LIST OF SCHEMES
Chapter 5 Instrumentation and Experimental Techniques
5.1 General reagents and solvents
Caution: Aryl amines should be treated as potential carcinogens and all azides considered potentially explosive and treated with care.
Precursors and solvents were purchased from Alfa Aesar, Sigma/Aldrich or Fisher Scientific and purified where appropriate or otherwise used as received. Dimethylsulphoxide (DMSO;
spectrophotometer grade), hydrochloric acid, ammonium hydroxide, aminobenzonitrile, 4-aminobenzoic acid, 2-ethynylpyridine, sodium azide, copper chloride, cobalt chloride, nickel chloride, cadmium chloride, phenylacetylene, iron chloride and sodium ascorbate were obtained from Sigma Aldrich. Dichloromethane, hexane, methanol, chloroform, ethyl acetate, diethyl ether, ethanol, magnesium sulphate (anhydrous) were purchased from Fisher Scientific. 4-Chloroaniline, tert–butanol, aniline, sodium nitrite and magnesium chloride were boughtfrom Aldrich and 4-fluoroanline, 4-methylaniline, 4-(trifluoromethyl)aniline hydrochloride from Alfa Aesar.
5.2 General Instrumentation and Characterisation Methods
1H 13C, COSY, 13C–1H correlated NMR spectra were recorded on an ECS-400 MHz, JEOL multi nuclear F.T spectrometer with Optiplex 380 Delta 5.02 software, with tetramethylsilane (TMS) as an internal standard for 1H NMR analysis. Chemical shifts are reported in ppm downfield from tetramethylsilane (TMS), at 298 K with coupling constants (J) reported in Hertz (Hz). Standard abbreviations indicating multiplicity were used as follows: m = multiplet, t = triplet, d = doublet and s = singlet.
Accurate mass spectrometry data, of samples, was collected at the EPSRC (engineering and Physical Sciences Research Council) mass spectrometry service centre, University of Wales, Swansea Thermofisher LTQ Orbitrap XL; HRMS (N-NSI) or (P+NSI) Positive or Negative ion (nano-electrospray) spectrometer, while the ionisation was electrospray (ESI+ and ES-) Thermofisher LTQ Orbitrap XL was used to analyse volatile molecules in the mass range m/z 50–2000 or m/z 200–4000 Daltons. Positive Electrospray (ESI-MS) mass spectra time of flight (TOF) (MALDI-TOF), were recorded on Voyager instrument DE-STR used to analyse volatile molecules in the mass range 200 to 200000 Daltons. Facility at Swansea University
94 and at the Department of Chemistry at University of Sheffield using (HRMS TOF/(ESI+)).
The instrument used was the ‘WATERS LCT premier’, the ionisation was electrospray (ESI+), the solvent was Water/Acetonitrile (1:3), (water: acetonitrile = 1:3). All strucral characteristion spectra are presented in the Appendices.
Single-crystal X-ray diffraction data and analyses were performed in the Chemical Crystallography Laboratory at the EPSRC National Crystallography Service, School of Chemistry, University of Southampton, United Kingdom. Single crystal diffraction data were collected using either a Nonius-kappa CCD area detector mounted at the window of an FR591 rotating anode generator (Mo Kα, λ=0.71073A); Rigaku Saturn 724+ area detector mounted at the window of an FR-E+ rotating anode generator (Mo Kα, λ=0.71073Å) equipped with HF Varimax optics (100µm focus).
Fourier transform infrared spectra (ATR-FTIR IR) and (FTIR) were recorded using a smart diamond ATR attachment on a Thermo-Nicolet FT-IR Spectrophotometer (AVATAR 320) over the range 4000 to 400 cm-1.
Electronic spectra and UV-VIS spectra were recorded in 1cm2 path length quartz cell in a Perkin-Elmer Lambda 40 spectrophotometer from 245-1000 nm, by dilution of a 10-3M stock solution in DMSO at 294K. Fluorescence measurements were undertaken in 1cm2 path length quartz cuvettes on solutions with an absorbance < 0.1 au using a Hitachi fluorescence spectrophotometer, and the data analysed using the Hitachi FL solution software. The fluorescence quantum yield was determined by (1,1':4'1"- terphenyl; PTP ) dye as a reference with The ligand, complexes and the reference dye were excited at 276 nm, maintaining nearly equal absorbance (0.0954), and the emission spectra were recorded from 285 to 800 nm. All experiments were carried out at a concentration of (1 x 10-6 M).
Melting points were determined with a Stuart Scientific melting point – SMP1 (Bibby, UK) apparatus. Preparative thin layer chromatography plates Analtech (PTLC) were undertaken on 20 x 20 CM 2000 microns 12 x 12 cm silica plates, 2mm thick (ANALTECH), eluted with EtOAc/hexane (1:1) unless otherwise stated. After development the plates were examined under UV- 254nm, the individual band removed, then extracted with a suitable solvent, filtered to remove the solid silica and the filtrate evaporated under vacuum to give the pure
95 product. Thin layer chromatography plate Analtech, Inc. 75 Blue Hen Drive Newark, DE 19713 WWW.analtech.com 20x20 CM 2000 MICRONS.
Gas chromatography electron impact mass spectroscopy (GCEIMS) was carried out in house on a Hewlett Packard (HP), model 5890GC interfaced to a HP 5972 mass selective detector (MSD) quadropole spectrometer with mass fragmentation by electron impact (EI) ionisation.
Gas chromatographic separation was undertaken on a RTX – 5MS column, (15m x 0.25mm x 0.25μm Restek; Cat no. 12620), helium gas carrier, column head pressure = 7psi, inlet temp, 275 oC and injector, 1 μl.
Conductivity measurements were carried out using aqueous DMSO solutions (1.0 x 10-3 M) at 294K using a Hanna digital conductivity meter (model EC 214) with a conductivity electrode, type H1 76300 Conductivity measurements were carried out by using 10-3M concentrations of the complexes in DMSO (294 K)
Following instructions from the manufacturer. Magnetic susceptibility of complexes were recorded at room temperature (294K) using a magnetic susceptibility balance (Johnson Matthey Catalytic Systems Division Equipment).
Bioligal activity studies were carried out on two human tumour cell lines, HepG2: Hepatoma Cells (hepatic carcinoma from a 15 years old child) (Cyprotex) and HCT116: Colorectal Cancer Cell (gift from Kids Can) at the school of environmental and life sciences Salford university.
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Chapter 6 : SYNTHESIS OF (1,2,3-TRIAZOL-4-YL)-PYRIDINE LIGANDS VIA A CLICK APPROACH
6.1 Introduction
The initial objective of this work, as previously stated, was to prepare novel metal complexes using bidentate ligands ((1,2,3-triazol-4-yl)-pyridine based) which were synthesised via the Cu(I)-catalysed alkyne–azide (CuAAC) (‘click chemistry’) reaction from a wide range of substrates. It was intended to assess the potential applications of these metal complexes in dye-based solar cells and for screening as potential anti-cancer drugs. During the course of this project a paper was published detailing the synthesis of the ligands, how the metal complexes and their X-ray structures were determined and what a novel packing pattern they displayed.
During the course of this research, many of the synthesised ligands have not been reported before, nor have they been characterised. Knowledge of their structure and characteristics is important to be able to estimate whether the coupling of these ligands to metallic ions would yield the required photochemical performance of the intended dye solar cells. The novelty of this work has been highlighted in the paper published in Acta Crystallographica Section B, 70, 379–389 (2014).
6.1.1 Synthesis of 4-(4-phenyl-1H-[1, 2,3]-triazol-1-yl)benzoic acid (L1)
Before embarking on this task, the click ligand 4-(4-phenyl-1H-[1,2,3]-triazol-1-yl)benzoic acid (L1) was targeted as a model compound to validate the conditions used to successfully effect the Cu-catalysed regioselective click reaction between 4-azidobenzoic acid and commercially available phenylacetylene (Scheme 6.1).
Scheme 6.1: Proposed preparation route for 4-(4-phenyl-[1H-1,2,3]-triazol-1-yl)benzoic acid (L1).
97 4-Azidobenzoic acid was chosen for use in this reaction in view of its easy preparation, from 4-aminobenzoic acid [1-3], as shown in the Scheme 6.2 (see below) using the Sandmeyer reaction.