Fluorescence Studies of Amine-substituted Azaanthracene Metal Complexes

by Arne Visscher
Doctoral thesis
Date of Examination:2016-06-16
Date of issue:2016-07-20
Advisor:Prof. Dr. Dietmar Stalke
Referee:Prof. Dr. Dietmar Stalke
Referee:Prof. Dr. Franc Meyer
Persistent Address: http://dx.doi.org/10.53846/goediss-5761

 

 

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Abstract

English

Former investigations of the Stalke group focussed on the hydrocarbon fluorophore anthracene. In this thesis, two representatives of the heteroaromatic congener azaanthracene with different fluorescence properties and potential usage as molecular sensors for metal cations were major fields of research. These compounds were 2- and 10-azaanthracene depicted in Figure 1.14, A and B, C, respectively. 2-Azaanthracene is a rare representative in the field of fluorescent sensors. Therefore, a suitable synthesis route for this aromatic system needed to be developed first. Its behaviour towards further substitution reactions to enable the “fluorophore-spacer-receptor” principle was of interest.Concerning the second representative 10-azaanthracene, two various fluorescence mechanisms should be studied. Depending on the existence of a spacer unit between the quencher and the fluorophore, either the photoinduced electron transfer (PET) or the intramolecular charge transfer (ICT) effect can be utilised for cation detection. The latter effect is feasible if the receptor is directly bonded to the aromatic system (B) and has a strong electronic influence on the pi-system. This is a rare motif in the acridine literature which is why different syntheses towards new 4-aminoacridine compounds were studied. The PET effect is present if the structural design depicted in Figure 1.14, C is used. Well established experimental procedures have led to the publication of various analogous structures in the last few years. For the course of this thesis, a variety of amine receptors were employed to determine their influence to the selectivity and sensitivity of the molecular sensor devices. The synthesised compounds and their metal complexes needed to be structurally investigated in detail by NMR and fluorescence spectroscopy in solution as well as in solid state by X-ray diffraction. With these analytical methods, the chelating motif of the ligand towards the target ion can be investigated. Especially the possible coordination of the acridine nitrogen atom to the analyte, often discussed in the literature, should be examined.
Keywords: acridine; azaanthracene; fluorescence; PET effect; zinc sensor; cadmium sensor
 
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