Cationic Complexes Research Articles

Compressed and Expanded Lattices - Barriers to Spin-State Switching in Mn3+ Complexes.

We report the structural and magnetic properties of two new Mn3+ complex cations in the spin crossover (SCO) [Mn(R-sal2323)]+ series, in lattices with seven different counterions in each case. We investigate the effect on the Mn3+ spin state of appending electron-withdrawing and electron-donating groups on the phenolate donors of the ligand. This was achieved by substitution of the ortho and para positions on the phenolate donors with nitro and methoxy substituents in both possible geometric isomeric forms. Using this design paradigm, the [MnL1]+ (a) and [MnL2]+ (b) complex cations were prepared by complexation of Mn3+ to the hexadentate Schiff base ligands with 3-nitro-5-methoxy-phenolate or 3-methoxy-5-nitro-phenolate substituents, respectively. A clear trend emerges with adoption of the spin triplet form in complexes 1a-7a, with the 3-nitro-5-methoxy-phenolate donors, and spin triplet, spin quintet and thermal SCO in complexes 1b-7b with the 3-methoxy-5-nitro-phenolate ligand isomer. The outcomes are discussed in terms of geometric and steric factors in the 14 new compounds and by a wider analysis of electronic choices of Mn3+ with related ligands by comparison of bond length and angular distortion data of previously reported analogues in the [Mn(R-sal2323)]+ family. The structural and magnetic data published to date suggest a barrier to switching may exist for high spin forms of Mn3+ in those complexes with the longest bond lengths and highest distortion parameters. A barrier to switching from low spin to high spin is less clear but may operate in the seven [Mn(3-NO2-5-OMe-sal2323)]+ complexes 1a-7a reported here which were all low spin in the solid state at room temperature.

The LiaFSR-LiaX System Mediates Resistance of Enterococcus faecium to Peptide Antibiotics and to Aureocin A53- and Enterocin L50-Like Bacteriocins.

Multidrug-resistant Enterococcus faecium strains are currently a leading cause of difficult-to-treat nosocomial infections. The emerging resistance of enterococci to last-resort antibiotics, such as daptomycin, prompts a search for alternative antimicrobials. Aureocin A53- and enterocin L50-like bacteriocins are potent antimicrobial agents that form daptomycin-like cationic complexes and have a similar cell envelope-targeting mechanism of action, suggesting their potential as next-generation antibiotics. However, to ensure their safe use, the mechanisms of resistance to these bacteriocins and cross-resistance to antibiotics need to be well understood. Here, we investigated the genetic basis of E. faecium's resistance to aureocin A53- and enterocin L50-like bacteriocins and compared it with that to antibiotics. First, we selected spontaneous mutants resistant to the bacteriocin BHT-B and identified adaptive mutations in the liaFSR-liaX genes encoding the LiaFSR stress response regulatory system and the daptomycin-sensing protein LiaX, respectively. We then demonstrated that a gain-of-function mutation in liaR increases the expression of liaFSR, liaXYZ, cell wall remodeling-associated genes, and hypothetical genes involved in protection against various antimicrobials. Finally, we showed that adaptive mutations or overexpression of liaSR or liaR alone results in cross-resistance to other aureocin A53- and enterocin L50-like bacteriocins, as well as antibiotics targeting specific components of the cell envelope (daptomycin, ramoplanin, gramicidin) or ribosomes (kanamycin and gentamicin). Based on the obtained results, we concluded that activation of the LiaFSR-mediated stress response confers resistance to peptide antibiotics and bacteriocins via a cascade of reactions, eventually leading to cell envelope remodeling. IMPORTANCE Pathogenic enterococci carry virulence factors and a considerable resistome, which makes them one of the most serious and steadily increasing causes of hospital epidemiological risks. Accordingly, Enterococcus faecium is classified into a top-priority ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) group of six highly virulent and multidrug-resistant (MDR) bacterial pathogens for which novel antimicrobial agents need to be developed urgently. Alternative measures, such as the use of bacteriocins, separately or in combination with other antimicrobial agents (e.g., antibiotics), could be a potential solution, especially since several international health agencies recommend and support the development of such interventions. Nevertheless, in order to exploit their efficacy, more basic research on the mechanisms of cell killing and the development of resistance to bacteriocins is needed. The present study fills some of the knowledge gaps regarding the genetic basis of the development of resistance to potent antienterococcal bacteriocins, pointing out the common and divergent features regarding the cross-resistance to antibiotics.

Insight into the Desolvation of Quaternary Ammonium Cation with Acetonitrile as a Solvent in Hydroxyl-Flat Pores: A First-Principles Calculation.

Supercapacitors have a wide range of applications in high-technology fields. The desolvation of organic electrolyte cations affects the capacity size and conductivity of supercapacitors. However, few relevant studies have been published in this field. In this experiment, the adsorption behavior of porous carbon was simulated with first-principles calculations using a graphene bilayer with a layer spacing of 4-10 Å as a hydroxyl-flat pore model. The reaction energies of quaternary ammonium cations, acetonitrile, and quaternary ammonium cationic complexes were calculated in a graphene bilayer with different interlayer spacings, and the desolvation behavior of TEA+ and SBP+ ions was described. The critical size for the complete desolvation of [TEA(AN)]+ was 4.7 Å, and the partial desolvation size ranged from 4.7 to 4.8 Å. The critical size for the complete desolvation of [SBP(AN)]+ was 5.2 Å, and the partial desolvation size ranged from 5.2 to 5.5 Å. As the ionic radius of the quaternary ammonium cation decreased, the desolvation size showed a positive trend. A density of states (DOS) analysis of the desolvated quaternary ammonium cations embedded in the hydroxyl-flat pore structure showed that the conductivity of the hydroxyl-flat pore was enhanced after gaining electrons. The results of this paper provide some help in selecting organic electrolytes to improve the capacity and conductivity of supercapacitors.

Novel Route to Cationic Palladium(II)-Cyclopentadienyl Complexes Containing Phosphine Ligands and Their Catalytic Activities.

The Pd(II) complexes [Pd(Cp)(L)n]m[BF4]m were synthesized via the reaction of cationic acetylacetonate complexes with cyclopentadiene in the presence of BF3∙OEt2 (n = 2, m = 1: L = PPh3 (1), P(p-Tol)3, tris(ortho-methoxyphenyl)phosphine (TOMPP), tri-2-furylphosphine, tri-2-thienylphosphine; n = 1, m = 1: L = dppf, dppp (2), dppb (3), 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: 1,6-bis(diphenylphosphino)hexane). Complexes 1-3 were characterized using X-ray diffractometry. The inspection of the crystal structures of the complexes enabled the recognition of (Cp-)⋯(Ph-group) and (Cp-)⋯(CH2-group) interactions, which are of C-H…π nature. The presence of these interactions was confirmed theoretically via DFT calculations using QTAIM analysis. The intermolecular interactions in the X-ray structures are non-covalent in origin with an estimated energy of 0.3-1.6 kcal/mol. The cationic palladium catalyst precursors with monophosphines were found to be active catalysts for the telomerization of 1,3-butadiene with methanol (TON up to 2.4∙104 mol 1,3-butadiene per mol Pd with chemoselectivity of 82%). Complex [Pd(Cp)(TOMPP)2]BF4 was found to be an efficient catalyst for the polymerization of phenylacetylene (PA) (catalyst activities up to 8.9 × 103 gPA·(molPd·h)-1 were observed).

Dispersive Micro-Solid Phase Extraction Using a Graphene Oxide Nanosheet with Neocuproine and Batocuproine for the Preconcentration of Traces of Metal Ions in Food Samples.

A dispersive micro-solid phase extraction (Dµ-SPE) method for the preconcentration of trace metal ions (Pb, Cd, Cr, Mn, Fe, Co, Ni, Cu, Zn) on graphene oxide with the complexing reagents neocuproine or batocuproine is presented here. Metal ions form cationic complexes with neocuproine and batocuproine. These compounds are adsorbed on the GO surface via electrostatic interactions. The factors affecting the separation and preconcentration of analytes such as pH, eluent (concentration, type, volume), amount of neocuproine, batocuproine and GO, mixing time, and sample volume were optimized. The optimal sorption pH was 8. The adsorbed ions were effectively eluted with 5 mL 0.5 mol L-1 HNO3 solution and determined by the ICP-OES technique. The preconcentration factor for the GO/neocuproine and GO/batocuproine in the range 10-100 and 40-200 was obtained for the analytes, with detection limits of 0.035-0.84 ng mL-1 and 0.047-0.54 ng mL-1, respectively. The method was validated by the analysis of the three certified reference materials: M-3 HerTis, M-4 CormTis, and M-5 CodTis. The procedure was applied to determine metal levels in food samples.

Mg-Fe Bonding in the MgFe(CO)n+ (n = 4-9) Cation Complexes: An Infrared Photodissociation Spectroscopic and Theoretical Study.

Heteronuclear magnesium-iron carbonyl cation complexes MgFe(CO)n+ (n = 4-9) are prepared in the gas phase and are detected by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The geometric structures and the metal-metal bonding are discussed with the aid of quantum chemical calculations. The MgFe(CO)9+ cation is a coordinatively saturated complex. Each complex is characterized to contain more than one isomer. The small complexes (n = 4-6) possess the Mg-Fe bonded [(OC)n-4Mg-Fe(CO)4]+ and/or [(OC)n-5Mg-Fe(CO)5]+ structures with all the carbonyl ligands terminally bonded. For the larger complexes with n = 7-9, the [(OC)n-4Mg-Fe(CO)4]+ structure is the major isomer experimentally observed. In addition, the [(OC)n-5Mg-OC-Fe(CO)4]+ isomer involving a linear bridging carbonyl ligand is also characterized. Bonding analyses indicate that each [(OC)n-4Mg-Fe(CO)4]+ complex contains a Mg-Fe electron-sharing σ bond. The metal-metal bond is described as a Mg(+I)-Fe(0) bond in MgFe(CO)4+ and as a Mg(+II)-Fe(-I) bond in the larger n = 5-9 complexes.

Cleavage of an Aromatic C–C Bond in Ferrocene by Insertion of an Iridium Nitrido Nitrogen Atom

The intermolecular cleavage of C-C bonds is a rare event. Herein, we report on a late transition-metal terminal nitrido complex, which upon oxidation undergoes insertion of the nitrido nitrogen atom into the aromatic C-C bond of ferrocene. This reaction path was confirmed through 15N and deuterium isotope labeling experiments of the nitrido complex and ferrocenium, respectively. Cyclic voltammetry and UV/vis spectroscopy monitoring of the reaction revealed that oxidation is the initial step, yielding the tentative radical cationic nitrido complex, which is experimentally supported by extended X and Q-band electron paramagnetic resonance (EPR) and ENDOR, UV/vis, vT 1H NMR, and vibrational spectroscopic data. Density functional theory (DFT) and multireference calculations of this highly reactive intermediate revealed an S = 1/2 ground state. The high reactivity can be traced to the increased electrophilicity in the oxidized complex. Based on high-level PNO-UCCSD(T) calculations and UV/vis kinetic measurements, it is proposed that the reaction proceeds by initial electrophilic exo attack of the nitrido nitrogen atom at the cyclopentadienyl ring and consecutive ring expansion to a pyridine ring.

The synthesis of novel water-soluble zinc (II) phthalocyanine based photosensitizers and exploring of photodynamic therapy activities on the PC3 cancer cell line.

In this study, Schiff base substituted phthalocyanine complexes (Zn1c, Zn2c) and their quaternized derivatives (Q-Zn1c, Q-Zn2c) were synthesized for the first time. Their structures have been characterized by FT-IR, 1H-NMR, UV-Vis, mass spectrometry and elemental analysis as well as. The photophysicochemical properties (fluorescence, singlet oxygen and photodegradation quantum yield) of these novel complexes were investigated in dimethylsulfoxide (DMSO) for both non-ionic and quaternized cationic phthalocyanine complexes and in aqueous solution for quaternized cationic phthalocyanine complexes. Water soluble cationic phthalocyanine compounds gave good singlet oxygen quantum yield (0.65 for Q-Zn1c, 0.66 for Q-Zn2c in DMSO; 0.65 for Q-Zn2c in aqueous solution). The binding of Q-Zn1c and Q-Zn2c to BSA/DNA was studied by using UV-Vis and fluorescence spectroscopy and these. Studies indicate that the mechanism of BSA quenching by quaternized zinc(II) phthalocyanines was static quenching. Quaternized zinc(II) phthalocyanines interacted with ct-DNA by intercalation. Quaternized zinc(II) phthalocyanines caused a decrease in cell viability and triggered apoptotic cell death after PDT was applied at a concentration that did not have a toxic effect on their own. Q-Zn1c and Q-Zn2c mediated PDT reduced the activity of SOD, CAT, GSH while increased MDA level in the prostate cancer cells. Furthermore, expression of apoptotic proteins after PDT was examined. The results revealed that the synthesized water soluble quaternized zinc(II) phthalocyanine complexes (Q-Zn1c and Q-Zn2c) are promising potential photosensitizers for PDT.

Probing Intermediates of Ion/Molecule Reactions by their Independent Gas‐Phase Synthesis and Fragmentation – The Thiomethoxymethyl Complexes [(bipy)M(CH2SCH3)]+ (M=Pt, Pd, Ni)

AbstractIn the ion/molecule reaction (IMR) of “rollover”‐cyclometalated [(bipy−H)Pt]+ with (CH3)2S, the loss of C2H4 from the encounter complex was observed as the main process some years ago. The cationic complex [(bipy)Pt(CH2SCH3)]+ was identified as a crucial intermediate by DFT calculations. In order to prove its key role experimentally, the cation has now been generated independently and studied by collision‐induced dissociation (CID). The main process is C2H4 loss, which proves [(bipy)Pt(CH2SCH3)]+ to be an intermediate also in the IMR of [(bipy−H)Pt]+ with (CH3)2S. Based on DFT calculations, the thiomethoxymethyl complexes [(bipy)M(CH2SCH3)]+ (M=Pd and Ni) would also serve as intermediates in the IMRs of [(bipy−H)M]+. While these IMRs cannot be studied explicitly, because the parent ions cannot be generated, the potential intermediate [(bipy)M(CH2SCH3)]+ has been subjected to CID. The main fragmentation channels for both metals corresponds to C2H4 loss. The CID experiments thus provide insights into the hypothetical IMRs of [(bipy−H)M]+ with (CH3)2S. The comparison of the DFT calculations for all three metals Ni, Pd, and Pt with the experimental findings uncovers subtle aspects of the underlying reaction mechanisms. This work highlights the suitability of CID experiments of potential reaction intermediates for the elucidation of reaction mechanisms of IMRs as well as the limitations of this approach.

NiII-Catalyzed Enantioselective Anti-Markovnikov Hydrophosphination of Unactivated Alkynes

A mechanism-inspired, reaction mode-controlled enantio- and regioselective anti-Markovnikov hydrophosphination of unactivated alkynes was accomplished by NiII catalysis. Alkenyl phosphine products could be obtained with high regio- and enantioselectivity and easily derivatized to structurally diverse chiral phosphine compounds. Mechanistic studies on both Ni0-catalyzed Markovnikov addition and NiII-catalyzed anti-Markovnikov addition have been carried out by combining experimental and computational methods. In the Ni0 system, an allyl nickel complex was obtained as the catalyst resting state whose structure was unambiguously determined by single-crystal XRD analysis. A sequential hydrometallation, ligand exchange, and reductive elimination mechanism was elucidated corroboratively by DFT calculations. In the NiII system, the cationic secondary phosphine nickel complex serves as the active catalyst. A migratory insertion and protonation sequence was operative to accomplish anti-Markovnikov hydrophosphination.

New Mn(III) complexes with tetradentate cis-N2O2, acacen-type ligands. Synthesis and characterization, single-crystal X-ray diffraction and DFT studies

One of the challenges of manganese(III) magnetochemistry is the design and synthesis of new building block systems to study and develop molecular magnets. In this context, two new Mn(III) complexes were synthesized using new tetradentate cis-N2O2 acacen ligands from the condensation of 1-anisyl-1,3-butanedione and 1,2-diaminoethane (2:1 ratio). All compounds were fully characterized by conventional spectroscopic techniques, such as FT-IR, HRMS, and UV–Vis, and rationalized with DFT and TD-DFT studies. The resulting cationic complexes were composed of N4O2 coordination spheres using a tetradentate ligand (N2O22−) in the equatorial plane and two axial pyridines with general formulae as [MnIII(L)(Py)2](X) (X = BF4−; ClO4−). Single-crystal X-ray diffraction revealed that both complexes are isostructural with typical axial anisotropy due to the Jahn-Teller effect by tetragonal distortion. A complete analysis of the crystalline structures revealed a nonclassical intermolecular interaction of CH···F and CH···O. Supported by Hirshfeld surfaces and 2D- fingerprint plots, it was possible to isolate and calculate the contribution of intermolecular interactions in the supramolecular arrangement. For both complexes, the magnetic susceptibility confirmed a high spin state (HS) with 4.8 µB and 4.9 µB related to the spin-only contribution to the magnetic moment.

Solution-Phase Synthesis of Vanadium Intercalated 1T′-WS2 with Tunable Electronic Properties

Metal ion intercalation into Group VI transition metal dichalcogenides enables control over their carrier transport properties. In this work, we demonstrate a low-temperature, solution-phase synthetic method to intercalate cationic vanadium complexes into bulk WS2. Vanadium intercalation expands the interlayer spacing from 6.2 to 14.2 Å and stabilizes the 1T' phase of WS2. Kelvin-probe force microscopy measurements indicate that vanadium binding in the van der Waals gap causes an increase in the Fermi level of 1T'-WS2 by 80 meV due to hybridization of vanadium 3d orbitals with the conduction band of the TMD. As a result, the carrier type switches from p-type to n-type, and carrier mobility increases by an order of magnitude relative to the Li-intercalated precursor. Both the conductivity and thermal activation barrier for carrier transport are readily tuned by varying the concentration of VCl3 during the cation-exchange reaction.

Sulfoaluminate cement-modified straw biochar as a soil amendment to inhibit Pb-Cd mobility in the soil-romaine lettuce system

Biochar is widely used to remediate soil polluted by potentially toxic elements (PTEs), while the effect of a new type of biochar, obtained from modified cement material, on the mobility of Pb and Cd in the soil-plant system is still unknown. In this study, soils doped with sulfoaluminate cement modified biochar (SBC) were characterized using a series of approaches including FTIR, XRD, and XPS, and combined with pot experiments to explore its synergistic effects on the speciation transformation, accumulation, and mobility of both Pb and Cd in a soil-romaine lettuce system in heavily contaminated soils containing 500 mg·kg−1-Pb and 3 mg·kg−1-Cd. The results showed that SBC effectively immobilized Pb and Cd in the soil and that this was achieved through cation exchange, complexation, and gel encapsulation. Moreover, SBC also changed the soil physicochemical properties and indirectly affected the speciation transformation of Pb and Cd. FTIR and XRD analyses revealed that the groups such as –OH, –COOH, SO42−, and SiO32−introduced by SBC stimulated the conversion from the soluble to the residual state of Pb. XPS analysis indicated that, the deviation of the C–O–C, C–OOH, and O–CO peak and the increased in area suggested that organic groups in the SBC were engaged in the immobilization mechanism of Pb and Cd. The transformation of residual Cd in other extractable fractions might be due to either enhanced soil reducibility or competitive adsorption with Pb. In 5% SBC soil, Pb was reduced by 27.69% and 64.84%, and Cd was reduced by 20.45% and 35.87% for shoots and roots of romaine lettuce, respectively. SBC showed a significantly positive correlation with SOM, while SOM showed a highly significantly negative correlation with both Pb and Cd in the roots. In summary, SBC can be strongly recommended as a green amendment to remediate Pb–Cd contaminated soil and to inhibit the mobility to plant.

Synthesis, crystal structure, DNA binding, molecular docking, DFT, Hirshfeld surface analysis, and cytotoxicity of copper (II) complex with malonamide and 2,9-dimethyl-1,10-phenanthroline

A new copper (II) complex, [Cu(dmp)(malon)(H2O)](NO3)2 where malon = malonamide and dmp = 2,9-dimethyl-1,10-phenanthroline, has been synthesized and characterized by elemental analysis, FT-IR, UV–Visible and single crystal XRD techniques. The complex was crystallized in a monoclinic system with space group P21/n. Single-crystal XRD studies have established that the copper (II) complex cation has a distorted square-pyramidal geometry, with Jahn-teller distortion occurring in the CuN2O3 core. The DFT/UB3LYP/LANL2DZ level of theory was used to optimize the structure of the present complex. The essential interactions within the crystal structure that lead to molecular packing were identified using Hirshfeld surface analysis. UV–Visible absorption titration, fluorescence, cyclic voltammetry, and viscometric titration studies were used to study the interactions of the present complex with calf thymus DNA (CT-DNA) and propose a partial intercalation binding mechanism. The complex demonstrated strong cytotoxic effects against the human hepatocellular carcinoma cell line (HepG2), and it was discovered to have effective antibacterial and antifungal properties. The efficient binding of the copper (II) complex was observed from molecular docking analysis.

Comparing the Activity of N-Heterocyclic Carbene Iron Complexes and Free Carbene Precursors in the Hydrosilylation of CO2

Piano-stool iron complexes with N-heterocyclic carbene (NHC) ligands have shown high potential in the activation and conversion of C═O bonds in aldehydes, ketones, and esters. Here we demonstrate the expansion of this activity to the functionalization of CO2 with amines to form N-formamide products in the presence of a silane (PhSiH3). This synthetically valuable utilization of CO2 as C1-synthon is catalyzed by iron complexes containing a variety of different NHC ligands. Structural variations of the NHC ligands did not reveal any correlation with catalytic activity, with imidazole and triazole-derived NHCs reaching similar conversions. However, the use of BF4– as counterion in cationic complexes, and also incorporating a Cp* instead of a Cp spectator ligand led to a marked decrease in catalytic activity. While NHC iron complexes reach mediocre activity (about 50% conversion at 5% catalyst loading in 24 h), the corresponding imidazolium and triazolium carboxylates as precursors of free carbenes display excellent catalytic activity with essentially full conversion after 1 h at 1 mol % loading. Experiments at variable iron complex loading as well as carbene trapping experiments with S8 together with spectroscopic investigations demonstrated a high stability of the Fe–CNHC bond during catalysis and lend strong support to a NHC iron unit as catalytically active species rather than free NHC resulting from Fe–NHC dissociation, even though free NHCs are excellent catalysts for this reaction. Optimized of reaction conditions, in particular the addition of another equivalent of silane allowed to reach high conversions of piperidine and CO2 to N-formylpiperidine using a triazolylidene iron complex as catalyst precursor.

Synthesis, Structures and Photophysical Properties of Tetra- and Hexanuclear Zinc Complexes Supported by Tridentate Schiff Base Ligands

The synthesis, structure and photophysical properties of two polynuclear zinc complexes, namely [Zn6L2(µ3-OH)2(OAc)8] (1) and [Zn4L4(µ2-OH)2](ClO4)2 (2), supported by tridentate Schiff base ligand 2,6-bis((N-benzyl)iminomethyl)-4-tert-butylphenol (HL) are presented. The synthesized compounds were investigated using ESI-MS, IR, NMR, UV-vis absorption spectroscopy, photoluminescence spectroscopy and single-crystal X-ray crystallography. The hexanuclear neutral complex 1 comprises six-, five- and four-coordinated Zn2+ ions coordinated by O and N atoms from the supporting ligand and OH- and acetate ligands. The Zn2+ ions in complex cation [Zn4L4(µ2-OH)2]2+ of 2 are all five-coordinated. The complexation of ligand HL by Zn2+ ions leads to a six-fold increase in the intensity and a large blue shift of the ligand-based 1(π-π)* emission. Other biologically relevant ions, i.e., Na+, K+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+ and Cu2+, did not give rise to a fluorescence enhancement.

Nucleophilic reactions of molybdenum cationic propargyl complexes

Nucleophilic reactions of molybdenum cationic propargyl complexes

New Organometallic Ru(II) Compounds with Lonidamine Motif as Antitumor Agents.

The combination of one molecule of organic and metal-based fragments that exhibit antitumor activity is a modern approach in the search for new promising drugs. In this work, biologically active ligands based on lonidamine (a selective inhibitor of aerobic glycolysis used in clinical practice) were introduced into the structure of an antitumor organometallic ruthenium scaffold. Resistant to ligand exchange reactions, compounds were prepared by replacing labile ligands with stable ones. Moreover, cationic complexes containing two lonidamine-based ligands were obtained. Antiproliferative activity was studied in vitro by MTT assays. It was shown that the increase in the stability in ligand exchange reactions does not influence cytotoxicity. At the same time, the introduction of the second lonidamine fragment approximately doubles the cytotoxicity of studied complexes. The ability to induce apoptosis and caspase activation in tumour cell MCF7 was studied by employing flow cytometry.

Antisolvent crystallization of ammonium dihydrogen phosphate (ADP) from aqueous solutions containing Al(III) and Fe(III) impurities by addition of ethanol

Experimental results of a study of the effect of concentration of Al(III) and Fe(III) ions on the metastable zone width (MSZW) of aqueous ADP saturated solutions, as determined by the maximum antisolvent content Δxmax in them for spontaneous three-dimensional (3D) nucleation, by feeding ethanol antisolvent to them at different rates RA and the nucleation and growth of crystals from these solutions are described and discussed. Crystal structure and segregation coefficients of impurity in the crystals were also studied by X-ray diffraction analysis and microwave plasma atomic absorption spectrometry, respectively. It was observed that: (1) the value of Δxmax for spontaneous 3D nucleation increases with an increase in ethanol feeding rate RA as well as impurity concentration ci, (2) the morphology and size of the ADP crystals changes with an increase in impurity concentration ci and antisolvent feeding rate RA, and (3) the effective segregation coefficients keff of the impurities in ADP crystals at a constant RA of ethanol feeding decreases with an increase in impurity concentration ci in the solution. The experimental data of the dependence of Δxmax on RA for solutions containing different impurity concentration ci were analyzed according to the approach based on the classical theory for 3D nucleation to calculate values of the preexponential factor A and the effective interfacial energy γeff of the theory, those of the morphology of ADP crystals from consideration of adsorption of impurity particles on the surfaces of growing crystals, and those of the dependence of segregation coefficient keff of the impurities on their concentration ci in the solution using a model based on competitive adsorption of solute and impurity molecules. It is argued that the formation of 3D nuclei of ADP during MSZW measurements and growth of these ADP nuclei as large crystals from aqueous solutions containing impurities and segregation of impurities in the crystals may be explained from consideration of different rates of ligand exchange of the surface-adsorbed complexes formed by interaction between univalently-charged cation complex present in aqueous solution and the H2PO4− ions of kinks in steps.

Bis(salicylamidine) Ligands (FAlen): A Variant of Salen with "à la Carte" Denticity.

Ethylene- and phenylene-bridged bis(salicylamidine) ligands have been readily prepared from ethylene or phenylenediamine and iminium chloride derivatives generated in situ from N,N-dialkylsalicylamides. The former, in its diprotonated form (FAlenH2), reacts with AlMe3 to afford a zwitterionic dimethyldiphenoxyaluminate complex with the FAlen ligand monoprotonated and in a bidentate κ2O,O' fashion. A phenylene-bridged proligand behaves differently, yielding a neutral methylaluminum complex bearing a κ3O,N,O'-coordinated FAlen ligand. From these complexes, methyl anion abstraction with B(C6F5)3 or a reaction with Schrock's alcohol leads to the corresponding aluminum cationic or alkoxy complexes in which a κ4O,N,N',O'-coordination mode of the FAlen ligand is observed. X-ray diffraction studies of the proligands and of the complexes show that the amidine functions feature a trans configuration when the N-amidine atom is not coordinated to the metal and conversely a cis configuration when it is. Density functional theory calculations show that trans-cis isomerization of the amidine functions occurs upon coordination with the metal ion with very low energy barriers. They also confirm the intuition that the denticity of the FAlen ligands in the complexes is directly related to the electron richness of the metal ion. At last, FAlen Al complexes are used as initiators for the controlled ring-opening polymerization of rac-lactide to afford poly(lactic acid) with slight isotactic bias.