1,721,049 research outputs found
Synthesis, X-ray structural analysis, antibacterial and DNA-binding studies of a lanthanum bis-(5,5′-dimethyl-2,2′-bipyridine) complex
No full textA new complex with the formula [La(5,5′-dmbpy) 2 (NO 3 ) 3 ] (a) [where (5,5′-dmbpy = 5,5′-dimethyl-2,2′-bipyridine)] has been synthesized. The compound was characterized by cyclic voltammetry, elemental analysis and spectroscopic methods (IR, UV–Vis, 1 H-NMR). Single crystals adapted for X-ray diffraction analysis were recorded by slow crystallization from a methanol solution. The complex is neutral being the lanthanum cation chelated by two bipyridine derivative neutral ligands and three bidentate nitrate groups. Electronic spectra show the transition of both ligand field and charge transfer bands. The fluorescence properties of the compound have been studied. The interactions of complex with FS-DNA (salmon sperm DNA) have been studied using UV–Vis, fluorescence spectroscopies and gel electrophoresis. The above-mentioned techniques were used in physiological buffer having pH 7.2. The binding constant (K b ) for interaction in (a) with DNA was obtained using UV–Vis spectroscopies (K b = 1.2 × 10 5 ) and fluorescence spectroscopies (K b = 1.50 × 10 5 ). The binding constant (K b ), the number of binding sites for each 1000 nucleotides (n) and the apparent bio molecular quenching constant (k q ) for FS-DNA were obtained through Stern–Volmer equation. Thermodynamic parameters data (∆H°, ΔS° and ΔG°) showed that hydrogen bonding and van der Waals interactions have an important function in the interaction of DNA–La(III) complex, and the binding mode is the groove binding. The DNA binding of La(III) complex is spontaneous as suggested by the negative ΔG°. Moreover, the DNA cleavage has been studied using agarose gel electrophoresis. The antibacterial effects of complex (a) have also been examined in vitro against standard bacterial strains
Nucleophilic substitution on a Ru-coordinated Cp ring by a carborane anion
No full textThe Cp ring in [RuCl(Cp)(PPh3)(2)] undergoes an apparent nucleophilic attack by the carbanion carb (Hcarb = 2-Me-1,2-dicarba-closo-dodecaborane), to give an H-/carb(-) exchange process, which is favoured by coordination of the hydride to the ruthenium centre
A Reinterpretation of the Imidazolate Au(I) Cyclic Trinuclear Compounds Reactivity with Iodine and Methyl Iodide with the Perspective of the Inverted Ligand Field Theory
No full textCoinage metal cyclic trinuclear compounds (CTCs) are an emerging class of metal coordination compounds that are valuable for many fine optoelectronic applications, even though the reactivity dependence by the different bridging ligands remains somewhat unclear. In this work, to furnish some hints to unravel the effect of substituents on the chemistry of Au(I) CTCs made of a specific class of bridging ligand, we have considered two imidazolate Au(I) CTCs and the effect of different substituents on the pyrrolic N atoms relative to classic metal oxidations with I2 or by probing electrophilic additions. Experimental suggestions depict a thin borderline between the addition of MeI to the N-methyl or N-benzyl imidazolyl CTCs, which afford the oxidized CTC in the former and the ring opening of the CTC and the formation of carbene species in the latter. Moreover, the reactions with iodine yield to the oxidation of the metal centers for the former and just of a metal center in the latter, even in molar excess of iodine. The analysis of the bond distances in the X-ray crystal structures of the oxidized highlights that Au(III)-C and Au(III)-N bonds are longer than observed for Au(I)-C and Au(I)-N bonds, as formally not expected for Au(III) centers. Computational studies converge on the attribution of these discrepancies to an additional case of inverted ligand field (ILF), which solves the question with a new interpretation of the Au(I)-ligand bonding in the oxidized CTCs, which furnishes a new interpretation of the Au(I)-ligand bonding in the oxidized CTCs, opening a discussion about addition/oxidation reactions. Finally, the theoretical studies outputs depict energy profiles that are compatible with the experimental results obtained in the reaction of the two CTCs toward the addition of I2, MeI, and HCl
Dynamic Reconfiguration of Pt(II) Supramolecular Assemblies via Ligand Exchange
No full textSupramolecular chemistry enables molecules to dynamically adapt and reorganize in response to their environment, providing a key route to achieving high levels of structural and functional complexity. This work explores a particular strategy for the dynamic and programmable self-assembly of luminescent platinum(II) complexes via sequential coordination-driven and hierarchical processes. The aggregation behavior and optical properties of square-planar Pt(II) complexes bearing a chromophoric terdentate NNN ligand and exchangeable monodentate ligands are highly dependent on the nature of the ancillary ligand, resulting in morphologically and photophysically distinct supramolecular structures. We demonstrate that these preassembled aggregates undergo dynamic ligand exchange reactions in solution, leading to metastable supramolecular states, including emissive gels, that are accessible exclusively through in situ exchange. Real-time fluorescence microscopy and NMR spectroscopy reveal both homogeneous and heterogeneous exchange pathways, governed by the identity of the initial complex and the incoming ligand. Remarkably, the system exhibits a degree of reversibility and structural memory. These findings establish a framework for stepwise self-assembly that bridges coordination chemistry with noncovalent interactions, offering a versatile platform for designing responsive nanostructures with tailored properties and a step toward adaptive, life-like materials with potential applications in sensing and optoelectronics
Olefin Trifluoroacetato Derivatives of Copper(I) and Their Olefin/CO Exchange Reaction
No full textCompounds of general formula Cu(CF3COO)(olefin) (olefin = cyclooctene (coe), 1,5-cyclooctadiene (cod), diethylfumarate (defu), methylcinnamate (meci)) have been prepared and the molecular structures have been solved by X-ray diffraction in the case of olefin = coe, defu, meci. The complexes are characterized by a dimeric [Cu2(ƒÝƒ{CF3CO2)2(olefin)2] core with bridging trifluoroacetates and a ƒØ2-bonded olefin. In the case of the defu and meci complexes, [Cu2(ƒÝƒ{CF3CO2)2(olefin)2] dimeric units are linked by the oxygen atom of a carbonyl group of the ester to give polymeric chains. The compound [Cu2(ƒÝƒ{CF3COO)2(meci)2]n is the first structurally characterized example of a metal-bonded methylcinnamate. By recrystallization of [Cu2(CF3COO)2(cod)2], a derivative featuring a cod / Cu molar ratio of 0.5 has been isolated and structurally characterized as [Cu2(ƒÝ-CF3COO)2(ƒÝ-cod)]n, which represents the first example of a polymeric metal complex containing a bridging cod ligand. The carbo..
From Au11 to Au13: Tailored Synthesis of Superatomic Di-NHC/PPh3-Stabilized Molecular Gold Nanoclusters
Full text linkHerein, we report a new method to synthesize molecular gold nanoclusters (AuNCs) stabilized by phosphine (PR3) and di-N-heterocyclic carbene (di-NHC) ligands. The interaction of di-NHC gold(I) complexes, with the general formula [(di-NHC)Au2Cl2] with well-known [Au11(PPh3)8Cl2]Cl clusters provides three new classes of AuNCs through a controllable reaction sequence. The synthesis involves an initial ligand metathesis reaction to produce [Au11(di-NHC)(PPh3)6Cl2]+ (type 1 clusters), followed by a thermally induced rearrangement/metal complex addition with the formation of Au13 clusters [Au13(di-NHC)2(PPh3)4Cl4]+ (type 2 clusters). Finally, an additional metathesis process yields [Au13(di-NHC)3(PPh3)3Cl3]2+ (type 3 clusters). The electronic and steric properties of the employed di-NHC ligand affect the product distribution, leading to the isolation and full characterization of different clusters as the main product. A type 3 cluster has been also structurally characterized and was preliminarily found to be strongly emissive in solution
Rhodium(I), palladium(II), and platinum(II) complexes containing new mixed phosphane-phosphite ligands - Effect of the catalytic system stability on the enantioselective hydroformylation of styrene
No full textThe new mixed phosphane-phosphite ligands 1 and 2, derived from 3,3′-di-tert-butyl-2,2′-dihydroxy-5,5′-dimethoxybiphenyl and (S)-binaphthol, respectively, reacted with [Rh(COD)(THF)2]CF3SO3 to give the compounds [Rh(COD)(1)]CF3SO3 and [Rh(COD)(2)]CF3SO3 in which the ligands 1 and (S)-2 are chelated to the rhodium centre. The reaction with [Rh(CO)2Cl]2 gave two different products, [Rh(CO)2(L)Cl] and [Rh(CO)(L)Cl] [L = 1 and (S)-2], containing L as a chelate. On the basis of the IR and NMR spectroscopic data, the proposed structure of the pentacoordinate species is a trigonal bipyramide in which the phosphane-phosphite ligand assumes an equatorial-axial coordination. The reactions of 1 and 2 with [Pd(C6H5CN)2Cl2] and [Pt(COD)I2] gave the corresponding compounds [Pd(L)Cl2] and [Pt(L)I2] in which the ligands are chelated to the metal centre. The crystal structure of the chloroform solvate of [Pd(L)Cl2] was fully characterised by an X-ray study. The chiral ligands (S)-2 and (S)-3 [derived from the orthobis(trimethylsilyl)-substituted (S)-binaphthol] were tested in the hydroformylation of styrene. The results obtained were discussed in light of the catalytic system stability
A reinterpretation of the Imidazolate Au(I) Cyclic Trinuclear Compounds reactivity with iodine and methyl iodide with the perspective of the Inverted Ligand Field Theory
Full text linkCoinage metal cyclic trinuclear compounds (CTCs) are an emerging class of metal coordination compounds that are valuable for many fine optoelectronic applications, even though the reactivity dependence by the different bridging ligands remains somewhat unclear. In this work, to furnish some hints to unravel the effect of substituents on the chemistry of Au(I) CTCs made of a specific class of bridging ligand, we have considered two imidazolate Au(I) CTCs and the effect of different substituents on the pyrrolic N atoms relative to classic metal oxidations with I2 or by probing electrophilic additions. Experimental suggestions depict a thin borderline between the addition of MeI to the N-methyl or N-benzyl imidazolyl CTCs, which afford the oxidized CTC in the former and the ring opening of the CTC and the formation of carbene species in the latter. Moreover, the reactions with iodine yield to the oxidation of the metal centers for the former and just of a metal center in the latter, even in molar excess of iodine. The analysis of the bond distances in the X-ray crystal structures of the oxidized highlights that Au(III)-C and Au(III)-N bonds are longer than observed for Au(I)–C and Au(I)–N bonds, as formally not expected for Au(III) centers. Computational studies converge on the attribution of these discrepancies to an additional case of inverted ligand field (ILF), which solves the question with a new interpretation of the Au(I)–ligand bonding in the oxidized CTCs, which furnishes a new interpretation of the Au(I)-ligand bonding in the oxidized CTCs, opening a discussion about addition/oxidation reactions. Finally, the theoretical studies outputs depict energy profiles that are compatible with the experimental results obtained in the reaction of the two CTCs toward the addition of I2, MeI, and HCl
Hydroalkoxylation of terminal and internal alkynes catalyzed by dinuclear gold(I) complexes with bridging Di(N-heterocyclic carbene) ligands
No full textA series of six dinuclear gold(I) complexes with bridging bidentate N-heterocycic carbene ligands (NHCs) of general formula Au2Br2LX (L = diNHC, X = 1–6) have been studied as catalysts in the intermolecular hydroalkoxylation of terminal and internal alkynes. The best catalytic results have been obtained by using Au2Br2L4, characterized by 2,6-diisopropylphenyl wingtip substituents and a methylene bridging group between the two NHC donors. Complex Au2Br2L4 has been structurally characterized for the first time in this work, showing the presence of intramolecular aurophiclic interaction in the solid state. In the adopted reaction conditions Au2Br2L4 is able to convert challenging substrates such as diphenylacetylene. Comparative catalytic tests by using the mononuclear gold(I) complexes AuIL7 and IPrAuCl have been performed in order to determine the possible presence of cooperative effects in the catalytic process
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