The relationship between structural and chemical properties of synthesized o-, m- and p-isomers of monoaldoxime derivatives of the pyridinium cation and their bis(pyridinium aldoxime) analogues has been established by means of spectroscopic techniques and X-ray diffraction. Ionization ability in the order o- > p- > m-isomer, determined in aqueous media, was found to be in good agreement with their structural differences and consequent resonance stabilization of their aldoximato zwitterions. Cytotoxic and antibacterial properties were tested for all compounds on selected human cell lines and bacterial strains. Their ability and mode of coordination were determined by monitoring their solution reactions with aquapentacyanoferrate(II) ion. Deduced kinetic parameters for the formation and dissociation of the corresponding pentacyano(ligand)ferrate(II) complexes have been correlated with - and -bonding properties of the examined pyridinium aldoxime ligands. Sterically influenced formation rates were in accordance with a number of donor atoms and the charge within the ligands. The slightly pH-dependent dissociation rates along with presence of the MLCT band in the electronic spectra strongly support the iron(II) coordination through the nitrogen atom of aldoxime group. According to the values of dissociation rate constants, all complexes can be classified as labile while all ligands as moderate -acceptors. Spectroscopic and thermogravimetric analysis of the isolated solids support the fact that all complexes are mononuclear pentacyano(ligand)ferrates(II).