Charge transfer in porphyrin-calixarene complexes: ultrafast kinetics, cyclic voltammetry, and DFT calculations

Transient absorption spectroscopy, cyclic voltammetry, and DFT calculations were used to describe charge transfer processes in a series of 5,10,15,20-tetrakis(N-methylpyridinium-n-yl) porphyrins (TMPyPn, n = 4,3,2) and TMPyPn/p-sulfonatocalix[m]arene (clxm, m = 4,6,8) complexes. Excitation of TMPyPn is accompanied by an increasing electron density at the methylpyridinium substituents in the order TMPyP2 < TMPyP3 < TMPyP4. The quenching of the excited singlet states of the complexes increases with the number of ionized phenolic groups of clxm and can be correlated with the partial transfer of the electron density from O(-) to the peripheral methylpyridinium substituents rather than to the porphyrin ring.     

A microfluidic system with optical laser tweezers to study mechanotransduction and focal adhesion recruitment

We present a new method to locally apply mechanical tensile and compressive force on single cells based on integration of a microfluidic device with an optical laser tweezers. This system can locate a single cell within customized wells exposing a square-like membrane segment to a functionalized bead. Beads are coated with extracellular matrix (ECM) proteins of interest (e.g. fibronectin) to activate specific membrane receptors (e.g. integrins). The functionalized beads are trapped and manipulated by optical tweezers to apply mechanical load on the ECM-integrin-cytoskeleton linkage. Activation of the receptor is visualized by accumulation of expressed fluorescent proteins. This platform facilitates isolation of single cells and excitation by tensile/compressive forces applied directly to the focal adhesion via specific membrane receptors. Protein assembly or recruitment in a focal adhesion can then be monitored and identified using fluorescent imaging. This platform is used to study the recruitment of vinculin upon the application of external tensile force to single endothelial cells. Vinculin appears to be recruited above the forced bead as an elliptical cloud, centered 2.1 ± 0.5 μm from the 2 μm bead center. The mechanical stiffness of the membrane patch inferred from this measurement is 42.9 ± 6.4 pN μm(-1) for a 5 μm × 5 μm membrane segment. This method provides a foundation for further studies of mechanotransduction and tensile stiffness of single cells.     

A diabolo-shaped Dy9 cluster: synthesis, crystal structure and magnetic properties

The reaction of Dy(NO(3))(3)·6H(2)O with the ligand 2-((1-hydroxybutan-2-ylimino)methyl)phenol (H(2)L, ) generates the nonanuclear compound [Dy(9)L(8)(μ(3)-OH)(8)(μ(4)-OH)(2)(CH(3)OH)(8)](OH)(CH(3)OH)(3) (Dy(9)), whose single-crystal X-ray structure reveals the presence of two square pyramidal pentanuclear units assembled via the apical metal center. The square pyramidal core of a previously reported [Dy(5)(μ(4)-OH)(μ(3)-OH)(4)(μ-η(2)-Ph(2)acac)(4)(η(2)-Ph(2)acac)(6)] (Dy(5); Ph(2)acac = dibenzoylmethanide), is structurally related to those herein described; however, the magnetic properties of Dy(9) and Dy(5) are drastically different. Indeed, Dy(5) shows slow relaxation of magnetization while no out-of-phase ac signal is noticed for Dy(9). The underlying mechanism is not clear due to the complexity of such systems; however, the different anisotropy of the respective structures, which is dictated by the combination of the metal topology, the ligands involved and the structural parameters of the molecule, is mostly responsible for the distinctive relaxation dynamics observed.     

Facile synthesis of Ag@Pd satellites-Fe3O4 core nanocomposites as efficient and reusable hydrogenation catalysts

Well-dispersed Ag@Pd supported on magnetite nanoparticles have been obtained through a simple colloidal impregnation method. The as-synthesised nanocomposite exhibits greatly enhanced catalytic reactivity and reusability towards 4-nitrophenol hydrogenation.     

A Mn(III)-superoxo complex of a zwitterionic calix[4]arene with an unprecedented linear end-on Mn(III)-O2 arrangement and good catalytic performance for alkene epoxidation

Reactions of [H(4)L][PF(6)](4) with 4 equiv. of Mn(OAc)(2)·4H(2)O in the presence of air gave rise to a mononuclear Mn(III)-superoxo complex [Mn(III)L(O(2))(H(2)O)](PF(6))(2), which contains a bowl-shaped cationic structure with a D(4d) symmetry. It has an unprecedented linear end-on Mn(III)-O(2) unit and exhibited good efficiency and selectivity in the catalytic oxidation of alkenes with O(2) plus isobutyraldehyde under mild conditions.     

Regioselective Rh-catalyzed direct carbonylation of indoles to synthesize indole-3-carboxylates

Rh-catalyzed C-H carbonylation of indoles under 1 atm of CO has been achieved. Various substituted indoles and indole with free N-H could be carboxylated with linear- and/or cyclic-alcohol to give the desired indole-3-carboxylates with up to 92% yield. A mechanism involving Rh(III) initiated C-H metallation is proposed.     

A facile route to water-soluble coronenes and benzo[ghi]perylenes

Click reactions at the bay-position of perylenes and a new route to benzo[ghi]perylenes and coronenes are presented. Irradiation with light leads to an electrocyclic reaction of the newly formed triazole ring(s) with the neighbouring bay-positions of the perylene core and after oxidation by air, the benzo[ghi]perylenes and coronenes are obtained. By using Newkome dendrimers as substituents for perylene diimides (PDIs), water solubility can be achieved after removal of the tert-butyl protecting groups. The aggregation and optical properties of the bay-functionalised PDIs, benzo[ghi]perylenes and coronenes are investigated by absorption and fluorescence spectroscopy.     

Synthesis,characterization, and antibacterial activities of copper(I) bromide complexes of thioureas: X-ray structure of [Cu(Metu)<Subscript>4</Subscript>]Br

Copper(I) complexes of thioureas having the general formulae [CuL_nBr] and [CuL_n]Br [where, n = 1 − 4 and L = thiourea (Tu), N-methylthiourea (Metu), N-ethylthiourea (Ettu), N,N^′-dipropylthiourea (Dprtu), N,N^′-dibutylthiourea (Dbtu) or N,N^′-diphenylthiourea (Dphtu)] were prepared and characterized by elemental analysis, IR, and NMR (¹H and ¹³C) spectroscopy. The crystal structure of one of them, [Cu(Metu)₄]Br (1), was determined by X-ray crystallography. The X-ray structure of 1 describes a tetrahedral geometry around copper(I) with all Metu ligands binding through sulfur atoms. An upfield shift in the ¹³C NMR and downfield shift in the ¹H NMR spectra are consistent with the thione coordination to copper(I). Antimicrobial activities of the complexes were evaluated by the minimum inhibitory concentration method. The results showed that only [Cu(Ettu)₃Br] was effective in inhibiting the growth of all the tested organisms (gram-positive, gram-negative bacteria, and Candida sp.), while the other complexes were not effective against all the organisms.     

Supramolecular assembly of new heteropolymetalic molecules based on tetraiminodiphenolate macrocycle and hexacyanometallate anions: Magnetostructural and spectroscopic properties

Herein we report on the synthesis, single crystal X-ray structure, spectroscopic and magnetic properties of [{Cu₂(tidf)(H₂O)}₂(μ-CN)₂Fe(CN)₄]·6H₂O (1), [Cu₂(tidf)(H₂O)₂][Ni(CN)₄] (2) and [Cu₂(tidf)(H₂O)₂][Fe(CN)₅NO]·H₂O (3) (tidf = a Robson type macrocyclic ligand obtained on condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane). Complex (1) is pentanuclear; two paramagnetic dicopper(II) units are linked by a hexacyanoferrate(II) ion through two cyano-bridges. All compounds exhibit extensive, three-dimensional, supramolecular structures supported by classic hydrogen bonding between the coordinated aqua ligands, water molecules and cyano groups. Magnetism as a function of the temperature of complexes 1-3 is consistent with a strong antiferromagnetism with exchange parameters 2J estimated −783(29), −913(2), −905(1), respectively.