Abstract:
This work aimed to develop, characterize, and investigate the cytotoxicity of five rhenium
(I) based compounds. The compounds designated Re2-pico, Re3-pico, Re4-pico,
Re(Phen), and Re2(Phen) were produced in yields of 35 to 60% using monodentate and
bidentate pyridine derivatives as ligands. The complexes were synthesized using a similar
protocol of refluxing in xylene for 4 hours using the appropriate stoichiometric ratios. Most
of the complexes exhibited different physical properties and solubility. The ligands in the
five complexes synthesized were found to all coordinate to the Rhenium metal centre
through the lone pair of electrons found on the Nitrogen atom in the pyridine ring. The
complexes’ structures were determined using FT-IR, ESI-MS, 1H-NMR, and Single
Crystal-XRD. Three of the crystalline complexes were successfully elucidated using
Single Crystal-XRD while the other two required more rigorous testing using other
characterization methods to elucidate their structures. The data obtained from the SC-
XRD was particularly helpful in characterization as it showed one of the complex's actual
structures was different from the proposed one. The Single crystal XRD data gave us
insight into the bond angles, bond length, geometry, and orientation of the atoms in space.
The 1H-NMR spectra showed characteristic aromatic peaks in the expected regions with
a downfield chemical shift which could be attributed to bonding to the rhenium metal
centre. MTT assay was used to determine the cytotoxicity of the compounds and the
protocol was optimized to get the best results possible in an efficient manner. An
absorbance plate reader determines the absorbance of samples in microplates by
sending light of known intensity through each well vertically and detecting the intensity
behind the sample. The absorbance values were measured at 450 nm using a microplate
reader and IC50 values were calculated using the Graphpad Prism 8 plotting software.
The experiment was repeated twice, with each complex and the control being measured
in triplicate. The most potent complex based on the calculations of the IC50 values was
Re2-pico, while the least potent was Re4-pico.
