Hetero-nanocomposites of magnetic and antifungal nanoparticles as a platform for magnetomechanical stress induction in Saccharomyces cerevisiae.

Copper(i) oxide (Cu2O) nanoparticles (NPs) of 30 nm with antifungal properties have been functionalized with 9 nm nickel ferrite (NiFe2O4) magnetic nanoparticles (MNPs) to construct hetero-nanocomposites (NCs) of a submicron hydrodynamic size for magnetomechanical stress induction in the yeast, Saccharomyces cerevisiae. A post-synthetic approach involving the assembly through hydrophobic interactions of the preformed NPs of non-uniform sizes, albeit coated with the same surfactant (oleylamine), is reported. Solvents of different polarity were implemented during the synthetic procedure resulting in NCs of similar composition consisting mainly of MNPs randomly decorated onto the bigger Cu2O NPs. The antifungal properties of the building NPs and the NCs were studied in terms of fungistatic and fungicidal activity, whereas the ionic leaching was found to be negligible, highlighting the nanosize effect. Although S. cerevisiae cells were found to be resistant to individual NiFe2O4 MNPs because of their small size, their sensitivity to NCs significantly increased upon short-time exposure to a rotating low-frequency magnetic field (10 min, 30 Hz, 35 G) and this arises from the collective properties. The magnetomechanical cell stress induction was accompanied by alteration of cellular membrane integrity and programmed cell death signaling.

Fabrication of hybrid molecular devices using multi-layer graphene break junctions.

We report on the fabrication of hybrid molecular devices employing multi-layer graphene (MLG) flakes which are patterned with a constriction using a helium ion microscope or an oxygen plasma etch. The patterning step allows for the localization of a few-nanometer gap, created by electroburning, that can host single molecules or molecular ensembles. By controlling the width of the sculpted constriction, we regulate the critical power at which the electroburning process begins. We estimate the flake temperature given the critical power and find that at low powers it is possible to electroburn MLG with superconducting contacts in close proximity. Finally, we demonstrate the fabrication of hybrid devices with superconducting contacts and anthracene-functionalized copper curcuminoid molecules. This method is extendable to spintronic devices with ferromagnetic contacts and a first step towards molecular integrated circuits.

Evaluation of nickel ferrite nanoparticles coated with oleylamine by NMR relaxation measurements and magnetic hyperthermia.

Nickel ferrite nanoparticles were synthesized via a facile solvothermal approach. Oleylamine (OAm) was used in all synthetic procedures as a stabilizing agent and solvent. By varying the polarity of the solvents, hydrophobic NiFe2O4 nanoparticles coated with OAm of relatively similar sizes (9-11.7 nm) and in a range of magnetization values (32.0-53.5 emu g(-1)) were obtained. The as-prepared hydrophobic nanoparticles were characterized by XRD, TEM, SEM, TGA and VSM and converted to hydrophilic by two different approaches. The addition of a positively charged ligand (cetyltrimethyl ammonium bromide, CTAB) and the ligand exchange procedure (2,3-dimercaptosuccinic acid, DMSA) have been successfully applied. The aqueous suspensions of NiFe2O4@CTAB and NiFe2O4@DMSA showed good colloidal stability after a long period of time. The different surface modification affected both the NMR relaxometric measurements and the hyperthermia effects. In both techniques CTAB modification demonstrated higher r2 relaxivity (278.9 s(-1) mM(-1) in an NMR spectrometer at 11.7 T) and SAR values (423.4 W g(-1) at an applied AC field with a particle concentration of 0.5 mg mL(-1)). The results indicate that a coating with a larger molecule as CTAB under the same size, shape and magnetization of NiFe2O4 NPs gave rise to NMR relaxometric properties and heating efficacy.

Heptanuclear antiferromagnetic Fe(III)-D-(-)-quinato assemblies with an S = 3/2 ground state-pH-specific synthetic chemistry, spectroscopic, structural, and magnetic susceptibility studies.

Iron is an essential metal ion with numerous roles in biological systems and advanced abiotic materials. D-(-)-quinic acid is a cellular metal ion chelator, capable of promoting reactions with metal M(II,III) ions under pH-specific conditions. In an effort to comprehend the chemical reactivity of well-defined forms of Fe(III)/Fe(II) toward α-hydroxycarboxylic acids, pH-specific reactions of: (a) [Fe3O(CH3COO)6(H2O)3]·(NO3)·4H2O with D-(-)-quinic acid in a molar ratio 1:3 at pH 2.5 and (b) Mohr's salt with D-(-)-quinic acid in a molar ratio 1:3 at pH 7.5, respectively, led to the isolation of the first two heptanuclear Fe(III)-quinato complexes, [Fe7O3(OH)3(C7H10O6)6]·20.5H2O (1) and (NH4)[Fe7(OH)6(C7H10O6)6]·(SO4)2·18H2O (2). Compounds 1 and 2 were characterized by analytical, spectroscopic (UV-vis, FT-IR, EPR, and Mössbauer) techniques, CV, TGA-DTG, and magnetic susceptibility measurements. The X-ray structures of 1 and 2 reveal heptanuclear assemblies of six Fe(III) ions bound by six doubly deprotonated quinates and one Fe(III) ion bound by oxido- and hydroxido-bridges (1), and hydroxido-bridges (2), all in an octahedral fashion. Mössbauer spectroscopy on 1 and 2 suggests the presence of Fe(III) ions in an all-oxygen environment. EPR measurements indicate that 1 and 2 retain their structure in solution, while magnetic measurements reveal an overall antiferromagnetic behavior with a ground state S = 3/2. The collective physicochemical properties of 1 and 2 suggest that the (a) nature of the ligand, (b) precursor form of iron, (c) pH, and (d) molecular stoichiometry are key factors influencing the chemical reactivity of the binary Fe(II,III)-hydroxycarboxylato systems, their aqueous speciation, and ultimately through variably emerging hydrogen bonding interactions, the assembly of multinuclear Fe(III)-hydroxycarboxylato clusters with distinct lattice architectures of specific dimensionality (2D-3D) and magnetic signature.

Aromatic chelator-specific lattice architecture and dimensionality in binary and ternary Cu(II)-organophosphonate materials.

Synthetic efforts linked to the design of defined lattice dimensionality and architecture materials in the binary/ternary systems of Cu(II) with butylene diamine tetra(methylene phosphonic acid) (H8BDTMP) and heterocyclic organic chelators (pyridine and 1,10-phenanthroline) led to the isolation of new copper organophosphonate compounds, namely, Na6[Cu2(BDTMP)(H2O)4]·[Cu2(BDTMP)(H2O)4]0.5·26H2O (1), [Cu2(H4BDTMP)(py)4]·2H2O (2), and [Cu2(H4BDTMP)(phen)2]n·6.6nH2O·1.5nMeOH (3). 1-3 are the first compounds isolated from the Cu(II)-BDTMP family of species. They were characterized by elemental analysis, spectroscopic techniques (FT-IR, UV-vis), magnetic susceptibility, TGA-DTG, cyclic voltammetry, and X-ray crystallography. The lattice in 1 reveals the presence of discrete dinuclear Cu(II) units bound to BDTMP(8-) and water molecules in a square pyramidal geometry. The molecular lattice of 2 reveals the presence of ternary dinuclear assemblies of Cu(II) ions bound to H4BDTMP(4-) and pyridine in a square pyramidal environment. The molecular lattice of 3 reveals the presence of dinuclear assemblies of Cu(II) ions bound to H4BDTMP(4-) and 1,10-phenanthroline in a square pyramidal environment, with the organophosphonate ligand serving as the connecting link to abutting dinuclear Cu(II) assemblies in a ternary polymeric system. The magnetic susceptibility data on 1, 2, and 3 suggest that compounds 1 and 3 exhibit a stronger antiferromagnetic behavior than 2, which is also confirmed from magnetization measurements. The physicochemical profiles of 1-3 (a) earmark the influence of the versatile H8BDTMP ligand as a metal ion binder on the chemical reactivity in binary and ternary systems of Cu(II) in aqueous and nonaqueous media and (b) denote the correlation of ligand hydrophilicity, aromaticity, denticity, charge, and H-bonding interactions with emerging defined Cu(II)-H8BDTMP structures of distinct lattice identity and spectroscopic-magnetic properties. Collectively, such structural and chemical factors formulate the interplay and contribution of binary and ternary interactions to lattice architecture and specified properties of new Cu(II)-organophosphonate materials with defined 2D-3D dimensionality.

Defective dicubanes of Co(II)/Co(III) complexes with triethanolamine and N-donors.

The mixed valence Co(II)/Co(III) tetranuclear clusters [Co(II)2Co(III)2(tea)2(pyr)2(NO3)4]·2CH3CN (1), [Co(II)2Co(III)2(µ3-OH)2(Htea)2(bpy)4](NO3)4 (2), and [Co(II)2Co(III)2(µ3-OH)2(Htea)2(phen)4](NO3)4·2CH3CN·2CH3OH (3) are described where tea and Htea are the fully and the doubly deprotonated form of triethanolamine, while as N-donors are pyridine, 2,2'-bipyridine and 1,10-phenanthroline. Complexes 1-3 contain the Co(II)2Co(III)2O6 core and can be described as defective dicubanes with different imperfectness. In 1, the central rhombic core Co2O2 is occupied by two Co(III) ions while the external cobalt atoms display Co(II) oxidation states; meanwhile 2 and 3 exhibit a reversal in their Co(II)2Co(III)2 oxidation state distribution. Two different theoretical models were used to explain the magnetic behavior: (i) spin-spin interaction model with local anisotropy terms where S = 3/2 for both metal centers and (ii) an anisotropic spin-spin interaction model applicable in the low temperature range (T < 40 K) using effective spins (Seff = 1/2) for both metal centers. For 1 a relatively strong next-nearest-neighbour antiferromagnetic exchange interaction between the Co(II) centers which are connected via diamagnetic Co(III) ion was found while for 2 and 3 the presence of ferromagnetic interaction is confirmed. The fitting results, concerning the first model, gave: J = 2.0(2)/3.2(2)/3.8(2) cm(-1), g = 2.35(1)/2.52(1)/2.57(1) and D = 11.0(1)/8.5(1)/7.8(1) cm(-1) while concerning the second model are: Jz = -7.1(2)/19.2(2)/22.1(2) cm(-1), gz = 6.8(1)/8.1(1)/8.3(1), Jxy/Jz = 0.34(2)/0.11(2)/0.14(2), and gxy/gz = 0.52(2)/0.28(2)/0.36(2) for 1-3. X-Band EPR spectrum of 1 has a very broad derivative centered at g = 5.3 while for 2 and 3 large g-variations were found in the range 20.0-1.0, indicative of an exchange interaction between Co(II) ions.

Hydrothermal synthesis and characterization of 2D M(II)-Quinate (M = Co,Zn) metal-organic lattice assemblies: solid-state solution structure correlation in M(II)-hydroxycarboxylate systems.

Co(II) and Zn(II) ions exhibit variable reactivity toward O-containing ligands in aqueous media, affording isolable materials with distinct solid-state lattice properties. d-(-)-quinic acid is a cellular α-hydroxycarboxylate metal ion binder, which reacts with Co(II) and Zn(II) under pH-specific hydrothermal conditions, leading to the isolation of two new species [Co(2)(C(7)H(11)O(6))(4)](n)·nH(2)O (1) and [Zn(3)(C(7)H(11)O(6))(6)](n)·nH(2)O (2). Compound 1 was characterized by elemental analysis, spectroscopic techniques (FT-IR, UV-visible, EPR), magnetic studies, and X-ray crystallography. Compound 2 was characterized by elemental analysis, spectroscopic techniques (FT-IR, ESI-MS), and X-ray crystallography. The 2D molecular lattices in 1 and 2 reveal the presence of octahedral M(II) units bound exclusively to quinate in a distinct fashion, thereby projecting a unique chemical reactivity in each investigated system. The magnetic susceptibility and solid-state/frozen solution EPR data on 1 support the presence of a high-spin octahedral Co(II) in an oxygen environment, having a ground state with an effective spin of S = 1/2. Concurrent aqueous speciation studies on the binary Zn(II)-quinate system unravel the nature and properties of species arising from Zn(II)-quinate interactions as a function of pH and molar ratio. The physicochemical profiles of 1 and 2, in the solid state and in solution, earmark the importance of (a) select synthetic hydrothermal reactivity conditions, affording new well-defined lattice dimensionality and nuclearity M(II)-quinate materials, (b) structural speciation approaches delineating solid state-aqueous solution correlations in the binary M(II)-quinate systems, and (c) pH-specific chemical reactivity in binary M(II)-quinate systems reflecting structurally unique associations of simple aqueous complexes into distinctly assembled 2D crystalline lattices.

pH-Dependent syntheses, structural and spectroscopic characterization, and chemical transformations of aqueous Co(II)-quinate complexes: an effort to delve into the structural speciation of the binary Co(II)-quinic acid system.

Cobalt(II) is an essential metal ion, which can react with biologically relevant substrates in aqueous media, affording discrete soluble forms. D-(-)-quinic acid is a representative metal ion binder, capable of promoting reactions with Co(II) under pH-specific conditions, leading to the isolation of the new species K[Co(C(7)H(11)O(6))(3)] x 3 CH(3)CH(2)OH (1), Na[Co(C(7)H(11)O(6))(3)] x 3 CH(3)CH(2)OH x 2.25 H(2)O (2), and [Co(C(7)H(11)O(6))(2)(H(2)O)(2)] x 3 H(2)O (3). Compounds 1-3 were characterized by elemental analysis, spectroscopic techniques (Fourier-transform infrared, UV-visible, electron paramagnetic resonance (EPR), electrospray ionization mass spectrometry), magnetic studies, and X-ray crystallography. Compound 1 crystallizes in the cubic space group P2(1)3, with a = 15.3148(19) A, V = 3592.0(8) A(3), and Z = 4. Compound 2 crystallizes in the orthorhombic space group P2(1)2(1)2(1), with a = 14.9414(8) A, b = 15.9918(9) A, c = 16.0381(9) A, V = 3832.1(4) A(3), and Z = 4. Compound 3 crystallizes in the monoclinic space group P2(1)/m, with a = 13.2198(10) A, b = 5.8004(6) A, c = 15.3470(12) A, beta = 108.430(7), V = 1116.45(17) A(3), and Z = 4. The lattices in 1-3 reveal the presence of mononuclear Co(II) units bound exclusively to quinate (1 and 2) or quinate and water ligands (3), thus projecting the unique chemical reactivity in each investigated system and suggesting that 3 is an intermediate in the synthetic pathway leading to 1 and 2. The octahedral sites of Co(II) are occupied by oxygens, thereby reflecting the nature of interactions between the divalent metal ion and quinic acid. The magnetic and EPR data on 1 and 3 support the presence of a high-spin octahedral Co(II) in an oxygen environment, having a ground state with an effective spin of S = 1/2. The significance of 3 is further reflected into the aqueous speciation of the binary Co(II)-quinic acid system, in which 3 appears as a competent participant linked to the solid state species 1. The physicochemical profiles of 1-3, in the solid state and in solution, earmark the importance of aqueous structural speciation, which projects chemical reactivity pathways in the binary Co(II)-quinate system, involving soluble Co(II) forms emerging through interactions with low molecular mass O-containing physiological substrates, such as quinic acid.

pH-specific synthetic chemistry and solution studies in the binary system of iron(III) with the alpha-hydroxycarboxylate substrate quinic acid: potential relevance to iron chemistry in plant fluids.

Iron is an essential metal ion in plant growth and development. Mobilization and further use of that metal by cellular structures in metabolic pathways entails the existence of soluble forms complexed with indigenous organic substrates, such as the low molecular mass d-(-)-quinic acid. In an effort to understand the relevant aqueous chemistry involving well-defined forms of iron, research efforts were carried out on the binary Fe(III)-quinic acid system. pH-specific reactions of FeCl(3).6H(2)O with quinic acid in a molar ratio 1:3 led to the isolation of the mononuclear Fe(III)-quinate complexes, K[Fe(C(7)H(11)O(6))(3)].(OH).3H(2)O (1), (NH(4))[Fe(C(7)H(11)O(6))(3)].(OH) (2), and Na[Fe(C(7)H(11)O(6))(3)].(OH).8H(2)O (3). Compounds 1-3 were characterized by analytical, spectroscopic techniques (UV/vis, FT-IR, Electron Paramagnetic Resonance (EPR), and Mossbauer spectroscopy), cyclic voltammetry, and magnetic susceptibility measurements. Compound 1 crystallizes in P2(1)3, with a = 15.1693(9) A, V = 3490.6(4) A(3), and Z = 4. Compound 2 crystallizes in P2(1)3, with a = 15.2831(9) A, V = 3569.7(4) A(3), and Z = 4. Compound 3 crystallizes in P2(1)3, with a = 15.6019(14) A, V = 3797.8(6) A(3), and Z = 4. The X-ray crystal structures of 1-3 reveal a mononuclear Fe(III) ion bound by three quinates in an octahedral fashion. Each quinate ligand binds Fe(III) through the alpha-hydroxycarboxylate group as a singly deprotonated moiety, retaining the alcoholic hydrogen. EPR measurements in solution suggest that 1 dissociates, releasing free quinate. Solution speciation studies of the binary system (a) unravel the aqueous species distribution as a function of pH and reagent molar ratio, and (b) corroborate the EPR results proposing the existence of a neutral Fe(III)-quinate complex form. The collective physicochemical properties of 1-3 formulate a well-defined profile for the Fe(III) assembly in aqueous media and project structural features consistent with solubilized Fe(III)-hydroxycarboxylate binary forms potentially mobilized into plant (bio)chemical processes.

Allelopathic potential of menthofuran monoterpenes fromCalamintha ashei.

A reversed-phase HPLC analysis was used to separate and quantify five menthofuran monoterpenes inCalamintha ashei leaf soaks and washes. (+)-Evodone and desacetylcalaminthone were the major constituents of both soaks and washes. Concentrations of (+)-evodone and desacetylcalaminthone were as high as 0.66 and 0.74 mM, respectively, in leaf soaks. The highest concentration of monoterpenes in leaf washes obtained by misting was 0.021 mM. Aqueous solubilities of the menthofurans were determined to exceed concentrations required for growth inhibition. Bioassays of individualCalamintha monoterpenes demonstrated effects on germination as low as 0.05 mM for (+)-evodone. An equimolar mixture of desacetylcalaminthone and (+)-evodone reducedRudbeckia hirta germination by 17% at a combined concentration of 0.025 mM forLeptochloa dubia. Confirmation of allelopathic effects byCalamintha ashei will require long-term bioassays ofCalamintha menthofurans on the growth of native sandhill species under conditions comparable to the harsh environment of the Florida scrub.