Electroactive Benzothiazole Hydrazones and Their [Mo6O19]2− Derivatives: Promising Building Blocks for Conducting Molecular Materials

The electroactive benzothiazole hydrazone AMBTH–H₂, a new member of the 2,2′‐azino‐bis(N‐alkylbenzothiazole) family, was synthesised in a five‐step procedure and characterised by using X‐ray diffraction along with two intermediates and the N‐methylbenzothiazole hydrazone MBTH–H₂. Both AMBTH–H₂ and MBTH–H₂ were coupled to [Mo₆O₁₉]^2? in acetonitrile in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine to give two new diazoalkane–hexamolybdates, which were isolated as tetrabutylammonium salts and characterised by using IR, UV/Vis and NMR spectroscopies, cyclic voltammetry and, for one of them, X‐ray diffraction. The packing arrangement molecules in crystals of AMBTH–H₂, the redox features of the AMBTH–hexamolybdate hybrid together with a good electronic communication between the organic π system and the molybdenum centres make these compounds very promising blocks for the synthesis of conducting molecular materials.     

Metal‐Directed Self‐Assembly of a Polyoxometalate‐Based Molecular Triangle: Using Powerful Analytical Tools to Probe the Chemical Structure of Complex Supramolecular Assemblies

A polyoxometalate‐based molecular triangle has been synthesized through the metal‐driven self‐assembly of covalent organic/inorganic hybrid oxo‐clusters with remote pyridyl binding sites. The new metallomacrocycle was unambiguously characterized by using a combination of ¹H NMR spectroscopy, 2D diffusion NMR spectroscopy (DOSY), electrospray ionization travelling wave ion mobility mass spectrometry (ESI‐TWIM‐MS), small‐angle X‐ray scattering (SAXS) and molecular modelling. The collision cross‐sections obtained from TWIM‐MS and the hydrodynamic radii derived from DOSY are in good agreement with the geometry‐optimized structures obtained by using theoretical calculations. Furthermore, SAXS was successfully employed and proved to be a powerful technique for characterizing such large supramolecular assemblies.     

Electrografting of Diazonium‐Functionalized Polyoxometalates: Synthesis,Immobilisation and Electron‐Transfer Characterisation from Glassy Carbon

Polyoxometalates (POMs) are attractive candidates for the rational design of multi‐level charge‐storage materials because they display reversible multi‐step reduction processes in a narrow range of potentials. The functionalization of POMs allows for their integration in hybrid complementary metal oxide semiconductor (CMOS)/molecular devices, provided that fine control of their immobilisation on various substrates can be achieved. Owing to the wide applicability of the diazonium route to surface modification, a functionalized Keggin‐type POM [PW₁₁O₃₉{Ge(p‐C₆H₄‐C?C‐C₆H₄‐${{\rm N}{{+\hfill \atop 2\hfill}}}$ )}]^3? bearing a pending diazonium group was prepared and subsequently covalently anchored onto a glassy carbon electrode. Electron transfer with the immobilised POM was thoroughly investigated and compared to that of the free POM in solution.     

Synthesis of key fragments of leiodelide A

The synthesis of all key fragments of the marine macrolide leiodelide A is described. The polyoxygenated northern subunit is derived from d-xylose, while the southern subunit is rapidly assembled via an aldol reaction and Horner-Wadsworth-Emmons olefination. This highly convergent approach will allow for rapid modification and assembly of several isomers of leiodelide A, which may be necessary considering the assignment of leiodelide B has been previously shown to be incorrect.     

Total suppression of superconductivity by high magnetic fields in YBa(2)Cu(3)O(6.6)

We have studied the variation of transverse magnetoresistance of underdoped YBCO(6.6) crystals, either pure or with reduced T(c) down to 3.5 K by electron irradiation, in fields up to 60 T. We find evidence that the superconducting fluctuation contribution to the conductivity is suppressed only above a threshold field H(c)'(T), which is found to vanish at T(c)' > T(c). In the pure YBCO(6.6) sample, H(c)' is already 50 T at T(c). We find that increasing disorder weakly depresses H(c)'(0), T(c)', and T(nu), the onset of the Nernst signal. Thus, these energy scales appear more characteristic of the 2D local pairing than the pseudogap temperature which is not modified by disorder.     

Synthesis and characterization of the Keggin-type ruthenium-nitrido derivative [PW11O39{RuN}]4- and evidence of its electrophilic reactivity

The ruthenium-nitrido POM derivative [PW11O39{RuVIN}]4- has been synthesized by reaction between [PW11O39]7- and [RuVINCl5]2- or [RuVINCl4]-. Its molecular structure has been confirmed from multinuclear 31P and 183W NMR spectroscopy together with an EXAFS study, while the oxidation state of the ruthenium bearing the nitrido ligand has been inferred both from 183W NMR and XANES analysis at the Ru-K edge. The potential of [PW11O39{RuVIN}]4- in N-atom transfer reactions has been demonstrated through reaction with triphenylphosphine, which ultimately leads to the release of the bis(triphenylphosphane)iminium cation [PPh3=N=PPh3]+ through several intermediates, among which the phosphoraniminato derivative [PW11O39{RuVNPh3}]3- has been structurally characterized. Its unusual oxidation state is in accordance with its EPR spectrum.     

Cyclodextrin-induced auto-healing of hybrid polyoxometalates

You'll never walk alone: An auto-healing process of the first host-guest complex involving a polyoxometalate hybrid and a cyclodextrin is reported. Indeed, this inclusion complex allows the complete restoration of the anchored organic moiety released by a basic stress, a process otherwise not fully reversible.