Stabilization of Aliphatic Phosphines by Auxiliary Phosphine Sulfides Offers Zeptomolar Affinity and Unprecedented Selectivity for Probing Biological CuI

Full elucidation of the functions and homeostatic pathways of biological copper requires tools that can selectively recognize and manipulate this trace nutrient within living cells and tissues, where it exists primarily as Cu^I. Buffered at attomolar concentrations, intracellular Cu^I is, however, not readily accessible to commonly employed amine and thioether‐based chelators. Herein, we reveal a chelator design strategy in which phosphine sulfides aid in Cu^I coordination while simultaneously stabilizing aliphatic phosphine donors, producing a charge‐neutral ligand with low‐zeptomolar dissociation constant and 10¹⁷‐fold selectivity for Cu^I over Zn^II, Fe^II, and Mn^II. As illustrated by reversing ATP7A trafficking in cells and blocking long‐term potentiation of neurons in mouse hippocampal brain tissue, the ligand is capable of intercepting copper‐dependent processes. The phosphine sulfide‐stabilized phosphine (PSP) design approach, which confers resistance towards protonation, dioxygen, and disulfides, could be readily expanded towards ligands and probes with tailored properties for exploring Cu^I in a broad range of biological systems.     

Template synthesis,characterization and electrochemical studies of copper(II) macrocyclic complexes derived from 4-methyl-2,6-di(formyl/benzoyl) phenol and diamines

Copper(II) macrocyclic complexes [Cu(L)Cl2]·2H2O (1,2) have been synthesized from the copper(II)-directed condensation of 4-methyl-2,6-diformylphenol (1) or 4-methyl-2,6-dibenzoylphenol (2) with diamines [1,2-diaminopropane (a), 1,3-diaminopropane (b) and o-phenylenediamine (c)] in EtOH in high yields. These complexes are monomeric, non-electrolytes and paramagnetic, indicating a distorted octahedral geometry around copper, which is supported by i.r., electronic, e.s.r. and magnetic susceptibility measurements. Electrochemical studies of (1) and (2) using c.v. indicate an irreversible cathodic peak (ca. –0.65 to –0.76 V) corresponding to reduction of copper(II) to copper(I) and the diffusion-controlled nature of the electrode process.     

Effect of charge-transfer enhancement on the efficiency and rotary mechanism of an oxindole-based molecular motor

Harvesting energy and converting it into mechanical motion forms the basis for both natural and artificial molecular motors. Overcrowded alkene-based light-driven rotary motors are powered through sequential photochemical and thermal steps. The thermal helix inversion steps are well characterised and can be manipulated through adjustment of the chemical structure, however, the insights into the photochemical isomerisation steps still remain elusive. Here we report a novel oxindole-based molecular motor featuring pronounced electronic push–pull character and a four-fold increase of the photoisomerization quantum yield in comparison to previous motors of its class. A multidisciplinary approach including synthesis, steady-state and transient absorption spectroscopies, and electronic structure modelling was implemented to elucidate the excited state dynamics and rotary mechanism. We conclude that the charge-transfer character of the excited state diminishes the degree of pyramidalisation at the alkene bond during isomerisation, such that the rotational properties of this oxindole-based motor stand in between the precessional motion of fluorene-based molecular motors and the axial motion of biomimetic photoswitches.

A novel oxindole-based light-driven molecular motor with pronounced push–pull character was investigated. The rotary mechanism stands in between the precessional motion of fluorene-based motors and the axial motion of biomimetic photoswitches.     

Fully Resolved NMR Correlation Spectroscopy

A new correlation experiment cited as “push‐G‐SERF” is reported. In the resulting phased 2D spectrum, the chemical shift information is selected along the direct dimension, whereas scalar couplings involving a selected proton nucleus are edited in the indirect domain. The robustness of this pulse sequence is demonstrated on compounds with increasing structural and spectral complexity, using state‐of‐the‐art spectrometers. It allows for full resolution of both dimensions of the spectrum, yielding a straightforward assignment and measurement of the coupling network around a given proton in the molecule. This experiment is intended for chemists who want to address efficiently the structural analysis of molecules with an overcrowded spectrum.     

One pot syntheses of thiazol‐2‐hydrazone,pyridino[2,3‐d]pyridazine,pyrazolo[3,4‐d]pyridazine,and isoxazolo[4,5‐d]pyridazine derivatives

Reactions of the pyridazine derivatives 1a–c with phenyl isothiocyanate followed by heterocyclization with ethyl chloroacetate gave the thiazolidinone derivatives 6a–c . The reactivity of 6a towards some chemical reagents was studied. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:258–262, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10026     

Swelling the micelle core surrounding single-walled carbon nanotubes with water-immiscible organic solvents

Solvatochromic shifts in the absorbance and fluorescence spectra are observed when surfactant-stabilized aqueous single-walled carbon nanotube (SWNT) suspensions are mixed with immiscible organic solvents. When aqueous surfactant-suspended SWNTs are mixed with o-dichlorobenzene, the spectra closely match the peaks for SWNTs dispersed in only pure o-dichlorobenzene. These spectral changes suggest that the hydrophobic region of the micelle surrounding SWNTs swells with the organic solvent when mixed. The solvatochromic shifts of the aqueous SWNT suspensions are reversible once the solvent evaporates. However, some surfactant-solvent systems show permanent changes to the fluorescence emission intensity after exposure to the organic solvent. The intensity of some large diameter SWNT (n, m) types increase by more than 175%. These differences are attributed to surfactant reorganization, which can improve nanotube coverage, resulting in decreased exposure to quenching mechanisms from the aqueous phase.     

Phenyliodine bis(trifluoroacetate)-mediated oxidative C-C bond formation: synthesis of 3-hydroxy-2-oxindoles and spirooxindoles from anilides

The reaction of phenyliodine bis(trifluoroacetate) (PIFA) with a series of anilides 1 (E = CO(2)Et) in CF(3)CH(2)OH was found to give 3-hydroxy-2-oxindole derivatives 2, while that with various anilides 1' (E = CON(R(4))Ar) afforded the C(2)-symmetric or unsymmetric spirooxindoles 3. These processes feature a metal-free oxidative C(sp(2))-C(sp(3)) bond formation, followed by oxidative hydroxylation or spirocyclization.