Structurally Simple Osmium(II) Polypyridyl Complexes as Photosensitizers for Photodynamic Therapy in the Near Infrared**

Five osmium(II) polypyridyl complexes of the general formula [Os(4,7-diphenyl-1,10-phenanthroline)₂ L ]²⁺ were synthesized as photosensitizers for photodynamic therapy by varying the nature of the ligand L . Thanks to the pronounced π-extended structure of the ligands and the heavy atom effect provided by the osmium center, these complexes exhibit a high absorption in the near-infrared (NIR) region (up to 740 nm), unlike related ruthenium complexes. This led to a promising phototoxicity in vitro against cancer cells cultured as 2D cell layers but also in multicellular tumor spheroids upon irradiation at 740 nm. The complex [Os(4,7-diphenyl-1,10-phenanthroline)₂(2,2′-bipyridine)]²⁺ was found to be the most efficient against various cancer cell lines, with high phototoxicity indexes. Experiments on CT26 tumor-bearing BALB/c mice also indicate that the Os^II complexes could significantly reduce tumor growth following 740 nm laser irradiation. The high phototoxicity in the biological window of this structurally simple complex makes it a promising photosensitizer for cancer treatment.     

Stability of self-assembled monolayers on titanium and gold

Methyl- and hydroxyl-terminated phosphonic acid self-assembled monolayers (SAMs) were coated on Ti from aqueous solution. Dodecyl phosphate and dodecyltrichlorosilane SAMs were also coated on Ti using solution-phase deposition. The stability of SAMs on Ti was investigated in Tris-buffered saline (TBS) at 37 degrees C using X-ray photoelectron spectroscopy, contact angle goniometry, and atomic force microscopy. For comparison purposes, a hydroxyl-terminated thiol SAM was coated on Au, and its stability was also investigated under similar conditions. In TBS, a significant proportion of phosphonic acid or phosphate molecules were desorbed from the Ti surface within 1 day, while the trichlorosilane SAM on Ti or thiol SAM on Au was stable for up to 7 days under similar conditions. The stability of hydroxyl-terminated phosphonic acid SAM coated Ti and thiol SAM coated Au was investigated in ambient air and ultraviolet (UV) light. In ambient air, the phosphonic acid SAM on Ti was stable for up to 14 days, while the thiol SAM on Au was not stable for 1 day. Under UV-radiation exposure, the alkyl chains of the phosphonic acid SAM were decomposed, leaving only the phosphonate groups on the Ti surface after 12 h. Under similar conditions, decomposition of alkyl chains of the thiol SAM was observed on the Au surface accompanied by oxidation of thiolates.     

Visible-Light-Driven One-Pot Synthesis of Benzimidazoles,Benzothiazoles, and Quinazolinones Catalyzed by Scalable and Reusable Ba-Doped CoMoO4 Nanoparticles Under Air Atmosphere

Herein we report a simple and efficient oxidative coupling of various aryl methyl amines with diverse coupling partners, such as o-phenylenediamine (benzene-1,2-diamine), 2-aminobenzenethiol and 2-aminobenzamide, to synthesize the corresponding heterocycles using scalable and reusable heterogeneous catalysts under visible light irradiation. A systematic investigation led to the synthesis of benzimidazoles, benzothiazoles and quinazolinones under air atmosphere in very good to excellent yields. The strategy is atom economical and found to be tolerance towards different functional groups, and wide range of substrate scope. Furthermore, the methodology was demonstrated for its suitability on scale up and reusability. The density functional theory (DFT) calculations and the analysis of band structures of pristine and Ba doped CoMoO₄ systems showed that the doping of Ba in place of Co improved the catalytic performance of the system.     

Stability and Hopf bifurcation analysis of novel hyperchaotic system with delayed feedback control

In this article, a novel four dimensional autonomous nonlinear systezm called hyperchaotic Rikitake system is proposed. Basic properties of the new system are investigated and the complex dynamical behaviors, such as time series, bifurcation diagram, and Lyapunov exponents are analyzed by dynamic analysis approaches. To control the new hyperchaotic system, the delayed feedback control is introduced. Regarding the time delay as a bifurcation parameter, stability and bifurcations with respect to time delay are investigated. Conditions assuring the existence of Hopf bifurcation and the distribution of roots to the associated characteristic equation are investigated by utilizing the polynomial theorem. Besides, the Hopf bifurcation is proved to occur when the bifurcation parameter (time delay) crosses through derived critical value. Finally, numerical simulations are provided to prove the consistence with the derived theoretical results. © 2015 Wiley Periodicals, Inc. Complexity 21: 180–193, 2016     

Gelatin Nanoparticles with Enhanced Affinity for Calcium Phosphate

Gelatin nanoparticles can be tuned with respect to their drug loading efficiency, degradation rate, and release kinetics, which renders these drug carriers highly suitable for a wide variety of biomedical applications. The ease of functionalization has rendered gelatin an interesting candidate material to introduce specific motifs for selective targeting to specific organs, but gelatin nanoparticles have not yet been modified to increase their affinity to mineralized tissue. By means of conjugating bone‐targeting alendronate to biocompatible gelatin nanoparticles, a simple method is developed for the preparation of gelatin nanoparticles which exhibit strong affinity to mineralized surfaces. It has been shown that the degree of alendronate functionalization can be tuned by controlling the glutaraldehyde crosslinking density, the molar ratio between alendronate and glutaraldehyde, as well as the pH of the conjugation reaction. Moreover, it has been shown that the affinity of gelatin nanoparticles to calcium phosphate increases considerably upon functionalization with alendronate. In summary, gelatin nanoparticles have been developed, which exhibit great potential for use in bone‐specific drug delivery and regenerative medicine.

     

New fluorous ponytailed 4‐[(2,2,2‐trifluoroethoxy)methyl]pyridinium halide salts

It is possible that fluorous compounds could be utilized as directing forces in crystal engineering for applications in materials chemistry or catalysis. Although numerous fluorous compounds have been used for various applications, their structures in the solid state remains a lively matter for debate. The reaction of 4‐[(2,2,2‐trifluoroethoxy)methyl]pyridine with HX (X = I or Cl) yielded new fluorous ponytailed pyridinium halide salts, namely 4‐[(2,2,2‐trifluoroethoxy)methyl]pyridinium iodide, C₈H₉F₃NO⁺·I⁻, (1), and 4‐[(2,2,2‐trifluoroethoxy)methyl]pyridinium chloride, C₈H₉F₃NO⁺·Cl⁻, (2), which were characterized by IR spectroscopy, multinuclei (¹H, ¹³C and ¹⁹F) NMR spectroscopy and single‐crystal X‐ray diffraction. Structure analysis showed that there are two types of hydrogen bonds, namely N—H…X and C—H…X. The iodide anion in salt (1) is hydrogen bonded to three 4‐[(2,2,2‐trifluoroethoxy)methyl]pyridinium cations in the crystal packing, while the chloride ion in salt (2) is involved in six hydrogen bonds to five 4‐[(2,2,2‐trifluoroethoxy)methyl]pyridinium cations, which is attributed to the smaller size and reduced polarizability of the chloride ion compared to the iodide ion. In the IR spectra, the pyridinium N—H stretching band for salt (1) exhibited a blue shift compared with that of salt (2).     

Synthesis of 4-arylpiperidines from 1-benzyl-4-piperidone: application of the Shapiro reaction and alkenylsilane cross-coupling

[reaction: see text] 1-Benzyl-3,4-unsaturated-4-piperidinyl benzyldimethylsilane has been prepared and observed to readily undergo palladium-catalyzed cross-coupling reactions with a variety of aryl iodides and aryl bromides to generate 3,4-unsaturated 4-arylpiperidines, often at ambient temperature.     

Synthesis and characterization of starch-graft-polycaprolactone as compatibilizer for starch/polycarprolactone blends

Polycaprolactone (PCL) was grafted onto starch through introduction of urethane linkages. The grafting reaction was carried out in two steps. The first step was the reaction of hydroxyl-terminated PCL with 2,4-tolylene diisocyanate. The isocyanate terminated PCL was then reacted with starch to obtain starch-graft-polycaprolactone (starch-g-PCL). The grafting reaction was confirmed by FT-IR spectroscopy. The compatibility of the starch/PCL blend was enhanced with a compatibilizer, starch-g-PCL, whose amount was 3 wt.-% of the blend. The tensile strength and morphology of the compatibilized blend were determined. It was found that the compatibilized starch/PCL blend has finer phase domains and an improved interfacial adhesion. Mechanical properties of the compatibilized blend were found to be significantly higher than those of the corresponding uncompatibilized starch/PCL blend.     

Functionalization of polyesters with maleic anhydride by reactive extrusion

Maleic anhydride (MAn) was grafted onto aliphatic and aromatic/aliphatic copolyesters by reactive extrusion in the presence of a free radical initiator using a twin‐screw extruder. The grafting reaction was confirmed by spectroscopic analyses. The presence of succinic anhydride groups was shown by FT‐IR spectroscopy, and NMR spectra indicate that the grafts consist of single succinic anhydride units. The 2D ¹H‐NMR spectra (COSY) indicate that grafting reactions take place at aliphatic dicarboxylic acid units of copolyesters. The graft content was determined by a nonaqueous titration method. The effects of concentration of initiator and monomer and reaction temperature on the graft content and intrinsic viscosity were studied. The low percentage grafting in poly(lactic acid) was observed due to the presence of limited free radical sites in the polymer backbone. Temperature and monomer and initiator concentrations affect the graft content, and the desired graft content with minimal degradation can be obtained by controlling these factors. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1693–1702, 1999     

Crystal structure and DFT analyses of a pentacoordinated PCP pincer nickel(II) complex

The reaction of NiCl₂ with 1,3‐bis[(diphenylphosphanyl)methyl]hexahydropyrimidine in the presence of 2,6‐dimethylphenyl isocyanide and KPF₆ afforded a new pentacoordinated PCP pincer Ni^II complex, namely {1,3‐bis[(diphenylphosphanyl)methyl]hexahydropyrimidin‐2‐yl‐κN²}(2,6‐dimethylphenyl isocyanide‐κC)nickel(II) hexafluoridophosphate 0.70‐hydrate, [Ni(C₉H₉N)(C₃₀H₃₀ClN₂P₂)]PF₆·0.7H₂O or [NiCl{C(NCH₂PPh₂)₂(CH₂)₃‐κ³P,C,P′}(Xylyl‐NC)]PF₆·0.7H₂O, in very good yield. Its X‐ray structure showed a distorted square‐pyramidal geometry and the compound does not undergo dissociation in solution, as shown by variable‐temperature NMR and UV–Vis studies. Density functional theory (DFT) calculations provided an insight into the bonding; the nickel dsp²‐hybridized orbitals form the basal plane and the nearly pure p orbital forms the axial bond. This is consistent with the NBO (natural bond orbital) analysis of analogous nickel(II) complexes.