Chemistry of vinylidene complexes. XVIII. Synthesis and molecular structure of the novel trinuclear μ3-vinylidene complex CpReFePt(μ3-CCHPh)(CO)6(PPh3)

The interaction between Cp(CO)₂RePt(μ-CCHPh)(PPh₃)₂ (1) and Fe₂(CO)₉ afforded the new heterometallic μ₃-vinylidene cluster CpReFePt(μ₃-CCHPh)(CO)₆(PPh₃) (2). An X-ray diffraction study shows the complex 2 possesses a trimetallic Re-Fe-Pt chain core. The bond lengths are Re-Fe 2.8221(8), Fe-Pt 2.5813(8) Å; the Re?Pt distance is 3.3523(7) Å; the bond angle Re-Fe-Pt is 76.55(3)°. The μ₃-CCHPh ligand is η¹-bound to the Re and Pt atoms and η²-coordinated to the Fe atom. The CC bond length is 1.412(4) Å. The Pt atom is coordinated by the PPh₃ and CO groups. Complex 2 is characterized by the IR and ¹H, ¹³C and ³¹P NMR spectra.     

Why are ionic liquids liquid? A simple explanation based on lattice and solvation energies

We have developed a simple and quantitative explanation for the relatively low melting temperatures of ionic liquids (ILs). The basic concept was to assess the Gibbs free energy of fusion (Delta(fus)G) for the process IL(s) --> IL(l), which relates to the melting point of the IL. This was done using a suitable Born-Fajans-Haber cycle that was closed by the lattice (i.e., IL(s) --> IL(g)) Gibbs energy and the solvation (i.e., IL(g) --> IL(l)) Gibbs energies of the constituent ions in the molten salt. As part of this project we synthesized and determined accurate melting points (by DSC) and dielectric constants (by dielectric spectroscopy) for 14 ionic liquids based on four common anions and nine common cations. Lattice free energies (Delta(latt)G) were estimated using a combination of Volume Based Thermodynamics (VBT) and quantum chemical calculations. Free energies of solvation (Delta(solv)G) of each ion in the bulk molten salt were calculated using the COSMO solvation model and the experimental dielectric constants. Under standard ambient conditions (298.15 K and 10(5) Pa) Delta(fus)G degrees was found to be negative for all the ILs studied, as expected for liquid samples. Thus, these ILs are liquid under standard ambient conditions because the liquid state is thermodynamically favorable, due to the large size and conformational flexibility of the ions involved, which leads to small lattice enthalpies and large entropy changes that favor melting. This model can be used to predict the melting temperatures and dielectric constants of ILs with good accuracy. A comparison of the predicted vs experimental melting points for nine of the ILs (excluding those where no melting transition was observed and two outliers that were not well described by the model) gave a standard error of the estimate (s(est)) of 8 degrees C. A similar comparison for dielectric constant predictions gave s(est) as 2.5 units. Thus, from very little experimental and computational data it is possible to predict fundamental properties such as melting points and dielectric constants of ionic liquids.     

Novel porphyrin conjugates with a potent photodynamic antitumor effect: differential efficacy of mono- and bis-beta-cyclodextrin derivatives in vitro and in vivo

In the present study we investigated the photosensitizing properties of two novel mono- and bis-cyclodextrin tetrakis (pentafluorophenyl) porphyrin derivatives in several tumor cell lines and in BALB/c mice bearing subcutaneously transplanted syngeneic mouse mammary carcinoma 4T1. Both studied sensitizers were localized mainly in lysosomes and were found to induce cell death by triggering apoptosis in human leukemic cells HL-60. In 4T1 and other cell lines both apoptotic and necrotic modes of cell death occurred depending on drug and light doses. Mono-cyclodextrin porphyrin derivative P(beta-CD)1 exhibited stronger in vitro phototoxic effect than bis-cyclodextrin derivative P(beta-CD)2. However, in vivo P(beta-CD)2 displayed faster tumor uptake with maximal accumulation 6 h after application, leading to complete and prolonged elimination of subcutaneous tumors within 3 days after irradiation (100 J cm(-2)). In contrast, P(beta-CD)1 uptake was slower (48 h) and the reduction of tumor mass was only transient, reaching the maximum at the 12 h interval when a favorable tumor-to-skin ratio appeared. Thus, P(beta-CD)2 represents a new photosensitizing drug displaying fast and selective tumor uptake, strong antitumor activity and fast elimination from the body.     

Alkynyl and poly-ynyl derivatives of carbon-tricobalt clusters

A series of alkynyl-tricobalt carbonyl clusters, Co₃(μ₃-C_nR)(μ-dppm)(CO)₇ [R = Bu^t, Ph, C₆H₄I, C₆H₄CCPh, SiMe₃, Fc, Au(PPh₃)] containing three, five or seven carbons in the chain, have been prepared by elimination of phosphine-gold(I) halides in reactions between Co₃(μ₃-CBr)(μ-dppm)(CO)₇ and Au(CCR)(PPh₃) or between Co₃{μ₃-CCCAu(PR₃)} (μ-dppm)(CO)₇ (R = Ph, tol) and ICCR′ (R′ = SiMe₃, Fc). The use of poly-substituted arenes or ferrocenes has enabled preparation of the complexes 1,4-{(OC)₇(μ-dppm)Co₃ (μ₃-CCC)}₂C₆H₃X-5 (X = H, Br), 1,3,5-{(OC)₇(μ-dppm)Co₃(μ₃-CCC)}₃C₆H₃ and 1,1′-{(OC)₇(μ-dppm)Co₃ (μ₃-CCC)}₂Fc′ [Fc′ = Fe(η-C₅H₄-)₂]. The X-ray determined molecular structures of 12 of the complexes are reported.     

Stokes’ first problem for a thermoelectric Newtonian fluid

This work is related to the flow of an electro-conducting Newtonian fluid presenting thermoelectric properties in the presence of magnetic field. The flow is considered to be governed an incompressible viscous fluid. The electro-conducting thermofluid equation heat transfer with one relaxation time is derived. The state space formulation developed in Ezzat (Can. J. Phys. Rev. 86:1242–1450, 2008) or one-dimensional problems is introduced. The Laplace transform technique is used. The resulting formulation is applied to a thermal shock problem; that is, a problem of a layer media and a problem for the infinite space in the presence of heat sources. A numerical method is employed for the inversion of the Laplace transforms. Numerical results are given and illustrated graphically for each problem. The effects of thermoelastic properties on the thermofluid flow are studied.     

Raman spectroscopy at different excitation wavelengths (1064, 785 and 532 nm) as a tool for diagnosis of colon cancer

Raman spectroscopy is structure sensitive non‐destructive method that allows observing the status of biological tissues with minimal impact. This method has a great potential in the diagnosis of various types of degenerative diseases including cancer damages. Near‐infrared Fourier transform (NIR‐FT)‐Raman (λ_ex ~1064 nm), NIR‐visible (Vis)‐Raman (λ_ex ~785 nm) and Vis‐Raman (λ_ex ~532 nm) spectra of normal and colorectal carcinoma colon tissue samples were recorded in macroscopic mode at 10–20 randomly chosen independent sites. In the cases of NIR‐Vis‐ and Vis‐Raman spectra, enhanced resonance effects were observed for tissue chromophores absorbing in the visible area. Evident spectral differences were noticed for Raman spectra of normal colon tissue samples in comparison with abnormal samples. The average Raman spectra of colon tissue samples were analysed by principal component analysis (PCA) to discriminate normal and abnormal tissues. PCA of combined dataset containing Raman intensities of chosen NIR‐FT, NIR‐Vis or Vis‐Raman bands led to discrimination of normal and abnormal colon tissue samples. Therefore, combination of these three Raman methods can be helpful for recognizing cancer lesions in colon for diagnostic purposes. Copyright © 2014 John Wiley & Sons, Ltd.     

Hydrogen-bonded network of hydration water around model solutes

Clustering of water molecules in the hydration shells of spherical structureless solutes was studied in dependence on thermodynamic state, solute radius R(sp) and strength U(0) of water-solute interaction. Two qualitatively different clustering states of hydration water have been found: an "ordered" state with a hydrogen-bonded (H-bonded) network, which includes most of the hydration water, and a "disordered" state with small H-bonded clusters of hydration water. The transition from the ordered to disordered state occurs upon increasing temperature and decreasing pressure. This percolation transition is rounded due to the finite solute size and occurs in some temperature (pressure) interval. A finite-size scaling was applied to determine the transition temperature T(∞) in the limit R(sp)→∞. Strengthening of the water-solute interaction strongly enhances the stability of the ordered state: the transition temperature increases by about 35 °C, when U(0) decreases by 1 kcal mol(-1). At T > T(∞) and fixed U(0), the stability of the H-bonded water network increases upon decreasing solute size.     

Self-healing superhydrophobic materials

Development of materials with self-healing properties is highly important task. This review covers recent development in the design of materials with durable, easy repairable and self-healing superhydrophobic properties.     

Facile preparation of amine and amino acid adducts of [60]fullerene using chlorofullerene C60Cl6 as a precursor

We report a general synthetic approach to the preparation of highly functionalized amine and amino acid derivatives of [60]fullerene starting from readily available chlorofullerene C(60)Cl(6). The synthesized water-soluble amino acid derivative of C(60) demonstrated pronounced antiviral activity, while the cationic amine-based compound showed strong antibacterial action in vitro.