Following in the same line of research initiated by the Catalysis and Inorganic
Synthesis Group within the ICMAB time ago, this work is mainly focused on the
synthesis of carborane derivatives with styrenyl groups via nucleophilic substitution
reactions, followed by the incorporation of these derivatives to different types of
platforms and structures in order to study their photoluminescence properties. Starting
from these compounds, in which the o-carborane cluster is of closo nature (therefore
neutral from electronic point of view), their corresponding nido (anionic) derivatives
have been obtained, by the cluster’s partial deboronation reaction in basic medium.
These derivatives have been fully characterised using common spectroscopic
techniques such as infrared spectroscopy, NMR spectroscopy, mass spectrometry,
elemental analysis and in some cases, X-ray diffraction. Subsequently,
photoluminescence studies have been performed, indicating that although the
derivatives of methyl-o-carborane and monosubstituted o-carborane exhibit an intense
fluorescence, their phenyl-o-carborane analogues show almost no light emission at all.
In order to explain such phenomenon, the cyclic voltammetry has been studied as well
as DFT theoretical calculations performed, leading to the conclusion that the lack of
fluorescence for the phenyl-o-carborane derivative is most probably due to a
photoinduced electronic transfer process (PET).
Different types of carbosilane and poly(aryl-ether) dendrimers have been chosen
as platforms to which the styrenyl group-containing compounds have been
incorporated into. To achieve this objective, these carboranyl derivatives have been
adequately functionalised to contain a terminal Si-H bond and, in this manner, to carry
out the hydrosilylation reaction of them with different type and generations of
dendrimers that contain a variable number of terminal alkenes. In this way, structures
bearing from 3 to 12 carborane clusters at the periphery have been obtained.
Polyanionic dendrimers have also been generated via partial deboronation reactions of
closo clusters to the respective nido derivatives, and isolated as alkaline salts. All of
these synthesised dendrimers have been fully characterised. For the poly(aryl-ether)
dendrimers, their thermal properties have been studied by thermogravimetric analysis
(TGA), as well as their photophysical properties. The influence of the different
substituents of the clusters (phenyl or methyl), number of clusters and the electronic
nature of the cage on the photoluminescence has been studied. Those compounds that contain methyl-o-carborane have shown the highest emission quantic yields. These
dendrimers, due to their elevated boron content, are considered to be good candidates
for future biomedical applications, among others Boron Neutron Capture Therapy
(BNCT) and other applications such as antivirals or bactericides.
The family formed by cubic silsesquioxanes or POSS constitutes another
interesting platform to be taken into account, when considering the incorporation of
our carborane derivatives bearing the styrenyl group. With the aim of retaining the
structure of these compounds, they have been reacted with octavinylsilsesquioxane via
olefin metathesis reactions, yielding macromolecules that contain 8 carborane clusters
at the periphery. As was previously accomplished for the poly(aryl-ether) dendrimers,
their corresponding polyanionic derivatives have been also obtained, using the same
partial deboronation reaction of the closo cluster to the respective nido species. All
resulting compounds have been fully characterised by different spectroscopic
techniques and elemental analysis. The thermal properties of neutral POSS with closocarboranes
have been studied by TGA, showing a remarkable thermal stability. This
fact lead us to carry out a more complete study of POSS, previously treated at 600 ºC
for 1 hour, using powder X-rays diffraction (XRD) technique and transmission electron
microscopy (TEM). Photoluminescence studies of neutral POSS have revealed a
different behaviour concerning emissions data, respect to their styrenyl-carborane
precursors. In this case, the phenyl-o-carborane derivative presents the highest
intensity of emission, whereas the monosubstituted o-carborane species shows a total
fluorescence quenching. DFT calculations have been done, both in fundamental and
excited states, corroborating the experimental results.
By analysing the photoluminescent properties of the isolated starting materials
and after anchoring them to different platforms (dendrimers and POSS), it has been
observed that the carborane cluster and its substituents play an important and
interesting role within these properties. Therefore, we decided to go even further and
synthesize, using diverse synthetic strategies (addition, hydrosilylation, nucleophilic
substitution or Heck reactions, etc), compounds bearing carborane clusters and
different fluorophore groups, such as fluorene, anthracene or stilbene. All of these
compounds have been adequately characterised and there photoluminescent
properties studied. In all cases, it has been observed that when the fluorophore group
is not directly bonded to the cluster and is situated away from it, the emission
intensities are quite elevated, whereas if there is an aromatic group directly bonded to the cluster (phenyl or fluorene) and the fluorophore group is close to it in space, a
quenching of the fluorescence is produced, which, depending on the type of
fluorophore, is more or less efficient. This phenomenon is in close agreement with the
results obtained for the phenyl-o-carborane derivatives, for the starting carboranestyrenyl-
carborane derivatives as well as for the poly(aryl-ether) dendrimers.
During the three months stage at the University of York, different compounds
derived from the o-carborane and incorporating at least 1 mesogen derivative of
cholesterol have been synthesised, with the aim of obtaining new materials with liquid
crystal properties. Once these compounds have been characterised, they have also
been analysed by differential scanning calorimetry (DSC) and polarised optical
microscopy (POM), to confirm that in general all compounds synthesised by
hydrosilylation reaction do not show mesogenic properties, with the exception of the
compound bearing 4 mesogens within its structure. On the other hand, all of the
compounds synthesised via olefinic metathesis, show interesting mesogenic properties,
exhibiting, in all cases, a chiral nematic mesophase (N*). Moreover, in the case of the
methyl-o-carborane derivative, a Blue Phase (BP*) and a chiral smectic mesophase A
(SmA*) are exhibited during the cooling cycle. These results indicate that for the latter
compounds, the incorporation of the carborane clusters does not destroy the
mesomorphic behaviour of the mesogen, but in addition, confers it new and interesting
mesogenic properties.
| Identifer | oai:union.ndltd.org:TDX_UAB/oai:www.tdx.cat:10803/116188 |
| Date | 10 May 2013 |
| Creators | Ferrer Ugalde, Albert |
| Contributors | Núñez Aguilera, Mª Rosario, Capdevila, Mercè, Universitat Autònoma de Barcelona. Departament de Química |
| Publisher | Universitat Autònoma de Barcelona |
| Source Sets | Universitat Autònoma de Barcelona |
| Language | Catalan |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | 217 p., application/pdf |
| Source | TDX (Tesis Doctorals en Xarxa) |
| Rights | info:eu-repo/semantics/openAccess, ADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs. |
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