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1H NMR spectroscopy at 400 MHz in toluene-d8 of evaporated mixtures of lithium ethoxide and titanium(iv) isopropoxide in ethanol, used to prepare the spinel Li4Ti5O12 by the sol–gel method, may help clarify why the atomic ratio 5Li : 5Ti and not 4Li : 5Ti is the right choice to obtain the pure phase when performing hydrolysis at room temperature. The mixtures xLiOEt/yTi(OPri)4 in ethanol undergo alcohol exchange at room temperature, and the evaporated residues contain double lithium–titanium ethoxide [LiTi3(OEt)13] rather than simple mixtures of single metal alkoxides; this is of great relevance to truly understanding the chemistry and structural changes in the sol–gel process. Detailed inspection of the 1H and 13C VT NMR spectra of mixtures with different Li/Ti atomic ratios unequivocally shows the formation of [LiTi3(OEt)13] in a solution at low temperature. The methylene signals of free lithium ethoxide and Li[Ti3(OEt)13] coalesce at 20 °C when the atomic ratio is 5 : 5; however, the same coalescence is only observed above 60 °C when the atomic ratio is 4 : 5. We suggest that the highest chemical equivalence observed by 1H NMR spectroscopy achieved through chemical exchange of ethoxide groups involves the highest microscopic structural homogeneity of the sol precursor and will lead to the best gel after hydrolysis. Variable temperature 1H NMR spectra at 400 MHz of variable molar ratios of LiOEt/Ti(OPri)4 are discussed to understand the structural features of the sol precursor. While the precursor with the atomic ratio 5Li : 5Ti shows no signal of free LiOEt at 20 °C, both 4Li : 5Ti and 7Li : 5Ti show free LiOEt at 20 °C in their 1H NMR spectra, indicating that the molar ratio 5Li : 5Ti gives the maximum rate of chemical exchange. DFT calculations have been performed to support the structure of the anion [Ti3(OEt)13]− at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: The unexpectedly aqueous stable bis-tellurium cationic complex [Co(dmgH)2{PhTe(CH2)3SO3Na}2]+(1+ ) (dmgH− =dimethylglyoximate) has been fully characterized in the solid state and in solution. The UV–Vis spectrum of 1+ differs from that of earlier cobaloximes, exhibiting a new low energy band centered at λ max =425nm (ε ∼26155dm3 mol−1 cm−1) and assigned with DFT calculations to allowed LMCT transitions. 1H, 13C, and 125Te NMR spectra show unequivocally that two diastereomers exist equally in water, 50% of the achiral C 2 h meso-[Co(dmgH)2{R,S-PhTe(CH2)3SO3Na}2]+ and 50% of the chiral C 2 rac-[Co(dmgH)2{PhTe(CH2)3SO3Na}2]+ (25% of each enantiomer [Co(dmgH)2{R,R-PhTe(CH2)3SO3Na}2]+ and [Co(dmgH)2{S,S-PhTe(CH2)3SO3Na}2]+). The solid-state structure of the meso diastereomer has been solved. Neutral mono-tellurium complexes [CoCl(dmgH)2{Te(p-MeO–C6H4)2}](2) and [CoCl(dpgH)2{Te(p-MeO–C6H4)2}](3) (dpgH− =diphenylglyoximate) have also been characterized in the solid (3) state and in solution (2 and 3). The structural results provide the first examples of Co(III)–Te bonds. The solid-state structure of the related cobaloxime salt [Co(dmgH)2(py)2][CoCl2(dmgH)2] obtained during one synthesis is also reported. [Copyright &y& Elsevier]

In this work, we have prepared and characterized some gold compounds wearing a N-heterocyclic carbene (NHC) ligand as well as alkynyl derivatives with different substituents. The study of their electrochemical behavior reveals that these complexes show an irreversible wave at potentials ranging between −2.79 and −2.91 V, referenced to the ferrocenium/ferrocene pair. DFT calculations indicate that the reduction occurs mainly on the aryl−C≡C fragment. The cyclic voltammetry experiments under CO2 atmosphere show an increase in the faradaic current of the reduction wave compared to the experiments under argon atmosphere, indicating a possible catalytic activity towards the carbon dioxide reduction reaction (CO2RR). [ABSTRACT FROM AUTHOR]

New 1,2-azolylamidino complexes fac-[RuCl(DMSO)3(NHC(R)az*-κ²N,N)]OTf [R = Me (2), Ph (3); az* = pz (pyrazolyl, a), indz (indazolyl, b)] are synthesized via chloride abstraction from their corresponding precursors cis,fac-[RuCl2(DMSO)3(az*H)] (1) after subsequent base-catalyzed coupling of the appropriate nitrile with the 1,2-azole previously coordinated. All the compounds are characterized by ¹H NMR, 13C NMR and IR spectroscopy. Those derived from MeCN are also characterized by X-ray diffraction. Electrochemical studies showed several reduction waves in the range of −1.5 to −3 V. The electrochemical behavior in CO2 media is consistent with CO2 electrocatalytic reduction. The catalytic activity expressed as [icat(CO2)/ip(Ar)] ranged from 1.7 to 3.7 for the 1,2-azolylamidino complexes at voltages of ca. −2.7 to −3 V vs. ferrocene/ferrocenium. Controlled potential electrolysis showed rapid decomposition of the Ru catalysts. Photocatalytic CO2 reduction experiments using compounds 1b, 2b and 3b carried out in a CO2-saturated MeCN/TEOA (4 : 1 v/v) solution containing a mixture of the catalyst and [Ru(bipy)3]2+ as the photosensitizer under continuous irradiation (light intensity of 150 mW cm−2 at 25 °C, λ > 300 nm) show that compounds 1b, 2b and 3b allowed CO2 reduction catalysis, producing CO and trace amounts of formate. The combined turnover number for the production of formate and CO is ca. 100 after 8 h and follows the order 1b < 2b ≈ 3b. [ABSTRACT FROM AUTHOR]

The complexes [MCI2(κ²-N∼N′)] (N∼N′ = 2-C5H4N-CH2-NHAr; Ar = 4-MeC6H4, a; 2,6-Me2C6H3, b; 4-MeOC6H4, c; 4-CF3C6H4, d; M = Pd, 1a-d; Pt, 2a-d) have been prepared and fully stereochemically characterized both in the solid state and in solution. Their behavior in DMSO-d6 solution is dependent on the substituents of the aryl group and on the metal. Complexes of palladium with substituents at the para position (la, 1c, 1d) display a dynamic ¹H NMR pattern when the solutions are heated. An enantiomeric exchange Sλ/Rδ is suggested to explain such behavior. On the basis of the calculated negative δS‡ values, an associative mechanism involving the solvent is proposed. Under the same conditions, analogous complexes of platinum (2a, 2c, 2d) proved to be unstable, and release of the N∼N′ ligand was observed. Complexes lb and 2b show temperature-variable ¹H NMR spectra without any evidence accounting for enantiomeric exchange or decoordination. DFT calculations on models of 1a and 1b show that diastereomeric exchange Sδ/Sλ is a process where the complex with the higher sterical hindrance, 1b, has a lower energy barrier. [ABSTRACT FROM AUTHOR]

A fluorescent probe for ω-aminoacids behaves as a molecular ruler, changing the yellow fluorescent emission into blue as a function of the distance between the terminal ammonium and the carboxylate groups, permitting the quantitative detection of ω-aminoacids, their metabolites and related drugs, such as pregabalin or gabapentin, from pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First report of a MW assisted syntheses of a ligands and its complexes. • All the reactions are carried out MW assisted, with high yields. • The characterization of the complexes includes photophysics and electrochemistry. • The complexes are phosphorescent. • Complete spectroscopic characterization also for starting materials. Abstract The synthesis of 3-(2pyridyl)pyrazole (pypzH) by conventional methods requires refluxing at high temperatures during more than 16 h, but this is reduced to two consecutive steps of 2 h at 100 °C, and of 10 min at 50 °C in a microwave (MW) assisted synthesis. Its coordination as chelating ligand to the " fac -ReIBr(CO) 3 " and "RuII(bipy) 2 " fragments also occurs MW assisted in 5 or 10 min, respectively. A new MW assisted synthetic method is also described for the synthesis of the starting material [Ru(bipy) 2 Cl 2 ]·2H 2 O. Both pypzH complexes are characterized by X-ray crystallography, and the study of their photophysical properties support their phosphorescence. The electrochemistry of the Ru complex indicates that electrochemical oxidation is followed by a chemical process. [ABSTRACT FROM AUTHOR]

The preparation of new monodisperse polycrystalline palladium nanoparticles uniformly distributed on the surface of polymers, by simply adding a palladium(ii) solution in water to the polymers, is described. The polymer supported palladium nanoparticles material was used as an efficient portable and reusable catalyst for the stereoselective semihydrogenation reaction of internal alkynes to (Z)-alkenes in green solvents. [ABSTRACT FROM AUTHOR]

Abstract: A new family of heteroleptic bis‐cyclometalated IrIII complexes with formula [Ir( C N ^ )2( N N ^ )]Cl ( C N ^ =2‐phenylpyridinate and N N ^ =2,2′‐dipyridylamine or N‐benzylated 2,2′‐dipyridylamines, were synthesized, characterized, and successfully used as photosensitizers in the catalytic photooxidation of an array of dialkyl, dibenzyl, alkyl aryl, and diaryl sulfides, as well as sulfur‐containing amino acids. Furthermore, the reactions proceeded with optimal chemoselectivity, and atom economy under mild conditions. Experimental observations support a dual mechanism in which singlet oxygen and superoxide are the actual oxidants. [ABSTRACT FROM AUTHOR]

The reaction of N-(2-phthalimidoethyl)-N-alkylisopropylamines and S2Cl2 gave 4-N-(2-phthalimidoethyl)-N-alkylamino-5-chloro-1,2-dithiol-3-thiones that quantitatively cycloadded to dimethyl or diethyl acetylenedicarboxylate to give stable thioacid chlorides, which in turn reacted with one equivalent of aniline or a thiole to give thioanilides or a dithioester. Several compounds of this series showed atropisomers that were studied by a combination of dynamic NMR, simulation of the signals, conformational analysis by DFT methods, and single crystal X-ray diffraction, showing a good correlation between the theoretical calculations, the experimental values of energies, and the preferred conformations in the solid state. The steric hindering of the crowded substitution at the central amine group was found to be the reason for the presence of permanent atropisomers in this series of compounds and the cause of a unique disposition of the thioxo group at close-to-right angles with respect to the plane defined by the 1,3-dithiole ring in the dithiafulvene derivatives, thus breaking the sulfur-sulfur hypervalent bond that is always found in this kind of compounds. [ABSTRACT FROM AUTHOR]

• Straightforward synthesis of Ir(III) complexes with aliphatic amines is reported. • These complexes display strong luminescence around 510 nm. • The reaction of formation of these complexes is useful to detect biogenic amines. The straightforward reaction of [Ir 2 (ppy) 4 (µ-Cl) 2 with an excess of aliphatic amines yields luminescent iridium complexes of general formula [IrCl(ppy) 2 (amine)] [amine = n -octylamine (1), t -butylamine (2), piperidine (3)]. The higher sterical hindrance of the amine in complex 2 was the responsible of its equilibrium with the starting materials. The luminescence of 1 and 3 has been studied showing emission at 508 and 509 nm respectively. As the aliphatic amines can be considered models of biogenic amines, this luminescence has been used to explore the viability of this reaction in the detection of biogenic amines. The exposition to vapors of biogenic amines of a solution of [Ir 2 (ppy) 4 (µ-Cl) 2 in CH 2 Cl 2 or in different solid supports, showed that it was possible to detect the amines in a quick and easy way, with limits of detection value (in solution of methylene chloride) of 4.8 µM for cadaverine. [ABSTRACT FROM AUTHOR]