Search results for "molecule"
showing 10 items of 5162 documents
Molecular structure of p -methylaniline and its van der Waals complexes with CF 3 H, CH 4 and CF 4 studied by laser induced fluorescence spectroscopy…
2002
The UV fluorescence excitation and dispersed fluorescence spectra of jet-cooled p-methylaniline have been obtained for the S1←S0 transition. The main spectral bands have been assigned by comparison with those of other relevant substituted benzenes and with the help of computed vibrational frequencies. The structure of p-methylaniline in both the S0 and S1 states has been studied at ab initio quantum chemical calculations at MP2 and CIS levels of theory using the 6-31+G∗ basis sets. Both low- and high-resolution laser induced fluorescence spectra of p-methylaniline van der Waals complexes with CF3H, CH4 and CF4 have been characterised following jet-expansion investigations. The equilibrium g…
Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the characterization of functionalized carbon nanotubes
2013
RATIONALE Functionalization of carbon nanotubes (CNTs) generates complex systems that require the development of suitable characterization protocols. New techniques have been explored, and existing analytical and spectroscopic methods to characterize functionalized CNTs have been adapted. Presently, chemical characterization of functionalized CNTs (f-CNTs) remains a difficult task. METHODS Matrix-assisted laser desorption/ionization (MALDI) analysis is performed on f-MWCNT samples prepared via grafting or absorption of anti-oxidant (AO) molecules on both MWCNT-COOH and MWCNT-OH. Covalently functionalized MWCNTs were subjected to thermal degradation and/or hydrolysis reaction before analysis…
Dynamic Molecular Graphs: “Hopping” Structures
2013
This work aims to contribute to the discussion about the suitability of bond paths and bond-critical points as indicators of chemical bonding defined within the theoretical framework of the quantum theory of atoms in molecules. For this purpose, we consider the temporal evolution of the molecular structure of [Fe{C(CH2 )3 }(CO)3 ] throughout Born-Oppenheimer molecular dynamics (BOMD), which illustrates the changing behaviour of the molecular graph (MG) of an electronic system. Several MGs with significant lifespans are observed across the BOMD simulations. The bond paths between the trimethylenemethane and the metallic core are uninterruptedly formed and broken. This situation is reminiscen…
Über polygermane
1980
Abstract The crystal structure of octaphenylcyclotetragermane, (Ph 2 Ge) 4 , has been determined and refined to an R value of 0.046. The symmetry of the molecule approximater D 2d . the Ge 4 ring is nearly planar and square (angle of pucker 3.9°, GeGe 246.5(5) pm). The 8 phenyl groups (GeC 196.2(10) pm) are arranged in two distinct sets (“parallel” touching and perpendicular to the Ge 4 ring) which exchange their positions in solution. The packing of the (Ph 2 Ge) 4 molecules in the crystal resembles a cubic body centred sphere packing. The homocyclic series (Ph 2 Ge) n with n 4, 5, 6 shows 13 C NMR signals in CDCl 3 solution monotonic dependent on the endocyclic GeGeGe angles.
Arylethynyl-Substituted Tristriazolotriazines: Synthesis, Optical Properties, and Thermotropic Behavior
2014
The synthesis of C3-symmetrical tristriazolotriazines with conjugated arms and lateral alkoxy side chains was performed by a threefold condensation of cyanuric chloride with tetrazoles. Conjugated π segments include phenyl, tolane, and its phenylethynyl-elongated homologue. Disclike and a dendritic molecule have been obtained, and two compounds with a 3,4,5-tris(octyloxy) substitution form broad thermotropic mesophases. The linear optical properties, solvatochromism of the fluorescence, acidochromism, and the two-photon absorption efficiency of selected compounds are reported.
Über gemischte Gruppe 14—Gruppe 14-Bindungen
1991
Abstract p-Tol6PbSn has been synthesized by reaction of p-Tol3PbLi with p-Tol3SnI in THF/ether (1:2) at −78°C. The crystal structures of p-Tol4Pb (I 4 ) and of p-Tol6Sn2, p-Tol6PbSn and p-Tol6Pb2 have been determined. The three dinuclear compounds crystallize not strickly isomorphous. They exhibit the same space group (R 3 and rather similar unit cell dimensions. Yet according to the solvent of crystallization, two types with differing atomic position parameters can be distinguished (“homoeotypism with differences of parameters” in the definition of Laves). In both types, the individual molecules have a chiral C3-symmetric conformation and the non-chiral unit cell encloses both enantiomers.…
Electric field induced alignment-orientation conversion in diatomic molecules: analysis and observation for NaK
1999
This article reports the observation of the molecular fluorescence circularity under irradiation with linearly polarised light. This alignment-orientation conversion phenomenon arises as a result of partial transformation from alignment of the ensemble of 1 P state molecular angular momenta into their orientation under the effect of non-linear dc Stark effect. Circularity rate up to 0.12 was observed in D 1 P! X 1 S fluorescence of 23 Na 39 K molecules in agreement with the theoretically predicted value.
The Zwitterion [8,8′-μ-CH2O(CH3)-(1,2-C2B9H10)2-3,3′-Co]0 as a Versatile Building Block To Introduce Cobalt Bis(Dicarbollide) Ion into Organic Molecu…
2012
The synthesis of a new bridged [8,8′-μ-CH2O(CH3)-(1,2-C2B9H10)2-3,3′-Co]0 derivative (2), arising from the acid-catalyzed reaction of cobalt bis(1,2-dicarbollide)(1−) ion with formaldehyde, is reported. The proposed reaction path is supported by the isolation of side products including two zwitterionic compounds, the known bridged [8,8′-μ-(CH3O)-(1,2-C2B9H10)2-3,3′-Co]0 derivative (3), the new zwitterion [(8-(CH3)2O-1,2-C2B9H10)-(1′,2′-C2B9H11)-3,3′-Co]0 (4), and two anionic compounds—the known [(8,8′-Cl2-1,2-C2B9H10)2-3,3′-Co]− and the newly characterized dimethoxy derivative [(8,8′-(CH3O)2-1,2-C2B9H10)2-3,3′-Co]− of the cobalt bis(dicarbollide) ion. Compound 2 serves as a versatile buildi…
Studies in organic mass spectrometry. Part 25. Benzyl ion formation in chemical ionisation (methane or isobutane) of someortho-alkylhetero-substitute…
2000
The behaviour of some ortho-alkylhetero-substituted diphenylcarbinols, including deuterium labelled derivatives, under chemical ionisation (methane or isobutane) conditions has been investigated. It has been determined that ortho-alkylhetero diphenylmethyl cations formed by water elimination from the protonated molecule undergo consecutive rearrangements which afford benzyl (or tropylium) ions previously observed for ortho-substituted diphenylcarbenium ions generated by electron ionisation. This reaction also occurs under low-energy collision conditions. Copyright © 2000 John Wiley & Sons, Ltd.
Synthesis, spectroscopic and structural characterization of [Cu(phen)(C5O5)(H2O)]·H2O, [Ni(terpy)(C5O5)(H2O)]·H2O and [Ni(terpy)2](NO3)2·0.5H2O
2005
Abstract The new mononuclear complexes [Cu(phen)(C5O5)(H2O)]·H2O (1), [Ni(terpy)(C5O5)(H2O)]·H2O (2) and [Ni(terpy)2](NO3)2·0.5H2O (3) [phen=1,10-phenanthroline, C 5 O 5 2 − =dianion of the 4,5-dihydroxycyclopent-4-ene-1,2,3-trione and terpy=2,2′:6′,2″-terpyridine] have been synthesized and characterized by single-crystal X-ray diffraction. The copper atom of 1 has a distorted square pyramidal environment with two phen-nitrogen and two croconate-oxygen atoms building the equatorial plane and a water molecule in the apical position. The nickel atom of 2 exhibits a distorted NiN3O3 octahedral coordination, which may be described either as tetragonally compressed or as skewed trapezoidal bipyr…