Single-crystal X-ray Diffractometry Research Articles

Ferromagnetic interactions in a 1D Heisenberg linear chain of 1-phenyl-3,7-bis(trifluoromethyl)-1,4-dihydro-1,2,4-benzotriazin-4-yls

1-Phenyl-3,7-bis(trifluoromethyl)-1,4-dihydro-1,2,4-benzotriazin-4-yl (2), was characterized by single crystal X-ray diffractometry and variable temperature SQUID magnetometry to investigate its structure-magnetism correlation.

Temperature-dependent interchromophoric interaction in a fluorescent pyrene-based metal-organic framework.

Compounds exhibiting tuneable fluorescence emission upon heating or cooling are considered smart materials as their optical properties can be exquisitely controlled by adjusting the external temperature. Herein, we report such a material, which is a porous pyrene-based metal-organic framework with a chemical formula of [Mg1.5(HTBAPy)(H2O)2]·3DMF (H4TBAPy = 1,3,6,8-tetrakis(p-benzoic acid)pyrene), named SION-7. The bulk solid material of SION-7 can display either monomer or excimer fluorescence emission due to the temperature-dependent extent of interchromophoric interactions between the HTBAPy3- ligands within the framework. Consequently, the fluorescence emission colours gradually change from blue at low temperature (80 K) to yellow-green at high temperature (450 K). Interestingly, while kept in a relatively wide temperature range of 80-200 K, SION-7 displays a structured monomer-like spectrum and its colour changes reversibly from deep to light blue. Ex situ variable-temperature (100-350 K) single-crystal X-ray diffractometry studies revealed the impact of solvent content on the optical properties of SION-7, and illustrated the correlation between the position of the phenylene groups of the HTBAPy3- ligands at different temperatures and the interchromophoric interaction. Our study demonstrates a step forward towards the design of tuneable thermofluorochromic materials sought by optoelectronics.

Studies on Silver Ions Releasing Processes and Mechanical Properties of Surface-Modified Titanium Alloy Implants.

Dispersed silver nanoparticles (AgNPs) on the surface of titanium alloy (Ti6Al4V) and titanium alloy modified by titania nanotube layer (Ti6Al4V/TNT) substrates were produced by the chemical vapor deposition method (CVD) using a novel precursor of the formula [Ag5(O2CC2F5)5(H2O)3]. The structure and volatile properties of this compound were determined using single crystal X-ray diffractometry, variable temperature IR spectrophotometry (VT IR), and electron inducted mass spectrometry (EI MS). The morphology and the structure of the produced Ti6Al4V/AgNPs and Ti6Al4V/TNT/AgNPs composites were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover, measurements of hardness, Young’s modulus, adhesion, wettability, and surface free energy have been carried out. The ability to release silver ions from the surface of produced nanocomposite materials immersed in phosphate-buffered saline (PBS) solution has been estimated using inductively coupled plasma mass spectrometry (ICP-MS). The results of our studies proved the usefulness of the CVD method to enrich of the Ti6Al4V/TNT system with silver nanoparticles. Among the studied surface-modified titanium alloy implants, the better nano-mechanical properties were noticed for the Ti6Al4V/TNT/AgNPs composite in comparison to systems non-enriched by AgNPs. The location of silver nanoparticles inside of titania nanotubes caused their lowest release rate, which may indicate suitable properties on the above-mentioned type of the composite for the construction of implants with a long term antimicrobial activity.

Synthesis, Characterization, and Computional Studies of Triazatetracyclo Acetamide

N-[(9E)-8,0 10,0 17-triazatetracyclo[8.7.0.02,7.011,18]heptadeca-1(17),2(7),3,5,11,13,15-heptaen-9-ylidene] acetamide (I) is synthesized and characterized by spectroscopy, microanalysis, and single crystal X-ray diffractometry. Compound 1 crystallizes in the monoclinic space group P21/n with a = 17.5552(17) A, b = 4.6163(4) A, c = 17.7662(17) A, β = 115.953(3)°, and Z = 4. The bond angles and bond lengths of the compound are computed using the density functional theory with B3LYP, BPW91, and wB97XD functionals and the 6-31G++(d,p) basis set. The frontier orbitals that contribute to the reactivity of triazatetracyclics are discussed.

Synthesis and Characterization of Non-Isolated-Pentagon-Rule Actinide Endohedral Metallofullerenes U@ C1(17418)-C76, U@ C1(28324)-C80, and Th@ C1(28324)-C80: Low-Symmetry Cage Selection Directed by a Tetravalent Ion.

For the first time, actinide endohedral metallofullerenes (EMFs) with non-isolated-pentagon-rule (non-IPR) carbon cages, U@C80, Th@C80, and U@C76, have been successfully synthesized and fully characterized by mass spectrometry, single crystal X-ray diffractometry, UV-vis-NIR and Raman spectroscopy, and cyclic voltammetry. Crystallographic analysis revealed that the U@C80 and Th@C80 share the same non-IPR cage of C1(28324)-C80, and U@C76 was assigned to non-IPR U@ C1(17418)-C76. All of these cages are chiral and have never been reported before. Further structural analyses show that enantiomers of C1(17418)-C76 and C1(28324)-C80 share a significant continuous portion of the cage and are topologically connected by only two C2 insertions. DFT calculations show that the stabilization of these unique non-IPR fullerenes originates from a four-electron transfer, a significant degree of covalency, and the resulting strong host-guest interactions between the actinide ions and the fullerene cages. Moreover, because the actinide ion displays high mobility within the fullerene, both the symmetry of the carbon cage and the possibility of forming chiral fullerenes play important roles to determine the isomer abundances at temperatures of fullerene formation. This study provides what is probably one of the most complete examples in which carbon cage selection occurs through thermodynamic control at high temperatures, so the selected cages do not necessarily coincide with the most stable ones at room temperature. This work also demonstrated that the metal-cage interactions in actinide EMFs show remarkable differences from those previously known for lanthanide EMFs. These unique interactions not only could stabilize new carbon cage structures, but more importantly, they lead to a new family of metallofullerenes for which the cage selection pattern is different to that observed so far for nonactinide EMFs. For this new family, the simple ionic A q+@C2 n q- model makes predictions less reliable, and in general, unambiguously discerning the isolated structures requires the combination of accurate computational and experimental data.

Dual-site aqua mononuclear nickel(II) complexes of non-heme tetradentate ligands: Synthesis, characterization and reactivity

Mononuclear compounds [Ni(BQCNMe2)(H2O)2](ClO4)21 and [Ni(BQCNH2)(H2O)2](ClO4)22 of N,N′-dimethyl-N,N′-di(quinolin-8-yl)cyclohexane-1,2-diamine (BQCNMe2) and N,N′-di(quinolin-8-yl)cyclohexane-1,2-diamine (BQCNH2) were synthesised and characterized by elemental analysis, IR/UV-Vis spectroscopy, cyclic voltammetry (CV)/differential pulse voltammetry (DPV) and X-ray powder pattern. [Ni(BQCNMe2)(en)](ClO4)23 and [Ni(BQCNMe2)(phen)](ClO4)24 were prepared by reacting 1 with ethylenediamine (en) and 1,10-phenanthroline (phen) respectively while [Ni(BQCNH2)(en)](ClO4)25 and [Ni(BQCNH2)(phen)](ClO4)26 were obtained from the reaction of 2. Compounds [Ni(BQENMe2)(en)](ClO4)27 and [Ni(BQENH2)(en)](ClO4)2.CH3CN 8 (BQENMe2 is N,N′-dimethyl-N,N′-bis(8-quinolyl)ethane-1,2-diamine) and BQENH2 is N,N′-bis(8-quinolyl)ethane-1,2-diamine) were synthesised similarly. Compounds 6 and 8 were characterized by single crystal X-ray diffractometry and their structural features are presented. The reactivity of 2 with H2O2/base was investigated. A new peak at 570 nm in the UV-Vis spectrum corresponding to 2a was obtained which on addition of 2-phenylpropionaldehyde (2-PPA) decays giving pseudo-first order rate constant of 9.2 × 10−3 s−1 and acetophenone as a major product. The catalytic hydroxylation of cumene and ethylbenzene by 1 and 2 in the presence of meta-chloroperbenzoic acid (m-CPBA) was investigated.

Ammonium cyamelurates: synthesis and crystalline structures

Contradictory literature on the alkali-assisted exfoliation of the melon and searching for the best precursors for different heptazine derivative synthesis led us to the synthesis of two cyameluric acid salts, (NH4)2[C6N7O3H] (ECN3) and (NH4)2(H9O4)[C6N7O3] (ECN5). These salts were characterized by single-crystal X-ray diffractometry for the first time. Ammonium cations bind C6N7O3H2− anions (ECN3) by means of Coulombic compression and hydrogen bonds. In ECN5, stability of the columns consisting of C6N7O33− anion triads is provided by Coulombic compression and hydrogen bonds between anions, ammonium cations, and hydroxonium (H9O4+). The planar cyamelurate anions of one triad are located strictly above each other with the distance of 3.710(3) A between the neighbor anions. Each triad is twisted relative to the adjacent one by an angle of 60° and is distant by 3.605(3) A.

Synthesis, Characterization and Computational Studies of Two Triazaspiro Tetracycles

Two new triazaspiro tetracycles have been synthesized, the compounds have been characterized using spectroscopy, microanalysis and single crystal X-ray diffractometry. The single crystal X-ray crystallography of 4-methyl-8I,10I,17I-triazaspiro[cyclohexane-1,9I-teracyclo[8.7.02,7.011,16]heptadecane]-1I(17),2I(7I),3I,5I,11I,13I,15I-heptaene (compound I) has been discussed. The DFT computed bond angles have been obtained for both compounds and contrasted with experimental results for compound I. The atoms that make up the frontier orbitals which contribute to the reactivity of the compounds have been discussed.

Cu(I) complexes with thiosemicarbazides derived from p-toluenesulfohydrazide: Structural, luminescence and biological studies

Reactions of thiosemicarbazide ligands (LR: R = cyclohexyl (Cy) or phenyl (Ph)) with [CuCl(PPh3)3] led to the formation of colorless Cu(I) complexes of composition [CuCl(PPh3)2(LR)]. Both complexes were characterized by spectroscopic methods and further studied by single crystal X-ray diffractometry. The crystal structures confirmed the tetrahedral geometry for the Cu(I) metal center, which is coordinated by a chlorido, two triphenylphosphane and by the thiosemicarbazide as a neutral S-donor monodentate ligand. Photophysical studies revealed that the complexes exhibit emission at room temperature with maxima around 480 nm. At 77 K, the emission is shifted to higher energy, a characteristic behavior of MLCT emitters. The main low lying molecular orbitals were calculated by TD-DFT and confirmed that the S0 → S1 transitions have mainly MLCT character as well as that the peripheral groups in the thiosemicarbazide ligand play an important role on this transition. Moreover, the emission bands are considerably suppressed in the presence of O2, indicating the triplet character of the emitter excited states. The intersystem crossing process is also suggested by the energy diagrams built through TD-DFT calculations. Overall, both experimental and theoretical analysis suggest 3MLCT radiative decays occurrence for the complexes. Furthermore, biological assays showed that the complexes are active on the intracellular amastigote form of Trypanosoma cruzi (Tulahuen Lac-Z strain), and present a significant cytotoxic effect against metastatic melanoma cells. Finally, no significant toxicity to LLC-MK2 cells was observed, resulting in a therapeutic index of about 30 for one of the complexes, in the same order of magnitude as that of the standard drug benznidazole.

The structure ofortho-(trifluoromethyl)phenol in comparison to its homologues – A combined experimental and theoretical study

AbstractThe molecular and crystal structure of commercially-availableortho-(trifluoromethyl)phenol were determined by means of single-crystal X-ray diffractometry (XRD) and represent the first structural characterization of anortho-substituted (trihalomethyl) phenol. The unexpected presence of a defined hydrate in the solid state was observed.Intermolecular contacts and hydrogen bonding were analyzed. The compound was further characterized by means of multi-nuclear nuclear magnetic resonance (NMR) spectroscopy (1H,13C{1H},19F) and Fourier-Transform infrared (FT-IR) vibrational spectroscopy. To assess the bonding situation as well as potential reaction sites for reactions with nucleophiles and electrophiles in the compound by means of natural bonding orbital (NBO) analyses, and density functional theory (DFT) calculations were performed for the title compound as well as its homologous chlorine, bromine and iodine compounds. As far as possible, experimental data were correlated to DFT data.

Zn thiosacharinates: From ionic to polymeric structures. Synthesis, characterization and cell proliferation inhibition studies

Abstract A series of Zn thiosacharinates complexes with nitrogen donor co-ligands were synthesized: [Zn(tsac)2(o-phen)], [Zn(tsac)2(TMDP)]n, [(4,4′-bipy)H2][Zn(tsac)4] [Zn(tsac)2(2,2′-bipy)], [Zn(tsac)2(2,2′-bquin)], (tsac, thiosaccharinate anion: 1,1-dioxo-1,2-benzisothiazole-3-thiolato, C7H4NO2S2−, o-phen: 1,10′-phenantroline, TMDP: trimethylenedipyridine, 2,2′-bipy: 2,2′-bipyridine, 4,4′-bipy: 4,4′-bipyridine, 2,2′-bquin: 2,2′-biquinoline). They were fully characterized by means of FTIR, 13C and 1H NMR, elemental analysis and conductivity measurements. Three of them, [Zn(tsac)2(o-phen)], [(4,4′-bipy)H2][Zn(tsac)4], [Zn(tsac)2(TMDP)]n were also characterized by X-ray single crystal diffractometry and their crystal structures are described herein. DFT geometry optimization for the [Zn(tsac)2(o-phen)] complex was performed and its vibrational spectra was predicted. Moreover, we studied the effects of the five complexes on cell proliferation, thus providing preliminary evidence for their therapeutic potential as anti-cancer drugs.

Syntheses and crystal structures of organoindium(III) 1-D coordination polymers with bis(diphenylphosphino)alkane dioxides

Bromomethyl-dibromo-indium(III), Br2InCH2Br, obtained from indium monobromide and methylene dibromide, reacts with hard and soft donor ligands to afford the corresponding indium(III) organometallic complexes. In this work, we investigated the conditions to prepare adducts of Br2InCH2Br using bis(diphenylphosphino)alkane dioxides acting as hard ligands. We report here the synthesis and crystal structures of two 1-D coordination polymers with the hard donor ligands Ph2P(O)(CH2)mP(O)Ph2 (m = 2, dppeO2 and m = 6, dpphO2). Compounds 1 and 2 with formulas [Br2In(CH2Br)(dppeO2)]n (1) and [Br2In(CH2Br)(dpphO2)]n (2) were characterized by IR and Raman spectroscopy and elemental analysis. We also obtained an ionic indium(III) compound with dppeO2 acting as a chelating ligand with formula [InBr2(dppeO2)2][InBr3(CH2Br)] (3). The crystal structures were determined for 1–3 using single crystal X-ray diffractometry. The geometry around the In(III) can be described as a trigonal bipyramid in 1 and 2, and the chains were packed onto the plane giving layers that are stabilized mainly by intermolecular interactions. Compound 3 has a square bipyramidal In(III) cation with formula [Br2L2In]+ and tetrahedral organoindium(III) anion with formula [Br3InCH2Br]–. Hirshfeld surface analysis employing 2-D fingerprint plots have been used to analyze intramolecular and intermolecular interactions present in the solid state of the structures.

A new triazine bearing a pyrazolone group capable of copper, nickel, and zinc chelation.

Interest in inorganic applications of triazines is growing. In this report, metal complexes of copper(ii), nickel(ii), and zinc(ii) and a novel class of chelates composed of a triazine ring substituted with a hydrazine group and pyrazolone are evaluated using spectrophotometric methods, single crystal X-ray diffractometry, and electrochemistry. Complexes with copper(ii) include a single chelate and chloride ion(s)/water to satisfy a trigonal bipyramidal coordination sphere. The nickel(ii) and zinc(ii) complexes are composed of two chelating groups that adopt an octahedral geometry around the metal ion. Irreversible redox activity was observed with the copper(ii) complex but no redox activity was observed with the ligand alone or zinc(ii) and nickel(ii) complexes. Use of the coumarin carboxylic acid assay shows that the ligand motif is capable of preventing redox cycling of copper in biological conditions and could thus serve as an antioxidant preventative agent. Cellular toxicity studies show that the new triazine molecule could have therapeutic applications in the μM concentration range based on the measured EC50 = 1.183 ± 0.002 mM. Altogether this work shows that by merging triazine chemistry into inorganic compounds, there is potential to explore a range applications thanks to the new architecture.

Synthesis, electronic structure and redox properties of the diruthenium sandwich complexes [Cp*Ru(μ-C10H8)RuCp*]x (x = 0, 1+; Cp* = C5Me5; C10H8 = naphthalene).

The dinuclear ruthenium complex [Cp*Ru(μ-C10H8)RuCp*] (1; Cp* = η5-C5Me5) was prepared by reduction of the cationic precursor [Cp*Ru(η6-C10H8)]PF6 with KC8. Diamagnetic 1 has a symmetric molecular structure with an anti-facial configuration of the Cp*Ru moieties coordinating to naphthalene. Density Functional Theory (DFT) studies showed an electronic structure similar to that of the analogous diiron complex [Cp*Fe(μ-C10H8)FeCp*]. Cyclic voltammetry and UV-vis spectroelectrochemistry showed that 1 can be reversibly oxidized to 1+ and 12+. Chemical oxidation with [Cp2Fe]BArF4 afforded the paramagnetic compound [1]BArF4, which was investigated by EPR, single-crystal X-ray diffractometry and DFT calculations. Reaction of 1 with Brookhart's acid gave the hydride complex [3]BArF4, which was characterized spectroscopically and crystallographically. Cyclic voltammetry showed that [3]+ is converted back to 1 upon reduction and oxidation.

A new Cu(II) three-dimensional network with 4,4′-oxybis benzoic acid: structural diversity, EPR, and magnetism

The copper derivative {[Cu4(oba)4(H2O)4]∙H2O}n (1) has been hydro(solvo)thermally synthesized by combining flexible 4,4′-oxybis benzoic acid (oba) and divalent copper nitrate. As a result of the potential coordination modes of carboxylate oxygens from the oba ligand, the aforementioned complex leads to the formation of an interesting 3D framework, as evidenced by single-crystal X-ray diffractometry. Concerning the topology in 1, the dimers [Cu2C4O8] are nodes of a 5-fold 4-connected uninodal net of the type lvt, with point symbol {42.84} and vertex symbol [4.4.84.84.88.88]. The encapsulation of the copper coordination polymer displays a moderate luminescent property. On temperature-dependent magnetic study, it reveals that the magnetic behaviour of 1 can be associated to a strong antiferromagnetic coupling between the two Cu(II) ions.

Neutral Luminescent Metal-Organic Frameworks: Structural Diversification, Photophysical Properties, and Sensing Applications.

Utilizing flexible bis(tridentate)polypyridyl ligands, the two new luminescent 2D metal organic frameworks {Zn2(tpbn)(2,6-NDC)2}n (1) and {[Zn2(tphn)(2,6-NDC)2]·4H2O}n (2), where tpbn = N,N',N″,N‴-tetrakis(2-pyridylmethyl)-1,4-diaminobutane, tphn = N,N',N″,N‴-tetrakis(2-pyridylmethyl)-1,6-diaminohexane, and 2,6-H2NDC = 2,6-naphthalenedicarboxylic acid, have been isolated in good yields under solvothermal conditions. Their solid-state molecular structures have been determined by single-crystal X-ray diffractometry. Both 1 and 2 have pentacoordinated Zn(II) centers with an N3O2 environment from three nitrogen atoms of the tpbn or tphn ligand and two carboxylate oxygen atoms from two different 2,6-NDC linkers. However, the binding modes of the tridentate part of polypyridyl ligands to the Zn(II) center are different in 1 and 2-meridional (tpbn) vs facial (tphn) due to an increase (1.5 times) in the methylene chain length. Thus, the binding mode of 2,6-NDC to the Zn(II) center differs: bis(monodentate) syn-anti in 1 and bis(monodentate) syn-syn in 2. This difference in binding modes of the components has a profound effect on the conformation of the six-membered ring (metal centers are considered as the vertices in it) within the 2D framework: honeycomb vs chair form for 1 and 2, respectively. In addition to further characterization by elemental analysis and UV-vis and FT-IR spectroscopy, their framework stabilities in water and thermal properties have been studied by powder X-ray diffraction and thermogravimetric analysis, respectively. On the basis of thermodiffractometry, 1 and 2 retain their crystallinity and overall structure up to 350 and 325 °C, respectively. Their luminescent properties have been utilized to demonstrate sensing of various solvents as well as nitro-aromatic compounds in water, which correlate well with their structural differences. Through the spectral overlap, lifetime measurements, and nature of the Stern-Volmer plots, the fluorescence quenching pathway for the nitro-analytes, particularly 2,4,6-trinitrophenol (TNP), is established for 1 and 2. Their recyclability and stability after sensing experiments are found to be excellent.

Structural and IR-Spectroscopic Characterization of Aqua Lithium Acesulfamate, an Outlier of the M(ace), M: Na+, K+, Rb+, Cs+, Isomorphic Series

The crystal structure of aqua lithium 6-methyl-1,2,3,-oxathiazine-4(3H)-one, 2.2-dioxide, for short Li(ace)H2O, was determined by X-ray diffraction methods. It crystallizes in the triclinic P $$\overline {1}$$ space group with a = 6.1750(9) A, b = 7.3969(9) A, c = 9.016(1) A, α = 105.88(1)°, β = 94.59(1)°, γ = 97.80(1)°, and Z = 2 molecules per unit cell. The crystal structure of Li(ace)H2O sharply departs from the other heavier alkaline-metal acesulfamates, namely the monoclinic isotypic M-ace (M from Na+ to Cs+) family of salts. Lithium is in a distorted LiO4 tetrahedral coordination with acesulfamate carbonyl, sulfoxide and water oxygen atoms. The FTIR spectrum of the new compound was also recorded and is briefly discussed. Some comparisons with other simple acesulfamate salts are also made. The synthesis of aqua lithium acesulfamate, Li(C4H4NO4S)H2O, and its structural characterization by single-crystal X-ray diffractometry are reported. The FTIR spectrum of the salt is analyzed by comparison with data of related compounds.

Deciphering composition and connectivity of a natural product with the assistance of MS and 2D NMR.

A complementary application of three analytical techniques, viz. multidimensional nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS), and single-crystal X-ray diffractometry was required to identify and refine two natural products isolated from Millettia versicolor and solvent of crystallization. The two compounds, namely 3-(2H-1,3-benzodioxol-5-yl)-6-methoxy-8,8-dimethyl-4H,8H-pyrano[2,3-h]chromen-4-one, or durmillone, (I), and (2E)-1-(4-{[(2E)-3,7-dimethylocta-2,6-dien-1-yl]oxy}-2-hydroxyphenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one, (II), could not be separated by routine column chromatography and cocrystallized in a 2:1 ratio with 0.13 molecules of ethanol solvent. Compound (II) and ethanol could not be initially identified by single-crystal X-ray analysis due to complex disorder in the aliphatic chain region of (II). Mass spectrometry ensured that (II) represented only one species disordered over several positions in the solid state, rather than several species cohabitating on the same crystallographic site. The atomic identification and connectivity in (II) were established by several 2D (two-dimensional) NMR techniques, which in turn relied on a knowledge of its exact mass. The derived connectivity was then used in the single-crystal analysis to model the disorder of the aliphatic chain in (II) over three positions and allowed identification of a partially occupied ethanol solvent molecule that was disordered over an inversion center. The disordered moieties were refined with restraints and constraints.

PtII, PdII and AuIII complexes with a thiosemicarbazone derived from diacethylmonooxime: Structural analysis, trypanocidal activity, cytotoxicity and first insight into the antiparasitic mechanism of action

New complexes of composition [MX(HL1)] (M = PtII, PdII, X = Cl− or I−) and [MX(L1)] (M = AuIII, X = Cl−; M = PtII, PdII, X = PPh3) have been synthesized using a potentially tridentate thiosemicarbazone (H2L1) containing an additional oxime binding site. Among other analytical methods, all the seven complexes have been structurally characterized by single crystal X-ray diffractometry. Interesting structural features such as the influence of the halide ligands on hydrogen bonds and the formation of supramolecular structures for the phosphine derivatives are discussed. The in vitro trypanocidal activity of the free ligand H2L1 and its derivatives against both extracellular trypomastigote and intracellular amastigote (IC50try/ama) forms of Trypanosoma cruzi (Tulahuen Lac-Z strain) and the cytotoxicity was assessed on LLC-MK2 cell line. The results showed that complexation of the thiosemicarbazone ligand H2L1 to PtII, PdII and AuIII metal centers enhances the in vitro trypanocidal activity and that the cytotoxicity is dependent on both the metal center and coligands. Within the studied series, the AuIII complex showed the greatest potential, being not the most active but the most selective compound with a similar selectivity index to that of the standard drug benznidazole. In order to get a preliminary insight into the mechanism of action of these compounds, in vitro experiments of fluorescence quenching and enzymatic activity were performed using the AuIII complex and Trypanosoma cruzi Old Yellow Enzyme (TcOYE) which indicated that the gold derivative was capable of abstracting the hydride from the prosthetic FMN group of the enzyme. Additionally, molecular docking studies followed by semiempirical simulations showed that the [AuCl(L1)] binds to the binary complex TcOYE/FMN, almost parallel to the FMN prosthetic group, in a close distance that an electron/proton transfer might occur among them.

Two new Zinc(II) and Cadmium(II) complexes of a semi-rigid bis(2-benzimidazole): Synthesis and characterization

ABSTRACTTwo new complexes Zn(TBimE)Cl2 1 and Cd(TBimE)(I)2 2 based on a semi-rigid ligand TBimE (TBimE = (E)-1,2-bis(2-benzimidazolyl)ethane) have been synthesized and their structures have been determined by X-ray single crystal diffractometry. X-ray diffraction analyses reveal that the “trans” TBimE is converted into “cis” conformation in the structures of the complexes, so that the TBimE can be used as a bidentate ligand to chelate the Zinc(II) and Cadmium(II) ions. Both 1 and 2 exhibit distorted tetrahedral geometries and the central metal atoms are coordinated by two N atoms from TBimE and two anions. The UV–Vis and emission spectra show that both the absorption and the emission of the complexes are assigned to the intraligand transitions and intraligand fluorescence, respectively.