Redox-Driven Transformation of a Discrete Molecular Cage into an Infinite 3D Coordination Polymer

Two M12L6 redox‐active self‐assembled cages constructed from an electron‐rich ligand based on the extended tetrathiafulvalene framework (exTTF) and metal complexes with a linear geometry (PdII and AgI) are depicted. Remarkably, based on a combination of specific structural and electronic features, the polycationic self‐assembled AgI coordination cage undergoes a supramolecular transformation upon oxidation into a three‐dimensional coordination polymer, that is characterized by X‐ray crystallography. This redox‐controlled change of the molecular organization results from the drastic conformational modifications accompanying oxidation of the exTTF moiety

Controlling the Host-Guest Interaction Mode through a Redox Stimulus

A proof-of-concept related to the redox-control of the binding/releasing process in a host-guest system is achieved by designing a neutral and robust Pt-based redox-active metallacage involving two extended-tetrathiafulvalene (exTTF) ligands. When neutral, the cage is able to bind a planar polyaromatic guest (coronene). Remarkably, the chemical or electrochemical oxidation of the host-guest complex leads to the reversible expulsion of the guest outside the cavity, which is assigned to a drastic change of the host-guest interaction mode, illustrating the key role of counteranions along the exchange process. The reversible process is supported by various experimental data (1 H NMR spectroscopy, ESI-FTICR, and spectroelectrochemistry) as well as by in-depth theoretical calculations performed at the density functional theory (DFT) level

A self-assembled M2L4 cage incorporating electron-rich 9-(1,3-dithiol-2-ylidene)fluorene units

An electron-rich redox-active M2L4 cage is depicted. The cage is constructed through coordination driven self-assembly of a 9-(1,3-dithiol-2-ylidene)fluorene bis-pyridyl ligand in the presence of the Pd(BF4)2(CH3CN)4 complex. The corresponding discrete structure has been fully characterized in the solution as well in the solid state (crystal structure), showing notably that each of the four ligands surrounding the cavity can be reversibly oxidized upon a one electron process

Capabilities of static TOF-SIMS in the differentiation of first-row transition metal oxides.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses were performed on the first-row transition metal oxides from scandium to zinc in positive and negative detection modes. The nature of the numerous M(x)O(y)(+/-) ionic species generated by 15 keV Ga(+) primary ion bombardment allows the identification of a given metal-oxygen system. To identify the metal valence in the oxide under investigation, several procedures were investigated: the detection of specific and characteristic ions, the use of ion abundance ratios and the use of a valence model. Owing to their importance in many fields of materials science, each of these speciation methodologies was evaluated for the differentiation of vanadium, titanium, chromium, manganese, iron, cobalt and copper oxides. Trivalent-hexavalent chromium distinction was first intensely investigated because it really corresponds to a model system for inorganic speciation. For each series of metal oxides, the more pertinent speciation criteria were then systematically tested. The limitations of the proposed methodologies are discussed. Their use is made complicated when pollutants or a superficial oxide layer, with a stoichiometry different from that of the bulk, are present. Finally, thermodynamic considerations relative to the stability of the M(x)O(y)(+/-) ions may also modify the relationship between the analyzed oxide and the observed positive and negative secondary ion mass spectra

Semi-targeted analysis of complex matrices by ESI FT-ICR MS or how an experimental bias may be used as an analytical tool.

Ammonia is well suited to favor deprotonation process in electrospray ionization mass spectrometry (ESI-MS) to increase the formation of [M - H]. Nevertheless, NH may react with carbonyl compounds (aldehyde, ketone) and bias the composition description of the investigated sample. This is of significant importance in the study of complex mixture such as oil or bio-oil. To assess the ability of primary amines to form imines with carbonyl compounds during the ESI-MS process, two aldehydes (vanillin and cinnamaldehyde) and two ketones (butyrophenone and trihydroxyacetophenone) have been infused in an ESI source with ammonia and two different amines (aniline and 3-chloronaniline). The (+) ESI-MS analyses have demonstrated the formation of imine whatever the considered carbonyl compound and the used primary amine, the structure of which was extensively studied by tandem mass spectrometry. Thus, it has been established that the addition of ammonia, in the solution infused in an ESI source, may alter the composition description of a complex mixture and leads to misinterpretations due to the formation of imines. Nevertheless, this experimental bias can be used to identify the carbonyl compounds in a pyrolysis bio-oil. As we demonstrated, infusion of the bio-oil with 3-chloroaniline in ESI source leads to specifically derivatized carbonyl compounds. Thanks to their chlorine isotopic pattern and the high mass measurement accuracy, (+) ESI Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) unambiguously highlighted them from the numerous CHO bio-oil components. These results offer a new perspective into the detailed molecular structure of complex mixtures such as bio-oils