Synthesis of Fluorescent Phosphorus Ligands
and their Applications in Medical Imaging and
Jennifer Fairbairn Wallis
Engineering Doctorate in Biopharmaceutical Process Development
Supervisor of Research: Dr Lee J. Higham
Industry Sponsor: High Force Research
School of Chemical Engineering – Newcastle University
This thesis reports the synthesis of novel, air-stable, fluorescent phosphorus-containing
compounds, based on a Bodipy backbone, and their applications in cell imaging and catalysis. The
syntheses of all the novel target compounds reported in this thesis are via a primary phosphine, an
under-utilised class of compound due to a hazardous reputation. Chapter 1 explores the stability of
primary phosphines, how they can be made user-friendly and the ability to create a library of novel
phosphorus compounds via the phosphorus-hydrogen bonds. The LJH group synthesised the first,
air-stable, fluorescent primary phosphine and Chapter 2 explores a second generation of this type
of ligand with an increased fluorescent quantum yield due to the addition of alkyne groups on the
boron atom. Chapter 3 details the coordination chemistry of primary phosphines to group 6 and 8
transition metals. Interestingly, the addition of the metals had different effects on the photophysical
properties, group 6 metal complexes retained high quantum yields, whereas group 8 metals
quenched the fluorescence, possibly due to the heavy atom effect.
Chapter 4 discusses the synthesis of fluorescent phosphonium salts which have the potential to be
used as trifunctional imaging agents. The three functions within the compounds include i) a
fluorophore, to provide in vitro fluorescence imaging, ii) a positive charge on the phosphorus atom
to introduce organelle specificity – in this case, to the mitochondria and iii) the inclusion of an 18F
radioisotope enables in vivo imaging techniques such as PET imaging. Chapter 5 shows further
versatility of fluorescent primary phosphines where we report the synthesis of a novel, chiral,
fluorescent phosphonite ligand that has been tested for its applications as a catalyst in asymmetric
hydrogenation reactions of a benchmark substrate. The results showed full conversion and an
enantiomeric excess (ee) of >99%. The final chapter discusses the importance of the aryl linker
between the Bodipy core and the phosphorus atom. The compounds synthesised in this chapter
show decreased fluorescence when the phosphorus atom is directly bound to the fluorophore and
have potential applications as a switch.
List of Publications
L. H. Davies, J. F. Wallis, M. R. Probert and L. J. Higham, Synthesis, Efficient multigram synthesis
of air-stable, fluorescent primary phosphines via palladium-catalyzed phosphonylation of aryl
bromides, 2014, 46, 2622-2628.
N. Fey, S. Papadouli, P. G. Pringle, A. Ficks, J. T. Fleming, L. J. Higham, J. F. Wallis, D.
Carmichael, N. Mézailles and C. Müller, Phosphorus, Sulfur, and Silicon and the Related Elements,
Setting P-Donor Ligands into Context: An Application of the Ligand Knowledge Base (LKB)
Approach, 2015, 190, 706-714.
S.Nigam, B. P. Burke, L. H. Davies, J. Domarkas, J. F. Wallis, P. G. Waddell, J. S. Waby, D. M.
Benoit, A. Seymour, C. Cawthorne, L. J. Higham and S. J. Archibald, Chem.Commun., Structurally
optimised Bodipy derivatives for imaging of mitochondrial dysfunction in cancer and heart cells,
2016, 52, 7114-7117.
L. H. Davies, J. F. Wallis, R. W. Harrington, P. G. Waddell & L. J. Higham, J. Coord. Chem., Air-
stable fluorescent primary phosphine complexes of molybdenum and tungsten, 2016, 69, 2069-
First, I would like to sincerely thank my supervisor Dr Lee J. Higham, for giving me this
opportunity and taking a chance on me! I have had the best time working with him and his research
group over the last few years. I have been given the chance to attend several international and
national conferences which have been quite an experience! Thank you for your patience and
guidance throughout this EngD course.
I would like to thank the EPSRC for funding, as well as High Force Research who were my
industrial sponsor. The team in the BBTC have been amazing throughout the years, so thank you
for all of your help.
A special thank you to Dr Laura Davies who taught me everything I know about Bodipy and all of
the special tricks required to synthesise them!
My time in the lab has been made significantly more entertaining and memorable by a number of
people: the old school LJH group members: Dr Arne Ficks, Dr Manuel Abelairas-Edesa, Dr Connor
Sibbald, Dr James Fleming, Dr Ana Cioran, the more recent LJH members: Charlotte Hepples,
Antonio Sanchez-Cid and Graeme Bowling (not forgetting adopted member Dr Tommy
Winstanley) and all of the other students within the Johnston Lab. A special mention to Manuel,
(we were the original Boss-Monkey team and he introduced me to Estrella Galicia and Faustino I),
James and Charlotte who have all assisted me with research in the lab, but have also created the
best memories outside of the lab, and hope that we will continue to meet up at our annual beer and
gin festivals throughout the year!
I could not have completed this work without the help of our fantastic crystallographer Dr Paul
Waddell, and NMR experts Dr Corinne Wills and Prof. William Mcfarlane, they have undoubtedly
helped me complete and understand this work.
Another special thank you to all of the academic research collaborators involved with this research,
especially Prof Steve Archibald and Dr Amy Reeve who both helped out with cell studies.
I have been lucky enough to work with several Erasmus and Masters Students and I’d especially
like to thank Francesca, Anna, Giorgia, Vince, Sophie, Tom and everyone else who contributed
towards the Bodipy research!
Finally I’d like to thank my amazing Dad for always believing in me and helping me get to where
I am today, even when I doubted myself he would always guide me and tell me I could do it - my
Mam would be so proud of what I have achieved. My sisters Katie and Rachael and my boyfriend
Chris have also been exceptionally patient during the last 5 years. I love you all!
β Beta particle
B3LYP Becke Parameter Lee-Yang-Parr
CT Computed Tomography
DFT Density Functional Theory
γ Gamma ray
HOMO Highest Occupied Molecular Orbital
HPLC High-Performance Liquid Chromatography
LMCT Ligand-to-Metal Charge Transfer
LUMO Lowest Unoccupied Molecular Orbital
99m Metastable isotope
MLCT Metal-to-Ligand Charge Transfer
MMCT Metal-to Metal Charge Transfer
MRI Magnetic Resonance Imaging
PET Positron Emission Tomography
PeT Photoinduced electron Transfer
RT Room Temperature
SOMO Singly Occupied Molecular Orbital
SPECT Single Photon Emission Computed Tomography
TLC Thin Layer Chromatography
CDCl3 Deuterated chloroform
DMSO Dimethyl sulfoxide
Et2O Diethyl ether
HP(O)(OEt)2 Diethyl phosphite
LiAlH4 Lithium aluminium hydride
MgSO4 Magnesium sulphate
Pd(OAc)2 Palladium(II) acetate
POBr3 Phosphoryl oxybromide
POCl3 Phosphoryl oxychloride
TFA Trifluoroacetic acid
°C Degrees Celsius
eV Electron Volts
ppm Parts per million
Experimental techniques terms:
APCI Atmospheric-Pressure Chemical Ionisation
δ Chemical shift
ε Molar Absorption Coefficient
EI Electron Ionisation
ESI Electrospray Ionisation
FTIR Fourier Transform Infrared Spectroscopy
HRMS High Resolution Mass Spectrometry
I Nuclear Spin
J Coupling Constant
LRMS Low Resolution Mass Spectrometry
NSI Nanospray Ionisation
NMR Nuclear Magnetic Resonance
ΦF Quantum yield
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