Search results for "Spectroscopy"
showing 10 items of 10293 documents
Influence of theZ/EIsomerism on the Pathway Complexity of a Squaramide‐Based Macrocycle
2020
The rising interest on pathway complexity in supramolecular polymerization has prompted the finding of novel monomer designs able to stabilize kinetically trapped species and generate supramolecular polymorphs. In the present work, the exploitation of the Z/E (geometrical) isomerism of squaramide (SQ) units to produce various self-assembled isoforms and complex supramolecular polymerization pathways in methylcyclohexane/CHCl3 mixtures is reported for the first time. This is achieved by using a new bissquaramidic macrocycle (MSq) that self-assembles into two markedly different thermodynamic aggregates, AggA (discrete cyclic structures) and AggB (fibrillar structures), depending on the solven…
Synthesis, UV/vis, FT-IR and Mössbauer spectroscopic characterization and molecular structure of the Bis[4-(2-aminoethyl)morpholine](tetrakis(4-metox…
2016
International audience; The synthesis, the UV-visible, FT-IR and Mossbauer spectroscopy and the crystal structure characterizations of the bis[4-(2-Aminoethyl)morpholine]tetrakis(4-metoxyphenyl)porphy-rinato)iron(II) complex are described. The title compound crystallizes in the triclinic, space group P-1, with a = 11.1253(4) angstrom, b = 11.2379(4) angstrom, c = 11.5488(4) angstrom, alpha = 72.304(2)degrees, beta = 86.002(2)degrees gamma = 72.066(2)degrees, V = 1308.28(8) angstrom(3), Z = 1. The Mossbauer data are consistent with an iron(II) low-spin (S = 0) porphyin species. The spin-state is confirmed by the value of the average equatorial iron-nitrogen pyrrole distance (Fe-Np = 1.988(2)…
Carbohydrate-supramolecular gels : adsorbents for chromium(VI) removal from wastewater.
2019
Abstract Hypothesis To overcome the contamination of water by heavy metals the adsorption of the pollutant on gel phases is an attractive solution since gels are inexpensive, potentially highly efficient and form a distinct phase while allowing diffusion of the contaminated water throughout the material. This work tests the chromium(VI) adsorbent capacity of new supramolecular gels for Chromium(VI) removal from wastewater. Experiments First hydrophobic imidazolium salts of carbohydrate anions were synthesised as new gelators. Subsequently, they were dissolved in a solvent by heating and, after cooling overnight, to give the formation of supramolecular gels. The properties of the resulting g…
Photocontrolled On-Surface Pseudorotaxane Formation with Well-Ordered Macrocycle Multilayers.
2016
The photoinduced pseudorotaxane formation between a photoresponsive axle and a tetralactam macrocycle was investigated in solution and on glass surfaces with immobilized multilayers of macrocycles. In the course of this reaction, a novel photoswitchable binding station with azobenzene as the photoswitchable unit and diketopiperazine as the binding station was synthesized and studied by NMR and UV/Vis spectroscopy. Glass surfaces have been functionalized with pyridine-terminated SAMs and subsequently with multilayers of macrocycles through layer-by-layer self assembly. A preferred orientation of the macrocycles could be confirmed by NEXAFS spectroscopy. The photocontrolled deposition of the …
Geminal Imidazolium Salts: A new Class of Gelators
2012
The gelling behavior of some geminal diimidazolium salts was investigated in solvents differing in polarity and hydrogen bond donor ability. The used salts, namely the 3,3'-di-n-decyl-1,1'(1,4-phenylenedimethylene)diimidazolium dibromide [p-Xyl-(decim)(2)][Br](2) (1), the 3,3'-di-n-dodecyl-1,1'(1,4-phenylenedimethylene)diimidazolium dibromide [p-Xyl-(dodecim)(2)][Br](2) (2), and the 3,3'-di-n-dodecyl-1,1'(1,4-phenylenedimethylene)diimidazolium ditetrafluoroborate [p-Xyl-(dodecim)(2)][BF(4)](2) (3), differ in the alkyl chain length and in the anion properties, such as size, shape, and coordination ability. In all cases in which gelation process was observed, the obtained gels were characteri…
Correlating Solution‐ and Solid‐State Structures of Conformationally Flexible Resorcinarenes: Significance of a Sulfonyl Group in Intramolecular Self…
2020
Abstract The synthesis of tetramethoxyresorcinarene podands bearing p‐toluene arms connected by ‐SO3‐ (1) and ‐CH2O‐ (2) linkers is presented herein. In the solid state, the resorcinarene podand 1 forms an intramolecular self‐inclusion complex with the pendant p‐toluene group of a podand arm, whereas the resorcinarene podand 2 does not show self‐inclusion. The conformations of the flexible resorcinarene podands in solution were investigated by variable‐temperature experiments using 1D and 2D NMR spectroscopic techniques as well as by computational methods, including a conformational search and subsequent DFT optimisation of representative structures. The 1H NMR spectra of 1 and 2 at room te…
Surface and Thin Film Analysis by Mössbauer Spectroscopy and Related Techniques
1996
The main trend in current high-tech development is miniaturization. This holds for complex electronic devices, such as microprocessors, as well as for coatings, such as Langmuir-Blodgett coatings, optical components, such as fiber couplers, chemical devices, such as microreactors, mechanical components, such as micromotors, and many others. Development and production of components with dimensions in the micron and submicron range require the availability of appropriate analytical tools for chemical, physical, and morphological analyses. In close interaction with the development of microcomponents, many, more and more efficient, analytical methods have been developed, many of which are “surf…
On the Interaction of Carbon Nanowires with Noble Metals through a Study of Their Surface-Enhanced Raman Spectra
2008
This paper deals with the interaction of linear carbon chains (polyynes) with silver and gold surfaces in the form of nanometer-sized clusters. Surface-enhanced Raman signals have been detected rev...
Determination of surface and interface magnetic properties for the multiferroic heterostructure Co/BaTiO3using spleed and arpes
2016
Co/BaTiO$_3$(001) is one of the most interesting multiferroic heterostructures as it combines different ferroic phases, setting this way the fundamentals for innovative technical applications. Various theoretical approaches have been applied to investigate the electronic and magnetic properties of Co/BaTiO$_3$(001). Here we determine the magnetic properties of 3 ML Co/BaTiO$_3$ by calculating spin-polarized electron diffraction as well as angle-resolved photoemission spectra, with both methods being well established as surface sensitive techniques. Furthermore, we discuss the impact of altering the BaTiO$_3$ polarization on the spectra and ascribe the observed changes to characteristic deta…
Optical Symmetry of Ferroelectric Liquid Crystal Cells
1990
We observe an exact optical symmetry in Surface Stabilized Ferroelectric Liquid Crystal (SSFLC) cells in polarized transmission optical microscopy and spectroscopy. A theoretical argument based on the intrinsic time reversibility of Maxwell's equations and energy conservation is developed to explain this symmetry. The results support the model of Clark and Rieker for zig-zag wall structure and illustrate the necessity of including the orientational binding of the director at the chevron interface.