C ONCLUSIONES

The detection of anions and transition metal cations in aqueous media is of great interest. Of special interest is so-called naked-eye detection with chromogenic receptors which oer easy read-out without complicated instruments. Compound 3a (Fig. 5.4) is reported in the literature as a detector for Hg²⁺ ions^[117]and 3b, as its metal complex, as anion sensor.^[118]The ligands consist of an azathia macrocycle, which can coordinate to transition metal ions, and p-nitroazobenzene as chromophore.

Upon addition of a range of metal nitrate salts, compound 3a shows only a colour change with the mercury(II) salt.^[117] Neither the addition of several group 1 and 2 metals as perchlorate salts nor dierent anions as TBA salts to a solution of 3b caused a change. Also with diverse transition metal ions like Ni²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Fe²⁺ and Ag⁺ no signicant eect was observed. Only with Cu²⁺, Hg²⁺ and Fe³⁺changes in the absorption spectrum were observed. The mercury(II) and iron(III) complexes of 3b also showed selective response to some anions such as nitrate or iodide.^[118]

To use the specic detection properties of this type of compound and probably also improve them, the nitro-group was substituted by a tpy-ligand. This led to an enlarged conjugated π-system and also oered the possibility for further coordination.

Figure 5.4: Structure of the detector ligand 3 .

Synthetic strategy and synthesis

The synthetic route to L6 (Scheme 5.4) followed the strategy reported by Kou et al.^[117] with some modications. Reaction of N -phenyldiethanolamine with methanesulfonyl chloride under basic con-ditions yielded compound P25. The macrocyclic compound P26 was obtained by the reaction with 3,6-dioxa-1,8-octanedithiol in the presence of potassium carbonate. 4-([2,2⁰:6⁰,2⁰⁰ -Terpyridin]-4⁰-yl)aniline was rst converted into the diazonium salt and then reacted with P26 to the ligand L6.^[119] Unfortunately, this last step was not reproducible. Although several attempts were made to reproduce it, none of them was successful. Changing the order of the reactions yielded inter-mediates, but never succeeded to the nal compound. Because of this, no ion sensing experiments were performed. L6 was characterized by ¹H and ¹³C NMR spectroscopy and mass spectrometric

5.4 Detector ligand L6 5 DIVERSE LIGANDS

Scheme 5.4: Synthetic route to ligand L6 .

5.5 Concluding remarks 5.5.1 ALP

The already established synthesis to ALPE was performed and slightly improved. A novel route to intermediate P16 (Scheme 5.2) was developed in theory and parts of it performed experimentally.

This new approach should improve the very low yields of the currently used method. To obtain the desired compound in good yields and high purity, further investgations are necessary.

5.5.2 ALP2

The synthetic pathway to the phosphonate ester ALPE2 has been developed further and the inter-mediate compounds have been characterized by mass spectrometry. Full ¹H and ¹³C NMR assign-ment of ALPE2 was performed with NMR spectroscopic methods. Dierent ways for the hydrolysis of the ester to the acid have been tried, but none was successful. This last step has to be part of further investigations to obtain the new anchoring ligand ALP2.

5.5.3 TA-PEG, TA-TEG

The two compounds TA-TEG and TA-PEG were successfully synthesized on a multigram scale and delivered to the partner-group at the University of Bologna. There, the materials were used for the modulation of the solubility of QDs.

5.5.4 Detector ligand L6

The new ligand L6 was synthesized once and characterized by standard methods. Unfortunately, the resynthesis was not possible and also other synthetic approaches did not succeed. As no re-liable synthesis for this ligand was established, further investigations of the targetted ion sensing experiments were not performed.

6 Summary

In this thesis, the synthesis and characterization of a series of polypyridine anchoring ligands have been presented. A part of these anchoring ligands have been used for the preparation of coordination complexes for detection applications. The transition metal complexes have been characterized and their sensing abilities have been examined. Futhermore, the anchoring ligands have been used for the functionalization of dierent kinds of surfaces. Additionally, some other ligands have been prepared for dierent types of applications.

In Chapter 2, several bpy and tpy-based ligands have been synthesized and fully characterized by

1H and ¹³C NMR spectroscopy, mass spectrometry, IR spectroscopy, melting point and absorption and photoluminescene spectroscopy. The ligand families of L2 and L4 have been prepared by a straightforward synthetic procedure. This strategy allows also variation in the linker chain length and the use of other anchoring groups.

In Chapter 3, a series of dierent Ru(II) complexes for detection applications are discussed. The complexes have been synthesized and characterized by standard analytical methods. Sensing tests have been performed and investigated by absorption and photoluminescence spectroscopy. Complex C2* performed well as detection compound for uoride anions, but also showed sensitivity towards acetate and hydroxide ions. Complexes C4 and C5 showed only little potential as cyanide detector compounds.

In Chapter 4, simple protocols have been established for the functionalization of dierent mate-rials with the anchoring ligands L2 and L4. For TiO2 surfaces, phosphonic and carboxylic acids have been used as anchoring groups, whereas thiols have been applied for gold nanoparticle. The functionalized surfaces have been characterized by absorption and photoluminescence spectroscopy.

Post-treatment of these materials with transition metal salts were performed and evidence for the formation of coordination complexes on the surface was obtained. Furthermore, three luminescent Ir(III) complexes with L4-SAc as ancillary ligand have been synthesized and characterized. Com-parison of the photoluminescent properties with the analogous unsubstituted bpy-complexes showed for C6, C7 and C8 blue-shifted emission maxima. For C7 and C8, the quantum yield was increased.

These changes can be attributed to the substituents on the bpy-ligand.

In Chapter 5, a new synthetic strategy to the DSSC anchoring ligand ALP was presented as well as to a new compound ALP2. For ALP, the improved synthesis should give higher yields than the one currently used. The preparation of the desired compound was not performed successfully, but the obtained intermediates showed promising results. For ALP2, the synthesis of the precursor

6 SUMMARY

were tried but did not work. Additionally, a possible new detection ligand L6 has been synthesized and characterized by¹H and¹³C NMR spectroscopy, IR spectroscopy and mass spectrometric meth-ods. Due to synthetic problems, only a small amount of L6 was obtained and no further sensing experiments were performed.

7 Experimental

7.1 General

1H, ¹³C, ¹⁹F and ³¹P NMR spectra were recorded using a Bruker Avance III-250, Avance III-400 and Avance III-500 NMR spectrometer. For full assignment additional COSY, HMBC and HMQC spetra were recorded on the Bruker Avance III-500. The chemical shifts δ were referenced to residual solvent peaks (chloroform: ¹H : 7.26 ppm,¹³C : 77.16 ppm, acetonitrile: ¹H : 1.94 ppm,¹³C : 118.26 ppm, DMSO: ¹H : 2.50 ppm,¹³C : 39.52 ppm, triuoroacetic acid: ¹H : 11.50 ppm).

Infrared spectra were recorded on a Shimadzu FTIR 8400 S Fourier-transform spectrophotometer with Golden Gate accessory for solid samples.

Solid state and solution absorption spectra were recorded on an Agilent 8453 spectrophotometer, for solution photo luminescence a Shimadzu RF-5301PC spectrouorometer was used. Solid state emission spectra were measured using a Hamamatsu Compact Fluorescence lifetime Spectrometer C11367-11 Quantaurus-Tau. Quantum yields were measured with a Hamamatsu absolute PL quan-tum yield spectrometer C11347 Quantaurus-QY.

Electron impact spectrometry was performed on a Finnigan MAT 95 spectrometer by Dr. P. Nadig.

Electrospray ionization (ESI) and MALDI-TOF mass spectra were recorded on Bruker esquire 3000 plus and Bruker Daltonics Microex mass spectrometers, respectively. LC-ESI-MS was measured on a Shimadzu Prominence UFLC and a Bruker amaZon X instrument. The microanalyses were performed with a Vario Micro Cube microanalyser by Sylvie Mittelheisser.

Microwave reactions were carried out in a Biotage Initiator^{T M} 8 reactor.

X-ray diraction data were collected on a Bruker-Nonius KappaAPEX diractometer with data reduction, solution and renement using the programs APEX2^[120] and SHELXL97.^[121]