Subrato Bhattacharya

Synthesis of glycoconjugate benzothiazoles via cleavage of benzotriazole ring.

A concise and efficacious benzotriazole-mediated novel two-step protocol has been developed for easy access to glycoconjugate benzothiazoles from protected carbohydrates. The benzotriazolemethanethione 3, prepared by the reaction of free alcohol with bis(1H-benzo[1,2,3]triazol-1-yl)methanethione, on treatment with silanes or stannane under heating or microwave irradiation undergoes free radical β-scission of N-N bond and affords diverse range of 2-O-substituted benzothiazoles 4 via cyclative elimination of molecular nitrogen. The structures of all of the compounds have been elucidated using IR, NMR, MS, and elemental analysis, and five of them have been characterized by single-crystal X-ray analysis.

The chemistry of cadmium-thiocarboxylate derivatives: synthesis, structural features, and application as single source precursors for ternary sulfides.

Novel heterobimetallic complexes [(PPh(3))(2)Cu(μ-SCOPh)(2)Cd(SCOPh)] (2a), [(PPh(3))(2)Cu(μ-SCOth)(2)Cd(SCOth)] (2b), [(PPh(3))(2)Ag(μ-SCOth)(2)Cd(SCOth)] (3a), [(PPh(3))(2)Ag(μ-SCOth)(2)Cd(H(2)O)(SCOth)] (3b), [(PPh(3))(2)Ag(μ-SCOPh)(2)Cd(SCOPh)] (3c), and a bimetallic complex [PPh(3)Cd(μ-SCOth)SCOth](2)·CH(2)Cl(2) (5) (th = thiophene) were prepared and characterized by single crystal X-ray diffraction analysis. A coordination polymer [Cd(SCOPh)(2)](n) (4) has also been characterized structurally that exhibited metal-like electrical conductivity. The heterobimetallic complexes on pyrolyzing under controlled conditions yielded ternary sulfides of composition CuCd(7)S(8), CuCd(10)S(11), Ag(2)Cd(8)S(9), and Ag(2)Cd(5)S(6), which have been characterized by SEM-EDX and X-ray diffractometry. Photophysical properties and electrical conductivities of the sulfides have also been studied.

Neutral five-co-ordinate gallium(III) and indium(III) complexes derived from sulfur ligands

Five-co-ordinated gallium(III) and indium(III) complexes, GaCl[PhC(S)CHC(O)Ph]2, GaCl(S2CNR2)2(R = Me, Pri or NR2= pyrrolyl) and InCl(S2CNPri2)2, have been synthesized and characterized. X-Ray crystallographic studies revealed a trigonal-bipyramidal structure for GaCl[PhC(S)CHC(O)Ph]2 and square-pyramidal structures for GaCl(S2CNMe2)2 and InCl(S2CNPri2)2. Also, Ga(S2CNC4H4)3 has been synthesized. Its molecular structure shows a GaS6 core approaching a trigonal-prismatic geometry.

ROS and RNS induced apoptosis through p53 and iNOS mediated pathway by a dibasic hydroxamic acid molecule in leukemia cells

Anticancer drugs induce apoptosis to cancer cells and also exhibit undesired toxicity to normal cells. Therefore development of novel agents triggering apoptosis and have low toxicity towards normal cells is most important. Hydroxamic acids suppress tumour cell growth through apoptosis but the underlying mechanism is poorly understood. Herein, we describe the apoptotic potential of a dibasic hydroxamic acid derivative, viz., oxayl bis (N-phenyl) hydroxamic acid (OBPHA), which induces apoptosis through generation of both ROS and NO in doxorubicin resistant T-lymphoblastic leukemia, CEM/ADR5000 cells. Present study discloses that OBPHA selectively kills cancerous cells irrespective of their drug resistant phenotype. We also determined the crystal structure of OBPHA to understand the structural requirements for apoptosis; the study reveals that the presence of substituted hydroxamic acid groups (-CO-NH-OH) favours the generation of NO possibly through auto degeneration. Along with the induction of caspase 3 mediated intrinsic apoptosis; OBPHA also activates p53 dependent signalling cascade and downregulates HDAC3 expression in a time dependent manner possibly due to increased ROS and NO production and simultaneous decrease in cellular GSH level. Thus ROS and NO mediated downstream signalling are essential for the anticancer effect of OBPHA. Therefore OBPHA, having a structurally relevant pharmacophore provides important insight into the development of new ROS and RNS generating chemicals inducing p53 dependent apoptosis.

Synthesis, structure, and catalytic activities of new Cu(I) thiocarboxylate complexes

Thiobenzoate complexes of Cu(I), [Cu(SCOPh)]n(1), [Cu(bpy)(µ-SCOPh)]2 (2), [Cu(dppf)(SCOPh)] (3), [where bpy = 2,2′-bipyridyl; dppf = [1,1′-bis(diphenylphosphino)ferrocene] were synthesized and structurally characterized by X-ray crystallography. NBO calculations were performed to understand the nature of the Cu–Cu (2.706 A) interaction in 2. All of the complexes were found to catalyze azide–alkyne cycloaddition for the regioselective synthesis of glycoconjugate triazoles under click reaction.

Synthesis of a one-dimensional coordination polymer containing pendant hydrosulfide groups

In view of the recent interest in compounds containing M-SH units, an organotin hydrosulfide compound, Me2Sn(SH)(O2CMe) (1) was prepared by controlled hydrolysis of the diorganotin thioacetate. Under similar mild hydrolytic conditions the corresponding benzoate could not be isolated. Instead, the thiobenzoate complex, Me2Sn(SOCPh)2 (3) was obtained in excellent yields indicating that there was no hydrolysis. Both 1 and 3 were characterized by X-ray crystallography. Some properties of the polymeric compound 1, such as spectral, electrical conductivity and NLO response were also studied. The reactivity and properties were explained using density functional calculations.

Studies of structural diversity due to inter-/intra-molecular hydrogen bonding and photoluminescent properties in thiocarboxylate Cu(I) and Ag(I) complexes

Seven new copper(I) thiocarboxylate and two silver thiocarboxylate complexes, containing 2-mercaptobenzimidazole (MB) and 2-mercapto-2-thiazoline (MT) have been synthesized and characterized by elemental analysis, IR, 1H NMR, 13C NMR and UV-Visible spectroscopic techniques. Molecular structures of all the complexes have been examined by single crystal X-ray diffraction analysis. In the case of complexes 1 ([(PPh3)2Cu(SCOMe)MB]) and 3 ([(PPh3)2Cu(SCOth)MB]), the direction of hydrogen bonding is changed from intra-molecular to inter-molecular by increasing the size of the R-group of the thiocarboxylate ligands. 7 ([Cu2(μ-SCOPh)2(μ-MT)(MT)]2) is a tetranuclear complex in which the distance between the two copper atoms is shorter than the sum of the covalent radii of the two atoms without having a formal covalent bond between them, as evidenced by NBO (DFT) calculation and bond critical point calculations using the AIM theory. In complex 8 two different molecules, [(PPh3)2Ag(SCOPh)MT] and [(PPh3)2Ag(SCOPh)] co-crystallized in the same lattice. The unit cell of complex 9 also possesses two structurally different molecules with the same molecular formula. Emission spectra of the complexes have been studied in both solution and solid states. Electronic spectral behaviors of the complexes 1 and 7 have been explained by TDDFT calculations.

Structural study on a sulfido-bridged dinuclear organotin(IV) complex with weak Sn ··· Sn bonding

A dinuclear anionic complex, Bu4N[Me2SnCl(S)ClSnMe2Br], has been synthesized in chloroform solution by reacting (Me2SnS)3, Me2SnCl2, and Bu4NBr. Attempts to isolate the anionic complex using tetramethylammonium cation were unsuccessful. The anion possesses two five-coordinate tin(IV) units bridged by sulfide and bromide. X-ray diffraction study revealed the possibility of a weak Sn–Sn bond in the complex. Theoretical (DFT) studies have been carried out to analyze the nature of metal–metal interaction in the complex.

A structural study on gallium and indium β-diketonates

In an attempt to prepare pentacoordinate chlorobis(β-diketonato) gallium(III) and indium(III) complexes only the corresponding tris-products, Ga(PhCOCHCOPh)3 (1), Ga(tBuCOCHCOtBu)3 (1a), and In(PhCOCHCOPh)3 (2), could be isolated. The crystal and molecular structures of 1 and 2 were determined. Both the complexes were found to have triclinc crystal system, with P1 space group. Cell parameters: 1 – a = 9.913(3) Å, b = 10.534(6) Å, c = 18.05(2) Å, α = 93.86(5)°, β = 94.40(4)°, γ = 106.58(4)°, V = 1805(2) Å3, z = 2; 2 – a = 10.507(3) Å, b = 11.448(3) Å, c = 16.322(4) Å, α = 107.38(2)°, β = 97.38(2)°, γ = 102.23(2)°, V = 1792(1) Å3, z = 2.

A Structural Study on Indium Tris-thiocarbamates

Indium tris(thiocarbamates) In(S2CNiPr2)3 (1), In(SOCNiPr2)3 (2) and In(S2CNC4H4)3 (3) have been synthesized and characterized. Variable temperature 1H NMR spectra of 1 and 2 are reported. The X-ray molecular structures of 1 and 3 are found to be quite similar; the symmetry of the In(S2C)3 unit in 3 is close to point group D3 with small asymmetry in the In-S bonds.