Diallylphosphines as New Bidentate Ligands in Iridium Complexes

Abstract

Addition of four equivalents of tButyldiallylphosphine to a solution of one equivalent of [(COE)₂Cl]₂ in CHCl₃ at low temperature produced two isomers of the metallated complex 2, formed by C-H activation. 2 evolve at 40°C to 3, by a hydride transfer from iridium to the cyclooctene (COE) ligand.     

Energetics of Water/Cyclodextrins Interactions

The heat capacities of solid -CD, 8.1 H₂O and -CD, 6.0 H₂O have been measured between 10 and 300 K by adiabatic calorimetry. Using earlier results obtained in similar experiments with anhydrous cyclodextrins and with -CD, 9.7 H₂O, a comparative analysis has been developed. The energetic behaviours of anhydrous and hydrated cyclodextrins (CDs) have been compared in order to investigate the role of water molecules in the stabilization of the cyclodextrin's rings and on their reactivities. Calculations, based on the additivity of thermodynamic properties, provide the energetic and entropic average contributions of water molecules in each cyclodextrin. From these results, we assumed that the water–water and water–CD interactions are rather different according to the cyclodextrin. In the (-CD, 9.7 H₂O) structure, the water molecules seem to be better organised in a relatively independent network. Concerning hydrated -CD and -CD, stronger water–CD interactions probably prevent an optimal organisation of the water–water bonds network. Differential scanning calorimetry was also used to follow the evolution of the thermal behaviour of -CD, nH₂O versus hydration ratio between 170 and 300 K. Our results indicate that the -CD ring needs at least 1.6 water molecules to be stabilized in the solid state.     

Effect of meta-tetra(hydroxyphenyl)chlorin (mTHPC)-mediated photodynamic therapy on sensitive and multidrug-resistant human breast cancer cells

Meta-tetra(hydroxyphenyl)chlorin (mTHPC) is in clinical trials for the photodynamic therapy (PDT) of localized-stage cancer. The PDT susceptibility of cells expressing multidrug resistance (MDR) phenotype is an attractive possibility to overcome the resistance to cytotoxic drugs observed during cancer chemotherapy. The accumulation, photocytotoxicity and intracellular localization of mTHPC were examined using the doxorubicin selected MCF-7/DXR human breast cancer cells, expressing P-glycoprotein (P-gp), and the wild-type parental cell line, MCF-7. No significant difference in mTHPC accumulation was observed between the two cell lines up to 3 h contact. The photodynamic activity of mTHPC, measured 24 h after irradiation with red laser light (lambda=650 nm), was significantly greater in MCF-7/DXR as compared to MCF-7 cells. A light dose of 2.5 J cm(-2) inducing 50% of cytotoxicity in MCF-7, resulted in 85% cytotoxicity in MCF-7/DXR. The presence of P-gp inhibitors SDZ-PSC-833 and cyclosporin A did not modify the mTHPC-induced cytotoxicity. The difference in intracellular mTHPC distribution pattern between two cell lines may contribute to different photocytotoxicity. Our results indicate that mTHPC mediated PDT could be useful in killing cells expressing MDR phenotype.     

Amino acid binding by 2-(guanidiniocarbonyl)pyridines in aqueous solvents: a comparative binding study correlating complex stability with stereoelectronic factors

A series of guanidiniocarbonylpyridine receptors has been synthesized, and these compounds bind amino acids (carboxylate forms) in aqueous DMSO with association constants ranging from K = 30 to 460 M(-1) as determined by NMR titration experiments. The differences in the complex stabilities can be correlated with steric and electrostatic effects with the aid of calculated complex structures. For example, the electrostatic repulsion between the pyridine nitrogen lone pair and the bound carboxylate makes anion binding less efficient than with the analogous pyrrole receptors previously introduced by us for carboxylate binding in water. Furthermore, steric interactions between the receptor side chain as in 2 b and the bound substrate also disfavor complexation.     

Chemically assisted vapour transport for bulk ZnO crystal growth

A chemically assisted vapour phase transport (CVT) method is proposed for the growth of bulk ZnO crystals. Thermodynamic computations have confirmed the possibility of using CO as a sublimation activator for enhancing the sublimation rate of the feed material in a large range of pressures (10⁻³ to 1 atm) and temperatures (800–1200 °C). Growth runs in a specific and patented design yielded single ZnO crystals up to 46 mm in diameter and 8 mm in thickness, with growth rates up to 400 μm/h. These values are compatible with an industrial production rate. N type ZnO crystals (μ=182 cm²/(V s) and n=7 10¹⁵ cm⁻³) obtained by this CVT method (Chemical Vapour Transport) present a high level of purity (10–30 times better than hydrothermal ZnO crystals), which may be an advantage for obtaining p-type doped layers ([Li] and [Al] <10⁺¹⁵ cm⁻³). Structural (HR-XRD), defect density (EPD), electrical (Hall measurements) and optical (photoluminescence) properties are presented.     

Alloying of electrodeposited silicon with lithium—a principal study of applicability as anode material for lithium ion batteries

The possibility to electrodeposit silicon directly on a copper current collector out of organic electrolyte and ionic liquid was investigated with the aim to alloy the deposited silicon with lithium to prove the possible use as negative electrode in lithium ion batteries. Cyclovoltammetric analyses have shown in comparison to electrodes containing high crystalline silicon similar behaviour during the electrochemical alloying and dealloying process. SEM analyses have shown a particle size of the deposited silicon in submicron range.     

Theoretical study in gas phase of linear and nonlinear optical properties of the ortho-, meta- and para-nitrophenol isomers

The linear (α), and nonlinear (β, γ) optical NLO properties of ortho-, meta- and para-nitrophenol (ONP, MNP and PNP) isomers have been calculated in gas phase by using ab initio (HF, MP2 and MP4) and density functional theory (DFT) (B3LYP, CAM-B3LYP) methods, with the 6-31+G(d,p) and 6-311+G(3d,3p) standard and the Sadlej specialized basis sets. These properties were evaluated both at static and at dynamic regime within the finite field FF numerical techniques and the time-dependent-Hartree–Fock approach at 1,910 nm, respectively. Additional calculations were performed for the β static hyperpolarizability of these isomers in presence of p-dioxane solvent with the Onsager Model and the SCRF-PCM approach, using B3LYP/6-31+G(d,p) and MP2/6-31+G(d,p) levels of theory. Additionally, CCSD/6-31+G(d,p) calculations were performed for the α, β and γ properties of PNP isomer. The B3LYP and MP2 α _ave results of the nitrophenol isomers are comparable to the experimental α _ave reports; while the tendency for the β _v calculated values (β _v PNP > β _v MNP > β _v ONP), that can be explained in terms of the O _x atomic charge of the –NO₂ group, does not follow exactly the experimental ones. The B3LYP γ _ave results are in correspondence to the experimental measurements, the correlation of which is r ² = 0.99. The use of FF methodology in conjunction with the B3LYP and MP2 methods and the 6-31+G(d,p) basis set show to be appropriate approaches to predict qualitative optical properties of Push–Pull like organic molecules, provided are considered the solvent effects or frequency dependence. However, to have a clear picture of the NLO properties of an isolated molecule, higher order correlation effects combined with specialized basis sets, frequency and solvent effects should be employed. We have demonstrated that MP4/Sadlej level of theory is able to reproduce NLO properties that can be considered equivalent to those from more sophisticated approaches, such as CCSD together with extended basis sets.     

SERS Labels for Red Laser Excitation: Silica‐Encapsulated SAMs on Tunable Gold/Silver Nanoshells

In a glass house : Silica‐encapsulated self‐assembled monolayers (SAMs) on tunable gold/silver nanoshells were used as labels for surface‐enhanced Raman scattering (SERS). This concept combines the spectroscopic advantages arising from maximum surface coverage and uniform molecular orientation of the Raman reporter molecules within the complete monolayer together with the high chemical and mechanical stability of the glass shell.

     

One-armed artificial receptors for the binding of polar tetrapeptides in water: probing the substrate selectivity of a combinatorial receptor library

We have recently developed a new class of one-armed artificial receptors 1 for the binding of the polar tetrapeptide N-Ac-D-Glu-L-Lys-D-Ala-D-Ala-OH (EKAA) 2 in water using a combined combinatorial and statistical approach. We have now further probed the substrate selectivity of this receptor library 1 by screening a second tetrapeptide substrate (3) with the inverse sequence N-Ac-D-Ala-D-Ala-L-Lys-D-Glu-OH (AAKE). This "inverse" substrate is also efficiently bound by our receptors, with K(ass) approximately 6000 M(-1) for the best receptors, as determined both by a quantitative on-bead binding assay and by UV and fluorescence titration studies in free solution. Hence, the inverse tetrapeptide 3 is in general bound two to three times less efficiently than the "normal" peptide 2 (K(ass) approximately 17,000 M(-1)), even though the complexation mainly involves long-range electrostatic interactions and both the receptor and substrate are rather flexible. Molecular modeling and ab initio calculations have been used to rationalize the observed substrate selectivity and to analyze the various binding interactions within the complex.