Reaction of salicylaldehyde-2-picolinylhydrazone (HL)
Schiff base ligand with precursor compounds [{(
p-cymene)RuCl2}2] 1, [{(C6H6)RuCl2}2] 2, [{Cp*RhCl2}2] 3 and [{Cp*IrCl2}2] 4 yielded the corresponding neutral mononuclear compounds 5-8, respectively. The in vitro antitumor evaluation of the compounds 1-8 against Dalton's
ascites lymphoma (DL) cells by fluorescence-based apoptosis study and by their half-maximal inhibitory concentration (IC50) values revealed the high antitumor activity of compounds 3, 4, 5 and 6. Compounds 1-8 render comparatively lower apoptotic effect than that of
cisplatin on model non-
tumor cells, i.e., peripheral blood mononuclear cells (PBMC). The antibacterial evaluation of compounds 5-8 by
agar well-diffusion method revealed that compound 6 is significantly effective against all the eight bacterial species considered with zone of inhibition up to 35 mm. Fluorescence imaging study of compounds 5-8 with plasmid
circular DNA (pcDNA) and HeLa
RNA demonstrated their fluorescence imaging property upon binding with
nucleic acids. The docking study with some key
enzymes associated with the propagation of
cancer such as
ribonucleotide reductase,
thymidylate synthase, thymidylate
phosphorylase and
topoisomerase II revealed strong interactions between
proteins and compounds 5-8. Conformational analysis by density functional theory (DFT) study has corroborated our experimental observation of the N, N binding mode of
ligand. Compounds 5-8 exhibited a HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) energy gap 2.99-3.04 eV. Half-sandwich
ruthenium,
rhodium and
iridium compounds were obtained by treatment of
metal precursors with salicylaldehyde-2-picolinylhydrazone (HL) by in situ
metal-mediated deprotonation of the
ligand. Compounds under investigation have shown potential antitumor, antibacterial and fluorescence imaging properties. Arene
ruthenium compounds exhibited higher activity compared to that of Cp*Rh/Cp*Ir in inhibiting the
cancer cells growth and pathogenic bacteria. At a concentration 100 µg/mL, the apoptosis activity of arene
ruthenium compounds, 5 and 6 (~30 %) is double to that of Cp*Rh/Cp*Ir compounds, 7 and 8 (~12 %). Among the four new compounds 5-8, the
benzene ruthenium compound, i.e., compound 6 is significantly effective against the pathogenic bacteria under investigation.