14 research outputs found
New building blocks for molecular spintronics
In der vorliegenden Arbeit werden die drei generellen Schritte beim Aufbau neuer Materialien aus funktionellen Bausteinen an Beispielen nachvollzogen. Im Einzelnen sind dies die Verknüpfung bekannter Funktionselemente und die Identifikation der Strukturelemente neuer Funktionen, die Darstellung von funktionalen Bausteinen mit Verknüpfungsstellen und die Verknüpfung der Bausteine und der Nachweis, dass die Funktion dadurch nicht verloren geht.
Die Synthese von neuen Bausteinen steht dabei ebenso im Fokus wie die ausgedehnte Analyse erhaltener Verbindungen. Zwei neue Ligandgerüste werden beschrieben, die hochfunktionale Triphenylamineinheiten enthalten. Des Weiteren werden Verbindung auf der Basis von Triaminobenzen, Triaminoguanidin, Mesalen-artigen Liganden und acetylsubstituierten Phloroglucin untersucht und sorgfältig bezüglich ihrer magnetischen Eigenschaften charakterisiert. Erhaltene Ergebnisse konnten anschließend erfolgreich in andere Materialklassen übertragen werden: Die magnetische Anomalität, wie sie in Verbindungen basierend auf Triaminobenzen gefunden wird, konnte erfolgreich in Carbazolverbindungen integriert werden.
Ein übergreifendes Ergebnis dieser Arbeit sind die Eigenschaften, die sich beim Einbau von Sulfonatgruppen in Verbindungen ergeben: Die Lösungseigenschaften der erhaltenen Verbindungen werden stark geändert, wobei die wasserlöslichen Produkte in Polyvinylalkoholfolien eingebettet werden können, was einen viel versprechenden Ansatz für zukünftige Materialien darstellt. Die Sulfonatsubtitution begünstigt auf Grund der Koordinationsfähigkeiten der Sulfonatgruppe die Ausbildung ausgedehnter Strukturen und bietet neue Strukturen durch die Bindung von Ammoniumgruppen mittels mehrfacher Wasserstoffbrückenbindungen an Mesalenartige Metallkomplexe
Der FachRef-Assistent : personalisiertes, fachspezifisches und transparentes Bestandsmanagement
Im Rahmen dieser Masterarbeit wurde eine personalisierte Webanwendung zur
Bestandspflege von gedruckten und Online-Medien entwickelt: der FachRef-Assistent.
Dieser führt automatisiert Analysen des Bestandes durch und erstellt Aussonderungsund
Erwerbungsvorschläge. Dabei wurde besonderer Wert auf Individualisierung,
Transparenz der Parameter, bibliothekarische Standards und generische Funktionen
gelegt.
Die Personalisierung erlaubt es, sowohl fachspezifische Nutzungseigenschaften als
auch Unterschiede zwischen verschiedenen Bereichen innerhalb eines Fachbereiches
zu berücksichtigen. Die verwendeten Parametersätze zur Analyse des Bestandes und
zur Erstellung von Aussonderungs- und Erwerbungslisten werden grundsätzlich im
XML-Format gespeichert und in die erzeugten Listen (ebenfalls im XML-Format)
integriert, um eine Nachverfolgung und Transparenz der Analysen auf lange Zeit zu
gewährleisten. Um die Anwendung so generisch wie möglich zu gestalten, wurden alle
Bibliothekssystem-spezifischen Funktionen in einem separaten Paket zusammengefasst.
Durch Adaption der entsprechenden Klassen lassen sich daher prinzipiell
auch andere Bibliothekssysteme befragen. Auch die Integration spezifischer Bedingungen
wie Standort, Aufstellungssystematik und Nutzergruppen wurde möglichst
generisch gestaltet.
Insgesamt stellt der in dieser Arbeit beschriebene FachRef-Assistent ein umfangreiches
Werkzeug zum datenbasierten Bestandsmanagement dar. Der Grad an
Automatisierung lässt sich dabei in vielen Schattierungen anpassen. Der FachRef-
Assistent hilft, durch die Aggregation von objektiven Kriterien eine höhere Effizienz zu erreichen und setzt dadurch sowohl Finanz- als auch Zeitressourcen frei, die somit
für andere Aufgaben zur Verfügung stehen.In the course of this master thesis a personalized web application for the weeding
of printed and online resources has been developed: the FachRef-Assistant. Special
attention has been paid to the criteria individualization, transparency of the
parameters used, library standards and generic funtions.
The personalization allows for the inclusion of subject specific usage properties as
well as the differences between different collections within one subject area. The parameter
sets used to analyze the stock and to prepare deinventarization and purchase
proposal lists are stored as XML files and are included in the generated lists. These
lists are similarly produced in XML format, ensuring a high degree of reproducibility
and transparency for an extended period of time. To keep the application as generic
as possible, all procedures specific to the local library system have been collected in
one package. Hence simple adaption of this package renders the FachREf-Assistant
compatible to other library systems. The inclusion of library specific properties such
as collections and systematics have been designed to be highly generic.
In summary, the FachRef-Assistent described in this thesis offers an extensive tool
for evidence based stock management. The dgegree of automation can be chosen
and adjusted in a wide range. The FachRef-Assistent supports the library staff
by aggregation of objective criteria to achieve a higher work efficency, setting free
additonal financial and time resources that may be used for new tasks and challenges
Azobenzene-Based Organic Salts with Ionic Liquid and Liquid Crystalline Properties
Two sets of new azobenzene-based bromide salts are synthesized, and their thermal photochromic properties are studied. Both sets are based on the imidazolium cation. The first set (1) features a symmetric biscation where two imidazolium head groups (Im) with different alkyl chains (Cn) are connected to a central azobenzene unit (Azo): [Azo(C1-Im-Cn)2]; n = 6, 8, 10, 12, 14. The other one contains an n-alkyl-imidazolium cation (Cn-Im) bearing a terminal azobenzene unit (C1-Azo) substituted with an alkoxy chain (O-Cm) of either two (2) or six (3) carbon atoms: [C1-Azo-O-Cm-Im-Cn]; m = 2, n = 8, 10, 12 and m = 6, n = 8, 10, 12, 14, 16. For both cation classes, the influence of alkyl chains of varying length on the thermal phase behavior was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). For five compounds (Azo(-C1-Im-C12)2 (1d), Azo(-C1-Im-C12)2 (1e), C1-Azo-O-C2-Im-C10 (2b), C1-Azo-O-C2-Im-C12 (2c), and C1-Azo-O-C6-Im-C16 (3e)), the formation of a liquid crystalline phase was observed. The biscationic salts (1) are all comparatively high melting organic salts (180–240 °C), and only the two representatives with long alkylchains (C12 and C14) exhibit liquid crystallinity. The monocationic salts with an O–C2 bridge (2) melt between 140 and 170 °C depending on the alkyl chain length, but from an alkyl chain of 10 and more carbon atoms on they form a smectic A liquid crystalline phase. The representatives of the third set with a O–C6 bridge qualify as ionic liquids with melting points less than 100 °C. However, only the representative with a hexadecyl chain forms a liquid crystalline phase. Representative single crystals for all sets of cations could be grown that allowed for single crystal structure analysis. Together with small-angle X-ray scattering experiments they allow for a more detailed understanding of the thermal properties. Through irradiation with UV-light (320–366 nm) all compounds undergo trans–cis isomerization, which reverses under visible light (440 nm).Reprinted (adapted) with permission from Cryst. Growth Des., 2015, 15 (9), pp 4701–4712. Copyright 2015 American Chemical Society.</p
Influence of the Counteranion on the Ability of 1-Dodecyl-3-methyltriazolium Ionic Liquids to Form Mesophases
DuEPublicA: Automated bibliometric reports based on the University Bibliography and external citation data
This paper describes a web application to generate bibliometric reports based on the University Bibliography and the Scopus citation database. Our goal is to offer an alternative to easy-to-prepare automated reports from commercial sources. These often suffer from an incomplete coverage of publication types and a difficult attribution to people, institutes and universities. Using our University Bibliography as the source to select relevant publications solves the two problems. As it is a local system, maintained and set up by the library, we can include every publication type we want. As the University Bibliography is linked to the identity management system of the university, it enables an easy selection of publications for people, institutes and the whole university.
The program is designed as a web application, which collects publications from the University Bibliography, enriches them with citation data from Scopus and performs three kinds of analyses:
1. A general analysis (number and type of publications, publications per year etc.),
2. A citation analysis (average citations per publication, h-index, uncitedness), and
3. An affiliation analysis (home and partner institutions)
We tried to keep the code highly generic, so that the inclusion of other databases (Web of Science, IEEE) or other bibliographies is easily feasible. The application is written in Java and XML and uses XSL transformations and LaTeX to generate bibliometric reports as HTML pages and in pdf format. Warnings and alerts are automatically included if the citation analysis covers only a small fraction of the publications from the University Bibliography. In addition, we describe a small tool that helps to collect author details for an analysis
The FachRef-Assistant: Personalised, subject specific, and transparent stock management
We present in this paper a personalized web application for the weeding of printed resources: the FachRef-Assistant. It offers an extensive range of tools for evidence based stock management, based on the thorough analysis of usage statistics. Special attention is paid to the criteria individualization, transparency of the parameters used, and generic functions. Currently, it is designed to work with the Aleph-System from ExLibris, but efforts were spent to keep the application as generic as possible. For example, all procedures specific to the local library system have been collected in one Java package. The inclusion of library specific properties such as collections and systematics has been designed to be highly generic as well by mapping the individual entries onto an in-memory database. Hence simple adaption of the package and the mappings would render the FachRef-Assistant compatible to other library systems.
The personalization of the application allows for the inclusion of subject specific usage properties as well as of variations between different collections within one subject area. The parameter sets used to analyse the stock and to prepare weeding and purchase proposal lists are included in the output XML-files to facilitate a high degree of transparency, objectivity and reproducibility
Azobenzene-Based Organic Salts with Ionic Liquid and Liquid Crystalline Properties
Two sets of new azobenzene-based
bromide salts are synthesized,
and their thermal photochromic properties are studied. Both sets are
based on the imidazolium cation. The first set (<b>1</b>) features
a symmetric biscation where two imidazolium head groups (Im) with
different alkyl chains (Cn) are connected to a central azobenzene
unit (Azo): [Azo(C1-Im-Cn)<sub>2</sub>]; <i>n</i> = 6, 8,
10, 12, 14. The other one contains an <i>n</i>-alkyl-imidazolium
cation (Cn-Im) bearing a terminal azobenzene unit (C1-Azo) substituted
with an alkoxy chain (O-<i>Cm</i>) of either two (<b>2</b>) or six (<b>3</b>) carbon atoms: [C1-Azo-O-<i>Cm</i>-Im-Cn]; <i>m</i> = 2, <i>n</i> =
8, 10, 12 and <i>m</i> = 6, <i>n</i> = 8, 10,
12, 14, 16. For both cation classes, the influence of alkyl chains
of varying length on the thermal phase behavior was investigated by
differential scanning calorimetry (DSC) and polarizing optical microscopy
(POM). For five compounds (Azo(-C1-Im-C12)<sub>2</sub> (<b>1d</b>), Azo(-C1-Im-C12)<sub>2</sub> (<b>1e</b>), C1-Azo-O-C2-Im-C10
(<b>2b</b>), C1-Azo-O-C2-Im-C12 (<b>2c</b>), and C1-Azo-O-C6-Im-C16
(<b>3e</b>)), the formation of a liquid crystalline phase was
observed. The biscationic salts (<b>1</b>) are all comparatively
high melting organic salts (180–240 °C), and only the
two representatives with long alkylchains (C12 and C14) exhibit liquid
crystallinity. The monocationic salts with an O–C2 bridge (<b>2</b>) melt between 140 and 170 °C depending on the alkyl
chain length, but from an alkyl chain of 10 and more carbon atoms
on they form a smectic A liquid crystalline phase. The representatives
of the third set with a O–C6 bridge qualify as ionic liquids
with melting points less than 100 °C. However, only the representative
with a hexadecyl chain forms a liquid crystalline phase. Representative
single crystals for all sets of cations could be grown that allowed
for single crystal structure analysis. Together with small-angle X-ray
scattering experiments they allow for a more detailed understanding
of the thermal properties. Through irradiation with UV-light (320–366
nm) all compounds undergo <i>trans–cis</i> isomerization,
which reverses under visible light (440 nm)
Ionothermal Synthesis, Crystal Structure, and Magnetic Study of Co<sub>2</sub>PO<sub>4</sub>OH Isostructural with Caminite
A new framework cobalt(II) hydroxyl
phosphate, Co<sub>2</sub>PO<sub>4</sub>OH, was prepared by ionothermal
synthesis using 1-butyl-4-methyl-pyridinium
hexafluorophosphate as the ionic liquid. As the formation of Co<sub>2</sub>PO<sub>4</sub>F competes in the synthesis, the synthesis conditions
have to be judiciously chosen to obtain well-crystallized, single
phase Co<sub>2</sub>PO<sub>4</sub>OH. Single-crystal X-ray diffraction
analyses reveal Co<sub>2</sub>PO<sub>4</sub>OH crystallizes with space
group <i>I</i>4<sub>1</sub>/<i>amd</i> (<i>a</i> = <i>b</i> = 5.2713(7) Å, <i>c</i> = 12.907(3) Å, <i>V</i> = 358.63(10) Å<sup>3</sup>, and <i>Z</i> = 4). Astonishingly, it does not crystallize
isotypically with Co<sub>2</sub>PO<sub>4</sub>F but rather isotypically
with the hydroxyl minerals caminite Mg<sub>1.33</sub>[SO<sub>4</sub>(OH)<sub>0.66</sub>(H<sub>2</sub>O)<sub>0.33</sub>] and lipscombite
Fe<sub>2–<i>y</i></sub>PO<sub>4</sub>(OH) (0 ≤ <i>y</i> ≤ 2/3). Phosphate tetrahedra groups interconnect
four rod-packed face-sharing <sub>∞</sub><sup>1</sup>{CoO<sub>6/2</sub>} octahedra chains to form
a three-dimensional framework structure. The compound Co<sub>2</sub>PO<sub>4</sub>OH was further characterized by powder X-ray diffraction,
Fourier transform–infrared, and ultraviolet–visible
spectroscopy, confirming the discussed structure. The magnetic measurement
reveals that Co<sub>2</sub>PO<sub>4</sub>OH undergoes a magnetic transition
and presents at low temperatures a canted antiferromagnetic spin order
in the ground state
Ionothermal Synthesis, Crystal Structure, and Magnetic Study of Co<sub>2</sub>PO<sub>4</sub>OH Isostructural with Caminite
A new framework cobalt(II) hydroxyl
phosphate, Co<sub>2</sub>PO<sub>4</sub>OH, was prepared by ionothermal
synthesis using 1-butyl-4-methyl-pyridinium
hexafluorophosphate as the ionic liquid. As the formation of Co<sub>2</sub>PO<sub>4</sub>F competes in the synthesis, the synthesis conditions
have to be judiciously chosen to obtain well-crystallized, single
phase Co<sub>2</sub>PO<sub>4</sub>OH. Single-crystal X-ray diffraction
analyses reveal Co<sub>2</sub>PO<sub>4</sub>OH crystallizes with space
group <i>I</i>4<sub>1</sub>/<i>amd</i> (<i>a</i> = <i>b</i> = 5.2713(7) Å, <i>c</i> = 12.907(3) Å, <i>V</i> = 358.63(10) Å<sup>3</sup>, and <i>Z</i> = 4). Astonishingly, it does not crystallize
isotypically with Co<sub>2</sub>PO<sub>4</sub>F but rather isotypically
with the hydroxyl minerals caminite Mg<sub>1.33</sub>[SO<sub>4</sub>(OH)<sub>0.66</sub>(H<sub>2</sub>O)<sub>0.33</sub>] and lipscombite
Fe<sub>2–<i>y</i></sub>PO<sub>4</sub>(OH) (0 ≤ <i>y</i> ≤ 2/3). Phosphate tetrahedra groups interconnect
four rod-packed face-sharing <sub>∞</sub><sup>1</sup>{CoO<sub>6/2</sub>} octahedra chains to form
a three-dimensional framework structure. The compound Co<sub>2</sub>PO<sub>4</sub>OH was further characterized by powder X-ray diffraction,
Fourier transform–infrared, and ultraviolet–visible
spectroscopy, confirming the discussed structure. The magnetic measurement
reveals that Co<sub>2</sub>PO<sub>4</sub>OH undergoes a magnetic transition
and presents at low temperatures a canted antiferromagnetic spin order
in the ground state
A Roadmap to Uranium Ionic Liquids: Anti-Crystal Engineering
In the search for uranium-based ionic liquids, tris(N,N-dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1-butyl-3-methylimidazolium (C(4)mim) cation. As dithiocarbamate ligands binding to the UO22+ unit, tetra-, penta-, hexa-, and heptamethylenedithiocarbamates, N,N-diethyldithiocarbamate, N-methyl-N-propyldithiocarbamate, N-ethyl-N-propyldithiocarbamate, and N-methyl-N-butyldithiocarbamate have been explored. X-ray single-crystal diffraction allowed unambiguous structural characterization of all compounds except N-methyl-N-butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X-ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase-transition behavior depending on the N,N-dialkyldithiocarbamato ligand with the aim to establish structure-property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N-dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N-methyl-N-propyldithiocarbamato)uranylate, tris(N-ethyl-N-propyldithiocarbamato)uranylate, and tris(N-methyl-N-butyldithiocarbamato)uranylate, lead to the formation of (room-temperature) ionic liquids, which confirms that low-symmetry ions are indeed suitable to suppress crystallization. These materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery