Showing papers by "Rosario Scopelliti published in 2012"
TL;DR: This work reproduced the loss of picolinate and acetylacetonate ancillary ligands in solution by the addition of Brønsted or Lewis acids and advantageously used this degradation reaction for the efficient synthesis of tris-heteroleptic cyclometalated iridium(III) complexes.
Abstract: Investigations of blue phosphorescent organic light emitting diodes (OLEDs) based on [Ir(2-(2,4-difluorophenyl)pyridine)(2)(picolinate)] (FIrPic) have pointed to the cleavage of the picolinate as a possible reason for device instability. We reproduced the loss of picolinate and acetylacetonate ancillary ligands in solution by the addition of Bronsted or Lewis acids. When hydrochloric acid is added to a solution of a [Ir(C(∧)N)(2)(X(∧)O)] complex (C(∧)N = 2-phenylpyridine (ppy) or 2-(2,4-difluorophenyl)pyridine (diFppy) and X(∧)O = picolinate (pic) or acetylacetonate (acac)), the cleavage of the ancillary ligand results in the direct formation of the chloro-bridged iridium(III) dimer [{Ir(C(∧)N)(2)(μ-Cl)}(2)]. When triflic acid or boron trifluoride are used, a source of chloride (here tetrabutylammonium chloride) is added to obtain the same chloro-bridged iridium(III) dimer. Then, we advantageously used this degradation reaction for the efficient synthesis of tris-heteroleptic cyclometalated iridium(III) complexes [Ir(C(∧)N(1))(C(∧)N(2))(L)], a family of cyclometalated complexes otherwise challenging to prepare. We used an iridium(I) complex, [{Ir(COD)(μ-Cl)}(2)], and a stoichiometric amount of two different C(∧)N ligands (C(∧)N(1) = ppy; C(∧)N(2) = diFppy) as starting materials for the swift preparation of the chloro-bridged iridium(III) dimers. After reacting the mixture with acetylacetonate and subsequent purification, the tris-heteroleptic complex [Ir(ppy)(diFppy)(acac)] could be isolated with good yield from the crude containing as well the bis-heteroleptic complexes [Ir(ppy)(2)(acac)] and [Ir(diFppy)(2)(acac)]. Reaction of the tris-heteroleptic acac complex with hydrochloric acid gives pure heteroleptic chloro-bridged iridium dimer [{Ir(ppy)(diFppy)(μ-Cl)}(2)], which can be used as starting material for the preparation of a new tris-heteroleptic iridium(III) complex based on these two C(∧)N ligands. Finally, we use DFT/LR-TDDFT to rationalize the impact of the two different C(∧)N ligands on the observed photophysical and electrochemical properties.
158 citations
Journal Article•
TL;DR: Investigations indicated that gold(III) could be eventually reduced to gold(I) during the process, and a π activation or an oxidative mechanism are most probable for the alkynylation reaction.
128 citations
TL;DR: Despite the poor photophysical properties of this series of complexes in solution, electroluminescent emission from the bluish-green to orange region of the visible spectrum is obtained when they are used as active compounds in light-emitting electrochemical cells.
Abstract: Herein we report a series of charged iridium complexes emitting from near-UV to red using carbene-based N⁁C: ancillary ligands. Synthesis, photophysical and electrochemical properties of this series are described in detail together with X-ray crystal structures. Density Functional Theory calculations show that the emission originates from the cyclometallated main ligand, in contrast to commonly designed charged complexes using bidentate N⁁N ancillary ligands, where the emission originates from the ancillary N⁁N ligand. The radiative process of this series of compounds is characterized by relatively low photoluminescence quantum yields in solution that is ascribed to non-radiative deactivation of the excited state by thermally accessible metal-centered states. Despite the poor photophysical properties of this series of complexes in solution, electroluminescent emission from the bluish-green to orange region of the visible spectrum is obtained when they are used as active compounds in light-emitting electrochemical cells.
119 citations
TL;DR: According to theoretical geometries for the lowest triplet state, the large halogen substituents contribute to sizable distortions of specific phenylpyridine ligands for ClIrPic and BrIrPic, which are likely to play a role in the emissive and nonradiative properties when coupled with the heavy-atom effect.
Abstract: A series of homologous bis-cyclometalated iridium(III) complexes Ir(2,4-di-X-phenyl-pyridine)2(picolinate) (X = H, F, Cl, Br) HIrPic, FIrPic, ClIrPic, and BrIrPic has been synthesized and characterized by NMR, X-ray crystallography, UV–vis absorption and emission spectroscopy, and electrochemical methods. The addition of halogen substituents results in the emission being localized on the main cyclometalated ligand. In addition, halogen substitution induces a blue shift of the emission maxima, especially in the case of the fluoro-based analogue but less pronounced for chlorine and bromine substituents. Supported by ground and excited state theoretical calculations, we rationalized this effect in a simple manner by taking into account the σp and σm Hammett constants on both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels. Furthermore, in comparison with FIrPic and ClIrPic, the impact of the large bromine atom remarkably decreases the photolumine...
101 citations
TL;DR: In this paper, a ruthenium-based coordination cage is described, whose geometry and topology can be altered dramatically by using two closely related solvents: chloroform and dichloromethane.
Abstract: The solvent-induced structural rearrangement of synthetic supramolecular structures typically requires a pronounced change in solvent polarity. We describe a ruthenium-based coordination cage, whose geometry and topology can be altered dramatically by using two closely related solvents: chloroform and dichloromethane. In chloroform, we observe an octanuclear prismatic cage, whereas a tetranuclear complex is formed in dichloromethane. The basis of this unusual solvent-sensitivity is the incorporation of metallacrown recognition units into a flexible, kinetically labile nanostructure.
101 citations
TL;DR: The nickel(II) hydride complex [(MeN2N)Ni-H] (2) was synthesized by the reaction of MeN2NH with Ph2SiH2 and was characterized by NMR and IR spectroscopy as well as X-ray crystallography as mentioned in this paper.
77 citations
TL;DR: A good catch: N-heterocyclic carbenes (NHCs) form stable adducts with nitrous oxide (N2O) under mild reaction conditions and display unique reactivity as evidenced by an alkylation reaction which leads to a rupture of the NN bond.
Abstract: A good catch: N-heterocyclic carbenes (NHCs) form stable adducts with nitrous oxide (N2O) under mild reaction conditions. The adducts display unique reactivity as evidenced by an alkylation reaction which leads to a rupture of the NN bond.
72 citations
TL;DR: The first example of an iridium(III) isocyanide complex that emits blue phosphorescence not only in solution but also as a neat solid is reported, which is the first example in the world of its kind.
Abstract: We report new bis-cyclometalated cationic iridium(III) complexes [(C∧N)2Ir(CN-tert-Bu)2](CF3SO3) that have tert-butyl isocyanides as neutral auxiliary ligands and 2-phenylpyridine or 2-(4′-fluorophenyl)-R-pyridines (where R is 4-methoxy, 4-tert-butyl, or5-trifluoromethyl) as C∧N ligands. The complexes are white or pale yellow solids that show irreversible reduction and oxidation processes and have a large electrochemical gap of 3.58–3.83 V. They emit blue or blue-green phosphorescence in liquid/solid solutions from a cyclometalating-ligand-centered excited state. Their emission spectra show vibronic structure with the highest-energy luminescence peak at 440–459 nm. The corresponding quantum yields and observed excited-state lifetimes are up to 76% and 46 μs, respectively, and the calculated radiative lifetimes are in the range of 46–82 μs. In solution, the photophysical properties of the complexes are solvent-independent, and their emission color is tuned by variation of the substituents in the cyclometal...
72 citations
TL;DR: Interestingly, the compounds containing the 2-(2'-pyridyl)imidazolate ligand showed selectivity towards cancer cells with respect to the non-tumorigenic ones, with the dinuclear compound [(PPh(3)Au)(2)(2-R-imidrazolate)](PF(6)) being the most active.
Abstract: The new gold(III) complexes: [Au{2-(2′-pyridyl)imidazolate}Cl2] and [Au{2,6-bis(2′-benzimidazolate)pyridine}(OCOCH3)] and the mono- and binuclear gold(I) complexes: [Au{2-(2′-pyridyl)imidazole}(PPh3)](PF6), [Au(2-phenylimidazolate)(DAPTA)] (DAPTA = 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane), [(PPh3Au)2(2-R-imidazolate)](PF6) (R = 2-C5H4N, Ph) have been synthesized and characterized. The structure of the [(PPh3Au)2{2-(2′-pyridyl)imidazolate)](PF6) complex was also characterized by X-ray crystallography. The antiproliferative properties of the complexes were assayed against human ovarian carcinoma cell lines, either sensitive (A2780) or resistant to cisplatin (A2780cisR), human mammary carcinoma cells (MCF7) and non-tumorigenic human kidney (HEK293) cells. Most of the studied compounds showed important cytotoxic effects. Interestingly, the compounds containing the 2-(2′-pyridyl)imidazolate ligand showed selectivity towards cancer cells with respect to the non-tumorigenic ones, with the dinuclear compound [(PPh3Au)2{2-(2′-pyridyl)imidazolate)](PF6) being the most active. Some compounds were also screened for their inhibitory effect of the zinc-finger protein PARP-1, essential for DNA repair and relevant to the mechanisms of cancer cell resistance to cisplatin. Interaction studies of the compounds with the model protein ubiquitin were undertaken by electrospray ionization mass spectrometry (ESI MS). The results are discussed in relation to the putative mechanisms of action of the cytotoxic gold compounds.
63 citations
TL;DR: The results highlight the utility of dative B-N bonds in structural supramolecular chemistry and crystal engineering.
Abstract: Multicomponent reactions between 1,4-benzenediboronic acid, catechol, and different pyridyl ligands are reported. The condensation of 1,4-benzenediboronic acid with catechol gives 1,4-bis(benzodioxaborole)benzene. Upon crystallization, the ester aggregates with the N-donor ligands through dative BN bonds. Depending on the nature of the pyridyl ligand, molecularly defined macrocycles or polymeric structures are obtained. 1D polymers are formed with 4,4-bipyridine and 1,2-di(4-pyridyl)ethylene, whereas a 2D network is obtained with the tetradentate ligand tetra(4-pyridylphenyl)ethylene. These results highlight the utility of dative BN bonds in structural supramolecular chemistry and crystal engineering.
62 citations
TL;DR: In this paper, the bis-cyclometalated cationic iridium(III) complex with N-aryl-substituted 1H-imidazo[4,5-f][1,10]phenanthroline was reported.
Abstract: We report the first bis-cyclometalated cationic iridium(III) complex with N-aryl-substituted 1H-imidazo[4,5-f][1,10]phenanthroline. The complex emits yellow-orange phosphorescence with a maximum at 583 nm, a quantum yield of 43%, and an excited-state lifetime of 910 ns in argon-saturated dichloromethane. Optimized orange light-emitting electrochemical cells with the new Ir(III) complex exhibit fast turn-on, a peak luminance of 684 cd m−2 and a peak efficacy of 6.5 cd A−1; in 850 h of continuous operation their luminance and efficacy decrease only by 20%.
TL;DR: In this article, the behavior of nano composites made of the aluminum oxide-hydroxide nano-structured solid support (AP200/19) and neutral blue emitting cyclometalated iridium(III) complexes was studied.
Abstract: The behavior toward oxygen sensing of nano- composites made of the aluminum oxide-hydroxide nano- structured solid support (AP200/19) and neutral blue emitting cyclometalated iridium(III) complexes was studied. The results are compared with the same dyes immobilized in polystyrene films. Since the photoluminescence of the complexes is totally quenched for oxygen concentrations just over 10%, these systems using the blue region of the visible spectrum are promising for oxygen detection at low concentration. In particular, dyes supported into the AP200/19 provide the best sensitivity to oxygen concentration, with the possibility to detect oxygen below 1% O2 in gas (0.01 bar).
TL;DR: The results suggest that the Cys176 thiolate ligand in [Fe]-hydrogenase can serve as the internal base to accept the proton after heterolytic splitting of H2.
Abstract: The thiolate ligand in the five-coordinate model complex 1 of [Fe]-hydrogenase is preferentially and reversibly protonated, even in the presence of an acyl ligand. The results suggest that the Cys176 thiolate ligand in [Fe]-hydrogenase can serve as the internal base to accept the proton after heterolytic splitting of H2.
TL;DR: In this paper, the first comprehensive comparative synthetic, structural, electrochemical, and spectroscopic study of an extended series of fluorocarbon-modified iridium(III) complexes is presented.
TL;DR: A reaction sequence involving an N-heterocyclic carbene and a vanadium complex that results in cleavage of both the N-O bond and theN-N bond is reported.
Abstract: Chemically induced bond cleavage of nitrous oxide typically proceeds by rupture of the N-O bond with concomitant O-atom transfer and liberation of dinitrogen. On a few occasions, N-N bond scission has been observed instead. We report a reaction sequence involving an N-heterocyclic carbene and a vanadium complex that results in cleavage of both the N-O bond and the N-N bond.
TL;DR: In this paper, the formation of palladium nanoparticles was observed and their role in the overall catalytic mechanism was discussed, and the palladium-containing salts were evaluated as pre-catalysts in Suzuki cross-coupling reactions in ionic liquids generally resulting in high conversions.
TL;DR: Ruthenium complexes with bridging dicarboxylate ligands were combined with 1,2-di-4-pyridylethylene (dpe) to give a tetranuclear rectangle or hexanuclear coordination cages that display a trigonal-prismatic geometry, as evidenced by single-crystal X-ray crystallography.
Abstract: Ruthenium complexes with bridging dicarboxylate ligands were combined with 1,2-di-4-pyridylethylene (dpe), 2,4,6-tri-4-pyridyltriazine (4-tpt), or 2,4,6-tri-3-pyridyltriazine (3-tpt) to give a tetranuclear rectangle or hexanuclear coordination cages. The cages display a trigonal-prismatic geometry, as evidenced by single-crystal X-ray crystallography. The 4-tpt-based cages are able to encapsulate polyaromatic molecules such as pyrene, triphenylene, or coronene, whereas the 3-tpt-based cages were found to be incompetent hosts for these guests.
TL;DR: The dinuclear Ru(II) complexes (arene)Ru(μ-Cl)3RuCl(C2H4)(PCy3) as mentioned in this paper and trinuclear complexes (trinuclear) Ru(III)/Ru(III) complexes with a chelating alkoxy ligand were identified as intermediates in all reactions.
TL;DR: The chiral stationary phase for high-performance liquid chromatography showed good chiral recognition ability towards various racemates, including phosphorescent iridium complexes and alkynyl complexes.
Abstract: Keywords: alkynyl complexes ; allenylidene complexes ; carbenes ; cumulenes ; phosphorescent iridium complexes Reference EPFL-ARTICLE-179446doi:10.1002/anie.201203329View record in Web of Science Record created on 2012-07-02, modified on 2017-12-03
TL;DR: In this paper, two bis(diphenylphosphino) amines, N,N-bis(diphosphino)- 3,3-dimethoxybenzidine 2 and N, N-bis-3,3dimethylphosphine benzidine 2, were prepared by aminolysis and corresponding oxides, sulfides and selenides were readily prepared by reaction with hydrogen peroxide, elemental sulfur or grey selenium, respectively.
TL;DR: The results demonstrate that borophosphonate cages are interesting building blocks for dynamic covalent chemistry and are constitutionally dynamic scaffolds with exchange reactions occurring on the hour time scale at room temperature.
Abstract: A versatile and experimentally facile procedure for the synthesis of borophosphonate cages of the general formula [tBuPO3BR′]4 is described. The method involves heating of tert-butylphosphonic acid with a boronic acid in toluene to give borophosphonates in [4+4] condensation reactions. The products display a heterocubane structure with bent P-O-B bridges as evidenced by crystallographic analyses. Scrambling experiments show that the borophosphonate cages are constitutionally dynamic scaffolds with exchange reactions occurring on the hour time scale at room temperature. The cages can be decorated with reactive groups such as aldehydes. Our results demonstrate that borophosphonate cages are interesting building blocks for dynamic covalent chemistry.
TL;DR: In this article, two new cationic iridium(III) complexes with cyclometalating 1-phenylindazole or 2phenyl-1,2,3-triazole ligands are presented, which exhibit yellow or green phosphorescence with quantum yields and excited state lifetimes of up to 45% and 840 ns in argon-saturated dichloromethane solution at room temperature.
TL;DR: In this article, a charged cyclometalated iridium(III) complexes with non-p-electron-conjugated ancillary chelates were synthesized and their electrochemical and photophysical properties studied.
Abstract: New charged cyclometalated iridium(III) complexes [Ir(ppy)2(L)](PF6) [ppy = 2-phenylpyridine; L = bis(pyrazol-1-yl)methane (for 1); L = bis(3,5-dimethylpyrazol-1-yl)methane (for 2)] were synthesized and their electrochemical and photophysical properties studied. These complexes with non-p-electron-conjugated ancillary chelates exhibit significantly blueshifted emission relative to those of commonly used derivatives with NN ancillary ligands such as bipyridine or phenanthroline. Both X-ray and theoretical analysis based on time-dependent density functional theory (TD-DFT) reveal that the binding of Ir to the bis(pyrazol-1-yl)methane ancillary ligand is much weaker than that to the phenylpyridine main ligand; the effect is enhanced in the excited state. As a result, the ancillary ligand does not participate in low-energy excitations and triplet emission, and the electronic transitions are concentrated on the main chromophoric ligands. The blueshift feature is attributed to emission originating from the main cyclometalated ligands, in contrast to emitters with the NN chromophoric ancillary ligand. In addition, complex 2 exhibits a one order of magnitude higher non-radiative decay rate than complex 1, which is attributed to the steric hindrance of the methyl groups that leads to a more loosely bound ancillary ligand.
TL;DR: Biscyclometalated cationic Ir(III) diimine complexes with 1-phenyl pyrazoles and 1-(4'-tert-butyl-2'-pyridyl) pyrazole ((NN)-N-Lambda) are white solids that have absorption onset below 425 nm and electrochemical gap of up to 3.5 V as discussed by the authors.
TL;DR: In this paper, the dinuclear complex of RHCl3(H2O)n with four equivalents of tert-butyl acetylene in methanol was isolated and analyzed by single-crystal X-ray diffraction.
Abstract: RhCl3 is shown to mediate unusual coupling reactions of tert-butyl acetylene. When RhCl3(H2O)n was heated with four equivalents of tert-butyl acetylene in methanol, the dinuclear complex [{Rh(μ-Cl)(CH2tBu)(tBuC=CHCOCH2tBu)}2] (2) was isolated. A larger excess of tert-butyl acetylene (12 equiv.) resulted in the formation of the dimer [{η5-C5H2tBu2(CH2tBu)}Rh(μ-Cl)3Rh(C24H42O2)] (3). Both complexes were analyzed by single-crystal X-ray diffraction.