Use of Unprecedented Intramolecular 1, 3-Dipolar Cycloaddition Reaction in meso-Nitrile Oxide-Containing BODIPYs as a New Pathway for the Preparation of Fused NIR Platforms.

Meso-nitrile oxide group in 1,7-Diphenyl-containing BODIPYs can be involved in highly unusual [3+2] intramolecular cycloaddition reaction with the formation of the dihydrobenzo[d]isoxazole-containing BODIPYs. Oxidation of these compounds results in the formation of unprecedented either benzisoxazole- or benzo[b]azepine-fused fully conjugated NIR absorbing BODIPYs. The photophysical properties and electronic structures of the target compounds were studied by an array of experimental and theoretical methods.

Novel antimony-based antimicrobial drug targets membranes of Gram-positive and Gram-negative bacterial pathogens.

Antimicrobial resistance (AMR) poses a significant worldwide public health crisis that continues to threaten our ability to successfully treat bacterial infections. With the decline in effectiveness of conventional antimicrobial therapies and the lack of new antibiotic pipelines, there is a renewed interest in exploring the potential of metal-based antimicrobial compounds. Antimony-based compounds with a long history of use in medicine have re-emerged as potential antimicrobial agents. We previously synthesized a series of novel organoantimony(V) compounds complexed with cyanoximates with a strong potential of antimicrobial activity against several AMR bacterial and fungal pathogens. Here, five selected compounds were studied for their antibacterial efficacy against three important bacterial pathogens: Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. Among five tested compounds, SbPh4ACO showed antimicrobial activity against all three bacterial strains with the MIC of 50-100 µg/mL. The minimum bactericidal concentration/MIC values were less than or equal to 4 indicating that the effects of SbPh4ACO are bactericidal. Moreover, ultra-thin electron microscopy revealed that SbPh4ACO treatment caused membrane disruption in all three strains, which was further validated by increased membrane permeability. We also showed that SbPh4ACO acted synergistically with the antibiotics, polymyxin B and cefoxitin used to treat AMR strains of P. aeruginosa and S. aureus, respectively, and that at synergistic MIC concentration 12.5 µg/mL, its cytotoxicity against the cell lines, Hela, McCoy, and A549 dropped below the threshold. Overall, the results highlight the antimicrobial potential of novel antimony-based compound, SbPh4ACO, and its use as a potentiator of other antibiotics against both Gram-positive and Gram-negative bacterial pathogens. IMPORTANCE: Antibiotic resistance presents a critical global public health crisis that threatens our ability to combat bacterial infections. In light of the declining efficacy of traditional antibiotics, the use of alternative solutions, such as metal-based antimicrobial compounds, has gained renewed interest. Based on the previously synthesized innovative organoantimony(V) compounds, we selected and further characterized the antibacterial efficacy of five of them against three important Gram-positive and Gram-negative bacterial pathogens. Among these compounds, SbPh4ACO showed broad-spectrum bactericidal activity, with membrane-disrupting effects against all three pathogens. Furthermore, we revealed the synergistic potential of SbPh4ACO when combined with antibiotics, such as cefoxitin, at concentrations that exert no cytotoxic effects tested on three mammalian cell lines. This study offers the first report on the mechanisms of action of novel antimony-based antimicrobial and presents the therapeutic potential of SbPh4ACO in combating both Gram-positive and Gram-negative bacterial pathogens while enhancing the efficacy of existing antibiotics.

NaGaSe2: A Water-Loving Multifunctional Non-van der Waals Layered Selenogallate.

A missing member of well-known ternary chalcometallates, a sodium selenogallate, NaGaSe2, has been synthesized by employing a polyselenide flux and stoichiometric reaction. Crystal structure analysis using X-ray diffraction techniques reveals that it contains supertetrahedral adamantane-type Ga4Se10 secondary building units. These Ga4Se10 secondary building units are further connected via corners to form two-dimensional (2D) [GaSe2]∞- layers stacked along the c-axis of the unit cell, and the Na ions reside in the interlayer space. The compound has an unusual ability to absorb water molecules from the atmosphere or a nonanhydrous solvent to form distinct hydrated phases, NaGaSe2·xH2O (where x can be 1 and 2), with an expanded interlayer space, as verified by X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), desorption, and Fourier transform infrared spectroscopy (FT-IR) studies. The in situ thermodiffractogram indicates the emergence of an anhydrous phase before 300 °C with the decrease of interlayer spacings and reverting to the hydrated phase within a minute of re-exposure to the environment, supporting the reversibility of such a process. Structural transformation induced through water absorption results in an increase of Na ionic conductivity by 2 orders of magnitude compared to that of the pristine anhydrous phase, as verified by impedance spectroscopy. Na ions from NaGaSe2 can be exchanged in the solid-state route with other alkali and alkaline earth metals in a topotactic or nontopotactic way, leading to 2D isostructural and three-dimensional networks, respectively. Optical band gap measurements show a band gap of ∼3 eV for the hydrated phase, NaGaSe2·xH2O, which is in good agreement with the calculated band gap using a density functional theory (DFT)-based method. Sorption studies further confirm the selective absorption of water over MeOH, EtOH, and CH3CN with a maximum water uptake of 6 molecules/formula unit at a relative pressure, P/P0, of 0.9.

Lithium selenometallates of triel elements, Li5MSe4 (M = Al and Ga), aliovalent doping and their ionic conductivity.

Ternary selenometallates, Li5MSe4 (M = Al(I) and Ga(II)), have been synthesized for the first time through high temperature solid-state reactions combining elements and Li2Se in stoichiometric compositions. Li5MSe4 crystallizes in the P21/m space group, forming a pseudo-2D layer type structure with edge sharing LiSe4 and MSe4 tetrahedra along the a-axis. These layers are interleaved by octahedrally coordinated Li ions located in the interlayer space. AC impedance spectroscopy measurements yield room temperature ionic conductivities of 0.60 × 10-7 and 0.58 × 10-7 S cm-1 with calculated activation energies of 0.51 and 0.48 eV for I and II, respectively. An aliovalent substitution of Sn4+ in Li5MSe4 yields compositions of Li4.66Al0.82Sn0.22Se4 (III) and Li4.37Ga0.89Sn0.24Se4 (IV), which crystallize in the P21/m and P3̄m1 space groups, respectively. Sn-doped samples show an ∼5-fold increase in ionic conductivity, 3.37 × 10-7 S cm-1 and 2.4 × 10-7 S cm-1 with activation energies of 0.54 and 0.28 eV, respectively, for III and IV. The optical band gap values of the compounds are 3.65 and 3.2 eV for I and II, respectively, as measured by diffuse reflectance spectroscopy. Density functional theory (DFT) calculations predicted a major contribution from the Se 4p-states in forming the top of the valence band and strongly hybridized the Se 4p and ns orbitals of Al and Ga in forming the bottom of the conduction band with almost no contribution from the Li s-states near the Fermi level indicating their ionic interactions with the ligand.

Non-Antibiotic Antimony-Based Antimicrobials.

A series of the eight novel organoantimony(V) cyanoximates of Sb(C6H5)4L composition was synthesized using the high-yield heterogeneous metathesis reaction between solid AgL (or TlL) and Sb(C6H5)4Br in CH3CN at room temperature. Cyanoximes L were specially selected from a large group of 48 known compounds of this subclass of oximes on the basis of their water solubility and history of prior biological activity. The synthesized compounds are well soluble in organic solvents and were studied using a variety of conventional spectroscopic and physical methods. The crystal structures of all reported organometallic compounds were determined and revealed the formation of the distorted trigonal bipyramidal environment of the Sb atom and monodentate axial binding of acido-ligands via the O atom of the oxime group. The compounds are thermally stable in the solid state and in solution molecular compounds. For the first time, this specially designed series of organoantimony(V) compounds is investigated as potential non-antibiotic antimicrobial agents against three bacterial and two fungal human pathogens known for their increasing antimicrobial resistance. Bacterial pathogens included Gram-negative Escherichia coli and Pseudomonas aeruginosa, and Gram-positive Staphylococcus aureus. Fungal pathogens included Cryptococcus neoformans and Candida albicans. The cyanoximates alone showed no antimicrobial impact, and the incorporation of the SbPh4 group enabled the antimicrobial effect. Overall, the new antimony compounds showed a strong potential as both broad- and narrow-spectrum antimicrobials against selected bacterial and fundal pathogens and provide insights for further synthetic modifications of the compounds to increase their activities.

Rational Design of Iron Spin-Crossover Complexes Using Heteroscorpionate Chelates.

The optical, structural, and magnetic properties of iron(II,III) sandwich complexes, Fe(Tp')2n+ (Tp' = bis(3,5-dimethylpyrazolyl)benzotriazolylborate), are described. The intensely colored FeII(Tp')2 (orange) and FeIII(Tp')2+ (purple) show strong MLCT bands. Geometric isomerism for M(Tp')2 is established crystallographically in the racemate of chiral cis-Fe(Tp')2. For the first time, paramagnetic 11B NMR describes solution-phase low-spin (LS, S = 0) to high-spin (HS, S = 2) crossover behavior in Fe(Tp')2. Thermochemical parameters for solution-phase SCO of Fe(Tp')2 demonstrate the endothermic LS to HS conversion and entropic preference of the HS state. Entropy changes for both Fe(Tp')2 isomers are significantly larger than for the majority of iron scorpionate SCO systems. Solid-state magnetic and thermochemical measurements show cis-Fe(Tp')2 to be thermally stable up to 520 K, allowing experimental investigation of a solid-state SCO magnetic hysteresis of over 45 K. A large solution vs solid-state SCO difference was observed: cis-Fe(Tp')2 shows Tc ≈ 270 K (solution) and Tc ≈ 385 K (solid), with the remarkably wide ΔTc ≈ 115 K; trans-Fe(Tp')2 shows Tc ≈ 278 K (solution) and Tc ≈ 372 K (solid). Solid-state Tc values are among the highest seen for iron(II) molecular systems. The large solution/solid ΔTc difference is explained by "anchoring" intermolecular interactions in the solid state that prevent thermal expansion of the LS iron(II) coordination sphere in its transition to the HS state. DFT calculations, validated against LS cis-Fe(Tp')2 crystallography and LS to HS SCO thermochemical parameters, demonstrate the role the benzotriazole rings play in its structural and optical properties. The Lewis basicity of M(Tp')2 is shown with the structural characterization of the air-stable tin(II) adduct [cis-Fe(Tp')2-SnCl2]; tin(II) coordination does not alter the iron(II) spin state. The Tp' chelate adds functionality (asymmetry, chirality, chemical reactivity) to the array of iron SCO materials for potential incorporation into nanoscale magnetic switches and spintronic devices.

Ternary alkali ion thiogallates, A5GaS4 (A = Li and Na), with isolated tetrahedral building units and their ionic conductivities.

Two new ternary thiogallates in the A5GaS4 (A = Li (i) and Na (ii)) series have been synthesized for the first time employing a gas passing route using oxide precursors and a high temperature solid state route using stoichiometric combinations of elements, respectively. Li5GaS4 crystallizes in the P21/m space group and the structure is built up of layers of corner sharing tetrahedra of LiS4 and GaS4 stacked along the a-axis and the octahedrally coordinated Li ions residing in the interlayer space. Na5GaS4 crystallizes in the Pbca space group and the structure consists of isolated (GaS4)5- tetrahedra held together by charge balancing sodium ions in distorted tetrahedral and octahedral coordination geometries. Measurements of ionic conductivity of the compounds showed room temperature ionic conductivities of 1.8 × 10-7 and 4.0 × 10-7 S cm-1 with activation energies of 0.54 and 0.28 eV, respectively, for I and II. Density functional theory calculations show close agreement in structural parameters with the measured data and predict band gaps of 2.75 eV (I) and 2.70 eV (II). Single point hybrid functional calculations result in band gaps of 3.95 and 3.65 eV correspondingly, in better agreement with the experimental value of ∼4.1 eV for both. Bond valence energy landscape maps suggest the absence of any suitable diffusion path for Li in Li5GaS4. On the other hand, BVEL maps of Na5GaS4 confirm that the tetrahedrally coordinated Na ions are responsible for ionic conduction, whereas the involvement of octahedrally coordinated Na ions in the conduction process could not be discerned.

New Solids in As-O-Mo, As(P)-O-Mo(W) and As(P)-O-Nb(W) Systems That Exhibit Nonlinear Optical Properties.

Interactions between well-mixed fine powders of As2O3, P2O5, MoO3, WO3 and Nb2O5 at different stoichiometry in quartz ampoules under vacuum at ~1000 °C in the presence of metallic molybdenum (or niobium), over several weeks, led to shiny dichroic crystalline materials being formed in cooler parts of the reaction vessel. An addition of small quantities of metals-Mo or Nb-was made with the aim of partially reducing their highly oxidized Mo(VI), W(VI) or Nb(V) species to corresponding Mo(V), W(V) and Nb(IV) centers, in order to form mixed valence solids. Sublimed crystals of four new compounds were investigated using a variety of techniques, with prime emphasis on the X-ray analysis, followed by spectroscopy (diffusion reflectance, IR, Raman and EPR), second harmonic generation (SHG), thermal analysis under N2 and air atmosphere, and single crystals electrical conductivity studies. The results evidenced the formation of new complex solids of previously unknown compositions and structures. Three out of four compounds crystallized in non-centrosymmetric space groups and represent layered 2D polymeric puckered structures that being stacked on each other form 3D lattices. All new solids exhibit strong second-harmonic-generation (SHG effect; based on YAG 1064 nm tests with detection of 532 nm photons), and a rare photosalient effect when crystals physically move in the laser beam. Single crystals' electrical conductivity of the four new synthesized compounds was measured, and the results showed their semiconductor behavior. Values of band gaps of these new solids were determined using diffusion reflectance spectroscopy in the visible region. Aspects of new solids' practical usefulness are discussed.

Tuning π-Acceptor/σ-Donor Ratio of the 2-Isocyanoazulene Ligand: Non-Fluorinated Rival of Pentafluorophenyl Isocyanide and Trifluorovinyl Isocyanide Discovered.

Isocyanoazulenes (CNAz) constitute a relatively new class of isocyanoarenes that offers rich structural and electronic diversification of the organic isocyanide ligand platform. This article considers a series of 2-isocyano-1,3-X2-azulene ligands (X = H, Me, CO2Et, Br, and CN) and the corresponding zero-valent complexes thereof, [(OC)5Cr(2-isocyano-1,3-X2-azulene)]. Air- and thermally stable, X-ray structurally characterized 2-isocyano-1,3-dimethylazulene may be viewed as a non-benzenoid aromatic congener of 2,6-dimethyphenyl isocyanide (2,6-xylyl isocyanide), a longtime "workhorse" aryl isocyanide ligand in coordination chemistry. Single crystal X-ray crystallographic {Cr-CNAz bond distances}, cyclic voltametric {E1/2(Cr0/1+)}, 13C NMR {δ(13CN), δ(13CO)}, UV-vis {dπ(Cr) → pπ*(CNAz) Metal-to-Ligand Charge Transfer}, and FTIR {νN≡C, νC≡O, kC≡O} analyses of the [(OC)5Cr(2-isocyano-1,3-X2-azulene)] complexes provided a multifaceted, quantitative assessment of the π-acceptor/σ-donor characteristics of the above five 2-isocyanoazulenes. In particular, the following inverse linear relationships were documented: δ(13COtrans) vs. δ(13CN), δ(13COcis) vs. δ(13CN), and δ(13COtrans) vs. kC≡O,trans force constant. Remarkably, the net electron withdrawing capability of the 2-isocyano-1,3-dicyanoazulene ligand rivals those of perfluorinated isocyanides CNC6F5 and CNC2F3.

New in vitro highly cytotoxic platinum and palladium cyanoximates with minimal side effects in vivo.

Several biologically active bivalent Pd and Pt complexes with two structurally similar cyanoxime ligands abbreviated as H(DECO): 2-oximino-2-cyano-N,N'-diethylacetamide, and H(PyrCO): 2-oximino-2-cyan-N-pyrrolidine acetamide were synthesized and characterized using spectroscopic methods, thermal analysis and X-ray crystallography. Structures revealed planar cis-geometry of studied complexes. Freshly obtained Pt(DECO)2, Pd(DECO)2, Pt(PyrCO)2 and Pd(PyrCO)2 complexes were used in for in vitro cytotoxicity assays using two different etiology human cancer cell lines HeLa and WiDr cells. Investigated compounds showed cytotoxicity levels at or above cisplatin. Pt(DECO)2 was also tested in vivo in healthy C57BL/6 mice. The complex was administered at three different dosage (0, 7.5, 15 mg/kg, i.p. once/week), over a total period of 8 weeks. No changes were observed in the animal weight in the treated mice compared to the control dextrose-treated group. The levels of erythrocytes, leukocytes, and hemoglobin were within the normal level suggesting low myelotoxicity. Negligible cardiotoxicity was observed from the histological evaluation of the hearts from the treated animals. Results from the tail nerve conduction velocity (NCV) and nerve histomorphometry suggested no impact of Pt(DECO)2 on peripheral nerves. The complex, however, induced certain hepatotoxicity and lead to the elevation of IL-6, a pro-inflammatory cytokine. Overall, Pt(DECO)2 showed minimal in vivo toxicity, thus presenting a promising candidate for future testing in animal models of cancer.

Planochromism of cyanoxime anions: computational and mechanistic studies in solid state and solutions.

The benzoylcyanoxime, NC-C(=N-OH)-C(O)-C6H5 (later H(BCO)), represents a new ampolydentate ligand that received attention in the light of useful biological properties of its coordination compounds. Colorless H(BCO), upon deprotonation, gains color that depends on the counter-cation and the system in general. Five derivatives of H(BCO), with colorless organic and inorganic mono-cations - Cs, Tl, Ag, N(CH3)4 and As(C6H5)4 - were synthesized and characterized by the X-ray analysis, vibrational and electronic spectroscopy. Compounds exhibited unexpected and significant differences in color, both in solid state and in solutions, that were challenging to explain, thereby warranting detailed investigation including high-level DFT/TDFT computations. It was found that the BCO- anion demonstrates negative solvatochromic in polar protic ROH (R = H, CH3, C2H5, C3H7, C4H9) solvents, and appears yellow in color, as tetraalkylammonium or alkali metal salts. In polar aprotic solvents, such as CH3CN, DMF, and DMSO, solutions of the BCO- anion are red. The color originates from n→π* transition in the anion. Solid state structures evidenced a considerable dependence on planarity of the BCO- anion on its color, as well as on the character of bonding in the C-N-O fragment: yellow color is associated with an oxime (bond length C-N is shorter than N-O), while red color is due to the nitroso character (bond length C-N is longer than the N-O). An addition of ethanol to red solutions of the BCO-containing salts leads to the color change to yellow, which is the result of the formation of an H-bond between the C-N-O fragment of cyanoxime and the solvent, also leading to the flattening of the structure. An explanation for this new color-changing effect was offered, based on experimental evidence and TD/DFT calculations. Glossary: H(BCO) is 1-cyano-1-oximino-acetophenone, or benzoylcyanoxime; BCO- is anion of the benzoylcyanoxime; AsPh4 + is tetraphenylarsonium cation; MMe4 + is tetramethyammonium cation; ROH - alcohols; DMF - dimethylformamide; DMSO - dimethylsulfoxide; AN - acetonitrile; DFT -Density Functional Theory; TDDFT - Time-Dependent Density Functional Theory.

Synthesis and Characterization of Anionic Lanthanide(III) Complexes with a Bidentate Sulfonylamidophosphate (SAPh) Ligand.

A series of new anionic lanthanide(III) complexes with the general formula NEt4[LnL4] (1-Ln; HL = dimethyl[(4-methylphenyl)sulfonyl]amidophosphate; Ln = La, Nd, Eu), were synthesized and characterized by IR, UV-vis, and NMR spectroscopies, the differential scanning calorimetry method, thermogravimetric and X-ray analysis, and photoluminescence measurements. Single-crystal structures of NEt4[EuL4] (1-Eu) were determined at 293 and 100 K and evidenced the single-crystal-to-single-crystal phase transition. Both phases are in the monoclinic crystal system in centrosymmetric groups of the same Laue class. The room temperature structure is in C2/c (No. 15), while low-temperature structure is in the P21/c (No. 14) space groups. The coordination environment geometry around the central europium(III) ion is a distorted square antiprism in both polymorphs, while the peripheral methoxy and tolyl groups show different orientations. This phenomenon indicates the occurrence of a thermally driven second-order phase transition during the cooling-heating process. The europium(III) complex exhibits an unusual emission spectrum, clearly dominated by the 5D0-7F4 bands, and an emission decay time equaling 3.5 ms, being among the highest values known for europium coordination compounds.

Chemistry and applications of cyanoximes and their metal complexes.

During the past three decades, considerable research effort has been dedicated to a new class of organic ligands - cyanoximes - which have the general formula NC-C([double bond, length as m-dash]NOH)-R, where R is an electron-withdrawing group. The presence of the CN group makes cyanoximes ∼10 000 times more acidic and better ligands than other known conventional monoximes and dioximes. Also, in numerous cases, this group provides extra nitrogen donor atoms to support the formation of bridges between metal centres in the obtained coordination polymers. With 36 different R groups, the most abundant is the family of mono-cyanoximes, followed by 7 bis-cyanoximes which include aromatic and aliphatic spacers and, lately, tris-cyanoxime representing a 'tripod'. The total number of obtained and characterized compounds is 44. These simple, low molecular weight molecules represent a series of new excellent ampolydentate ligands - 'molecular Lego', or building blocks - for coordination and organometallic chemistry. Uncomplexed ligands, their alkali metal salts, and metal complexes show a large spectrum of biological activity, ranging from growth regulation in plants and antimicrobial activity, to significant in vitro and in vivo cytotoxicity against human cancers. Currently, there are more than three hundred cyanoxime-based complexes, synthesized and studied using a variety of different spectroscopic methods and X-ray analysis. In this review, the preparation and stereochemistry of cyanoxime ligands, their structures and properties, and the most interesting coordination compounds with a broad spectrum of practical applications are summarized.

Nanomedicine-Assisted Combination Therapy of NSCLC: New Platinum-Based Anticancer Drug Synergizes the Therapeutic Efficacy of Ganetespib.

Purpose: K-RAS is the most common mutated oncogene associated with Non-Small-Cell Lung Cancer (NSCLC). So far, there are no promising chemotherapies for the direct inhibition of K-RAS, and considered to be undruggable. In this work, we have introduced a new platinum-based cyanoximate complex, Pt(MCO)2, as an anti-cancer drug to enhance the therapeutic efficacy of Hsp90 inhibitor drug, ganetespib for the combination therapy of NSCLC. Methods: We have synthesized polyacrylic acid (PAA)-coated magnetic nanoparticles (MNPs) and used as drug delivery system. These MNPs were decorated with folic acid in order to target folate receptor-expressing NSCLC. The individual and combination of drugs as well as an optical dye DiI were co-encapsulated successfully inside the PAA-coating of MNPs to evaluate synergistic treatment option for NSCLC. The magnetic resonance (MR) and optical imaging modalities assisted for the monitoring drug loading and NSCLC treatment. Results: To evaluate the therapeutic efficacy of these customized MNPs, various cell-based assays including cell viability, apoptosis and necrosis, cell migration, comet and ROS experiments were performed. Results showed minimal toxicity for functional MNPs with no therapeutic drug and more than 60% cell death within 48 h of treatment, when single drug was encapsulated. Importantly, more than 90% cells were dead when both drugs were delivered. Overall, the results indicated that the Pt(MCO)2 drug enhances the therapeutic efficacy of ganetespib by more than 30% toxicity towards the targeted treatment of NSCLC, while showed minimal toxicity to the normal healthy tissues. Conclusion: We successfully developed new dual-modal magnetic nanomedicines for the rapid and controlled release of combination of drugs for the effective treatment of NSCLC. The MR and fluorescence modalities help monitoring the delivery of drugs, where the new platinum-based drug Pt(MCO)2 synergizes the therapeutic efficacy of ganetespib.

Soft chemical routes to electrochemically active iron phosphates.

New iron phosphates with related structures have been synthesized using hydrothermal and ion-exchange routes, and their electrochemical properties were investigated. First, NaFe(HPO4)2 was synthesized employing a hydrothermal route and its structure was determined from single-crystal X-ray diffraction data. Subsequent Na+ and partial proton ion exchange with Li+ ion produced a known phase, Li2Fe(H0.5PO4)2, and complete deprotonation of Li2Fe(H0.5PO4)2 with Li+ by employing a solid-state ion-exchange route produced the new phase Li3Fe(PO4)2. The structure of the latter was solved from synchrotron powder X-ray data by employing ab initio methods. All of these phases are highly crystalline, built up of similar connectivities between FeO6 octahedra and PO4 tetrahedral units. Magnetic susceptibility measurements and room-temperature 57Fe Mössbauer spectroscopic studies confirm the 3+ oxidation state of the compounds and their antiferromagnetic ordering with Li2Fe(H0.5PO4)2 showing some interesting metamagnetic behavior. The compounds are stable up to 400 °C and undergo facile electrochemical lithium/sodium insertion through the reduction of Fe3+ to Fe2+. Galvanostatic charge-discharge studies indicate that up to 0.6 lithium ion and 0.5 sodium ion per formula unit can be inserted at average voltages of 3.0 and 2.75 V for lithium and sodium ion batteries, respectively, for NaFe(HPO4)2. The partially Li ion exchanged compound Li2Fe(H0.5PO4)2 showed better cycle life and experimentally achievable capacities up to 0.9 Li insertion with strong dependence on particle size. The electrochemical Li insertion in Li3Fe(PO4)2 was also investigated. The electrochemistry of these three related phases were compared with each other, and their mechanism of Li insertion was investigated by ex situ PXRD.

Crystal and electronic structure of a hexacarbonyldiiron cluster tethered to naphthalene-2-thiolate ligands.

The structure of the previously reported complex bis(µ-naphthalene-2-thiolato-κ2S:S)bis(tricarbonyliron)(Fe-Fe), [Fe2(C10H7S)2(CO)6], has been characterized by X-ray diffraction. In the solid state, the dinuclear complex adopts a butterfly-like shape, with an equatorial-axial spatial orientation of the naphthalene groups covalently coupled to the [S2Fe2(CO)6] unit. The asymmetric unit contains three independent [(µ-naphthalene-2-thiolato)2Fe2(CO)6] molecules. These molecules show intermolecular π-π stacking interactions between the naphthalene rings, which was confirmed by Hirshfield surface analysis. The electronic spectrum of the complex recorded in acetonitrile shows a band centered at 350 nm (ℇ = 4.6 × 103 M-1 cm-1) and tailing into the visible region. This absorption can be attributed to a π→π* electronic transition within the naphthalene moiety and a metal-based d→d transition.

Zinc Complexes with Cyanoxime: Structural, Spectroscopic, and Catalysis Studies in the Pivaloylcyanoxime-Zn System.

Reaction of 2-hydroxyimino-4,4-dimethyl-3-oxo-pentanenitrile (common abbreviation HPiCO, pivaloyl-cyanoxime) with zinc sulfate in an aqueous solution results in the formation of the two new complexes: [Zn(PiCO){H(PiCO)2}(H2O)] (I) and tetranuclear Zn complex [Zn4(µ3-OH)2(PiCO)6 (H2O)4] (II). Both complexes were characterized by elemental analysis, IR- and UV-visible spectra, DSC/TGA studies, and X-ray analysis. In complex II, the PiCO- cyanoxime anion adopts three bidentate binding modes: O-monodentate, chelating (κ2), and bridging (η2) coordinations. Also, the ligand represents the mixture of two diasteromers (cis-anti and cis-syn) that form five- and six-membered chelate rings with Zn atoms and cocrystallize in one unit cell at population of 0.57-0.43. There are two crystallographically different Zn-centers in the ASU, and two µ3-bridging hydroxo-groups arrange via inversion center the formation of an elegant tetranuclear complex. Each Zn atom has a molecule of coordinated water and is in the distorted octahedral environment. Because of the structural flexibility and multidentate propensity of the pivaloyl-cyanoxime, complex II may act as a structural model of naturally occurring Zn-containing enzymes. Indeed, compound I exhibits an efficient catalytic performance for transesterification reaction of various esters in ethanol under mild reaction conditions. Therefore, obtained results allow assignment of observed activity as green catalysis.

Shortwave infrared luminescent Pt-nanowires: a mechanistic study of emission in solution and in the solid state.

Several complexes of "PtL2" composition containing two cyanoxime anions - 2-oximino-2-cyano-N-piperidineacetamide (PiPCO-) and 2-oximino-2-cyano-N-morpholylacetamide (MCO-) - have been obtained and characterized both in solution and in the solid state. Complexes exist as two distinct polymorphs: monomeric yellow complexes and dark-green [PtL2]n 1D polymers, while for the MCO- anion a red, solvent containing dimeric [Pt(MCO)2·DMSO]2 complex has also been isolated. The interconversion of polymorphs was investigated. The monomeric PtL2 units are arranged into anisotropic extended solid [PtL2]n polymers with the help of PtPt metallophilic interactions. Crystal structures of monomeric PtL2 (L = PiPCO-, MCO-) and red dimeric [Pt(MCO)2·DMSO]2 complexes were determined and revealed the cis-arrangement of cyanoxime anions. The Pt-Pt distance in the "head-to-tail" red dimer was found to be 3.133 Å. The structure of the polymeric [Pt(PiPCO)2]n compound was elucidated using the EXAFS method and evidenced the formation of Pt-wires with ∼3.15 Å intermetallic separation. The EPR spectra of both 1D polymers at variable temperatures indicate the absence of Pt(iii) species. Both pure dark-green [PtL2]n polymers showed a considerable room temperature electrical conductivity of 20-30 S cm-1, which evidences the formation of a mixed valence Pt(ii)/Pt(iv) system. We discovered that these 1D polymeric [PtL2]n complexes show an intense NIR fluorescence beyond 1000 nm, while yellow monomeric PtL2 complexes are not emissive at all. The room temperature excitation spectra of 1D polymeric [PtL2]n complexes demonstrated their strong emission beyond 1000 nm regardless of the used excitation wavelength between 350 and 800 nm, which is typical of systems with delocalized charge carriers. For the first time the formation of mixed valence "metal wires" held together by metallophilic interactions is directly linked both with an intense fluorescence in the NIR region of the spectrum and with the electrical conductivity. The effect of the concentration of [PtL2]n complexes dispersed in the dielectric salt matrix on the photoluminescence wavelength and intensity was investigated. Both polymers show a quantum yield that is remarkably high for this region of the spectrum, reaching ∼2%. Variable temperature emission of polymeric [PtL2]n in the -190-+60 °C range was studied as well.

Temperature-dependent shape-responsive fluorescent nanospheres for image-guided drug delivery.

Temperature-responsive nanoparticles used in conjunction with hyperthermia promise to provide synergistic effects for increasing drug efficacy. We propose a near-infared (NIR) fluorescent system based on a upper critical solution temperature (UCST) polymer, ISP2, integrated with a NIR fluorescent dye HITC for in vivo tracking. The system forms a nanoparticle that increases its volume as temperature increases, similar to the expansion of a Hoberman sphere. The nanospheres nearly doubled in size, from 80 nm to 140 nm, during a temperature increase from 40°C to 60°C.

Conjugated foldamers with unusually high space-charge-limited current hole mobilities.

Charge carrier mobility and its optimization play a critical role in the development of cutting-edge organic electronic and optoelectronic devices. Even though space-charge-limited current (SCLC) hole mobilities as high as 1.4 cm(2) V(-1) s(-1) have been reported for microscopically sized highly ordered liquid-crystalline conjugated small molecules, the SCLC hole mobility of device-sized thin films of conjugated polymers is still much lower, ranging from 10(-6) to 10(-3) cm(2) V(-1) s(-1). Herein, we report the synthesis, characterizations, and thin-film SCLC mobility of three discotic conjugated polymers, INDT-TT, INDT-BT, and INDT-NDT. Optical studies indicate that polymer INDT-NDT adopts a folded conformation in solutions of good or poor solvents, whereas polymer INDT-TT stays as random monomeric chains in good solvents and interchain aggregates in poor solvents. INDT-BT polymer chains, however, stay as foldamers in dilute solutions of good solvents but interchain aggregates in concentrated solutions or poor solvents. Circular dichroism spectroscopy provides clear evidence for the helical folding of INDT-NDT in solutions. Thin films spin-coated from 1,2-dichlorobenzene solutions of the polymers show SCLC hole mobility of 2.20 × 10(-6), 8.79 × 10(-5), and 2.77 × 10(-2) cm(2) V(-1) s(-1) for INDT-TT, INDT-BT, and INDT-NDT, respectively. HRTEM and powder XRD measurements show that INDT-NDT pristine thin films contain nanocrystalline domains, whereas the INDT-TT and INDT-BT films are amorphous. Thin films of INDT-NDT:PC71BM blends show increased crystallinity and further improved SCLC hole mobility up to 1.29 × 10(-1) cm(2) V(-1) s(-1), one of the highest SCLC mobility values ever recorded on solution-processed organic semiconducting thin films. The persistent folding conformation of INDT-NDT is believed to be responsible for the high crystallinity of its thin films and its high SCLC mobilities.