Search results for "Yield"
showing 10 items of 1338 documents
Synthesis and Characterization of New Keggin-Based Structure Tungstocobaltates: K9[Co3+W11O39] and its Vanadium Derivatives, K8[Co2+W11V4+O40], K7[Co…
1995
Abstract Good yield synthesis of the potassium salts of four new interrelated : olyoxometalates, [Co3+W11O39]9-(I), [Co2+W11V4+O4]8-(II), [Co2+W11V5+O40]7-(III), and [Co3+W11V5+O40]6-(IV), are reported. The title compounds have been characterized by IR and UV-Vis.-NIR spectroscopies, cyclic voltammetry and magnetic measurements. IR spectra confirm that I has the lacunary structure of an undecatungstate anion, while II through IV have a substituted α-Keggin structure with the vanadium atom located at an octahedral site replacing one tungsten atom. Optical data confirm the oxidation states for both, the Co and V atoms, as formulated for I through IV.
Zirconocene complexes bearing novel 3-dimethylamino-1,2-dihydropentalene derived ligand systems.
2010
Coupling of the N,N-dimethylacrylamides 6a-c with cyclopentadienide resulted in the formation of the substituted 3-dimethylamino-1,2-dihydropentalnenes 2a-c. Deprotonation followed by metallation with CpZrCl(3)·DME gave the substituted zirconocenes 12a-c. The reaction of 3-dimethylamino-1-methyl-dihydropentalene 2a with ZrCl(2)(NMe(2))(2)·2THF resulted in a unique coupling between a pair of the aminodihydropentalene derivatives to yield an unsymmetrically bridged novel ansa-zirconocene framework (9a). Treatment of the 1,1-dimethyl-substituted substrate 2b with this Zr-amido reagent in contrast resulted in a clean deprotonation and formation of the unbridged bis(dimethylaminohydropentalenyl)…
A systematic study of the optical properties of mononuclear hybrid organo-inorganic lanthanoid complexes
2020
A series of hybrid organo-inorganic mononuclear lanthanoid complexes, [n-NBu4]3[LnH(PW11O39)(phen)2]·H2O, denoted as LM4-1-Ln (Ln = DyIII, TbIII, EuIII, NdIII, ErIII, HoIII and GdIII), were synthesized via hydrothermal synthesis and were structurally characterized by X-ray diffraction. The optical properties of all complexes have been investigated in the solid state. The temperature-dependent emission spectra of LM4-1-Dy, LM4-1-Tb and LM4-1-Eu complexes show intense lanthanoid emissions in the visible region, while LM4-1-Nd shows near-infrared (NIR) luminescence. The EuIII complex shows typical strong red emissions from the 5D0 → 7F0,1,2,3,4 transitions, with the CIE colour coordinates (0.6…
Benzoato and Thiobenzoato Ligands in the Synthesis of Dinuclear Palladium(III) and ‐(II) Compounds: Stability and Catalytic Applications
2015
New palladium(III) compounds of formula Pd2[(C6H4)PPh2]2[OXC(C6H5)]2Cl2 [3a (X = O); 3b (X = S)] were obtained by the oxidation of the analogous palladium(II) ones with PhICl2 and were characterized by 31P, 1H, and 13C NMR spectroscopy at 223 K. Compound 3a was also structurally characterized by single-crystal X-ray diffraction methods, which revealed a Pd–Pd distance of 2.5212(10) A. DFT calculations were conducted to study the stability of all of these new palladium(III) and -(II) compounds with focus on the influence of the OS substitution of the donor atom in the ligand. The palladium(II) compounds Pd2[(C6H4)PPh2]2[OXC(C6H5)]2 [2a (X = O), 2b (X = S)] were also tested as precatalyst in …
Identifying lifetime as one of the key parameters responsible for the low brightness of lanthanide-based OLEDs.
2021
OLEDs based on lanthanide complexes have decisive optical advantages but are hampered by low brightness. Despite the efforts to optimize several parameters such as quantum yield and charge carrier mobility, there seems to be another key parameter that hinders their performances. Experimental data are therefore collected for mixed-ligand europium complexes with bathophenanthroline and different classes of anionic ligands and screened to identify the key parameter responsible for this situation, which turns out to be the long lifetime of their excited states. A broad literature search supports this conclusion, showing that lanthanide complexes are inferior to other classes of OLED emitters of…
Cationic Iron Aminocarbene Complexes as Dienophiles in Diels‐Alder Reaction with Cyclopentadiene
1996
The cationic iron (alkynyl)aminocarbene complexes [Cp(CO)2Fe(C(NHR)CCSiMe3][PF6], (R C6H5, p-CH3C6H4) 1 derived from aromatic amines smoothly react with cyclopentadiene in dichloromethane to yield the cycloadducts 2. No reaction was observed for complexes derived from sterically demanding aliphatic amines, like L-alanine tert-butyl ester. For comparison, the alkynyl-substituted acyl iron compounds Cp(CO)2Fe(CO)CC (R SiMe3, C6H5) 3 were investigated, requiring TiCl4 catalysis to undergo the cycloaddition reaction. The structures of the cycloadducts 4 were determined by X-ray crystallography.
Carbonyl Transition Metal Complexes of a Silaborate Ligand
1998
Reaction between three equivalents of the silaborate [NEt4][MeSiB10H12] (2) and one equivalent of [Ru3(CO)12] resulted in almost quantitative formation of the mononuclear transition metal complex [NEt4][Ru(CO)3(η5-MeSiB10H10)] (5), which was characterized by X-ray structure analysis. The trinuclear ruthenium complex [NEt4][Ru3(CO)8(η5-MeSiB10H10)] (7) was synthesized in high yield from the reaction of one equivalent of 2 and [Ru3(CO)12]. The cluster 7 reacts with two equivalents of PMe2Ph with substitution of two carbonyl groups to give the substitution product [NEt4][Ru3(CO)6(PMe2Ph)2(η5-MeSiB10H10)] (8).
Spontaneous Resolution of a Triple‐Stranded Dinickel(II) Helicate Generated via Intermolecular Transamination Reaction of S ‐Methylisothiocarbohydraz…
2008
The reaction of S-methylisothiocarbohydrazide hydroiodide [H2NNHC(SCH3)NNH2·HI] with NiCl2·6H2O in water at room temperature yielded a triple-stranded dinickel(II) helicate [NiII(L1–L1)3NiII]I4·4H2O (14+·4I–·4H2O), where L1–L1 = H2NNHC(SCH3)NNC(SCH3)NHNH2, in 35 % yield, which spontaneously separates in enantiomers upon crystallization. The enantiomers do not racemize at room temperature, even not after 15 h of heating at 90 °C. X-ray diffraction structures of both enantiomers, chiroptical and magnetic properties of 14+·4I–·4H2O are reported. Demetallation of the complex by treatment with S2– resulted in 3,6-bis(methylthio)-1,4-dihydro-1,2,4,5-tetrazine (2). Compound 2 undergoes 2-e– oxidat…
N-Heterocyclic Phosphenium, Arsenium, and Stibenium Ions as Ligands in Transition Metal Complexes: A Comparative Experimental and Computational Study
2005
Reaction of 2-chloro-1,3,2-diazaarsolenes and -diazaphospholenes with Tl[Co(CO)4] gives instable complexes of type [Co(ER2)(CO)4] which decarbonylated to yield [Co(ER2)(CO)3]. Spectroscopic and X-ray diffraction studies revealed that the tetracarbonyl complexes can be formulated as ion pair for E = P and as covalent metalla-arsine for E = As, and the tricarbonyl complexes as carbene-like species with a formal E=Co double bond. A similar reactivity towards Tl[Co(CO)4] was also inferred for 1,3,2-diazastibolenes although the products were not isolable and their constitution remained uncertain. Evaluation of structural and computational data suggests that the weak and polarized Co–As bond in […
Tuning the photophysical properties of anti-B18H22: efficient intersystem crossing between excited singlet and triplet states in new 4,4'-(HS)2-anti-…
2013
The tuning of the photophysical properties of the highly fluorescent boron hydride cluster anti-B18H22 (1), by straightforward chemical substitution to produce 4,4'-(HS)2-anti-B18H20 (2), facilitates intersystem crossing from excited singlet states to a triplet manifold. This subsequently enhances O2((1)Δg) singlet oxygen production from a quantum yield of ΦΔ ∼ 0.008 in 1 to 0.59 in 2. This paper describes the synthesis and full structural characterization of the new compound 4,4'-(HS)2-anti-B18H20 (2) and uses UV-vis spectroscopy coupled with density functional theory (DFT) and ab initio computational studies to delineate and explain its photophysical properties.