Effects of organoantimony compounds on fungal pathogens Cryptococcus neoformans and Candida albicans

Cryptococcus neoformans is an opportunistic pathogen that causes pulmonary cryptococcosis and cryptococcal meningitis in immune-compromised individuals. Candida albicans, also opportunistic, can cause pulmonary candidiasis, genitourinary tract infections, candidemia, and oral candidiasis. Fungal infections are responsible for approximately 1.7 million annual deaths. With few antifungal drugs, high toxicity, and increased resistance to antifungals, the importance of finding new antifungal therapies is crucial. We hypothesized that novel organoantimony compounds would effectively restrict fungal growth. We tested approximately 20 compounds against C. neoformans and C. albicans in minimum inhibitory concentration (MIC) assays. Compounds A, B, E, I, F, and G were effective against C. neoformans with MIC concentrations of 10.94 ug/ml, 19.79 ug/ml, 18.75 ug/ml, 12.5 ug/ml, 20.83 ug/ml, and 2.60 ug/ml, respectively. Compounds E and G were effective against C. albicans at 15.625 ug/ml and 25 ug/ml, respectively. Compounds I and G were fungicidal against C. neoformans at concentrations 50 ug/ml and 25 ug/ml, respectively, and compound G was fungicidal against C. albicans at 50 ug/ml. Cytotoxicity assays showed that antifungal compounds A, B, E, I, F, and G were non-toxic. RNA sequencing studies have identified several C. neoformans genes involved with the compounds' inhibitory effects.Lew Wentz FoundationMicrobiology and Molecular Genetic

A 1-D coordination polymer route to catalytically active Co@C nanoparticles

Pyrolysis of a 1-D polymeric cobalt(II) coordination complex ([Co(BDC)(Mim)2]n, H2BDC = benzenedicarboxylic acid; Mim = N-methylimidazole) results in the formation of carbon embedded fcc cobalt nanoparticle composites, Co@C. The as-prepared Co@C shows an agglomerated secondary structure with a highly embedded carbon shell comprising of cobalt nanoparticles of 20-100 nm. These Co@C particles show excellent catalytic activity in the reduction of nitrophenol to aminophenol, studied as a model reaction, and evolves as a promising candidate for the gas phase reduction process

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

Demetallation of a Ni(II) tetraazamacrocyclic complex by cyanoxime resulting in the formation of a stereospecific trinuclear compound [Na(H2O)6]+[NaNi2L6]-(L = NC-C(NO)-C(O)NH )

The reaction between the NiA(ClO4)2 and NaHL2 {where A=14ane[N4], the macrocyclic ligands derived from the product of template condensation of 2,6-diacetylpyridine with aliphatic 3,3\u27-diaminodipropylamine, NH2(CH2)3NH(CH2)3NH2; and L=2-cyano-2-isonitrosoacetamide anion, ACO-(amidecyanoxime, NCC(NO)-C(O)NH2-)} has led to the formation of a highly unusual trimetallic bis-[fac-(triscyanoximato) nickel(II)] anionic complex anion instead of the expected Ni(II) macrocyclic complex with coordinated cyanoxime ligands. Two equivalent and symmetric trigonal-prismatic NiL3- units are connected to form the [NaNi2L6]- anion by the presence of a central sodium cation. The latter is located between two NiL3- anions and has an octahedral NaO6 geometry comprised of oxygen atoms of the nitroso group of the cyanoxime ligand. The oxime ligand is planar and adopts a cis-anti configuration in the complex

Synthesis of the monosubstituted arylcyanoxime and its Na, Tl(I) and Ag(I) compounds

Nitrosation of 2-chlorophenyl acetonitrile with t-butylnitrite under basic conditions (Meyer reaction) resulted in a high-yield preparation of the first substituted arylcyanoxime, 2-chlorophenyl(oximino)acetonitrile, H(2Cl-PhCO) (HL). The obtained cyanoxime is readily deprotonated in solution by metal hydroxides or carbonates with the formation of yellow sodium, tetrabutylammonium, thallium(I) and silver(I) derivatives. The crystal structure of the Tl(I) complex was determined. Thallium(I) salt (TlL) crystallizes in the monoclinic space group P21 n with a = 3.8382(7), b = 11.0065(18), c = 20.901(4) Å, and β = 92.447(3)°, V = 882.2(3) Å3, Z = 4; T = 193 K (Mo Kα radiation). The structure was solved by direct methods to a final R of 0.0689 (wR2 = 0.1650) for I \u3e 2σ(I). The crystal structure of the complex is a one-dimensional coordination polymer that consists of centrosymmetric [TlL]2 dimers in which Tl2O2 rhombohedra are connected to each other at 90.72°. The crystal structure of TlL is an interesting example of the ruffled metal-organic network composed of Tl-O-Tl-O zigzag chains with close (3.838 Å) intermetallic distances comparable to those in metallic thallium (3.42 Å). The cyanoxime anion bridges metal centers and acts as a tridentate ligand where oxygen atoms of the oxime group bond to three different Tl(I) cations with three different bond lengths

Cyclic tetranuclear iron-carbonyl complex containing thiobisbenzenethiolate ligands: Synthesis and structural characterization

A new macromolecular double-butterfly Fe/S carbonyl cluster, [Fe2(CO)6]2(μ-4,4\u27-thiobisbenzenethiolato)2 (1), a model for the active site of [Fe-Fe] hydrogenases, has been prepared and characterized by spectroscopic methods and X-ray crystallography. The molecular structure of 1 contains two units of S2Fe2(CO)6 covalently linked to two thiobisbenzene groups to form a 26-membered metallocycle with the benzene substituents on sulfur adopting an ae stereochemistry. The Fe-Fe bond in 1 is 2.5046(5) Å which is close to that of the enzyme and related complexes. Crystals of 1 obtained from dichlormethane solution of [Fe2(CO)6]2(μ-4,4\u27-thiobisbenzenethiolato)2 contain two dichloromethane molecules trapped in the cavity of 1. Infrared spectrum of 1 has peaks at 2071, 2030, and 1972 cm-1 charateristic of the presence of the Fe2(CO)6 core. Spectroscopic evidence suggest significant electronic interaction between the thiobisbenzene moieties and the S2Fe2(CO)6 units in 1

Organoantimony(V) Cyanoximates: Synthesis, Spectra and Crystal Structures

A series of 25 new organoantimony(V) cyanoximates has been synthesized and studied using IR, visible, and NMR spectroscopy and X-ray analysis. Crystal structures were determined for compounds (C6H5)4Sb{ONC(CN)C(O)NH2} (1) and (C6H5)4Sb{ONC(CN)C(O)N(CH3)2} (2). Both complexes crystallized in the monoclinic space group P21/c (Z = 4) with unit cell parameters (Å, grad) of a = 14.921(3), b = 10.165(2), c = 17.571(7), β = 113.26(6) for compound 1, and a = 16.415(4), b = 10.406(3), c = 17.152(3), β = 117.79(2) for compound 2. For 5438 and 5056 independent reflections the refinement yielded R-factors 0.022 and 0.037 for the structures of 1 and 2, respectively. Cyanoxime anions are bound to the antimony(V) atoms in a monodentate fashion via the oxygen atoms of the oxime groups. The ligands adopt trans-anti configuration in these compounds. The coordination polyhedron in both complexes is a distorted trigonal bipyramid with the axial location of the cyanoxime ligand. A similar binding mode of other anions in synthesized organoantimony(V) complexes has been offered on the basis of the similarity of their IR spectra to those of the compounds whose structures were determined crystallographically. The exact assignment of vibrations involving the oxime group was carried out using synthesized 15N (53%) isotopomers

Classic Isomeric 1, 2-and 2, 1-nitrosonaphthols are Oximes in Solid State and Solutions

A detailed characterization by UV-visible, IR and NMR (1H, 13C, 15N) spectroscopies of two isomeric 1,2- and 2,1-nitrosonaphthols (1 and 2) has been carried out. The crystal structures of these iconic compounds, which were widely used in analytical chemistry in the past, were determined and evidenced their quinone-oxime nature in solid state. Compound 1 exists in the crystal as a syn- diastereomer in the closed form due to a strong intramolecular H-bond, while compound 2 is an anti- diastereomer forming a dimer with two intermolecular H-bonds. The oxime character of 1 and 2 in solutions was confirmed after careful studies of the NMR spectra of both compounds in solvents of different polarity and donor properties: CD2Cl2, acetone-d6 and DMSO-d6. An equilibrium state between oxime syn- and anti- isomers exists and can be modulated in a controlled way by changing media\u27s polarity. Both compounds were also prepared labeled with 15N (50%) for recording their NMR nitrogen-15 spectra, and for the identification/assignment of vibrations with the participation of the \u3eC=N-OH fragment. During synthesis of compound 1 a persistent, very polar, red-colored impurity 3 was detected, isolated and crystallographically characterized. It was found to be a rather unusual π-complex between the final compound 1 and its precursor 2-naphthol. The red color originates from the CT-band in the visible region of the UV/Vis-spectrum where the naphthol acts as a donor with 1 being an acceptor. Both are separated at 3.03 A

Cyclic Tetranuclear Iron-Carbonyl Complex Containing Thiobisbenzenethiolate Ligands: Synthesis and Structural Characterization

A new macromolecular double-butterfly Fe/S carbonyl cluster, [Fe2(CO)6]2(μ-4,4′-thiobisbenzenethiolato)2 (1), a model for the active site of [Fe-Fe] hydrogenases, has been prepared and characterized by spectroscopic methods and X-ray crystallography. The molecular structure of 1 contains two units of S2Fe2(CO)6 covalently linked to two thiobisbenzene groups to form a 26-membered metallocycle with the benzene substituents on sulfur adopting an ae stereochemistry. The Fe-Fe bond in 1 is 2.5046(5) Å which is close to that of the enzyme and related complexes. Crystals of 1 obtained from dichlormethane solution of [Fe2(CO)6]2(μ-4,4′-thiobisbenzenethiolato)2 contain two dichloromethane molecules trapped in the cavity of 1. Infrared spectrum of 1 has peaks at 2071, 2030, and 1972 cm⁻¹ charateristic of the presence of the Fe2(CO)6 core. Spectroscopic evidence suggest significant electronic interaction between the thiobisbenzene moieties and the S2Fe2(CO)6 units in 1

2-Cyano-2-isonitrosoacetamide and its Ag(i) complexes. Silver(i) cyanoximate as a non-electric gas sensor

The 2-cyano-2-isonitrosoacetamide, NC-C(N[double bond, length as m-dash]OH)-C(O)NH2 (1), its Na+, Cs+ salts and four silver(I) complexes with N-donor ligands were synthesized and characterized using a variety of techniques including IR, UV-vis spectroscopy, solid state photoluminescence, X-ray analysis, and solution electrical conductivity. All four reported here Ag(I) complexes were crystallographically characterized and revealed completely different structures. Thus, the combination of chelate and bridging function of the cyanoxime anion in Ag{NC-C(N[double bond, length as m-dash]O)-C(O)NH2} (complex 6) leads to a unique layered 2D coordination polymer of silver(I) with pronounced argentophilic interactions at 3.194 Å. The structure of Ag{NC-C(N[double bond, length as m-dash]O)-C(O)NH2}·2Pic (Pic = 2-methylpyridine; complex 7) represents the monomeric complex containing bidentate chelate anion 1-. The crystal structure of monomeric Ag{NC-C(N[double bond, length as m-dash]O)-C(O)NH2}·2NH3 (complex 8) reveals the formation of a linear Ag(NH3)2+ cation non bonded to the metal cyanoxime anion 1-. This is the first structure of a silver(I) diammine cation with an oxime-based anion. Similarly to 8, the crystal structure of Ag(14ane[N4]){NC-C(N[double bond, length as m-dash]O)-C(O)NH2}·CH3CN with tetraaza-meso(macrocyclic) ligand (complex 9) contains a metal center not bound to the cyanoxime ligand as well. Instead, the agostic interaction at 2.591 Å between the methylene group of the macrocyclic ligand and silver(I) center was found in 9. This is the shortest CH2-Ag distance between an aliphatic group and metal observed so far in non-organometallic silver complexes with neutral ligands. We also documented a remarkable visible-light insensitivity of complex 6. Room temperature solid state photoluminescence of this compound was examined in details, including studies of its emission in the presence of several gases of industrial importance: H2, CO, NO, NH3, SO2, acetylene C2H2 and ethylene C2H4. A significant sensitization of 6 to visible light after the exposure was observed, which is a useful property that may be utilized in development of battery-less colorimetric sensors for these gases