Structural Study of Nickel(II), Copper(II), and Palladium(II) Complexes of 2‐Pyridineformamide 3‐Hexamethyleneiminylthiosemicarbazone

Reduction of 2‐cyanopyridine by sodium in the presence of 3‐hexamethyleneiminylthiosemicarbazide produces 2‐pyridineformamide 3‐hexamethyleneiminylthiosemicarbazone, HAmhexim. Complexes with nickel(II), copper(II) and palladium(II) have been prepared and the following complexes structurally characterized: [Ni(Amhexim)OAc], [{Cu(Amhexim)}₂C₄H₄O₄]·2DMSO·H₂O, [Cu(HAmhexim)Cl₂] and [Pd(Amhexim)Cl]. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur atom when coordinating as the anionic or neutral ligand, respectively. [{Cu(Amhexim)}₂C₄H₄O₄] is a binuclear complex with the two copper(II) ions bridged by the succinato group in [Cu‐(HAmhexim)Cl₂] the Cu atom is 5‐coordinate and close to a square pyramid structure and in [Ni(Amhexim)OAc] and [Pd(Amhexim)Cl] the metal atoms are planar, 4‐coordinate.     

2-Metylthiazolium salts as 1,4-dinucleophiles. Thiazolo[3,2-a]pyridinium salts from westphal condensation

Condensation of 2-methylthiazoliura salts with 1,2-dicarbonyls in the presence of base, yielded thiazolo-[3,2-a]pyridinium derivatives. Results with different substrates are discussed.     

Ruthenium nanoparticles canopied by heptagon-containing saddle-shaped nanographenes as efficient aromatic hydrogenation catalysts

The search for new ligands capable of modifying the metal nanoparticle (MNP) catalytic behavior is of increasing interest. Herein we present the first example of RuNPs stabilized with non-planar heptagon-containing saddle-shaped nanographenes (Ru@1 and Ru@2). The resemblance to graphene-supported MNPs makes these non-planar nanographene-stabilized RuNPs very attractive systems to further investigate graphene–metal interactions. A combined theoretical/experimental study allowed us to explore the coordination modes and dynamics of these nanographenes at the Ru surface. The curvature of these saddle-shaped nanographenes makes them efficient MNP stabilizers. The resulting RuNPs were found to be highly active catalysts for the hydrogenation of aromatics, including platform molecules derived from biomass (i.e. HMF) or liquid organic hydrogen carriers (i.e. N-indole). A significant ligand effect was observed since a minor modification on the hept-HBC structure (C CH₂ instead of C O) was reflected in a substantial increase in the MNP activity. Finally, the stability of these canopied RuNPs was investigated by multiple addition experiments, proving to be stable catalysts for at least 96 h.

Ruthenium nanoparticles stabilized with non-planar polycyclic aromatic hydrocarbons (PAHs) are active catalysts in the hydrogenation of aromatic substrates under mild conditions.     

Synthesis of new porphyrin/fullerene supramolecular assemblies: a spectroscopic and electrochemical investigation of their coordination equilibrium in solution

Two new fullerene ligands have been designed to provide relatively simple frameworks to build supramolecular systems containing both fullerene and Zn-porphyrin moieties. The coordination of the fullerene ligands to the Zn-porphyrin was supported by UV-vis titration, nuclear magnetic resonance and electrochemical data. The resulting spectrophotometric data were processed both graphically and computationally to yield the stoichiometry, stability constant, and molar absorptivity of the species in equilibrium.     

Synthesis of enantiomerically pure vinylcyclopropylboronic esters via cross-metathesis

The potent antibiotic ambruticin caused us to investigate two new aspects of cyclopropylboronic ester chemistry: we established the analytical basics for all 1,2,3-trisubstituted diastereoisomers as well as the cross-metathesis as a tool to synthesise vinylcyclopropylboronic esters.     

Ion-selective electrodes based on p-tert-butyl-homooxacalixarene di(ethyl)amides

The diethyl amides of p-tert-butyldihomooxacalix[4]arene (1), p-tert-butylhexahomotrioxacalix[3]arene (2) and p-tert-butylcalix[4]arene (3) were used as active materials in ion-selective membrane electrodes to check the detection of different kinds of cations (Na⁺, K⁺, Cs⁺, Mg^2 + , Ca^2 + , Mn^2 + , Cu^2 + , Zn^2 + , Cd^2 + , Pb^2 +  and tetramethylammonium cation). The electrode characteristics and selectivity coefficients were determined and compared. Optimisation of the PVC membrane composition was achieved using three different plasticisers (bis(2-ethylhexyl) adipate, o-nitrophenyl octyl ether and bis(2-butylpentyl) adipate). Amide 3 shows selectivity for Na⁺, whereas compounds 1 and 2 exhibit the highest selectivity for Pb^2 +  among all the studied cations. The X-ray crystal structure of dihomooxacalix[4]arene tetra(diethyl)amide (1) was determined, revealing it to be in the cone conformation.     

Regiospecific one‐pot synthesis of new trifluoromethyl substituted heteroaryl pyrazolyl ketones

A convenient and general method for the regiospecific synthesis of three novel series of 1‐(2‐thenoyl)‐, 1‐(2‐furoyl)‐ and 1‐(isonicotinoyl)‐3‐alkyl(aryl)‐5‐hydroxy‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐pyrazoles, in good yields (53 – 91 %), from the cyclocondensation reactions of 1,1,1‐trifluoro‐4‐alkoxy‐4‐alkyl(aryl)‐but‐3‐en‐2‐ones, where alkyl = H and Me; aryl = ‐C₆H₅, 4‐CH₃C₆H₄, 4‐CH₃OC₆H₄, 4‐FC₆H₄, 4‐ClC₆H₄, 4‐BrC₆H₄, 4‐NO₂CgH₄ with 2‐thiophenecarboxylic hydrazide, furoic hydrazide and isonicotinic acid hydrazide, respectively, is reported. Subsequently dehydration reaction of phenyl substituted 2‐pyrazolines with P₂O₅ furnished the corresponding 1H‐pyrazoles as mixture of regioisomers and in low yields (35 – 36 %).     

Vibrational spectrum and internal rotation in 2,5-dimethylpyrazine

The infrared and Raman spectra of 2,5-dimethylpyrazine have been recorded and assigned on the basis of a C_2h molecular geometry previously determined by MINDO/3. The potential energy function corresponding to the internal rotation of both methyl groups has been used to solve the Schrödinger equation, and to obtain the energy levels of that motion on the basis of a molecular symmetry G₃₆. The rotation of each substituent is found to be almost independent of the other.     

Convenient synthesis of furan-3-carboxylic acid and derivatives

A convenient synthesis of furan-3-carboxylic acid and derivatives from aromatization of 4-trichloroacetyl-2,3-dihydrofuran followed by nucleophilic displacement of the trichloromethyl group by hydroxide, alcohols, and amines, is presented.