Chiral Heterometallic Cu8Ln4 Complexes with Enantiopure Schiff Base Ligands: Synthesis, Structural, Spectroscopic and Magnetic Studies.

The enantiomerically pure Schiff base ligands H2L-S and H2L-R yield chiral heterometallic dodecanuclear complexes of the form [Cu8Ln4(OH)8(OMe)4(O2CBut)8(L-S or L-R)4(H2O)4] where LnIII=Gd (1S), Tb (2S), Dy (3S, 3R), Ho (4S, 4R), Er (5S) or Y (6S, 6R) and H2L=(S or R)-2-{[(1-hydroxypropan-2-yl)imino]methyl}-6-methoxyphenol. The complexes are isomorphous and crystallize in the non-centrosymmetric polar space group C2 in enantiomeric conformation. The chirality of the Schiff base ligands originates from the respective S- or R- enantiomer of 2-aminopropan-1-ol, is imparted to the complexes and to the crystals that belong to non-centrosymmetric space group. The chirality and enantiomeric conformation of all complexes are retained in dmso solutions as confirmed by Circular Dichroism spectra which consist of mirror images, expected for enantiomeric pairs. All complexes consist of four distorted cubane-like subunits [Cu2Ln2(µ3-OH)2(µ3-OMe)(µ3-OR)], which share the LnIII ions and result in a cyclic distorted tetragonal arrangement; each edge of the {LnIII 4} quadrilateral is occupied by two µ-OH- ions that further bridge to a CuII ion. Magnetic susceptibility measurements revealed ferromagnetic interactions for 3S with LnIII=Dy and antiferromagnetic interactions for all other complexes. AC susceptibility data of 3S under 1 kOe external dc field indicate slow magnetic relaxation phenomena below 2 K.

Reactions of Cadmium(II) Halides and Di-2-Pyridyl Ketone Oxime: One-Dimensional Coordination Polymers.

The coordination chemistry of 2-pyridyl ketoximes continues to attract the interest of many inorganic chemistry groups around the world for a variety of reasons. Cadmium(II) complexes of such ligands have provided models of solvent extraction of this toxic metal ion from aqueous environments using 2-pyridyl ketoxime extractants. Di-2-pyridyl ketone oxime (dpkoxH) is a unique member of this family of ligands because its substituent on the oxime carbon bears another potential donor site, i.e., a second 2-pyridyl group. The goal of this study was to investigate the reactions of cadmium(II) halides and dpkoxH in order to assess the structural role (if any) of the halogeno ligand and compare the products with their zinc(II) analogs. The synthetic studies provided access to complexes {[CdCl2(dpkoxH)∙2H2O]}n (1∙2H2O), {[CdBr2(dpkoxH)]}n (2) and {[CdI2(dpkoxH)]}n (3) in 50-60% yields. The structures of the complexes were determined by single-crystal X-ray crystallography. The compounds consist of structurally similar 1D zigzag chains, but only 2 and 3 are strictly isomorphous. Neighboring CdII atoms are alternately doubly bridged by halogeno and dpkoxH ligands, the latter adopting the η1:η1:η1:µ (or 2.0111 using Harris notation) coordination mode. A terminal halogeno group completes distorted octahedral coordination at each metal ion, and the coordination sphere of the CdII atoms is {CdII(η1 - X)(µ - X)2(Npyridyl)2(Noxime)} (X = Cl, Br, I). The trans-donor-atom pairs in 1∙2H2O are Clterminal/Noxime and two Clbridging/Npyridyl; on the contrary, these donor-atom pairs are Xterminal/Npyridyl, Xbridging/Noxime, and Xbridging/Npyridyl (X = Br, I). There are intrachain H-bonding interactions in the structures. The packing of the chains in 1∙2H2O is achieved via π-π stacking interactions, while the 3D architecture of the isomorphous 2 and 3 is built via C-H∙∙∙Cg (Cg is the centroid of one pyridyl ring) and π-π overlaps. The molecular structures of 1∙2H2O and 2 are different compared with their [ZnX2(dpkoxH)] (X = Cl, Br) analogs. The polymeric compounds were characterized by IR and Raman spectroscopies in the solid state, and the data were interpreted in terms of the known molecular structures. The solid-state structures of the complexes are not retained in DMSO, as proven via NMR (1H, 13C, and 113Cd NMR) spectroscopy and molar conductivity data. The complexes completely release the coordinated dpkoxH molecule, and the dominant species in solution seem to be [Cd(DMSO)6]2+ in the case of the chloro and bromo complexes and [CdI2(DMSO)4].

Mitochondriotropic agents conjugated with NSAIDs through metal ions against breast cancer cells.

Two copper(I) polymorphs of formula [Cu(SALH)(TPP)3] (1a and 1b) were prepared by the conjugation of the Non-Steroidal Anti-Inflammatory Drug (NSAID) salicylic acid (SALH2) with the mitochondriotropic agent triphenylphosphine (TPP) via metal ion. For comparison, the isomorph [Ag(SALH)(TPP)3] (2) was prepared. The conjugates 1a, 1b and 2 were characterized by melting point (m.p.), Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy, Ultraviolet-Visible (UV-Vis) spectroscopy and nuclear magnetic resonance (1H NMR). The crystal structures of 1a, 1b and 2 were confirmed by X-ray diffraction crystallography (XRD). The ex vivo binding affinity of 1-2 towards CT (calf thymus)-DNA was studied by UV, fluorescence, viscosity and DNA Thermal Denaturation studies. Their inhibitory activity against lipoxygenase (LOX) (an enzyme which is mainly located in the mitochondrion) was determined. The in vitro activity of 1-2 was evaluated against human breast cancer cell lines MCF-7 (hormone depended (HD)) and MDA-MB 281 (hormone independent (HI)) cells. Compounds 1-2 inhibit stronger than cisplatin the cancerous cells. The molecular mechanism of action of 1-2 was suspected by the MCF-7 cells morphology and confirmed by DNA fragmentation, Acridine Orange/Ethidium Bromide (AO/EB) Staining and mitochondrial membrane permeabilization tests.

First total synthesis of type II abyssomicins: (±)-abyssomicin 2 and (±)-neoabyssomicin B.

The intramolecular Diels-Alder reaction (IMDA) of a butenolide derivative, as an entry to the type II abyssomicin scaffold, and the total synthesis of (±)-abyssomicin 2 and (±)-neoabyssomicin B are reported for the first time. A facile route to the IMDA precursor, the formation of a type I intermediate and two paths to (±)-neoabyssomicin B are also discussed.

Synthesis and structural, magnetic and spectroscopic characterization of iron(III) complexes with in situ formed ligands from methyl-2-pyridyl ketone transformations.

Reactions of methyl-2-pyridyl ketone, pyCOMe, with FeCl3·6H2O in various solvents gave complexes [Fe4Cl6(OMe)2(L1)2]·0.7MeCN·0.4MeOH (1·0.7MeCN·0.4MeOH) and [Fe3Cl4(bicine)(L2)]·Me2CO·0.2H2O (2·Me2CO·0.2H2O). The ligands (L1)2- = pyCO(Me)CHCOpy (in 1) and (L2)2- = pyCO(Me)CH2CO(OMe)py (in 2) are formed in situ, through an aldol reaction-type mechanism between the carbanion pyC(O)CH2- (formed by the nucleophilic attack of the MeO- in pyCOMe) and pyCOMe which results in the formation of a new C-C bond. The intermediate compound undergoes attack in the -CH2- or -CO- group by a MeO- group, and the new ligands (L1)2- and (L2)2-, respectively, are formed. The molecular structure of 1 consists of three corner-sharing [Fe2O2] rhombic units in cis-arrangement. The two terminal FeIII ions display distorted square pyramidal geometry and the two central FeIII ions are distorted octahedral. The molecular structure of 2 consists of two corner-sharing [Fe2O2] rhombic units, with the two terminal FeIII ions in distorted square pyramidal geometry and the central FeIII in distorted octahedral. The differentiation in the coordination environment of the FeIII ions in 1-2 is reflected in the values of the Mössbauer hyperfine parameters. In agreement with theoretical calculations, the square pyramidal sites exhibit a smaller isomer shift value in comparison to the octahedral sites. Magnetic studies indicate antiferromagnetic interactions leading to an S = 0 ground state in 1 and to an S = 5/2 ground state in 2, consistent with Electron Paramagnetic Resonance spectroscopy. Mössbauer spectra of 2 indicate the onset of relaxation effects below 80 K. At 1.5 K the spectrum of 2 consists of magnetic sextets. The determined hyperfine magnetic fields are consistent with the exchange coupling scheme imposed by the crystal structure of 2. Theoretical calculations shed light on the differences in the electronic structure between the square pyramidal and the octahedral sites.

A family of mono-, di-, and tetranuclear DyIII complexes bearing the ligand 2,6-diacetylpyridine bis(picolinoylhydrazone) and exhibiting slow relaxation of magnetization.

The systematic investigation of the general reaction scheme DyIII/X-/LH2, where X- = Cl-, CF3SO3-, ClO4-, MeCO2-, and LH2 is the pocket-type ligand 2,6-diacetylpyridine bis(picolinoylhydrazone), resulting from the condensation of 2,6-diacetylpyridine with picolinic acid hydrazide, has led to a new family of mono-, di-, and tetranuclear metal complexes of the formulae [DyCl2(LH2)(MeOH)]Cl (1), [Dy2(O3SCF3)2(LH)2(MeOH)1.42(H2O)0.58](O3SCF3)2 (2), [Dy2(LH)2(MeOH)2(H2O)2](ClO4)4 (3), and [Dy4(OH)2(O2CMe)6(L)2] (4), respectively. The organic chelate undergoes metal-assisted amide-iminol tautomerism and adopts the neutral zwitterionic, and single- and double-deprotonated forms, respectively, upon coordination with the metal center(s). Interestingly, the different forms of the ligand LH2/LH-/L2- act independently as penta-, hexa-, and heptadentate, either as single-chelating or chelating and bridging, thus yielding new DyIII compounds of various nuclearities and different magnetic properties. All complexes 1-4 exhibit frequency-dependent, out-of-phase (χ''M) tails of signals in zero external dc field, characteristic of the onset of quantum tunnelling of magnetization. Attempts to suppress the tunnelling through the application of an external dc field were mostly successful in the case of complex 1, where entirely visible peaks of χ''M have been observed and rendered possible the fit of the data to the Arrhenius equation, thus yielding the parameters: Ueff = 10.9(1) K and τ0 = 1.9(1) × 10-6 s, where Ueff is the effective energy barrier for the magnetization reversal and τ0 is the pre-exponential factor. The combined results demonstrate the ability of pyridyl-bis(acylhydrazone) ligands to yield chemically, structurally, and magnetically interesting compounds through their rich interconversion between various amide-iminol resonance forms.

Two different coordination modes of the Schiff base derived from ortho-vanillin and 2-(2-aminomethyl)pyridine in a mononuclear uranyl complex.

This work describes the reaction of the potentially tetradentate Schiff-base ligand N-(2-pyridylmethy)-3-methoxysalicylaldimine (HL) with UO2(O2CMe)2·2H2O and UO2(NO3)2· 6H2O in MeOH in the absence or presence of an external base, respectively. The product from these reactions is the mononuclear complex [UO2(L)2] (1). Its structure has been determined by single-crystal, X-ray crystallography. The anionic ligand adopts two different coordination modes (1.1011, 1.1010; Harris notation) in the complex. The new compound was fully characterized by solid-state (IR, Raman and Photoluminescence spectroscopies) and solution (UV-Vis and 1H NMR spectra, conductivity measurements) techniques.

Effects of the halogenido ligands on the Kumada-coupling catalytic activity of [Ni{ t BuN(PPh2)2-κ2P}X2], X = Cl, Br, I, complexes.

Novel nickel(ii) complexes bearing ( t butyl)bis(diphenylphosphanyl)amine and different halogenido ligands, [Ni(P,P)X2] = [Ni{ t BuN(PPh2)2-κ2P}X2], (X = Cl, Br, I) are prepared, characterized by IR and NMR spectroscopy, mass spectrometry and X-ray crystallography, and tested as catalysts in the Kumada cross-coupling reaction of model substituted iodobenzenes and p-tolylmagnesium bromide. The data obtained together with DFT calculations indicate that these new catalysts operate in the Ni(i)-Ni(iii) mode. The highest catalytic activity and selectivity are exhibited by [Ni(P,P)Cl2], which is most easily reduced by the used Grignard reagent to the Ni(i) state. This process is much more energy demanding in the case of the bromido and iodido complexes, causing the appearance of the induction period. [Ni(P,P)Cl2] is also very active in the cross-couplings of substrates with iodine atoms sterically shielded by ortho substituents. The data obtained are in good accordance with the described positive effect of the increased electron-releasing power of N-substituents R' on the overall catalytic performance of [Ni{R'N(PPh2)2-κ2P}X2] complexes.

Conjugation of triphenylantimony(V) with carvacrol against human breast cancer cells.

The organoantimony derivative of formula trans-O,O-[Ph3SbV(Carv)2] (TPAC) (CarvH = carvacrol) is obtained by the oxidation of triphenylstibine (Ph3SbIII) with hydrogen peroxide in the presence of carvacrol (CarvH). Physical methods such as X-ray Fluorescence (XRF) spectroscopy, single crystal and powder X-ray diffraction analysis (XRD and PXRD), Attenuated Total Reflection Fourier Transform Infra-red (ATR-FTIR) spectroscopy, Thermogravimetric Differential Thermal Analysis (TG-DTA) and Differential Scanning Calorimetry (DTG/DSC), confirm the retention of the formula of TPAC throughout the sample mass in solid state, while UV-Vis spectroscopy in the solution. TPAC is the first example of carvacrol (the main ingredient of oregano) covalently bonded to any metal ion. Only the trans-O,O-[Ph3Sb(Carv)2] isomer was isolated suggesting stereo-selectivity of the preparation route. TPAC inhibits in vitro both human breast adenocarcinoma cell lines: MCF-7 (positive to hormones receptor (HR +)), MDA-MB-231 (negative to hormones receptor (HR-)) stronger than normal human fetal lung fibroblast cells (MRC-5). The MCF-7 cells morphology, DNA fragmentation, Acridine Orange/Ethidium Bromide (AO/EB) Staining, cell cycle arrest and mitochondrial membrane permeabilization tests suggest an apoptotic pathway for cell death, especially, through the mitochondrion damage. The binding type of TPAC toward the calf thymus CT-DNA was initially deduced ex vivo from the differentiation of the DNA solution viscosity. Fluorescence spectroscopy confirms the interaction mode suggested. Spectroscopic evidence (FTIR, UV-Vis) suggest that glutathione (GSH) (a tripeptide over-expressed in tumor cells) induces conversion of non-active pentavalent antimony, which is contained in TPAC, to active trivalent one, providing a new strategy for the development of targeted chemotherapeutics.

Synthesis, Crystal Structure, and Broadband Emission of (CH3)3SSnCl3.

We report here on the synthesis, crystal structure, optoelectronic and vibrational properties, as well as the DFT calculations of the novel trimethylsulfonium tin trichloride (CH3)3SSnCl3. The air-stable compound is prepared by reacting the (CH3)3SCl and SnCl2 solid precursors in evacuated silica tubes at 100 °C. According to powder X-ray diffraction and Rietveld refinement, it crystallizes at room temperature in the orthorhombic space group Pbca (No. 61) with isolated pyramids of [SnCl3]- and (CH3)3S+ units. UV-vis reflectance and photoluminescence spectroscopies reveal a direct energy band gap of 3.85 eV, accompanied by a broad Stokes-shifted luminescence signal. Photoexcitation of the compound at room temperature and at -196 °C results in broadband luminescence with weak magenta emission centered at 400 nm using an excitation at 250 nm. First principal calculations provide insight into the physical properties through the electron and phonon density of states. Multitemperature Raman spectroscopy and differential scanning calorimetry reveal a reversible phase transition at ca. 70 °C that affects the vibrational modes of the [SnCl3]-. By dissolving (CH3)3SSnCl3 in dimethylformamide in ambient air for a week, oxidation of tin occurs in the "defect" perovskite ((CH3)3S)2SnCl6. The crystal structure of ((CH3)3S)2SnCl6 is also determined with high accuracy via single-crystal X-ray diffraction (cubic space group Pa-3 (No. 205)) and compared with (CH3)3SSnCl3 via Hirshfeld surface analysis.

Effective Labeling of Amine Pharmacophores through the Employment of 2,3-Pyrazinedicarboxylic Anhydride and the Generation of fac-[M(CO)3(PyA)P] and cis-trans-[M(CO)2(PyA)P2] Complexes (PyA = Pyrazine-2-carboxylate, P = Phosphine, M = Re, 99mTc).

The fac-[M(CO)3(PyA)(P)] and cis-trans-[M(CO)2(PyA)(P)2] neutral complexes (M is Re or 99mTc), based on the mixed ligand strategy with pyrazine-2-carboxylic acid (PyAH) as the bidentate N,O and triphenylphosphine as the monodentate P ligand, are presented. Through the employment of the anhydride of pyrazine-2,3-dicarboxylic acid (PyDA), the PyAH scaffold was conveniently derivatized with the model bioactive amine 1-(2-methoxyphenyl)piperazine, the active part of the 5-HT1A antagonist WAY100635. Reaction of either PyAH or the pharmacophore-bearing PyAH ligand (L1H) with fac-[M(CO)3]+ core in water yielded the intermediate fac-[M(CO)3(PyA)(H2O)] complexes. The labile aqua ligand was easily replaced by PPh3 to yield the fac-[Re(CO)3(PyA)(PPh3)] complexes, while in toluene under reflux, the cis-trans-[Re(CO)2(PyA)(PPh3)2] complexes were obtained. The latter complexes were alternatively obtained from mer-[Re(CO)3(PPh3)2Cl] by refluxing with the PyA ligand in toluene. The analogous 99mTc complexes were synthesized quantitatively, showing excellent stability in competition studies. The methodology described herein represents a practical procedure for the effective integration of the fac-[M(CO)3]+ core with amine-bearing biologically active compounds for diagnosis/therapy.

Pentanuclear Thorium(IV) Coordination Cluster from the Use of Di(2-pyridyl) Ketone.

The Th(NO3)4·5H2O/di(2-pyridyl) ketone [(py)2CO] reaction system gives a pentanuclear cluster containing the doubly deprotonated form of the gem-diol derivative of the ligand. The cluster consists of a tetrahedral arrangement of four ThIV ions centered on the fifth ion, which is the first characterized ThIV5 complex. The analysis of its structure reveals that this is a Kuratowski-type coordination compound.

Evaluation of Insulin-Like Activity of Novel Zinc Metal-Organics toward Adipogenesis Signaling.

Diabetes mellitus is a debilitating disease, plaguing a significant number of people around the globe. Attempts to develop new drugs on well-defined atoxic metalloforms, which are capable of influencing fundamental cellular processes overcoming insulin resistance, has triggered an upsurge in molecular research linked to zinc metallodrugs. To that end, meticulous efforts were launched toward the design and synthesis of materials with insulin mimetic potential. Henceforth, trigonelline and N-(2-hydroxyethyl)-iminodiacetic acid (HEIDAH2) were selected as organic substrates seeking binding to zinc (Zn(II)), with new crystalline compounds characterized by elemental analysis, FT-IR, X-rays, thermogravimetry (TGA), luminescence, NMR, and ESI-MS spectrometry. Physicochemical characterization was followed by in vitro biochemical experiments, in which three out of the five zinc compounds emerged as atoxic, exhibiting bio-activity profiles reflecting enhanced adipogenic potential. Concurrently, well-defined qualitative-quantitative experiments provided links to genetic loci responsible for the observed effects, thereby unraveling their key involvement in signaling pathways in adipocyte tissue and insulin mimetic behavior. The collective results (a) signify the quintessential role of molecular studies in unearthing unknown facets of pathophysiological events in diabetes mellitus II, (b) reflect the close associations of properly configured molecular zincoforms to well-defined biological profiles, and (c) set the stage for further physicochemical-based development of efficient zinc antidiabetic metallodrugs.

Dinuclear Lanthanide(III) Complexes from the Use of Methyl 2-Pyridyl Ketoxime: Synthetic, Structural, and Physical Studies.

The first use of methyl 2-pyridyl ketoxime (mepaoH) in homometallic lanthanide(III) [Ln(III)] chemistry is described. The 1:2 reactions of Ln(NO3)3·nH2O (Ln = Nd, Eu, Gd, Tb, Dy; n = 5, 6) and mepaoH in MeCN have provided access to complexes [Ln2(O2CMe)4(NO3)2(mepaoH)2] (Ln = Nd, 1; Ln = Eu, 2; Ln = Gd, 3; Ln = Tb, 4; Ln = Dy, 5); the acetato ligands derive from the LnIII-mediated hydrolysis of MeCN. The 1:1 and 1:2 reactions between Dy(O2CMe)3·4H2O and mepaoH in MeOH/MeCN led to the all-acetato complex [Dy2(O2CMe)6(mepaoH)2] (6). Treatment of 6 with one equivalent of HNO3 gave 5. The structures of 1, 5, and 6 were solved by single-crystal X-ray crystallography. Elemental analyses and IR spectroscopy provide strong evidence that 2-4 display similar structural characteristics with 1 and 5. The structures of 1-5 consist of dinuclear molecules in which the two LnIII centers are bridged by two bidentate bridging (η1:η1:µ2) and two chelating-bridging (η1:η2:µ2) acetate groups. The LnIII atoms are each chelated by a N,N'-bidentate mepaoH ligand and a near-symmetrical bidentate nitrato group. The molecular structure of 6 is similar to that of 5, the main difference being the presence of two chelating acetato groups in the former instead of the two chelating nitrato groups in the latter. The geometry of the 9-coordinate LnIII centers in 1, 5 and 6 can be best described as a muffin-type (MFF-9). The 3D lattices of the isomorphous 1 and 5 are built through H-bonding, π⋯π stacking and C-H⋯π interactions, while the 3D architecture of 6 is stabilized by H bonds. The IR spectra of the complexes are discussed in terms of the coordination modes of the organic and inorganic ligands involved. The Eu(III) complex 2 displays a red, metal-ion centered emission in the solid state; the TbIII atom in solid 4 emits light in the same region with the ligand. Magnetic susceptibility studies in the 2.0-300 K range reveal weak antiferromagnetic intramolecular GdIII…GdIII exchange interactions in 3; the J value is -0.09(1) cm-1 based on the spin Hamiltonian H = -J(SGd1·SGd2).

Metal-Organic Frameworks: Synthetic Methods and Potential Applications.

Metal-organic frameworks represent a porous class of materials that are build up from metal ions or oligonuclear metallic complexes and organic ligands. They can be considered as sub-class of coordination polymers and can be extended into one-dimension, two-dimensions, and three-dimensions. Depending on the size of the pores, MOFs are divided into nanoporous, mesoporous, and macroporous items. The latter two are usually amorphous. MOFs display high porosity, a large specific surface area, and high thermal stability due to the presence of coordination bonds. The pores can incorporate neutral molecules, such as solvent molecules, anions, and cations, depending on the overall charge of the MOF, gas molecules, and biomolecules. The structural diversity of the framework and the multifunctionality of the pores render this class of materials as candidates for a plethora of environmental and biomedical applications and also as catalysts, sensors, piezo/ferroelectric, thermoelectric, and magnetic materials. In the present review, the synthetic methods reported in the literature for preparing MOFs and their derived materials, and their potential applications in environment, energy, and biomedicine are discussed.

Novel silver glycinate conjugate with 3D polymeric intermolecular self-assembly architecture; an antiproliferative agent which induces apoptosis on human breast cancer cells.

The new water soluble silver(I) complex of glycine (GlyH) with formula [Ag3(Gly)2NO3]n (AGGLY) was synthesized. The compound was characterized by melting point (m.p.), Fourier-transform infrared (FT-IR), Ultraviolet-visible (UV-vis) and Nuclear Magnetic Resonance (1H-,13C NMR) spectroscopic techniques and X-ray crystallography. The in vitro cytotoxic activity of AGGLY against human breast adenocarcinoma cell lines: MCF-7 (hormone depended (HD)) and MDA-MB-231 (hormone independent (HI)) was determined. For comparison other adenocarcinoma cells such as human cervical adenocarcinoma (HeLa) cells and lung adenocarcinoma cells (A549) were also screened. AGGLY inhibits both breast cancer cell lines stronger than cisplatin. On the contrary, AGGLY, exhibits lower toxicity against fetal lung fibroblast (MRC-5) cells than cisplatin. Its genotoxicity against MRC-5 cells was detected from the presence or absence of micronucleus using fluorescence microscopy, while the in vivo genotoxicity was evaluated using Allium cepa model. The MCF-7 cells morphology suggests apoptotic pathway for their death. The apoptotic pathway was confirmed by cell cycle arrest, Acridine Orange/Ethidium Bromide (AO/EB) Staining, and permeabilization of the mitochondrial membrane tests. The molecular mechanism of action was further studied by the binding affinity of AGGLY towards the calf thymus (CT) DNA.

Further synthetic investigation of the general lanthanoid(iii) [Ln(iii)]/copper(ii)/pyridine-2,6-dimethanol/carboxylate reaction system: {CuLn} coordination clusters (Ln = Dy, Tb, Ho) and their yttrium(iii) analogue.

In addition to previously studied {CuGd6}, {CuGd4}, {CuLn7} and {CuLn8} coordination clusters (Ln = trivalent lanthanide) containing pdm2- or Hpdm- ligands (H2pdm = pyridine-2,6-dimethanol) and ancillary carboxylate groups (RCO2-), the present work reports the synthesis and study of three new members of a fifth family of such complexes. Compounds [Cu5Ln4O2(OMe)4(NO3)4(O2CCH2But)2(pdm)4(MeOH)2] (Ln = Dy, 1; Ln = Tb, 2; Ln = Ho, 3) were prepared from the reaction of Ln(NO3)3·xH2O (x = 5, 6), CuX2·yH2O (X = ClO4, Cl, NO3; y = 6, 2 and 3, respectively), H2pdm, ButCH2CO2H and Et3N (2 : 2.5 : 2 : 1 : 9) in MeCN/MeOH. Rather surprisingly, the copper(ii)/yttrium(iii) analogue has a slightly different composition, i.e. [Cu5Y4O2(OMe)4(NO3)2(O2CCH2But)4(pdm)4(MeOH)2] (4). The structures of 1·4MeCN·1.5MeOH and 4·2MeOH were solved by single-crystal X-ray crystallography. The five CuII and four DyIII centres in 1 are held together by two µ5-O2-, four µ-MeO-, two syn,synη1:η1:µ ButCH2CO2-, four η2:η1:η2:µ3 pdm2- (each of these groups chelates a CuII atom and simultaneously bridges two DyIII atoms through its two -CH2O- arms) and two µ-MeOH ligands. The four terminal nitrato groups each chelate (η1:η1) a DyIII centre. The five CuII atoms are co-planar (by symmetry) forming a bow-tie arrangement; the four outer CuII atoms form a rectangle with edges of 3.061(1) and 6.076(1) Å. The four DyIII centres also form a rectangle that lies above and below the plane of the CuII centres, with edges of 3.739(1) and 5.328(1) Å. The two strictly planar rectangles are almost perpendicular. Two trigonal bipyramidal µ5-O2- groups link the perpendicular Cu5 and Dy4 frameworks together. The molecule 4 has a very similar structure to that of 1, differences being the replacement of the two chelating nitrato groups of 1 by two chelating ButCH2CO2- ligands in 4 and the coordination polyhedra of the LnIII and YIII atoms (Snub diphenoids in 1 and biaugmented trigonal prisms in 4). Dc magnetic susceptibility data (χM) on analytically pure samples of 1-3, collected in the 300-2 K range, indicate that ferromagnetic exchange interactions dominate leading to large spin ground states. The χMT vs. T data for 4 suggest moderately strong antiferromagnetic CuIICuII exchange interactions. Studies of the dynamic magnetic properties of the {Cu5Ln4} clusters show that 1 behaves as a SMM at zero field and 2 is a very weak field-induced SMM, while 3 exhibits only weak tails in the χ''Mvs. T plots at various ac frequencies at zero dc field.

Trinuclear NiII-LnIII-NiII Complexes with Schiff Base Ligands: Synthesis, Structure, and Magnetic Properties.

The reaction of the Schiff base ligand o-OH-C6H4-CH=N-C(CH2OH)3, H4L, with Ni(O2CMe)2∙4H2O and lanthanide nitrate salts in a 4 : 2 : 1 ratio lead to the formation of the trinuclear complexes [Ni2Ln(H3L)4(O2CMe)2](NO3) (Ln = Sm (1), Eu (2), Gd (3), Tb (4)). The complex cations contain the strictly linear NiII-LnIII-NiII moiety. The central LnIII ion is bridged to each of the terminal NiII ions through two deprotonated phenolato groups from two different ligands. Each terminal NiII ion is bound to two ligands in distorted octahedral N2O4 environment. The central lanthanide ion is coordinated to four phenolato oxygen atoms from the four ligands, and four carboxylato oxygen atoms from two acetates which are bound in the bidentate chelate mode. The lattice structure of complex 4 consists of two interpenetrating, supramolecular diamond like lattices formed through hydrogen bonds among neighboring trinuclear clusters. The magnetic properties of 1-4 were studied. For 3 the best fit of the magnetic susceptibility and isothermal M(H) data gave JNiGd = +0.42 cm-1, D = +2.95 cm-1 with gNi = gGd = 1.98. The ferromagnetic nature of the intramolecular Ni···Gd interaction revealed ground state of total spin S = 11/2. The magnetocaloric effect (MCE) parameters for 3 show that the change of the magnetic entropy (-ΔSm) reaches a maximum of 14.2 J kg-1 K-1 at 2 K. A brief literature survey of complexes containing the NiII-LnIII-NiII moiety is discussed in terms of their structural properties.

Synthesis, characterization, DNA binding and cytotoxicity studies of two novel Cu(II)-2-(2'-pyridyl) quinoxaline complexes.

Two novel copper (II) complexes, namely [Cu(2,2'-pq)(NO3)](NO3) (1) and [Cu(2,2'-pq)2(NO3)](NO3)·6H2O(2) where 2,2'-pq is 2-(2'-pyridyl quinoxaline) were synthesized and characterized by various spectral methods. Complex 2 characterized by single crystal X-ray diffraction showed a distorted trigonal bipyramidal geometry and crystallized together with an hexamer, (H2O)6 cluster, with R66(12) topology and chair conformation. The interaction of Calf Thymus DNA (CT-DNA) with 1 and 2 was investigated by UV-Visible absorption spectra, Viscosity, Cyclic Voltammetry, Fluorescence and Circular Dichroism (CD), indicating that both complexes can bind to DNA both by means of intercalation and groove binding. Their DNA interaction mode depends on their concentrations and the differences between their structures. Cleavage experiments were performed by agarose gel electrophoresis using pBR322 DNA both in dark and after illumination. Furthermore, the cytotoxicity of both complexes was evaluated against MCF-7 and healthy cells (HEK-293) by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays; moreover their cell uptake against MCF-7 tumor cells and HEK-293 normal cells was revealed by using confocal laser scanning. Both complexes have the potential to act as effective anticancer drugs with 2 to present an IC50 smaller than that of cis-platin and also to be useful for optically probing tumor cells since it fluoresces at blue and green when is treated with MCF-7 cells.

Unusual 31P Hyperfine Strain Effects in a Conformationally Flexible Cu(II) Complex Revealed by Two-Dimensional Pulse EPR Spectroscopy.

Strain effects on g and metal hyperfine coupling tensors, A, are often manifested in Electron Paramagnetic Resonance (EPR) spectra of transition metal complexes, as a result of their intrinsic and/or solvent-mediated structural variations. Although distributions of these tensors are quite common and well understood in continuous-wave (cw) EPR spectroscopy, reported strain effects on ligand hyperfine coupling constants are rather scarce. Here we explore the case of a conformationally flexible Cu(II) complex, [Cu{Ph2P(O)NP(O)Ph2-κ2O,O'}2], bearing P atoms in its second coordination sphere and exhibiting two structurally distinct CuO4 coordination spheres, namely a square planar and a tetrahedrally distorted one, as revealed by X-ray crystallography. The Hyperfine Sublevel Correlation (HYSCORE) spectra of this complex exhibit 31P correlation ridges that have unusual inverse or so-called "boomerang" shapes and features that cannot be reproduced by standard simulation procedures assuming only one set of magnetic parameters. Our work shows that a distribution of isotropic hyperfine coupling constants (hfc) spanning a range between negative and positive values is necessary in order to describe in detail the unusual shapes of HYSCORE spectra. By employing DFT calculations we show that these hfc correspond to molecules showing variable distortions from square planar to tetrahedral geometry, and we demonstrate that line shape analysis of such HYSCORE spectra provides new insight into the conformation-dependent spectroscopic response of the spin system under investigation.