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showing 10 items of 56203 documents
Highly Anisotropic Rhenium(IV) Complexes: New Examples of Mononuclear Single-Molecule Magnets
2013
The rhenium(IV) complex (NBu4)2[ReBr4(ox)] (1) (ox = oxalate and NBu4(+) = tetra-n-butylammonium cation) has been prepared and its crystal structure determined by X-ray diffraction. The structure is made up of discrete [ReBr4(ox)](2-) anions and bulky NBu4(+) cations. Each [ReBr4(ox)](2-) anion is surrounded by six NBu4(+) cations, which preclude any significant intermolecular contact between the anionic entities, the shortest rhenium···rhenium distance being 9.373(1) Å. Variable temperature dc and ac magnetic susceptibility measurements and field-dependent magnetization experiments on polycrystalline samples of 1 reveal the occurrence of highly anisotropic magnetically isolated Re(IV) cent…
Synthesis and solid state structure for a series of poly(1-pyrrolylmethyl)benzene derivatives. Control of the interplaying π–π and C–H⋯π interactions?
2006
The syntheses of new hexa- and 1,2,4,5-tetra-1-pyrrolylmethyl-benzene (1 and 2, respectively) compounds and their crystal structures, along with those for the related disubstituted o-, m- and p-di-1-pyrrolylmethyl-benzene (3–5) derivatives are reported. The arrangements of molecules in the 1-D structure for 2–5 are controlled by the interplay of two different weak interactions: π–π and C–H⋯π (Ph) interactions. The absence of such interactions in the packing of 1 seems to be related to the arrangement of the pyrrolylmethyl arms with respect to the benzene core, which prevents the π cloud of the aromatic ring to be part of any intermolecular interaction. In addition, C–H⋯π (pyrrolyl) interact…
A spin-crossover complex based on a 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) ligand functionalized with a carboxylate group
2014
Combining Fe(ii) with the carboxylate-functionalized 2,6-bis(pyrazol-1-yl)pyridine (bppCOOH) ligand results in the spin-crossover compound [Fe(bppCOOH)2](ClO4)2 which shows an abrupt spin transition with a T1/2 of ca. 380 K and a TLIESST of 60 K due to the presence of a hydrogen-bonded linear network of complexes.
Synthesis and characterization of binuclear μ-oxalato nickel(II), copper(II) and zinc(II) complexes with 3,3′-diamino-N-methyl-dipropylamine or trans…
1999
Abstract New binuclear complexes of the type [(Ni(Medpt)NO3)2ox] (1) (Medpt=3,3′-diamino-N-methyl-dipropylamine, H2ox=oxalic acid), [(Ni(dach)2)2ox]NO3·2H2O (2) (dach=trans-1,2-diaminocyclohexane), [(Cu(Medpt))2ox]X2·yH2O (X=NO3, y=2 2/3 (3); X=ClO4, y=0 (4)) and [(Zn(dach)2)2ox](ClO4)2·2H2O (5) have been prepared and characterized by IR and UV–Vis spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between six-coordinated (N3O3 or N4O2) Ni(II) (compounds 1 or 2), five-coordinated (N3O2) Cu(II) (compounds 3 and 4) or six-coordinated (N4O2) Zn(II) (compound 5). The crystal structure of [(Cu(Medpt))2ox](NO3)2·2 2/3 H2O (3) has been determined by single-crystal X-…
Carbon monoxide activation by a molecular aluminium imide: C-O bond cleavage and C-C bond formation
2020
Anionic molecular imide complexes of aluminium are accessible via a rational synthetic approach involving the reactions of organo azides with a potassium aluminyl reagent. In the case of K2 [(NON)Al(NDipp)]2 (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethyl-xanthene; Dipp=2,6-diisopropylphenyl) structural characterization by X-ray crystallography reveals a short Al-N distance, which is thought primarily to be due to the low coordinate nature of the nitrogen centre. The Al-N unit is highly polar, and capable of the activation of relatively inert chemical bonds, such as those found in dihydrogen and carbon monoxide. In the case of CO, uptake of two molecules of the substrate…
Electrochemical and spectroelectrochemical studies of β-phosphorylated Zn porphyrins
2013
The electrochemical and spectroelectrochemical properties of two β-phosphorylated Zn porphyrins, [2-diethoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (1) and [2-diisopropoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (2), are reported in CH 2 Cl 2 and PhCN containing tetrabutylammonium perchlorate (TBAP) or tetrabutylammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. Under certain solution conditions, three one-electron reductions are observed, with the last process being attributed to the product of a chemical reaction following formation of the porphyrin dianion. Two or three oxidations are observed for the same compounds, again depending upon the solution c…
Encapsulation of tetramethylphosphonium cations
2009
International audience; The weak interactions and capsule formation of tetramethylphosphonium (TMP) cation with resorcinarenes 1 and 2 and the corresponding pyrogallarenes 3 and 4 were studied in the solid state by single crystal X-ray diffraction, in solution by NMR and in the gas phase by mass spectrometry. In methanol-D4, the NMR titration studies reveal that the association constants for the 1:1 complexes of TMP@3 and TMP@4 are much higher (TMP@4:390±37 M-1) than for the corresponding TMP@1 and TMP@2 (TMP@2:130±10 M-1) complexes. In the gas phase both monomeric 1:1 TMP@1-TMP@4 complexes as well as the dimeric 1:2 capsule complexes, TMP@12-TMP@42 were observed. The 1:1:2 molar mixtures o…
Diabetes and renin-angiotensin-aldosterone system: Implications for covid-19 patients with diabetes treatment management
2020
In the context of the COVID-19 continuous spreading, this paper focuses on the increased risk of diabetic patients regarding the metabolic control and the uncertainties related to SARS-CoV-2 infection. Chronic hyperglycaemia negatively affects the immune system, which triggers an increase of morbidity and mortality for viral infections. A key aspect of COVID-19 resides in the involvement of renin-angiotensin-aldosterone (RAAS) system that causes a cascade of reactions mediated by vasoactive peptides with implications in vasoconstriction, vascular permeability, oxidative stress remodelling and tissue injuries. Activation of RAAS at pulmonary level, is responsible for the local damage. Many q…
Reactivity of di-n-butyl-dicyclopentadienylzirconium towards amido stabilized stannylenes
2009
Abstract Reaction of Sn[(N(C 6 H 3 i Pr 2 -2,6)(SiMe 3 )] 2 and [{Sn(N(C 6 H 3 i Pr 2 -2,6)(SiMe 3 )(μ-Cl) 2 ] with di- n -butyl-dicyclopentadienylzirconium yielded the trimetallic a carbene-like complex {[(N(C 6 H 3 i Pr 2 -2,6)(SiMe 3 )]( n -Bu)Sn} 2 Cp 2 Zr. The oxidation of {[(N(C 6 H 3 i Pr 2 -2,6)(SiMe 3 )]( n -Bu)Sn} 2 Cp 2 Zr by oxygen gives the five-membered dioxadistannazirconacyclic complex {[(N(C 6 H 3 i Pr 2 -2,6)(SiMe 3 )]( n -Bu)Sn} 2 O 2 Cp 2 Zr.
Effect of different concentrations of specific inhibitor of matrix metalloproteinases on the shear bond strength of self-adhesive resin cements to de…
2017
Background Considering the probability of chemical and enzymatic reactions between matrix metalloproteinases (MMPs) in the dentin structure and their specific inhibitors, the aim of the present study was to evaluate the effect of different concentrations of specific inhibitor of MMPs (galardin) on the shear bond strength of self-adhesive resin cements to dentin. Material and Methods Forty-eight sound human premolars were mounted in self-cured acrylic resin after removal of the enamel on the buccal and lingual surfaces. The dentin surfaces achieved were polished and prepared with 600-grit silicon carbide paper. The samples were divided into 3 groups (n=16) based on the concentration of galar…