl2, the redox potentials for Rh2II,III/Rh2II,II were estimated as E1/2 = 0.07 V and −0.28 V (vs. Fc+/Fc) for cis-[Rh2(4-Me-pf)2(O2CCF3)2(4-phpy)2] and cis-[Rh2(4-Me-pf)2(O2CCMe3)2(4-phpy)2], respectively, negatively shifted by 0.16 and 0.12 V compared with those of corresponding parent dinuclear complexes. The results were interpreted that the axial interaction with 4-phpy ligands makes the Rh2II,II core oxidized easily. The oxidized complex cis-[Rh2(4-Me-pf)2(O2CCMe3)2(4-phpy)2]BF4 is paramagnetic, which was confirmed by effective magnetic moment value μeff = 1.90 μB at 300 K per Rh2II,III unit (S = 1/2). The polymer complexes [Rh2(4-Me-pf)2(O2CR)2(L)]n (L = pyz and 4,4′-bpy) showed Type II gas-adsorption properties for N2.

Binuclear Co(II) complexes with macrocycle and carboxylato ligands: structure, cytotoxicity and thermal behavior

In vitro cytotoxic evaluation, formation constants and thermal stability of four mixed-ligand Co(II) complexes with tpmc = N,N',N",N'"-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane and carboxylate/dicarboxylate co-ligands of formulas [Co2(benz)2tpmc](ClO4)2•3H2O (1), benz– = benzoate anion; [Co2(L)tpmc](ClO4)2•nH2O, L = pht2– (phthalate dianion), n=2 (2), L = ipht2– (isophthalate dianion), n=4 (3) and L = tpht2–(terephthalate dianion), n=4 (4) are reported. The stoichiometric composition of the compounds in the solution were determined spectrophotometrically using Job's methods. Formation constants, K and Gibbs free energy, ΔG values were calculated. The thermal behavior of the complexes was investigated by simultaneous TG/DSC and TG – MS measurements. The cytotoxic effect of the complexes, the free ligands, the DMSO solvent and cis-platin, as referent cytostatic drug, was evaluated on Human cervix adenocarcinoma (HeLa), human melanoma (Fem-x) and human colon carcinoma (LS174) cell lines. The IC50 values were between 12.7–42.3 μM. The first crystal structure determination of the Co(II) complex [Co2(µ-pht)tpmc](ClO4)2•H2O with boat conformation of tpmc ligand, was also done. The complex crystallizes in monoclinic crystal system, C2/c space group. The geometries around both Co(II) atoms are highly distorted octahedral. The Co(II) ions exhibit CoN4O2 coordination environments with the four nitrogen donor atoms of the tpmc ligand and two oxygen atoms belonging to the one carboxylate group of pht2− ligand. The carboxylate groups of pht2− are coordinated in an endo-bidentate mode. The tpmc ligand adopted a boat conformation in which the two coordinated Co(II) atoms are located on the same side of the ring, with Co•••Co distance amounting 5.4799(5) Å.

Interconversion between Möbius chiroptical states sustained by hexaphyrin dynamic coordination.

Harnessing the chiroptical properties of molecular Möbius rings is motivated by fundamental aspects while challenged by synthetic difficulties. Focusing on Möbius aromatic Zn(ii) hexaphyrin complexes, interconversion between two chiral states was achieved through binding and release of an amino ligand (forward/backward stimuli), leading to different chiroptical switching phenomena (amplification, on-off, inversion). The amine either supplies the chirality or behaves as an achiral effector regulating the Zn(ii)-binding of a second (chiral) carboxylato ligand. These results highlight the Möbius [28]hexaphyrin scaffold as an attractive chiral switchable unit.

Thermally stable and robust gadolinium-based metal-organic framework: Synthesis, structure and heterogeneous catalytic O-arylation reaction

Hydrothermal treatment of gadolinium nitrate and 2,6-naphthalenedicarboxylic acid (H2NDC) afforded a new metal-organic framework compound, {[Gd4(NDC)6(H2O)6]·2H2O}n(1). Compound 1 has been characterized by single-crystal X-ray crystallography, elemental analysis, FT-IR spectroscopy, therrmogravimetric analysis (TGA) and powder X-ray diffraction analysis. It is crystallized in the monoclinic system with the P21/n space group. Four crystallographically distinct Gd (III) centres are interconnected with each other through bridged carboxylato oxygen atoms and water molecules to form tetranuclear secondary building units, which are further connected through the carboxylato ligand and the network propagates along the crystallographic ac plane to form a 2D structure. Subsequent reinforcement from the remaining carboxylato oxygen atoms gives rise to a robust 3D framework structure. Thermogravimetric analysis demonstrates that compound 1 is fairly stable after dehydration under a nitrogen atmosphere.Notably, compound 1 is capable of catalyzing the O-arylation reaction efficiently between substituted phenols and bromoarene under heterogeneous conditions at 80 °C to afford unsymmetrical diarylethers.

New hexanuclear FeIII clusters with the gem-diol hydrated form of di(2-pyridyl)ketone and carboxylato ligands: Crystal structures and magnetic properties

The hexanuclear compounds [Fe6O2Cl2{(py)2CO2}2(pyOH)2(pyCOO)2(ButCOO)6] (1) and [Fe6O2{(py)2CO2}2(pyCOO)4(ButCOO)6] (2) were obtained by condensation of the trinuclear μ3-oxo-centered iron(III) pivalate [Fe3O(ButCOO)6(H2O)3]+ in the presence of di(2-pyridyl)ketone [(py)2CO] in MeCN at ambient temperature. Both complexes contain an analogous core which can be described as two {Fe3O}7+ units joined by gem-diolato (py)2CO22− bridges. Variable-temperature magnetic susceptibility measurements in polycrystalline samples of 1 and 2 reveal strong antiferromagnetic couplings between the iron(III) ions leading to S = 0 ground states.

The impact of highly electron withdrawing carboxylato ligands on the stability and activity of platinum(IV) pro-drugs

Recent developments in the design of platinum(IV) pro-drug candidates have demonstrated the importance of the coordination sphere of the complex in determining the resistance to reduction by endogenous reductants and the stability in biologically relevant environments. Diaminetetracarboxylatoplatinum(IV) complexes exhibit many desirable properties as platinum(IV) pro-drugs, exhibiting unusual resistance to reduction by endogenous reductants and in blood serum, but are rapidly reduced within cells. In this study, we used 19F NMR to monitor the aquation of complexes with highly electron withdrawing trifluoroacetato ligands in the axial positions of platinum(IV) and reinterpreted the reduction of these complexes by ascorbate and cysteine and their biological behaviour in the light of the aquation results. We concluded that the potential for aquation needs to be taken into account in interpreting reduction and cytotoxicity studies. While we show that this is possible for the reduction studies, we conclude that it is not possible for cytotoxicity studies and other studies in complex biological environments. We also note that the low stability of the complexes is not expected to be compatible with their use as pro-drugs.

Manganese(II) complexes of tolfenamic acid or naproxen in polymeric structures or encapsulated in [15-MC-5] manganese(III) metallacrowns: Structure and biological activity

The interaction of MnCl2 with the non-steroidal anti-inflammatory drugs tolfenamic acid (Htolf) or naproxen (Hnap) in the presence of salicylhydroxamic acid (H3shi) led- to the formation of the hexanuclear mixed-valence MnIIMnIII5 clusters [Μn6(tolf)2(shi)5(py)6], 1 and [Μn6(nap)(Hsal)(shi)5(py)6], 2 (where H2sal = salicylic acid) which were characterized as 15-metallacrown-5 complexes accommodating the Mn(II) ion and the monoanionic carboxylato ligands tolf−1, nap−1 and Hsal−1. The interaction of Mn(II) with deprotonated naproxen led to the formation of the polymeric Mn(II) complex [Μn(nap)2(CH3OH)]n, 3. All three complexes were characterized by physicochemical and spectroscopic techniques and by single-crystal X-ray crystallography. The in vitro cytotoxic effects of the complexes were evaluated against three cancer cell lines (HeLa, MCF-7 and A549 cells) as well as their combinatory activity with the well-known chemotherapeutic drugs irinotecan, cisplatin, paclitaxel and 5-fluorouracil. The interaction of complexes 1–3 with calf-thymus (CT) DNA and bovine serum albumin (BSA) was investigated in vitro by diverse techniques. In addition, the cytotoxic activity of the previously reported polymeric complex [Μn(tolf)2(DMF)2]n, 4 was also investigated and its behavior towards CT DNA and BSA was compared to that of complexes 1–3.

Synthesis, characterization and behavior in water/DMSO solution of Ru(II) arene complexes with bioactive carboxylates

The reactions of [RuCl(μ-Cl)(η6-p-cymene)]2 with sodium carboxylates, in methanol or acetonitrile solution, afforded the complexes [RuCl(κ2O-RCO2)(η6-p-cymene)] (RCO2 = valproate, 1; aspirinate, 2; diclofenate, 3), in 79–96% yields. Analogously, [RuCl(κ2O-dfCO2)(η6-benzene)], 4, was obtained in admixture with minor by-products from [RuCl(μ-Cl)(η6-benzene)]2 and sodium/silver diclofenate. The sequential reaction of [RuCl(μ-Cl)(η6-p-cymene)]2 with sodium salicylate and PPh3 gave [Ru(κ2O,O′-salCO2)(PPh3)(η6-p-cymene)], 5, in 70% yield. The hydride complex [Ru2Cl2(μ-Cl)(μ-H)(η6-p-cymene)2], 6, was produced in 36% yield from [RuCl(μ-Cl)(η6-p-cymene)]2 and sodium formate. An optimization of the experimental work-up allowed to isolate [RuCl(μ-Cl)(η6-p-cymene)]2 with an improved yield respect to the literature (98% vs. 65%). The bidentate coordination mode of the carboxylato ligands in 1–5 was unambiguously ascertained by IR and NMR spectroscopy, moreover the solid state structure of 1 was elucidated by single crystal X-ray diffraction. Complexes 1–3 experience rapid and quantitative dissociation of the carboxylato anion in DMSO/water/NaCl mixtures, mainly converting into [RuCl2(DMSO)(η6-p-cymene)], 7.

Triphenylbismuth(v) di[(iso)nicotinates] - transmetallation agents or divergent organometalloligands? First organobismuth(v)-based silver(i) coordination polymers.

The reaction of Ph3BiCl2 with alkali salts of isonicotinic and nicotinic acids afforded Ph3Bi[O(O)CC5H4N-4]2 (1) and Ph3Bi[O(O)CC5H4N-3]2 (2), respectively, which were characterized by multinuclear NMR spectroscopy in solution, mass spectrometry and IR spectroscopy in the solid state. Their molecular structures were established by single-crystal X-ray diffraction. For both 1 and 2 the molecules contain a trigonal bipyramidal C3BiO2 core, with the phenyl groups in equatorial positions. The potential use of 1 and 2 as ditopic organometalloligands was investigated. The reaction of 1 or 2 with Me3SnCl (1 : 2 molar ratio) resulted in carboxylato ligand exchange and the formation of Me3Sn[O(O)CC5H4N-4] (3) and Me3Sn[O(O)CC5H4N-3] (4) besides Ph3BiCl2. The crystals of both 3 and 4 contain 1-D coordination polymers built through intermolecular N → Sn interactions. The treatment of Ni[S2P(OiPr)2]2 with 1 and 2, respectively, resulted, in addition to di(carboxylato)nickel(ii) derivatives, in isolation of Ph3Bi and the disulphane [(iPrO)2P(S)S]2. New coordination polymers were obtained by reacting 1 and 2 with various silver(i) salts: [Ag{Ph3Bi[O(O)CC5H4N-4]2}(OTf)] (5), [Ag{Ph3Bi[O(O)CC5H4N-3]2}(OTf)]·CH2Cl2 (6·CH2Cl2), [Ag{Ph3Bi[O(O)CC5H4N-4]2}](SbF6)·2THF (7·2THF), [Ag{Ph3Bi[O(O)CC5H4N-3]2}](SbF6)·CH2Cl2 (8·CH2Cl2) and [Ag{Ph3Bi[O(O)CC5H4N-3]2}(NO3)]·CH2Cl2 (9·CH2Cl2). The crystal structures of 5 and 6 can be described as 1-D chains linked by triflate bridges in pairs of chains and 2-D networks, respectively. Compound 7 features a 2-D grid-like topology of the network, with tecton 1 acting as a tridentate ligand through both nitrogen and one oxygen atoms. The linker 2 molecules adopt either cis (compound 6) or trans (compounds 8 and 9) conformation. Complexes 8 and 9 are 1-D chain polymers exhibiting zig-zag and wavy motifs, respectively. The dimensionality of the structures is extended by the presence of supramolecular interactions (ππ, AgAg, AgO).

Synthesis, structure, and properties of a lantern-type dinuclear rhodium(II) complex cis-[Rh2(4-Me-pf)2(O2CCMe3)2], 4-Me-pf− = N,N′-di-p-tolylformamidinate anion

A lantern-type dinuclear complex cis-[Rh2(4-Me-pf)2(O2CCF3)2] (1) (4-Me-pf− = N,N′-di-p-tolylformamidinate anion) was reacted with an excess of pivalic acid in an aqueous NaOH solution with CHCl3/MeOH (1:3 vol./vol.) at room temperature for 24 h with stirring to give cis-[Rh2(4-Me-pf)2(O2CCMe3)2] (2). A single crystal obtained by recrystallization of 1 from an acetonitrile solution was employed for X-ray crystal structure analysis. The analysis showed that the obtained complex was a cis-[Rh2(4-Me-pf)2(O2CCMe3)2(MeCN)2] (2(MeCN)2) with a lantern-type dinuclear structure and a cis-(2:2) arrangement of the two formamidinato and two carboxylato ligands around the dirhodium(II) core, similar to the previously reported crystal structures for 1(H2O)2·0.5C6H6 and 1(MeCN)2. Complex 2 showed absorption bands at 613, 506, 435, and 344 nm in MeCN, while complex 1 showed the bands at 516, 460, and 326 nm in MeCN. All the bands observed for 1 and 2 were reasonably assigned using time-dependent density functional theory calculation. Moreover, it was confirmed that the electron-donating t-butyl groups on the carboxylato bridges of 2 give rise to negative shifts in the redox potentials (E 1/2 = 0.32 and 1.22 V (vs. SCE) in CH2Cl2) for Rh 2 II,II /Rh 2 II,III and Rh 2 II,III /Rh 2 III,III processes relative to those of 1 (E 1/2 = 0.71 and 1.47 V (vs. SCE) in CH2Cl2) that has electron-withdrawing fluorine groups on the carboxylate bridges.

Impact of the equatorial coordination sphere on the rate of reduction, lipophilicity and cytotoxic activity of platinum(IV) complexes

The impact of the equatorial coordination sphere on the reduction behavior (i.e. rate of reduction) of platinum(IV) complexes with axial carboxylato ligands was studied. Moreover, the influence of equatorial ligands on the stability, lipophilicity and cytotoxicity of platinum(IV) compounds was evaluated. For this purpose, a series of platinum(IV) complexes featuring axial carboxylato ligands (succinic acid monoesters) was synthesized; anionic carboxylato (OAc−, oxalate) and halido (Cl−, Br−, I−) ligands served as leaving groups and am(m)ine carrier ligands were provided by monodentately (isopropylamine, ammine+cyclohexaneamine) or bidentately (ethane-1,2-diamine) coordinating am(m)ines. All platinum(IV) products were fully characterized based on elemental analysis, high resolution mass spectrometry and multinuclear (1H, 13C, 15N, 195Pt) NMR spectroscopy as well as by X-ray diffraction in some cases. The rate of reduction in the presence of ascorbic acid was determined by NMR spectroscopy and the lipophilicity of the complexes was investigated by analytical reversed phase HPLC measurements. Cytotoxic properties were studied by means of a colorimetric microculture assay in three human cancer cell lines derived from cisplatin sensitive ovarian teratocarcinoma (CH1/PA-1) as well as cisplatin insensitive colon carcinoma (SW480) and non-small cell lung cancer (A549).

The Structural Chemistry of Stable High‐Spin Nitrosyl–Iron(II) Compounds with Aminecarboxylato Co‐Ligands in Aqueous Solution

Four crystalline nitrosyl–iron compounds of the {FeNO}7(S = 3/2) type with aminecarboxylato co‐ligands were prepared from aqueous solutions of iron(II) sulfate, an equimolar amount of one of the co‐ligands ethylenediamine‐N,N′‐diacetate (edda), nitrilotriacetate (nta), N,N′‐bis(2‐hydroxyethyl)ethylenediamine‐N,N′‐diacetate (bhedda) or ethylenediamine‐N,N,N′,N′‐tetraacetate (edta) and gaseous nitric oxide. The hemihydrate [Fe(edda)(H2O)(NO)]·0.5H2O (1·0.5H2O), a hydrated coordination polymer [{Fe(H2O)4}{Fe(NO)(nta)}2]n/n·2H2O = [Fe(H2O)4(2)2]n/n·2H2O with [Fe(NO)(nta)]– (2) monoanions, the solvent‐free complex [Fe(bhedda)(NO)] (3) and another coordination polymer [Fe(H2O)2{Fe(NO)(Hedta)}2]n/n = [Fe(H2O)2(4)2]n/n with [Fe(Hedta)(NO)]– (4) monoanions were investigated by crystallography and IR and UV/Vis spectroscopy. Structural peculiarities, such as a tilt of the NO ligand toward the O atom of a neighbouring carboxylato ligand, were analysed by DFT calculations. The stability of the aqueous solutions of the target compounds against inert‐gas stripping was related to the low amount of the less stable aqua complex [Fe(H2O)5(NO)]2+ in the aqueous equilibria in addition to the intrinsic stability of the species.

Co(II) ethylene glycol carboxylates for Co3O4 nanoparticle and nanocomposite formation

Ethylene glycol-functionalized Co(II) carboxylates [Co(CO2CH2(OC2H4) n OMe)2] (2a, n = 1; 2b, n = 2), [Co(CO2CHPh(OC2H4)2OMe)2] (2c) and [Co(CO2CMe2(O–C2H4)2OMe)2] (2d) have been synthesized by the reaction of [Co(OAc)2·4H2O] with the corresponding acids MeO(C2H4O) n CRR′CO2H (n = 1, 2; R=H, R′=Me; R=H, R′=Ph). Based on the IR spectroscopic studies, the binding motif of the carboxylato ligands to cobalt is discussed. Thermogravimetry and mass spectrometry studies were carried out in order to investigate the thermal decomposition mechanism of 2a–2d in the solid state. Based on the result obtained, complex 2b was chosen as single-source precursor for the generation and stabilization of Co3O4 nanoparticles (NPs) by solid-state thermal decomposition in air. Depending on the decomposition time, NPs with different chemical composition (consisting of Co3O4, CoO and Co) and with crystallite sizes ranging from 9 to 18 nm were obtained. Furthermore, the preparation of cobalt oxide-based nanocomposites by twin polymerization of 2,2′-spirobi[4H-1,3,2-benzodioxasiline] (3) in the presence of 2b is reported. After treatment of the as-prepared hybrid material by either oxidation or etching, the respective mesoporous carbon/silica (IUPAC type IV isotherms) matrices were obtained. Quenched solid and nonlinear density functional theory calculations gave a surface area of 1040 cm2 g−1 for the respective carbon and 336 cm2 g−1 for the appropriate silica material. Powder X-ray diffraction measurements confirm the formation of Co3O4 NPs in both components. High-angle annular dark field scanning transmission electron microscopy revealed well-distributed particles within the silica matrix, whereas no particles were found in the carbon material. The electrochemical properties of the composite materials have been investigated by cyclic voltammetry. The respective silica material shows five reduction events (Co3O4 to CoO, CoO to Co), while no redox potentials occurred for the Co3O4 NPs embedded in the carbon matrix.

Simulating the active sites of copper-trafficking proteins. Density functional structural and spectroscopy studies on copper(I) complexes with thiols, carboxylato, amide and phenol ligands

A series of mononuclear binary and ternary Cu(I) complexes with formato, formamide, methylphenol, and methanethiolato ligands were optimized at DFT-B3LYP/6-31G** (BS1) and DFT-B3LYP/6-311++G** (BS2) levels of theory. The solvent effect was taken into account via PCM method (BS1W and BS2W, respectively). The coordination arrangement for [CuI(SCH3/S(H)CH3)(OOCH)]−/0 and [CuI(SCH3/S(H)CH3)(O(H)(C6H4)CH3)]0/+ was pseudo-linear and for [CuI(SCH3/S(H)CH3)(OOCH)(OC(H)NH2)]−/0 was pseudo-trigonal. The [CuI(S-S(H)CH3/CuI(S-SCH3)]+/0 link even to amide carbonyl and to general O(H)R residues (R=C6H5CH3). [CuI(SCH3)2(O(H)(C6H4)CH3)]− went towards dissociation of the O(H)(C6H4)CH3 ligand, whereas [CuI(S(H)CH3)2(O(H)(C6H4)CH3)]+ converged nicely, maintaining the hydroxy function linked to the metal. The trends of total electronic energies seemed to be significant, suggesting that linear CuIS2 coordination is more suitable than CuIS, CuIS3 and CuIS4 arrangements. The formation energies of [CuI(S(H)CH3/SCH3)(OOCH)]0/−1 were higher than those of [CuI(S(H)CH3/SCH3)2]+/− on starting from [CuI(S(H)CH3/CuI(SCH3)]+/0 by ca. 11–9 kcal mol−1 (BS2W). The structural arrangements, bond distances, and angles as well as computed spectroscopic parameters resulted in good agreement with experimental data for corresponding synthetic complexes and with metal site regions of several copper(I)-proteins. These data help in interpreting structural data of complex biological systems and in constructing reliable force fields for molecular mechanics computations.