Synthesis and biological studies of ruthenium, rhodium and iridium metal complexes with pyrazole-based ligands displaying unpredicted bonding modes

Mono, bis and bridged half-sandwich platinum group metal complexes with thienyl pyrazole and furyl pyrazole have been synthesized, characterized and their activity over four bacterial strains and interaction towards biomolecule (CT-DNA) have been assessed. Orbital occupancy and energy gaps between H...

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Bibliographic Details
Published in:Inorganica Chimica Acta 2017-06, Vol.462, p.223-235
Main Authors: Basava Punna Rao, A., Gulati, Khushboo, Joshi, Nidhi, Deb, Debojit Kumar, Rambabu, D., Kaminsky, Werner, Poluri, Krishna Mohan, Kollipara, Mohan Rao
Format: Article
Language:English
Subjects:
Antibacterial
Antibiotics
Arene
Benzene
Bonding
Chemical synthesis
Coordination compounds
Density functional theory
Deoxyribonucleic acid
DNA
DNA binding studies
Electrophoresis
Energy gap
Fluorescence
Formulations
Furyl pyrazole
Iridium
Ligands
Molecular orbitals
Pyrazole
Rhodium
Ruthenium
Single crystals
Thienyl pyrazole
X-ray diffraction
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Summary:Mono, bis and bridged half-sandwich platinum group metal complexes with thienyl pyrazole and furyl pyrazole have been synthesized, characterized and their activity over four bacterial strains and interaction towards biomolecule (CT-DNA) have been assessed. Orbital occupancy and energy gaps between HOMO and LUMO on complexation have been rationalized by the density functional theory (DFT). Staphylococcus aureus; Bacillus thuringiensis; Escherichia coli and Pseudomonas aeruginosa have been considered for antibacterial activity. CT-DNA has been chosen as a biomolecule to elucidate the possible interaction between the new complexes and biomolecule. [Display omitted] •New mono, di and bridged half-sandwich d6 metal complexes have been synthesised.•Ligand moiety in pyrazole resulted in the formation of mono and dinuclear complexes.•Complexes are selective towards the gram-negative E. coli bacterium.•Biological study reveals an electrostatic interaction between complexes and CT-DNA. A series of new mono, di thienyl pyrazole (L1) and bridged furyl pyrazole (L2) complexes of arene ruthenium, rhodium and iridium {arene=benzene, p-cymene and Cp∗} have been synthesized and characterized by spectroscopic techniques. The formulations of these mono and di thienyl pyrazole complexes are as follows: [(arene)M(L1)Cl2], where M=Ru, arene=benzene (1), p-cymene (2); M=Rh, arene=Cp∗ (3) and M=Ir, arene=Cp∗ (4) [(arene)M(L1)2Cl]Cl, where M=Ru, arene=benzene (5), p-cymene (6); M=Rh, arene=Cp∗ (7) and M=Ir, arene=Cp∗ (8). The bridged furyl pyrazole complexes are formulated as [{(arene)MCl}2L2]PF6, where M=Ru, arene=benzene (9), p-cymene (10); M=Rh, arene=Cp∗ (11) and M=Ir, arene=Cp∗ (12). The structure of the complexes 1–7 and 10 has been established by single crystal X-ray diffraction studies. The orbital occupancy over the metal on complexation and energy gap between HOMO and LUMO of the complexes 1–6 have been analyzed by the density functional theory (DFT). The variation of the heterocyclic moiety in pyrazole ligands significantly alters bonding mode of the ligand. The in vitro antibacterial activity of the complexes 1–6 has been measured by the agar well diffusion assay by using human pathogenic gram-negative and gram-positive bacterial strains. The binding ability of the complexes 1–6 to the CT-DNA has been carried out by using various biophysical techniques viz. UV–Visible, fluorescence spectroscopy and agarose gel electrophoresis.
ISSN:0020-1693
1873-3255
DOI:10.1016/j.ica.2017.03.037