Search results for "Rom"
showing 10 items of 37506 documents
Planar Benzo[1,2-b:4,5-b′]dithiophene Derivatives Decorated with Nitronyl and Imino Nitroxides
2018
Four weakly antiferromagnetic interacting biradicals of benzo[1,2- b:4,5- b']dithiophene (BDT) and BDT extended with two thiophenes (BDTTh2) linked with nitronyl and imino nitroxides (NN and IN) as BDT-NN, BDT-IN, BDTTh2-NN, and BDTTh2-IN were designed, synthesized, and characterized. Short intermolecular π-π distances were found (3.42 A) for BDT-NN, whereas larger ones were found for BDT-IN (3.54 A) and BDTTh2-NN (3.67 A), respectively. Intramolecular magnetic interaction ( Jintra,exp/ kB) of BDT-NN (-26 K) is much larger than for BDT-IN (-5.3 K), while it is reduced for the dithiophene-extended molecule BDTTh2-NN (-2.3 K). Intermolecular interactions ( zJinter,exp/ kB) of BDT-NN (-6.5 K) …
Effect of quaternary ammonium salts on spectral properties of zinc octacarboxyphthalocyanine
2020
Abstract The paper presents results of the research on the influence of quaternary ammonium salts on UV–vis absorption and emission spectra of zinc octacarboxyphthalocyanine (ZnPcOC). Quaternary ammonium salts which show biological activity play a crucial role. In ZnPcOC solutions with a proper concentration of tetrabutylammonium salts (TBAX), a strong bathochromic shift band (λmax = 760 nm – “R” band) showing red fluorescence appears in time. The presence of tetrabutylammonium salt causes pH increase and, consequently, a gradual dissociation of carboxyl groups in ZnPcOC molecule. It seems that –COO— anions present in the ZnPcOC complex can interact with tetraalkylammonium cations, causing …
Late-Stage Modification of Electronic Properties of Antiaromatic and Diradicaloid Indeno[1,2-b]fluorene Analogues via Sulfur Oxidation
2020
The ability to alter optoelectronic and magnetic properties of molecules at a late stage in their preparation is in general a nontrivial feat. Here, we report the late-stage oxidation of benzothiop...
Thermo-Chromium: A Contactless Optical Molecular Thermometer.
2017
The unparalleled excited-state potential-energy landscape of the chromium(III)-based dye [1]3+ ([Cr(ddpd)2 ]3+ ; ddpd=N,N'-dimethyl-N,N'-dipyridin-2-yl-pyridin-2,6-diamine) enables a strong dual emission in the near infrared region. The temperature dependence of this dual emission allows the use of [1]3+ as an unprecedented molecular ratiometric thermometer in the 210-373 K temperature range in organic and in aqueous media. Incorporation of [1]3+ in biocompatible nanocarriers, such as 100 nm-sized polystyrene nanoparticles and solutol micelles, provides nanodimensional thermometers operating under physiological conditions.
A Strongly Luminescent Chromium(III) Complex Acid
2018
The synthesis, structure, reactivity, and photophysical properties of a novel acidic, luminescent chromium(III) complex [Cr(H2 tpda)2 ]3+ (23+ ) bearing the tridentate H2 tpda (2,6-bis(2-pyridylamino)pyridine) ligand are presented. Excitation of 23+ at 442 nm results in strong, long-lived NIR luminescence at 782 nm in water and in acetonitrile. X-ray diffraction analysis and IR spectroscopy reveal hydrogen-bonding interactions of the counter ions to the NH groups of 23+ in the solid state. Deprotonation of the NH groups of 23+ by using a non-nucleophilic Schwesinger base in CH3 CN switches off the luminescence. Re-protonation by using HClO4 restores the emission. In water, the pKa value of …
Crystallographic snapshots of host–guest interactions in drugs@metal–organic frameworks: towards mimicking molecular recognition processes
2018
We report a novel metal–organic framework (MOF) featuring functional pores decorated with hydroxyl groups derived from the natural amino acid L-serine, which is able to establish specific interactions of different natures, strengths and directionalities with organic molecules of technological interest, i.e. ascorbic acid, pyridoxine, bupropion and 17-β-estradiol, based on their different sizes and chemical natures. The ability of 1 to distinctly organize guest molecules within its channels, through the concomitant effect of different directing supramolecular host–guest interactions, enables gaining unique insights, by means of single-crystal X-ray crystallography, into the host–guest intera…
Diferratricarbaboranes of thesubcloso-[(η5-C5H5)2Fe2C3B8H11] Type, the First Representatives of the 13-Vertex Dimetallatricarbaborane Series
2003
Treatment of the [2-Cp-9-tBuNH-closo-2,1,7,9-FeC 3 B 8 H 1 0 ] (1) ferratricarbollide (Cp = η 5 -C 5 H 5 -) with Na + C 1 0 H 8 - in 1,2-dimethoxyethane (DME) at room temperature produced an air-sensitive transient anion with a tentatively identified nido-[tBUNH-CpFeC 3 B 8 H 1 0 ] 2 - constitution. In-situ reaction of this low-stability ion with [CpFe(CO) 2 I] or [CpFe(CO) 2 ] 2 generated three violet diferratricarbaboranes identified as paramagnetic subcloso complexes [4,5-Cp 2 - -4,5,1,6,7-Fe 2 C 3 B 8 H 1 1 ] (2; yield 2%), [4,5-Cp 2 - -4,5,1,7,12-Fe 2 C 3 B 8 H 1 1 ] (3; yield 2%), and [7-tBuNH-4,5-Cp 2 - -4,5,1,7,12-Fe 2 C 3 B 8 H 1 0 ] (4; yield 14%). These first representatives of t…
A hybrid magnet with coexistence of ferromagnetism and photoinduced Fe(iii) spin-crossover
2011
International audience; The insertion of a [Fe(sal2-trien)]+ complex cation into a 2D oxalate network results in a hybrid magnet with coexistence of magnetic ordering and photoinduced spin-crossover (LIESST effect) in compound [FeIII(sal2-trien)][MnIICrIII(ox)3]*(CH2Cl2) (1). A complete photomagnetic characterization together with a detailed structural analysis of the low-spin (LS) and high-spin (HS) structures of 1 is presented in order to understand such unusual behavior. This very rare and unexpected property in a FeIII spin-crossover complex, has been attributed to the strong distortion exhibited by the metastable HS state. Furthermore, 1 has shown that, in contrast to what has been pre…
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…
A Decade of Electrochemical Dehydrogenative C,C-Coupling of Aryls.
2019
The importance of sustainable and green synthetic protocols for the synthesis of fine chemicals has rapidly increased during the last decades in an effort to reduce the use of fossil fuels and other finite resources. The replacement of common reagents by electricity provides a cost- and atom-efficient, environmentally friendly, and inherently safe access to novel synthetic routes. The selective formation of carbon-carbon bonds between two distinct substrates is a crucial tool in organic chemistry. This fundamental transformation enables access to a broad variety of complex molecular architectures. In particular, the aryl-aryl bond formation has high significance for the preparation of organ…