Sarmistha Halder

Synthesis, structure, spectroscopic properties and cytotoxic effect of some thiosemicarbazone complexes of palladium

Reaction of salicylaldehyde thiosemicarbazone (H2L1), 2-hydroxyacetophenone thiosemicarbazone (H2L2) and 2-hydroxynaphthaldehyde thiosemicarbazone (H2L3) (general abbreviation H2L, where H2 stands for the two dissociable protons, one phenolic proton and one hydrazinic proton) with Na2[PdCl4] affords a family of polymeric complexes of type [{Pd(L)}n]. Reaction of the polymeric species with two monodentate ligands (D), viz. triphenylphosphine (PPh3) and 4-picoline (pic), has yielded complexes of type [Pd(L)(D)]. These mixed-ligand complexes have also been obtained from reaction of the thiosemicarbazones with [Pd(PPh3)2Cl2] and [Pd(pic)2Cl2]. Crystal structures of [Pd(L1)(PPh3)] and [Pd(L2)(pic)] have been determined. The [Pd(L)(D)] complexes show characteristic 1H NMR spectra and intense absorptions in the visible and ultraviolet region. They also fluoresce in the visible region at ambient temperature. In vitro cytotoxicity screenings of the complexes along with four human clinical drugsviz.cisplatin, BCNU, 5-fluorouracil (5-FU) and hydroxyurea have been carried out in two human tumor cell lines, namely promyelocytic leukemia HL-60 and histiocytic lymphoma U-937. [Pd(L2)(PPh3)] shows the lowest IC50 value and is found to be much more cytotoxic than the reference anticancer drugs in both the cell lines. An apoptosis study in HL-60 with [Pd(L2)(PPh3)] confirms that at 10 µM concentration it induces apoptosis to a greater extent than cisplatin and camptothecin.

Mononuclear palladium and heterodinuclear palladium–ruthenium complexes of semicarbazone ligands: synthesis, characterization, and application in C–C cross-coupling reactions

Reaction of salicylaldehyde semicarbazone (L1), 2-hydroxyacetophenone semicarbazone (L2), and 2-hydroxynaphthaldehyde semicarbazone (L3) with [Pd(PPh3)2Cl2] in ethanol in the presence of a base (NEt3) affords a family of yellow complexes (1a, 1b and 1c, respectively). In these complexes the semicarbazone ligands are coordinated to palladium in a rather unusual tridentate ONN-mode, and a PPh3 also remains coordinated to the metal center. Crystal structures of the 1b and 1c complexes have been determined, and structure of 1a has been optimized by a DFT method. In these complexes two potential donor sites of the coordinated semicarbazone, viz. the hydrazinic nitrogen and carbonylic oxygen, remain unutilized. Further reaction of these palladium complexes (1a, 1b and 1c) with [Ru(PPh3)2(CO)2Cl2] yields a family of orange complexes (2a, 2b and 2c, respectively). In these heterodinuclear (Pd–Ru) complexes, the hydrazinic nitrogen (via dissociation of the N–H proton) and the carbonylic oxygen from the palladium-containing fragment bind to the ruthenium center by displacing a chloride and a carbonyl. Crystal structures of 2a and 2c have been determined, and the structure of 2b has been optimized by a DFT method. All the complexes show characteristic 1H NMR spectra and, intense absorptions in the visible and ultraviolet region. Cyclic voltammetry on all the complexes shows an irreversible oxidation of the coordinated semicarbazone within 0.86–0.93 V vs. SCE, and an irreversible reduction of the same ligand within −0.96 to −1.14 V vs. SCE. Both the mononuclear (1a, 1b and 1c) and heterodinuclear (2a, 2b and 2c) complexes are found to efficiently catalyze Suzuki, Heck and Sonogashira type C–C coupling reactions utilizing a variety of aryl bromides and aryl chlorides. The Pd–Ru complexes (2a, 2b and 2c) are found to be better catalysts than the Pd complexes (1a, 1b and 1c) for Suzuki and Heck coupling reactions.

Comparative anti-proliferative activity of some new 2-(arylazo)phenolate–palladium (II) complexes and cisplatin against some human cancer cell lines

Abstract In this study, we report the synthesis of four 2-(arylazo)phenol–Pd(II) complexes and their anti-proliferative property against the human lung cancer (A549), cervical cancer (HeLa), and ovarian teratocarcinoma (PA-1) cell lines with cisplatin as the gold standard. One of the complexes, [Pd(L2)2], induced robust apoptosis in all the chosen cells, as revealed by annexin-V-positive/propidium iodide dual staining, increased sub-G1 cell cycle population, and significant morphological changes in the treated cells. The Pd complex inflicted mitochondrial dysfunction leading to mitochondrial membrane potential loss, reactive oxygen species generation and release of cytosolic cytochrome c that activated caspase-9 and caspase-3 proteins which finally caused programmed cell death.

Formation of organorhodium complexes via C–H bond activation of 1,3-di(phenylazo)benzene

Reaction of a potential NCN-pincer ligand, viz. 1,3-di(phenylazo)benzene (L), with [Rh(PPh(3))(3)Cl] affords, via a C-H bond activation, an interesting dinuclear Rh(II) complex (1), and with RhCl(3)·3H(2)O affords a mononuclear Rh(III) complex (2) containing a catalytically useful Rh-OH(2) fragment.