Charge-transfer complexes from decamethylferrocene and 1,4-quinone derivatives: neutral-ionic phase diagrams for metallocene complexes

Charge-transfer (CT) complexes of ferrocenes with 1,4-quinone derivatives were investigated. Deca- and octamethylferrocene complexes with 1,4-naphthoquinone derivatives were prepared and structurally characterized; these were neutral 1:2 DA complexes with mixed-stack structures. The formation of complexes with 1,4-benzoquinones was examined by applying solvent-drop grinding. CT energies and phase transitions in these neutral and other ionic complexes were investigated. Their electronic states are discussed on the basis of the phase diagrams derived for mixed-stack ferrocene-based CT complexes, taking into account their dependence on the DA ratio, dimensionality, and intermolecular interactions.     

Theoretical study on the DNA interaction properties of copper(II) complexes

Theoretical studies on DNA-cleavage and DNA-binding properties of a series of Cu(II) complexes [Cu(bimda)(diimine)] 1–5 have been carried out by density functional theory (DFT). The optimized structures of Cu(II) complexes were docked into parallel, antiparallel and mixed G-quadruplexes, with which the binding energies of complexes 1–5 were obtained. The cytotoxicities of these complexes can be predicted preliminarily by the binding energies. To explore the energy changes of Cu(II) complexes in duplex DNA, the optimized structures of these complexes were docked into the duplex DNA, and the obtained docking models were further optimized using QM/MM method. The DNA-cleavage abilities of complexes 1–5 can be predicted accurately and explained reasonably by the computed intra-molecular reorganization energies of these complexes. This work reported here has implications for the understanding of the interaction Cu(II) complexes with the DNA, which might be helpful for the future directing the design of novel anticancer Cu(II) complexes.     

Syntheses of new water-soluble dicobalt complexes having two cobaltcarbon bonds and their ability for DNA cleavage

One-pot syntheses of new water-soluble dicobalt complexes having two cobaltcarbon bonds are reported. The complexes were characterized by ¹H NMR and UV-vis spectroscopies as well as ESI-MS. These complexes were photosensitive, and photo-cleavage of the cobaltcarbon bonds upon irradiation with visible light produced methyl radicals which were detected by ESR spin-trapping techniques. The dicobalt complexes exhibited high ability for DNA cleavage in comparison with that for the corresponding monocobalt complex.     

Synthesis,characterization, antibacterial studies and quantum-chemical investigation of the new fluorescent Cr(III) complexes

Coordination of the ligands derived from benzimidazole with Cr(III) led to the formation of new fluorescent Cr (III) complexes. The structures of the new complexes were established by spectral, analytical data and Job’s method and an octahedral geometry was proposed for the complexes. Also, the DFT methods were employed to gain a deeper insight into geometry and spectral properties of the new Cr (III) complexes. The DFT-calculated vibrational modes of Cr(III) complexes are in good agreement with the experimental values, confirming suitability of the optimized geometries for the complexes. Fluorescent ligands and chromium complexes were spectrally characterized by UV–Vis and fluorescence spectroscopy. Results revealed that Cr(III) complexes generate fluorescence in dilute solution of DMSO. Calculated electronic absorption spectra were also provided by time-dependent density functional theory (TD-DFT) method. The new complexes exhibited potent antibacterial activity against a panel of strains of Gram negative bacterial and Gram positive species and their MIC was also determined. Two strains of Gram positive and two strains of Gram negative bacteria.     

异核稀土双亚砜配合物的合成、表征和荧光性质

合成得到一系列异核土双乙烷配合物和异核稀土双乙烷与１,１０－啡咯啉的配合物,通过元素分析,电感耦合等离子体法,电导,红外和紫外光谱对配合进行了表征,并研究了这些配合物的固体和溶液的荧光光谱。     

MS<Superscript>n</Superscript> characterization of protonated cyclic peptides and metal complexes

MSⁿ experiments involving low energy collisionally activated dissociation (CAD) in a quadrupole ion trap were used to characterize the fragmentation of alkali, alkaline earth and transition metal complexes of five cyclic peptides, and the results were compared with those obtained for protonated cyclic peptides. Complexes with metal ions produced enhanced abundances of the most diagnostic fragments for elucidating the primary structures. For cyclosporin A, nickel and lithium complexes gave additional sequence information compared with the protonated peptide. For depsipeptides, sodium and lead complexes were superior to the protonated peptide or other metal complexes for sequencing residues, and CAD of the lead complexes led to preferential cleavage of two residues at a time. For cyclic lipopeptides, complexes with silver, nickel and strontium ions provided enhanced abundances of key fragment ions.     

Effect of buffer,electric field,and separation time on detection of aptamer-ligand complexes for affinity probe capillary electrophoresis

The separation and detection of complexes of aptamers and protein targets by capillary electrophoresis (CE) with laser-induced fluorescence was examined. Aptamer-thrombin and aptamer-immunoglobulin E (IgE) were used as model systems. Phosphate, 3-(N-morpholino)propanesulfonic acid with phosphate, and tris(hydroxyamino)methane-glycine-potassium (TGK) buffer at pH 8.4 were tested as electrophoresis media. Buffer had a large effect with TGK providing the most stable complexes for both protein-aptamer complexes. Conditions that suppressed electroosmotic flow, such as addition of hydroxypropylmethylcellulose to the media or modification of the capillary inner wall with polyacrylamide, were found to prevent detection of complexes. The effect of separation time and electric field were evaluated by monitoring complexes with electric field varied from 150-2850 V/cm and effective column lengths of 3.5 and 7.0 cm. As expected, shorter times on the column greatly increased peak heights for the complexes due to a combination of less dilution by diffusion and less dissociation on the column. High fields were found to have a detrimental effect on detection of complexes. It is concluded that the best conditions for detection of noncovalent complexes involve use of the minimal column length and electric field necessary to achieve separation. The results will be of interest in developing affinity probe CE assays wherein aptamers are used as affinity ligands.     

Synthesis,DNA and Photocleavage Studies of Ru(II) Polypyridyl Complexes: [Ru(dppz)(pyz)4](ClO4)2 and [Ru(dppz)(dmpyz)4](ClO4)2 Complexes

In view of the growing interest for the synthesis of metal complexes and their interaction with DNA, we have synthesized and characterized two complexes containing ruthenium as metal center. The complexes are of the type [Ru(dppz)L₄](ClO₄)₂ where L are biologically important ligands such as pyrazole and dimethylpyrazole. The characterization of these complexes is done by ¹H NMR, ¹³C NMR, elemental analysis and mass spectroscopy. The interaction of these complexes with CT DNA was monitored and binding constants were determined using absorption and fluorescence spectroscopy. The mode of binding was found to be intercalative for both complexes and was determined using hydrodynamic viscosity studies. The complexes were further studied for photocleavage studies with supercoiled plasmid pBR322 DNA.     

Mass spectral behavior of some homoleptic and mixed aryldichalcogenide bis(diphenylphosphino)ferrocenenickel(II), palladium(II), and platinum(II), and bis(diisopropylphosphino)ferrocenepalladium(II) complexes

The mass spectral behavior of a number of organometallic complexes containing the Group 10 metals Ni, Pd, and Pt, together with various thiolate ligands were studied. For Pd, two main types of complexes, differing by the substituents on the phosphorus atom were studied. Types I and II were substituted with bis(diphenylphosphino)ferrocene and bis(diisopropylphosphino)ferrocene ligands, respectively. The Ni complexes, except for one, and the Pd Type I complexes had no molecular radical cations (M(+.)) in their EI spectra. On the other hand, all the Pt complexes showed intense M(+.) ions in their EI spectra indicating that these complexes were more stable as radical cations than those of Ni and Pd. The FAB and MALDI spectra of all the complexes displayed intense quasi-molecular ions (MH(+)) and the fragmentations in both modes were similar. The MALDI spectra of several complexes displayed only M(+.) ions while one gave evidence of both MH(+) and M(+.) ions. Several Pd Type II complexes yielded intense M(+.) in their EI spectra.     

Synthesis,structure and catalytic polymerization activity of half‐sandwich cyclometallated iridium complexes

A series of mononuclear half‐sandwich cyclometallated iridium complexes with Schiff base ligands were synthesized in good yields. Five air‐stable C,N‐chelate mode complexes were obtained smoothly through metal‐mediated C─H bond activation. Treatments of dimeric metal complexes [Cp*IrCl₂]₂ with ligands L1–L5 afforded the corresponding C,N‐chelate mononuclear half‐sandwich iridium(III) complexes 1 – 5 . These iridium complexes exhibit high catalytic activity for norbornene polymerization. Both steric and electronic effects of the substituted groups have influences on the behaviors of the polymerization process. All complexes were characterized using infrared and NMR spectroscopies and elemental analysis. Molecular structures of complexes 1 , 2 and 5 were further confirmed using single‐crystal X‐ray analysis.     

Inclusion complexes of PBN-type nitrone spin traps and their superoxide spin adducts with cyclodextrin derivatives: parallel determination of the association constants by NMR titrations and 2D-EPR simulations

(1)H NMR and electron paramagnetic resonance (EPR) titrations were used to determine the association constants of the complexes of alpha-phenyl-N-tert-butylnitrone (PBN) analogues and their superoxide spin adducts, respectively, with methylated beta-cyclodextrins. A 1:1 stoichiometry for the nitrones with randomly methylated beta-cyclodextrin and 2,6-di-O-methyl-beta-cyclodextrin and 1:1 and 1:2 stoichiometries for the corresponding cyclodextrin-nitroxide complexes were observed. After the superoxide radical spin trapping reaction, EPR titrations afforded the association constants of the corresponding cyclodextrin-nitroxide complexes. Two-dimensional EPR simulations indicated a bimodal inclusion of the nitroxide free radical spin adducts into the cyclodextrins. For all the nitrone-cyclodextrin and nitroxide-cyclodextrin complexes, the association constants were always higher for the nitroxide complexes than for the nitrone complexes. A cooperative system concerning the complexation of the nitroxide spin adduct with a cyclodextrin was evidenced by EPR titrations. The efficiency of the cyclodextrin inclusion technique to trap superoxide and to resist bioreduction by sodium l-ascorbate was also investigated.     

Formation of hexacoordinate complexes of PhCCSiF3 with 2,2'-bipyridine and with 1,10-phenanthroline through intermolecular silicon...nitrogen interactions

Bidentate intermolecular Si...N interactions were utilized to form new hypervalent complexes of trifluoro-phenylethynyl-silane with 2,2'-bipyridine and with 1,10-phenanthroline. X-ray structures obtained for these complexes display a somewhat distorted octahedral geometry about the silicon atom. Binding constants ranging from 170 to 1600 M(-1) at 25 degrees C in CDCl3 were measured for the formation of these complexes, suggesting that such hypervalent complexes of silicon could be used as new motifs in supramolecular chemistry.     

Computational study of the interaction of indole-like molecules with water and hydrogen sulfide

The characteristics of the interaction between water and hydrogen sulfide with indole and a series of analogs obtained by substituting the NH group of indole by different heteroatoms have been studied by means of ab initio calculations. In all cases, minima were found corresponding to structures where water and hydrogen sulfide interact by means of X-H···π contacts. The interaction energies for all these π complexes are quite similar, spanning from -13.5 to -18.8 kJ/mol, and exhibiting the stability sequence NH > CH(2) ≈ PH > Se ≈ S > O, for both water and hydrogen sulfide. Though interaction energies are similar, hydrogen sulfide complexes are slightly favored over their water counterparts when interacting with the π cloud. σ-Type complexes were also considered for the systems studied, but only in the case of water complexes this kind of complexes is relevant. Only for complexes formed by water and indole, a significantly more stable σ-type complex was found with an interaction energy amounting to -23.6 kJ/mol. Oxygen and phosphorous derivatives also form σ-type complexes of similar stability as that observed for π ones. Despite the similar interaction energies exhibited by complexes with water and hydrogen sulfide, the nature of the interaction is very different. For π complexes with water the main contributions to the interaction energy are electrostatic and dispersive contributing with similar amounts, though slightly more from electrostatics. On the contrary, in hydrogen sulfide complexes dispersion is by far the main stabilizing contribution. For the σ-type complexes, the interaction is clearly dominated by the electrostatic contribution, especially in the indole-water complex.     

Insight of the Structures and Properties on 2-Thioxanthine Complexes with One Hg~(2+) and Two Cl~- Ions:a Theoretical Investigation

The molecular structures of fifteen possible 2-thioxanthine(2TX) complexes with one Hg~(2+) and two Cl-ions were fully optimized using density functional theory B3PW91/6-311++G** method. The effective pseudo potential LANL2DZ basis set was used for metal Hg~(2+)ion. The vibrational analysis was also carried out at the same level. The bond lengths, bond angles, zero point energies, Gibbs free energies, thermodynamic energies and relative energies of all the complexes were obtained. The NBO analysis for natural charge and the second order perturbation energy values was carried out for three stable complexes and the IR spectroscopy of the two complexes was assigned to the experimental data. The results show that the 2-thioxanthine complexes with one Hg~(2+) and two Cl-ions were formed and the complexes resulting from the thione tautomer are more stable than that of the thiol ones. The order of three complexes with relative lower energy is 2TX(1,3,7)-Hg~(2+)-2, 2 TX(1,3,7)-Hg~(2+)-1 and 2 TX(1,3,9)-Hg~(2+). The calculated IR spectroscopy of the two complexes agreed with the experimental data.     

Electro-synthesis approach for some metal ion complexes derived from thiosemicarbazide; characterization,conformational, inhibitory simulation and Hirshfeld surface properties

Series of Co (II), Cu (II), Zn (II) and Sn (II) complexes derived from thiosemicarbazide ligand (HTSC), was synthesized by environmentally favorable method (electrochemical). All isolated complexes, were deliberately characterized by available analytical and spectral tools. The proposed molar ratio was 1:2 (M:L) as the only isolated one, beside the significant contribution for solvent molecules. The octahedral configuration was proposed for all complexes. Conformational analysis was implemented using advanced program to determine the best structural forms for complexes. Moreover, essential parameters were calculated to export important features for studied complexes. Meanwhile, Hirshfeld crystal surface properties, were interested to illustrate strength of packing interaction forces. Furthermore, distinction of site types inside the molecule and their H-donor or H-acceptor ability. Antimicrobial study was conducted against different microorganisms, to assert on the importance of new complexes in therapeutic field. Furthermore and to strengthen the study, the inhibition simulation was performed with respect to all complexes against selected pathogen proteins. Essential interaction data, were exported for each docking process, to classify inhibition efficiency. Co (II) and Cu (II) complexes were the complexes that played well in therapeutic simulation treatments against Bacillus subtilis (1bn8) and Candida albicans kinase (4c0t) proteins.     

人红细胞摄取环己二胺合铂(Ⅱ)配合物的手性选择性研究

合成了六种以不同手性的1,2-环己二胺(1,2-dach)作为载体配体的铂(Ⅱ)配合物,用元素分析、红外及分子图形方法对其组成和结构进行了表征.测定了它们跨人红细胞膜的一级反应动力学常数.用膜蛋白巯基滴定、荧光标记、自旋标记ESR谱等方法研究了它们与膜蛋白、膜脂的相互作用;用脂质体模拟了这些配合物的细胞摄入.结果表明:这些配合物主要通过简单扩散进入红细胞,其跨膜速率对环己二胺的手性具有明显的选择性.这种选择性主要来源于配合物与膜脂作用过程中的手性识别。     

Synthesis and Characterisation of Schiff Base‐like Iron(II) Complexes with Imidazole as Axial Ligand

Four new six‐coordinate and one pentacoordinate iron(II) complexes with imidazole as axial ligand were synthesised and characterised. For two of the complexes crystals suitable for X‐ray structure analysis were obtained and an extended network of hydrogen bonds was observed in both cases. Magnetic susceptibility studies revealed, that two of the octahedral complexes are high‐spin complexes in the entire temperature range, whereas for the other two gradual spin transitions are observed.     

Stability constants of complexes of uranium/VI/ and plutonium/VI/ with succinate ions

The stability constants of the complexes formed by U/VI/ and Pu/VI/ with succinate ions were determined in 0.5M NaClO₄ medium at 30°C following the Bjerrum-Calvin pH titration technique. The stability constants obtained agreed with values reported in literature following the same technique. The values for the second complexes were reported for the first time. U/VI/ complexes were found to have stabilities higher than the corresponding Pu/VI/ complexes in accordance with the acidities of the cations.     

Influence of metal and ligand types on stacking interactions of phenyl rings with square-planar transition metal complexes

In order to find out whether metal type influences the stacking interactions of phenyl rings in square-planar complexes, geometrical parameters for Cu, Ni, Pd and Pt complexes, with and without chelate rings, were analyzed and compared. By searching the Cambridge Structural Database, 220 structures with Cu complexes, 211 with Ni complexes, 285 with Pd complexes, and 220 with Pt complexes were found. The results show that the chelate ring has a tendency to make the stacking interaction with the phenyl ring independent of metal type in the chelate ring. However, there are some differences among metals for complexes without a chelate ring. There are a number of structures containing Pd and Pt complexes, without chelate rings, that have short carbon-metal distances and parallel orientations of the phenyl ring with respect to the coordination plane. It was found that some of these complexes have a common fragment, CN, as a part of the ligands. This indicates that the CN supports stacking interactions of square planar complexes with the phenyl ring.      

Schiff base complexes of vanadium(III, IV, V) as catalysts for the electroreduction of O2 to H2O in acetonitrile

Fifteen Schiff base ligands were synthesized and used to form complexes with vanadium in oxidation states III, IV, and V. Electrochemical and spectral characteristics of the complexes were evaluated and compared. In acidified solutions in acetonitrile the vanadium(IV) complexes undergo reversible disproportionation to form V(III) and V(V) complexes. With several of the ligands the V(III) complexes are much more stable in the presence of acid than is the previously studied complex with salen, an unelaborated Schiff base ligand (H(2) salen = N,N'-ethylenebis(salicylideneamine)). Equilibrium constants for the disproportionation were evaluated. The vanadium(III) complexes reduce dioxygen to form two oxo ligands. The reaction is stoichiometric in the absence of acid, and second-order rate constants were evaluated. In the presence of acid some of the complexes investigated participate in a catalytic electroreduction of dioxygen.