Tanmay Chatterjee

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.

Ammonium–crown ether based host–guest systems: N–H⋯O hydrogen bond directed guest inclusion featuring N–H donor functionalities in angular geometry

This article demonstrates crown ether based host–guest adduct formation in a series of crystalline solids 1–7, in which ammonium-type cationic guests have been integrated with various crown ethers. Addition of more than two equivalents of perchloric acid to an acetonitrile solution of 3-aminopyridine (3AmPy), 4,4′-diaminodiphenylmethane (DADPM) or 4,4′-diaminodiphenylether (DADPE) generates the doubly protonated anilinium (or ammonium) cationic species (written as 3AmPyH2, DADPMH2 and DADPEH2 respectively) which act as guests to the various crown ether hosts present in solution. The relevant compounds crystallize as their perchlorate salts and they have been structurally characterized through X-ray diffraction. The major driving force towards host–guest complexation in the compounds 1–7 is found to be the N–H⋯O hydrogen-bond interactions between the aforementioned guests and the crown ether hosts.

Cyclometalated Iridium(III) Complexes Containing 4,4′-π-Conjugated 2,2′-Bipyridine Derivatives as the Ancillary Ligands: Synthesis, Photophysics, and Computational Studies

This article demonstrates a series of cyclometalated Ir(III) complexes of the type [Ir(III)(C^N)2(N^N)](PF6), where C^N is 2-phenylpyridine, and N^N corresponds to the 4,4-π-conjugated 2,2-bipyridine ancillary ligands. All these compounds were synthesized through splitting of the binuclear dichloro-bridged complex precursor, [Ir(C^N)2(μ-Cl)]2, with the appropriate bipyridine ligands followed by the anion exchange reaction. The linear and nonlinear absorption properties of the synthesized complexes were investigated. The absorption spectra of all the title complexes exhibit a broad structureless feature in the spectral region of 350-700 nm with two bands being well-resolved in most of the cases. The structures of all the compounds were modeled in dichloromethane using the density functional theory (DFT) algorithm. The nature of electronic transitions was further comprehended on the basis of time-dependent DFT analysis, which indicates that the origins of various bands are primarily due to intraligand charge transfer transitions along with mixed-metal and ligand-centered transitions. The synthesized compounds are found to be nonemissive at room temperature because of probable nonradiative deactivation pathways of the T1 state that compete with the radiative (phosphorescence) decay modes. However, the frozen solutions of compounds Ir(MS 3) and Ir(MS 5) phosphoresce at the near-IR region, the other complexes remaining nonemissive up to 800 nm wavelength window. The two-photon absorption studies on the synthesized complexes reveal that values of the absorption cross-section are quite notable and lie in the range of 300-1000 GM in the picosecond case and 45-186 GM in the femtosecond case.

Coordination of lanthanide cation to an Anderson type polyoxometalate anion leads to isomorphous metal-oxide based one-dimensional inorganic solids: Synthesis, crystal structure and spectroscopy

AbstractOne-dimensional isomorphous inorganic polymers containing Anderson type heteropoly anion as a basic building unit, namely [La(H2O)7Cr(OH)6Mo6O18]n⋅4nH2O (1), [Gd(H2O)7Cr(OH)6Mo6O18]n⋅4nH2O (2), [Gd(H2O)7Al(OH)6Mo6O18]n⋅4nH2O (3), and [Eu(H2O)7Al(OH)6Mo6O18]n⋅4nH2O (4) have been synthesized and studied by the powdered X–ray diffraction, TGA, IR, electronic and ESR spectroscopy, and unambiguously by single crystal X-ray crystallography. Isomorphous compounds 1-4 are crystallized in orthorhombic system with Pca21 space group. The crystal structure analysis reveals a one-dimensional extended chain in which the Anderson type heteropolyanion, acting as the building unit, is linked by rare earth metal ions in a zig-zag fashion. In the crystal structure, all types of oxygens of the heteropolyanion, lattice waters, lanthanum coordinated waters are extensively involved in O—H ⋯O hydrogen bonding interactions. Compounds are additionally characterized by UV-visible and ESR spectroscopy.n Graphical AbstractA series of four one-dimensional isomorphous inorganic solids namely, [La(H2O)7Cr(OH)6Mo6O18]n•4nH2O (1), [Gd(H2O)7Cr(OH)6Mo6O18]n•4nH2O (2), [Gd(H2O)7Al(OH)6Mo6O18]n•4nH2O (3), and [Eu(H2O)7Al(OH)6Mo6O18]n•4nH2O (4) have been synthesized and characterized by the powdered X–ray diffraction studies, TG analysis, IR-, electronic- and ESR-spectroscopy, and unambiguously by single crystal X˗ray crystallography.