Cyclo- and polyphosphazenes grafted with tridentate ligands coordinated to iron(II) and ruthenium(II) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Palmerston North
Loading...
Date
2011
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
This thesis sought to explore the chemical and physical properties of a series of cyclotriand
polyphosphazenes with substituted tridentate ligands coordinated to iron(II) and
ruthenium(II). There were two main objective of this research i) to graft spin crossover
(SCO) groups to a polymer backbone, potentially making a new malleable material, ii)
to demonstrate that ruthenium(II) complexes can be used to link groups to a
polyphosphazene backbone.
Seven cyclotriphosphazene (L1–L7) and four polyphosphazene (L1P–L4P) ligands1 were
synthesised with 2,6-di(pyridine-2-yl)pyridine-4(1H)-onate (OTerpy); 4-(2,6-
di{pyridin-2-yl}-pyridine-4-yl)phenolate (OPhTerpy); 2,6-di(1H-benzimidazol-2-
yl)pyridine-4(1H)-onate (Obbp); and 4-(2,6-di{1H-pyrazol-1-yl}pyridine-4-
yl)phenolate (OPhbpp) moieties. These ligands were subsequently coordinated to either
iron(II) or ruthenium(II) and the optical, vibrational, electrochemical and magnetic
properties of the subsequent small molecule complexes and polymers were measured.
Sixteen iron(II) complexes were synthesised by reacting iron(II) salts with the
respective ligand (L1–L7). Where X-ray crystal structures have been obtained, each of
the small molecule iron complexes were homoleptic. Using electronic absorbance,
resonance Raman (rR), magnetic and Mössbauer spectroscopy, it was shown that the
polymer complex cores in the resulting cross-linked polymers were the same as those of
the small molecule analogues (SMA). In addition, these techniques confirmed that the
iron complexes formed with the ligands L1, L2, L1P and L2P were each determined to be
low spin (LS), while those formed with L3 displayed SCO, and the iron complex formed
with L4 remained high spin (HS) for all temperatures while its polymeric analogue
remained LS for all measurable temperatures.
Fourteen ruthenium(II) small molecule complexes were synthesised by reacting
ruthenium complexes of the appropriate co-ligands (2,2':6',2"-terpyridine (Terpy); 2,6-
di(pyridin-2-yl)-4-phenylpyridine (PhTerpy); 2,6-di(1H-benzimidzol-2-yl)pyridine
(bbp); and 2,6-di(1H-pyrazol-1-yl)pyridine) with the respective ligand (L1–L4). Using
electronic absorption and rR spectroscopy it was determined that only the polymers L1P
and L2P formed complexes ([Ru(L1P)(Terpy)]Cl2, [Ru(L1P)(PhTerpy)]Cl2,
[Ru(L2P)(Terpy)]Cl2 and [Ru(L2P)(PhTerpy)]Cl2) analogous to that of their SMA
([Ru(L1)(Terpy)](PF6)2, [Ru(L1)(PhTerpy)](PF6)2, [Ru(L2)(Terpy)](PF6)2 and
[Ru(L2)(PhTerpy)](PF6)2), and are therefore the most suitable for linking groups to
polyphosphazenes.
Although the ruthenium-bbp-terpy based complexes proved to be unsuitable for
attaching groups to a phosphazene due to the low loading of metal complex on the
polymer (L3P), the SMA ([Ru(L1)(bbp)](PF6)2, [Ru(L2)(bbp)](PF6)2,
[Ru(L3)(Terpy)](PF6)2 and [Ru(L3)(PhTerpy)](PF6)2) displayed a dependence on the
basicity of the solution. As it was increased, the imidazole groups were deprotonated
causing a bathochromic shifting of the metal-to-ligand charge transfer, oxidation
potential and selected vibrational modes.
Description
CIF files are with the hard copy in the library.
Keywords
Polyphosphazenes, Iron, Ruthenium, Cyclotriphosphazene, Molecule synthesis