Showing papers by "Rosario Scopelliti published in 2011"
TL;DR: A modular approach for the synthesis of cage structures is described, and an amine exchange process with ethylenediamine allows the clean conversion of a dodecanuclear cages into a hexanuclear cage without disruption of the metallamacrocyclic structures.
Abstract: A modular approach for the synthesis of cage structures is described. Reactions of [(arene)RuCl2]2 [arene = p-cymene, 1,3,5-C6H3Me3, 1,3,5-C6H3(i-Pr)3] with formyl-substituted 3-hydroxy-2-pyridone ligands provide trinuclear metallamacrocycles with pendant aldehyde groups. Subsequent condensation reactions with di- and triamines give molecular cages with 3, 6, or 12 Ru centers in a diastereoselective and chemoselective (self-sorting) fashion. Some of the cages can also be prepared in one-pot reactions by mixing [(arene)RuCl2]2 with the pyridone ligand and the amine in the presence of base. The cages were comprehensively analyzed by X-ray crystallography. The diameter of the largest dodecanuclear complex is ∼3 nm; the cavity sizes range from 290 to 740 A3. An amine exchange process with ethylenediamine allows the clean conversion of a dodecanuclear cage into a hexanuclear cage without disruption of the metallamacrocyclic structures.
145 citations
TL;DR: Several well-defined Ni catalysts are discovered that are significantly more active and efficient than the pincer complex [((Me)N(2)N)NiCl] for the coupling of secondary alkyl halides.
Abstract: A structure–activity study was carried out for Ni catalyzed alkyl–alkyl Kumada-type cross coupling reactions. A series of new nickel(II) complexes including those with tridentate pincer bis(amino)amide ligands (RN2N) and those with bidentate mixed amino-amide ligands (RNN) were synthesized and structurally characterized. The coordination geometries of these complexes range from square planar, tetrahedral, to square pyramidal. The complexes had been examined as precatalysts for cross coupling of nonactivated alkyl halides, particularly secondary alkyl iodides, with alkyl Grignard reagents. Comparison was made to the results obtained with the previously reported Ni pincer complex [(MeN2N)NiCl]. A transmetalation site in the precatalysts is necessary for the catalysis. The coordination geometries and spin-states of the precatalysts have a small or no influence. The work led to the discovery of several well-defined Ni catalysts that are significantly more active and efficient than the pincer complex [(MeN2N)N...
99 citations
TL;DR: These series show that modifying the substitution pattern on the ligands can alter the photophysical and electrochemical properties of the complexes, and it is shown that compared to complexes containing phenyl-pyridine ligands, highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular Orbitals (LUMOs) are more delocalized over the entire main ligand in complexes containing Phenyl-imidazole.
Abstract: Phenyl-imidazole-based ligands with various substitution patterns have been used as the main ligand for heteroleptic bis-cyclometalated iridium complexes. Two series of complexes have been prepared and their photophysical and electrochemical properties were studied. The phosphorescence emission maxima range from about 490 to 590 nm, that is, from greenish-blue to orange. The first series is of the form Ir(L)2(acac) (L: a phenyl-imidazole based ligand; acac: acetylacetonate). In the first complex, 1a, L is 1,4,5-trimethyl-2-phenyl-1H-imidazole. Then, methyl groups are replaced with phenyl groups and chlorines are grafted on the cyclometalated phenyl ring. The second series is of the form Ir(4,5-dimethyl-1,2-diphenyl-1H-imidazole)2(La) (La: ancillary ligand being acetylacetonate, acac, N,N-dimethylamino-picolinate, NPic, picolinate, Pic, or 2-(diphenylphosphino)acetic acid, P). These series show that modifying the substitution pattern on the ligands can alter the photophysical and electrochemical properties...
98 citations
TL;DR: Crystalline and soft molecular networks can be constructed using dative BN bonds using a one-step, three-component reaction involving a triboronic acid, a catechol, and a bipyridyl linker.
Abstract: The BN connection: Crystalline and soft molecular networks can be constructed using dative BN bonds (see picture). The networks are obtained in a one-step, three-component reaction involving a triboronic acid, a catechol, and a bipyridyl linker.
94 citations
TL;DR: The salts that are liquid at room temperature were evaluated as electrolyte additives in dye-sensitized solar cells, giving rise to efficiencies 7.35 and 7.85% under 100 and 10% Sun, respectively, in combination with the standard Z907 dye.
Abstract: A series of novel ionic liquids composed of imidazolium, pyridinium, pyrrolidinium, and ammonium cations with tricyanomethanide or tetracyanoborate anions were prepared. The ionic liquids were characterized by NMR and IR spectroscopy and ESI-mass spectrometry, and their physical properties were investigated. Solid state structures of the N-propyl-N-methylpyrrolidinium and triethylpropylammonium tetracyanoborate salts were obtained by single crystal X-ray diffraction. The salts that are liquid at room temperature were evaluated as electrolyte additives in dye-sensitized solar cells, giving rise to efficiencies 7.35 and 7.85% under 100 and 10% Sun, respectively, in combination with the standard Z907 dye.
90 citations
TL;DR: The trigonal prismatic cages as discussed by the authors are able to encapsulate polyaromatic molecules such as triphenylene or coronene, and feature six dative boron-nitrogen bonds as structure-directing elements.
Abstract: The multicomponent reaction of diboronic acids with a catechol and a tripyridyl linker results in the formation trigonal prismatic cages. The cages feature six dative boron–nitrogen bonds as structure-directing elements. The size of the cages can be varied by changing the diboronic acid building block. The cages are able to encapsulate polyaromatic molecules such as triphenylene or coronene.
88 citations
TL;DR: The synthesis, structure, and reactivity of a five-coordinate model complex of [Fe]-hydrogenase are described, which suggests that the iron center in [Fe],hydrogenases could be five- coordinate in the resting state.
Abstract: The synthesis, structure, and reactivity of a five-coordinate model complex of [Fe]-hydrogenase are described. The work suggests that the iron center in [Fe]-hydrogenases could be five-coordinate in the resting state.
77 citations
TL;DR: The steric and electronic characteristics of the imidazolium functionalized bipyridine ligands were assessed via the synthesis of rhenium carbonyl complexes, which facilitated the rationalization of the catalytic properties of the nanoparticles.
Abstract: The imidazolium functionalized bipyridine compounds, {4,4'-bis-[7-(2,3-dimethylimidazolium)heptyl]-2,2'-bipyridine}(2+) ([BIHB](2+)) and {4,4'-bis[(1,2-dimethylimidazolium)methyl]-2,2'-bipyridine}(2+) ([BIMB](2+)), were prepared and used as Rh nanoparticle stabilizers. The dispersed Rh nanoparticles were used as catalysts in the biphasic hydrogenation of various arene substrates. The catalytic activity was strongly influenced by the stabilizer employed and followed the trend [BIHB](2+) > bipy > [BIMB](2+). The steric and electronic characteristics of the imidazolium functionalized bipyridine ligands were assessed via the synthesis of rhenium carbonyl complexes, which facilitated the rationalization of the catalytic properties of the nanoparticles.
57 citations
TL;DR: A library of emission spectra of 90 bis-cyclometallated iridium complexes has been obtained using a simple combinatorial approach performed at room temperature, opening the way for a rational approach to the engineering of the emission colour purity at a molecular level.
Abstract: A library of emission spectra of 90 bis-cyclometallated iridium complexes has been obtained using a simple combinatorial approach performed at room temperature. Trends in emission maxima are rationalized using Hammett parameters and invoking inter ligand energy transfer (ILET) processes. The screening approach allowed us to observe trends in the broadness of emission spectra opening the way for a rational approach to the engineering of the emission colour purity at a molecular level. Finally limitations to the screening strategy are discussed using a case study that involves two different monodentate ligands.
56 citations
TL;DR: A series of Fe complexes were synthesized and characterized as small molecule mimics for the active site of [Fe]-hydrogenase (Hmd), which contain the essential ligands of the enzyme, namely, acyl, CO, pyridone, and sulfur ligands.
Abstract: A series of Fe complexes were synthesized and characterized as small molecule mimics for the active site of [Fe]-hydrogenase (Hmd). The collection includes both structurally new compounds and analogues of previously reported models. These complexes contain the essential ligands of the enzyme, namely, acyl, CO, pyridone, and sulfur ligands. They serve as IR and Mossbauer spectroscopic models for the Fe center in [Fe]-hydrogenase. The field-dependent Mossbauer study of representative model complexes shows that the sign and absolute value of the quadrupole splitting are sensitive to the change in the ligand environment of the Fe center.
39 citations
TL;DR: A cyclic tetranuclear cyclometallated iridium(III) complex using cyanide anions as bridging ligands and displaying a tetrahedrally distorted square geometry has been obtained with high yield.
TL;DR: In this article, five different types of β-diketiminate ligands, bearing electron-donating to strongly electron-withdrawing substituents, were synthesized and used in the synthesis of Cp* ruthenium complexes (Cp* = η5-C5Me5).
TL;DR: The cyclopentadienyl Ru complexes Cp*RuCl(cod) (cod = 1,5-cyclooctadiene) and [Cp∧RuCl2]2 (Cp ∧ = η5-1methoxy-2,4-di-tert-butyl-3-neopentylcyclopentyl-cyclopentienyl) are able to catalyze the decomposition of benzyl azides to give 1,3,5triphenyl-2.4-diazapenta
TL;DR: An improved synthesis of pincer ligand bis[(2-dimethylamino)phenyl]amine ((Me)N(2)NH) was reported, and the Ru complex showed activity in catalytic transfer hydrogenation of aryl and alkyl ketones.
Abstract: An improved synthesis of pincer ligand bis[(2-dimethylamino)phenyl]amine (MeN2NH) was reported. Reaction of the Li complex of MeN2N with suitable Pd, Pt, and Ru precursors gave the corresponding metal complexes. The structures of the Pd, Pt, and Ru complexes were determined. The Ru complex showed activity in catalytic transfer hydrogenation of aryl and alkyl ketones.
TL;DR: In this paper, a tetra-phosphinoylated p-tert-butyl calixarene, B(4)bL(4), functionalized with phosphinoyl pendant arms, was shown to have high coordination ability toward f elements and a great potentiality toward actinide/rare earth separation.
TL;DR: In the title compound, [Cu(C6H9N3)2](PF6)2, the Cu atom is located on a crystallographic center of inversion with two amino and two imidazole N atoms bonded to the metal in a trans configuration.
Abstract: In the title compound, [Cu(C6H9N3)2](PF6)2, the Cu atom is located on a crystallographic center of inversion. The coordination environment of the Cu atom is square-planar with two amino and two imidazole N atoms bonded to the metal in a trans configuration.