Synthesis and characterisation of pyrazine-based ligands for the analysis of metal-metal communication : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry at Massey University, Manawatū, New Zealand
Loading...
Date
2018
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
Pyrazine is an attractive molecule that has been incorporated as a bridging ligand between
two metal centres. These complexes have been shown to exhibit both magnetic and
electrochemical exchange between the metal centres through the pyrazine unit. Addition
of functionality onto the 2 and 5 position of pyrazine can reinforce the coordination of 3d
octahedral metal ions to the pyrazine ring.
The Schiff base condensation of A1 with various primary amine reactants produced three
unique ligand systems. The confirmed synthesis of these ligands was verified with a
variety of characterisation techniques. A single crystal structure was generated for one
ligand system (L3), which revealed both imine – π stacking interactions, as well as alkane
hydrogen – pyridine interactions.
Several complexations were attempted with the three ligand systems synthesised.
Manganese and cobalt complexes were successfully synthesised with L3, the single
crystal structures generated showed cyclohelicate triangles, which were unique at the
time. The electrochemical analysis of these complexes in MeCN showed similar redox
processes as was seen in the electrochemical analysis of L3. Signs of possible metal-metal
communication within the cyclohelicate triangles was also noticed, with oxidation (and
reduction) processes present. Further analysis is necessary to verify these interpretations,
including magnetic analysis. Complexations with identical metal salts and L2 could not
be characterised by SCXRD Other techniques such as mass spectrometry and
conductivity measurements indicated the likely formation of a polymorphic – potentially
cyclohelical structure with this ligand. Complexations with L1 incorporated the inclusion
of a larger collection of metal salts. Unfortunately, due to time constraints, only three
complexes were suitably characterised. From the various characterisation methods used, it was deduced that all three complexes were likely simple M2L1 systems, where the
coordination of the 6-coordinate 3d metal centres were accompanied by the coordination
of either water, solvent, counterion or a combination of these.
Description
Figures 1.2, 1.11 & 1.14 re-used with publishers' permission.
Keywords
Ligands, Synthesis, Pyrazines, Schiff bases, Complex compounds