Search results for "COMPOUND"

Two-Photon Absorption Properties and Structures of BODIPY and Its Dyad, Triad and Tetrad.

2018

A series consisting of a dyad, a triad and a tetrad containing either two, three and four BODIPY units, respectively, has been synthesized and fully characterized and compared to two mono-BODIPY analogs (used as references). The one- and two-photon photophysical properties have been measured and the X-ray structures of four of the BODIPY derivatives have been determined. In the 700-900 nm range, the two-photon absorption (TPA) cross sections range from 30 GM to 160 GM for these compounds.

Anodic Degradation of Lignin at Active Transition Metal-based Alloys and Performance-enhanced Anodes

2018

Arene C−H Activation at Aluminium(I): meta Selectivity Driven by the Electronics of S N Ar Chemistry

2020

The reactivity of the electron-rich anionic Al(I) ('aluminyl') compound K 2 [(NON)Al] 2 (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di- tert -butyl-9,9-dimethylxanthene) towards mono- and disubstituted arenes is reported. C-H activation chemistry with n -butylbenzene gives exclusively the product of activation at the arene meta position. Mechanistically, this transformation proceeds in a single step via a concerted Meisenheimer-type transition state. Selectivity is therefore based on similar electronic factors to classical S N Ar chemistry, which implies the destabilization of transition states featuring electron-donating groups in either the ortho or the para positions. In the cases of tolu…

High-Pressure Behavior of Nickel Sulfate Monohydrate: Isothermal Compressibility, Structural Polymorphism, and Transition Pathway

2020

Single crystals of synthetic nickel sulfate monohydrate, α-NiSO4·H2O (space-group symmetry C2/c at ambient conditions), were subject to high-pressure behavior investigations in a diamond-anvil cell up to 10.8 GPa. By means of subtle spectral changes in Raman spectra recorded at 298 K on isothermal compression, two discontinuities were identified at 2.47(1) and 6.5(5) GPa. Both transitions turn out to be apparently second order in character, as deduced from the continuous evolution of unit-cell volumes determined from single-crystal X-ray diffraction. The first structural transition from α- to β-NiSO4·H2O is an obvious ferroelastic C2/c–P1̅ transition. It is purely displacive from a structur…

Chemical shift reagents in the study of polycyclic alcohols IX—1H NMR spectra of myrtenol and some other primary alcohols

1974

Structure proof of (—)-myrtenol, 3-cyclopentenyl-1-methanol and 5-norbornene-2-endo-methanol has been obtained from their proton magnetic resonance spectra in carbon tetrachloride containing different added amounts of tris(dipivaloylmethanato)europium. For each alcohol, a 1:1 complex structure with Eu(dpm)3 could be computed, in which the calculated pseudocontact shift effects on all skeleton protons of the ring system were consistent with the observed shift effect values. A considerable contact contribution of opposite sign to that of the pseudocontact part of the effect could be estimated for the methylene protons of the CH2OH group.

Oxotris(oxalate)niobate(V): An oxalate delivery agent in the design of building blocks

2018

This work concerns the oxalate delivery process that occurs when using (NH4)3[NbO(C2O4)3]·6H2O as a suitable oxalate source in the synthesis of two compounds, [Cu(dmphen)(C2O4)(H2O)] (1) and [{Cu(dmphen)(CH3OH)}2(μ-C2O4)](ClO4)2 (2) (dmphen = 2,9-dimethyl-1,10-phenanthroline). {[Fe{HB(pz)3}(CN)2(μ-CN)]2[{Cu(dmphen)}2(μ-C2O4)]}∙xCH3OH (3) (2.0 ≤ x ≤ 2.4) was obtained by reacting 2 and PPh4[Fe{HB(pz)3}(CN)3]∙H2O [ = tetraphenylphosphonium and = tris(pyrazolyl)borate]. Crystal structures of 1–3 have been determined by single-crystal X-ray diffraction experiments: 1 is a mononuclear trigonal bipyramidal copper(II) species, 2 is a centrosymmetric oxalato-bridged dicopper(II) complex, and 3 consi…

Structurally characterized dipalladium(ii)-oxamate metallacyclophanes as efficient catalysts for sustainable Heck and Suzuki reactions in ionic liqui…

2018

A new generation of dipalladium-oxamate metallacyclophanes of formulas (n-NBu4)4 [Pd2(ppba)2] (1), (n-NBu4)4[Pd2(dpvba)2] (2), (n-NBu4)4[Pd2(dpazba)2] (3), (n-NBu4)4[Pd2(dpeba)2] (4) and (n-NBu4)4[Pd2(tpeba)2] (5) [n-NBu4+ = tetra-n-butylammonium cation, H4ppba = N,N′-1,4-phenylenebis(oxamic acid), H4dpvba = N,N′-4,4′-diphenylethenebis(oxamic acid), H4dpazba = N,N′-4,4′-diphenylazobis(oxamic acid), H4dpeba = N,N′-4,4′-diphenylethynebis(oxamic acid) and H4tpeba = N,N′-1,4-di(4-phenylethynyl)phenylenebis(oxamic acid)] was prepared. The crystal structure of the solvated species of 2–4, namely (n-NBu4)4[Pd2(dpvba)2]·6MeOH·2Et2O (2a), (n-NBu4)4[Pd2(dpazba)2]·8MeOH (3a), and (n-NBu4)2[Pd2(dpeba)2…

Squaramide-Catalyzed Asymmetric aza-Friedel-Crafts/N,O-Acetalization Domino Reactions Between 2-Naphthols and Pyrazolinone Ketimines

2017

N-Boc ketimines derived from pyrazolin-5-ones were explored to develop an unprecedented domino aza-Friedel-Crafts/N,O-acetalization reaction with 2-naphthols. The novel method requires a catalyst loading of only 0.5 mol % of a bifunctional squaramide catalyst, is scalable to gram amounts, and provides a new series of furanonaphthopyrazolidinone derivatives bearing two vicinal tetra-substituted stereogenic centers in excellent yields (95-98 %) and stereoselectivity (>99:1 d.r. and 97-98 % ee). A different reactivity was observed in the case of 1-naphthols and other electron-rich phenols, which led to the aza-Friedel-Crafts adducts in 70-98 % yield and 47-98 % ee.

One-Pot, Clean Synthesis of Vanillic Acid from Ferulic Acid

2016

Ferulic acid dissolved in water is selectively oxidized to vanillic acid in high yield (≈60 %) under remarkably mild and green conditions, namely at room temperature with air as primary oxidant, over a catalytic amount of nanostructured Bi2WO6. The process is general and opens the route to the selective oxidation of natural substances into derivatives of significant applicative relevance.

Fluorescence Quenching in BODIPYs Having Ir‐ and Rh‐Tethered Complexes

2016

The effect of Rh- and Ir-centers on the optical properties of the BODIPY core has been studied. To this end, novel metal complexes tethered to BODIPY have been prepared through an easy and versatile procedure using N-directed C–H activation reactions. The organometallic moiety has a tremendous influence on the emissive properties of the BODIPY fragment. A photoinduced electron transfer (PET) mechanism is suggested to be the main mechanism responsible for the suppression of the BODIPY fluorescence emission in the newly formed dyads. The efficiency of the PET depends on both the distance between the chromophores in the dyad and the nature of the transition metal (Rh vs. Ir).