Crystal structure, thermal stability and theoretical investigation on four 1,3-bis(1,2,4-triazol-1-yl)propane-based copper(II) complexes

Self-assembly of flexible 1,3-bis(1,2,4-triazol-1-yl)propane (btp), inorganic Cu(II) salt and rigid benzene-based carboxylate coligand generates four complexes, {[Cu(btp)₂(CH₃OH)(H₂O)]·H₂O·2ClO₄}_n (1), {[Cu(btp)(Hbtc)₂]·0.5H₂O}_n (2), [Cu(btp)₂(H₃btea)₂]_n (3), and [Cu(btp)(nb)₂] (4) (H₃btc = 1,3,5-benzenetricarboxylic acid, H₄btea = 1,2,4,5-benzenetetracarboxylic acid, Hnb = p-nitrobenzoic acid), which are fully structural characterized by single-crystal X-ray crystallography, elemental analysis, IR, and TG-DTA techniques. Structural determinations reveal that the polymeric two-dimensional (2D) Cu-btp grid-like layer for 1, 1D linear single- and double-stranded chains for 2 and 3, as well as the discrete binuclear structure for 4, are jointly directed by the coordination polyhedrons of the Cu(II) ion and the exo-bidentate bridging btp core ligand with various conformations. The theoretical calculations suggest that the trans-trans btp is the most stable conformation, and the metal binding site is collectively determined by the electron density of N donors and the spatial orientation of the btp ligand. Unexpectedly, the polycarboxylate anions in 1-4 can only act as terminal coligands not popular bridging connectors. The thermal stability of the resulting complexes is also compared.     

Vital working hour schemes: The dynamic balance between various interests

“Balancing Interests”, the theme of the 17th International Symposium on Shift Work and Working Time held in Hoofddorp, The Netherlands (September 2005), refers to the ambition to reach an optimal balance between the various aspects of shift work. Economic, ergonomic, physical, and psychosocial factors all interact in determining the impact of shift work at the individual, organizational, and societal level. It is the challenge of this multidisciplinary field of research to model all relevant factors in such a way that it will allow us to optimize the dynamic trade-off between the yield and the risk of shift work. The organizers of the 17th International Symposium and the co-editors of these proceedings are convinced that the high quality of the contributions will bring us closer to this ultimate goal.     

Versatile characterization of thiol-functionalized printed metal electrodes on flexible substrates for cheap diagnostic applications

Background

Cheap, reliable, point-of-care diagnostics is a necessity for the growing and aging population of the world. Paper substrate and printing method, combined together, are the cheapest possible method for generating high-volume diagnostic sensor platforms. Electrical transduction tools also minimize the cost and enhance the simplicity of the devices.

Methods

Standard surface characterization techniques, namely contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the growth of the organic thiol layers on top of the printed metal electrodes on paper substrates. The results were compared with those obtained by impedimetric electrical characterization method.

Results

This article reports the fabrication and characterization of printed metal electrodes and their functionalization by organic layers on paper and plastic substrates for biosensing and diagnostic applications. Impedimetric measurement is proposed as a simple, yet elegant, method of characterization of the organic layer growth.

Conclusions

Very good correlation was observed between the results of organic layer growth from different measurement methods, justifying the use of paper as a substrate, printing as a method for fabricating metal and organic layers and impedance as a suitable measurement method for hand-held diagnostic devices.

General significance

This result paves the way for the fabrication of more advanced bio-recognition layers for bio-affinity sensors using a printing technology that is compatible with flexible and cheap paper substrates. This article is part of a Special Issue entitled Organic Bioelectronics — Novel Applications in Biomedicine.     

The Interference of Flexible Working Times with the Utility of Time: A Predictor of Social Impairment?

Periodic components inherent in actual schedules of flexible working hours and their interference with social rhythms were measured using spectrum analysis. The resulting indicators of periodicity and interference were then related to the reported social impairments of workers. The results show that a suppression of the 24 and the 168 h (seven‐day) components (absence of periodicity) in the work schedules predicts reported social impairment. However, even if there are relatively strong 24 and 168 h components left in the work schedules, their interference with the social rhythm (using the phase difference between working hours and the utility of time) further predicts impairment. The results thus indicate that the periodicity of working hours and the amount of (social) desynchronization induced by flexible work schedules can be used both for predicting the impairing effects of the specific work schedules on social well‐being as well as for the design of socially acceptable flexible work hours.     

Free Energy Simulations Over Creation/Annihilation Paths for a Flexible Solute

The inclusion of molecular flexibility into free energy simulations over creation/annihilation paths has been analyzed. A new formalism is presented for such simulations with the intramolecular degrees of freedom being active during the simulation and a recently introduced path is reviewed that allows the inclusion of the flexibility using separate simulations.     

A computational H5N1 neuraminidase model and its binding to commercial drugs

In order to understand the mechanisms of ligand binding and interaction between two commercial drugs (ligands), zanamivir and oseltamivir and H5N1 Influenza Virus Neuraminidase subtype N1, a three-dimensional model of N1-ligand (GenBank accession no. AAS654617) was initially generated by homology modeling using the 13 high-resolution X-ray structures of neuraminidase N2 and N9 as the template. With the aid of the molecular mechanics and molecular dynamics methods, the final implicit solvent refined model was obtained. It was, then, assessed by PROCHECK, PROSA and VERIFY3D. With this model, a flexible docking study was performed. The results show strong hydrogen bond interactions between the glycerol side chains of zanamivir and Arg29 of the N1. Common hydrogen bonds between the carboxyl groups and Arg279 were found for both drugs. It was also found that the Glu30, Asp62, Arg63, Arg204, Trp310, Tyr313, Glu336, Ile338, Trp348, Ala349 were observed to facilitate the enzyme-ligand non-bonding interactions as they are located within the radius of 5 Å from all atoms of both drugs. Charge distribution was evaluated using the semi-empirical AM1 method. The results show that the total net charges of the –NH side chain of zanamivir is less negative than that of oseltamivir. This is in contrast to what is observed for the amide and alkyl (ether/glycerol) side chains. In comparison of the binding free energies between the X-ray N2-ligand and N9-ligand complexes, N1-ligand binding is found to be less potent than N2 and N9 subtypes, while N2-ligand and N9-ligand are roughly comparable. In addition, it is interesting to observe that the binding free energies for all three subtypes of the zanamivir complexes are lower than those of oseltamivir.     

Synthesis and crystal structures of dimeric W(Mo)/Cu/S and polymeric W/Cu/S neutral clusters with flexible 1,4-bis(3,5-dimethylpyrazol-1-yl)butane as a linker ligand

Reactions of [MES₃]²⁻ (M = W, Mo; E = S, O) with CuCl and bbd [1,4-bis(3,5-dimethylpyrazol-1-yl)butane] in DMF affords two new double nest-shape clusters, [WOS₃Cu₃Cl(μ-bbd)]₂ (1) and [MoOS₃Cu₃Cl(μ-bbd)]₂ (2) and a novel one-dimensional polymeric complex [WS₄Cu₂(μ-bbd)]_n (4). The complexes have been characterized by elemental analysis, IR and UV-Vis spectroscopy, and single-crystal X-ray diffraction. In the core structure of the isostructural dimeric [MOS₃Cu₃Cl(μ-bbd)]₂ clusters, the copper atoms have a distorted trigonal planar geometry, with CuS₂N and CuS₂Cl core environments. The [MOS₃Cu₃] fragments are interconnected by a pair of flexible μ-bbd ligands via their nitrogen donor atoms to form a centrosymmetric macrocyclic twin-nest-shaped cluster in which the two fragments are also linked by direct secondary Cu…Cl interactions. Complex 4 represents the first example of a polymeric heterothiometallic cluster, interconnected by bbd ligands, to be structurally characterized by X-ray crystallography. In the repeat unit of 4, the skeleton of the cluster core [CuS₂WS₂Cu] has an essentially linear Cu…W…Cu arrangement. The W atom retains the tetrahedral geometry of the parent [WS₄]²⁻ anion. These cluster cores are linked by bbd bridges having alternately two different conformations to construct a zigzag structure. Complexes [MoS₄Cu₃Cl(bbd)_0.5]₂ (3) and [WS₄Cu₄(NCS)₂(bbd)₂]_n (5) have been synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopy, but we have been unable to grow suitable crystals of 3 and 5 for X-ray analysis.     

Co(II), Zn(II) and Cu(II) compounds with 1,4; 1,3 or 1,2-bis-(benzimidazole-1-yl-methylene)-benzene as a flexible spacer ligand: Synthesis, characterization and X-ray structures of some polynuclear species

New dinuclear and polynuclear Co(II), Zn(II) and Cu(II) compounds with the ligands 1,4-bis-(benzimidazole-1-yl-methylene)-benzene (bbpx), 1,3-bis-(benzimidazole-1-yl-methylene)-benzene (bbmx) and 1,2-bis-(benzimidazole-1-yl-methylene)-benzene (bbox) are reported. With Co(II) and Zn(II) and the ligands bbpx, bbmx and bbox six new dinuclear and polynuclear compounds are described, i.e. [CoCl₂(bbpx)]_n(DMF)_2n (1), [CoCl₂(bbmx)]₂(DMF)₂ (2), [ZnCl₂(bbmx)]₂(DMF)₂ (3), [CoCl₂(bbmx)]_n(DMF)_n/2(CH₃OH)_n/4 (4), [CoCl₂(bbox)]_n(DMF)_3n/2 (5) and [ZnCl₂(bbox)]_n(DMF)_3n/2 (6). Also one polynuclear Cu(II) compound is reported, i.e. [Cu(bbpx)₂(C₂N₃)_1.5(OH)_0.5]₂(DMF)_4.15(CH₃OH)_1.75(H₂O)_3.5. The X-ray structures, physical and electronic properties are discussed.