Rajendra Prasad Paitandi

Interaction of ferrocene appended Ru(II), Rh(III) and Ir(III) dipyrrinato complexes with DNA/protein, molecular docking and antitumor activity

Efficacy of the ferrocene appended piano-stool dipyrrinato complexes [(η(6)-C6H6)RuCl(fcdpm)] (1), [(η(6)-C10H14)RuCl(fcdpm)] (2), [(η(6)-C12H18)RuCl(fcdpm)] (3) [(η(5)-C5Me5)RhCl(fcdpm)] (4) and [(η(5)-C5Me5)IrCl(fcdpm)] (5) [fcdpm = 5-ferrocenyldipyrromethene] toward anticancer activity have been described. Binding of the complexes with calf thymus DNA (CT-DNA) and BSA (bovine serum albumin) have been thoroughly investigated by UV-Vis and fluorescence spectroscopy. Binding constants for 1-5 (range, 10(4)-10(5) M(-1)) validated their efficient binding with CT-DNA. Molecular docking studies revealed interaction through minor groove of the DNA, on the other hand these also interact through hydrophobic residues of the protein, particularly cavity in the subdomain IIA. In vitro anticancer activity have been scrutinized by MTT assay, acridine orange/ethidium bromide (AO/EtBr) fluorescence staining, and DNA ladder (fragmentation) assay against Daltons Lymphoma (DL) cells. Present study revealed that rhodium complex (4) is more effective relative to ruthenium (1-3) and iridium (5) complexes.

Triazole-appended BODIPY–piperazine conjugates and their efficacy toward mercury sensing

An expeditious synthesis of new click reaction-based BODIPY–piperazine conjugates separated by alkyl spacers (4–7) has been described. The compounds under investigation have been thoroughly characterized by various physicochemical techniques viz., elemental analyses, IR, HRMS, NMR (1H, 13C, 11B and 19F), electronic absorption, emission and theoretical studies. The comparative sensing abilities of 4–7 toward a range of metal ions have been investigated by various methods. Among these compounds, only 7 exhibited appreciable selectivity towards Hg2+, while the others remained inactive in the presence of various metal ions. Binding constant and Jobs plot analysis indicated 1 : 1 stoichiometry between 7 and Hg2+. HRMS data and theoretical studies undoubtedly indicated the formation of a 7·Hg2+ complex and interaction of Hg2+ with the probe via nitrogen atoms in the piperazine and triazole units.

Anticancer Activity of Iridium(III) Complexes Based on a Pyrazole-Appended Quinoline-Based BODIPY

A pyrazole-appended quinoline-based 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (L1, BODIPY) has been synthesized and used as a ligand for the preparation of iridium(III) complexes [Ir(phpy)2(L1)]PF6 (1; phpy = 2-phenylpyridine) and [(η5-C5Me5)Ir(L1)Cl]PF6 (2). The ligand L1 and complexes 1 and 2 have been meticulously characterized by elemental analyses and spectral studies (IR, electrospray ionization mass spectrometry, 1H and 13C NMR, UV/vis, fluorescence) and their structures explicitly authenticated by single-crystal X-ray analyses. UV/vis, fluorescence, and circular dichroism studies showed that complexes strongly bind with calf-thymus DNA and bovine serum albumin. Molecular docking studies clearly illustrated binding through DNA minor grooves via van der Waals forces and their electrostatic interaction and occurrence in the hydrophobic cavity of protein (subdomain IIA). Cytotoxicity, morphological changes, and apoptosis have been explored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Hoechst 33342 staining. IC50 values for complexes (1, 30 μM; 2, 50 μM) at 24 h toward the human cervical cancer cell line (HeLa) are as good as that of cisplatin (21.6 μM) under analogous conditions, and their ability to kill cancer cells lies in the order 1 > 2. Because of the inherent emissive nature of the BODIPY moiety, these are apt for intracellular visualization at low concentration and may find potential applications in cellular imaging and behave as a theranostic agent.

Substituent-directed ESIPT-coupled Aggregation-induced Emission in Near-infrared-emitting Quinazoline Derivatives

A series of ESIPT (excited state intramolecular proton transfer) active systems (HQz1-HQz6) derived from quinazoline have been reported. The ESIPT emission for these derivatives gets completely quenched in solvents with diverse polarities which have been restored via aggregation-induced emission (AIE) with large Stokes shift (up to 314 nm). It varied from 450 to 701 nm just by altering substituents at the para position of hydroxy group in the central phenyl ring. As well, HQz1-HQz6 displayed solid state emission [∼455 (blue) to ∼704 nm (red)]. The formyl group on the central hydroxy-phenyl ring of these derivatives induces ESIPT by increasing acidity of the hydroxy proton which has been followed by 1 H NMR studies. Further, it has been clearly shown that emission colour and aggregate morphology can be fine tuned by incorporating apt substituents. The present study offers a simple route to obtain colour tunable ESIPT emission via AIE which is very important for biological imaging and fabrication of optoelectronic devices.