Singlet oxygen mediated DNA degradation by copper nanoparticles: potential towards cytotoxic effect on cancer cells

The DNA degradation potential and anti-cancer activities of copper nanoparticles of 4-5 nm size are reported. A dose dependent degradation of isolated DNA molecules by copper nanoparticles through generation of singlet oxygen was observed. Singlet oxygen scavengers such as sodium azide and Tris [hydroxyl methyl] amino methane were able to prevent the DNA degradation action of copper nanoparticles confirming the involvement of activated oxygen species in the degradation process. Additionally, it was observed that the copper nanoparticles are able to exert cytotoxic effect towards U937 and Hela cells of human histiocytic lymphoma and human cervical cancer origins, respectively by inducing apoptosis. The growth characteristics of U937 and Hela cells were studied applying various concentrations of the copper nanoparticles

Interface-engineered templates for molecular spin memory devices

The use of molecular spin state as a quantum of information for storage, sensing and computing has generated considerable interest in the context of next-generation data storage and communication devices(1, 2), opening avenues for developing multifunctional molecular spintronics(3). Such ideas have been researched extensively, using single-molecule magnets(4, 5) and molecules with a metal ion(6) or nitrogen vacancy(7) as localized spin-carrying centres for storage and for realizing logic operations(8). However, the electronic coupling between the spin centres of these molecules is rather weak, which makes construction of quantum memory registers a challenging task(9). In this regard, delocalized carbon-based radical species with unpaired spin, such as phenalenyl(10), have shown promise. These phenalenyl moieties, which can be regarded as graphene fragments, are formed by the fusion of three benzene rings and belong to the class of open-shell systems. The spin structure of these molecules responds to external stimuli(11, 12) (such as light, and electric and magnetic fields), which provides novel schemes for performing spin memory and logic operations. Here we construct a molecular device using such molecules as templates to engineer interfacial spin transfer resulting from hybridization and magnetic exchange interaction with the surface of a ferromagnet ; the device shows an unexpected interfacial magnetoresistance of more than 20 per cent near room temperature. Moreover, we successfully demonstrate the formation of a nanoscale magnetic molecule with a well-defined magnetic hysteresis on ferromagnetic surfaces. Owing to strong magnetic coupling with the ferromagnet, such independent switching of an adsorbed magnetic molecule has been unsuccessful with single-molecule magnets(13). Our findings suggest the use of chemically amenable phenalenyl-based molecules as a viable and scalable platform for building molecular-scale quantum spin memory and processors for technological development

Development of a facile antibody–drug conjugate platform for increased stability and homogeneity† †Electronic supplementary information (ESI) available: Synthetic schemes and characterization data, experimental procedures, Fig. S1 and S2. See DOI: 10.1039/c6sc05149a Click here for additional data file.

Despite the advances in the design of antibody–drug conjugates (ADCs), the search is still ongoing for novel approaches that lead to increased stability and homogeneity of the ADCs. We report, for the first time, an ADC platform technology using a platinum(ii)-based linker that can re-bridge the inter-chain cysteines in the antibody, post-reduction. The strong platinum–sulfur interaction improves the stability of the ADC when compared with a standard maleimide-linked ADC thereby reducing the linker–drug exchange with albumin significantly. Moreover, due to the precise conserved locations of cysteines, both homogeneity and site-specificity are simultaneously achieved. Additionally, we demonstrate that our ADCs exhibit increased anticancer efficacy in vitro and in vivo. The Pt-based ADCs can emerge as a simple and exciting proposition to address the limitations of the current ADC linker technologies

Palladium-carbon σ-bonded complexes bearing diphosphazane and diphosphazane monosulphide ligands^†

2422-2426The reactions of the diphosphazanes and diphosphazane monosulphides, Ph2P(E)N(R)PPh2 [E = lone pair, R = CHMe2 (1); E = lone pair, R = (S)-*CHMePh (2); E = S, R = CHMe2 (3); E = S, R = (S)-*CHMePh (4)] with [PdMeCl(COD)] yield the neutral chelate complexes of the type [PdMe{ҡ2-Ph2P(E)N(R)PPh2}Cl] (5,6, 8 and 9). The reactions of 1-3 with chlorobridged cyclometallated palladium azobenzene dimmers, [Pd {(C6H3-R'-4)-N=N-(C6H4-R' -4)(μ-Cl)]2 (Rʹ = H or OC6H13) in the presence of NH4PF6 yield cationic cyclopalladated complexes, [{ҡ2-(C6H3- R'-4)- N =N-(C6H4-R'-4)} Pd { ҡ2- Ph2P(E)N(R) PPh2}](PF6) (10-15). The molecular structure of [Pd{ҡ2-(C6H3-OC6H13-4)-N = N-(C6H4-OC6 H13-4)} {ҡ2-Ph2P(S)N(CHMe2)PPh2}](PF6) (15) has been determined by X-ray diffraction; the palladium bound carbon atom occupies the trans position with respect to the sulphur atom of the chelated diphosphazane monosulphide ligand

Steric and electronic effects in stabilizing allyl-palladium complexes of "P-N-P" ligands, X<SUB>2</SUB>PN(Me)PX<SUB>2</SUB> (X = OC<SUB>6</SUB>H<SUB>5</SUB> or OC<SUB>6</SUB>H<SUB>3</SUB>Me<SUB>2</SUB>-2,6)

The chemistry of &#951;3-allyl palladium complexes of the diphosphazane ligands, X2PN(Me)PX2 [X = OC6H5 (1) or OC6H3Me2-2,6 (2)] has been investigated.The reactions of the phenoxy derivative, (PhO)2PN(Me)P(OPh)2 with [Pd(&#951;3-1,3-R',R"-C3H3)(&#956;-Cl)]2 (R' = R" = H or Me; R' = H, R" = Me) give exclusively the palladium dimer, [Pd2{&#956;-(PhO)2PN(Me)P(OPh)2}2Cl2] (3); however, the analogous reaction with [Pd(&#951;3-1,3-R',R"-C3H3)(&#956;-Cl)]2 (R' = R" = Ph) gives the palladium dimer and the allyl palladium complex [Pd(&#951;3-1,3-R',R"-C3H3)(1)](PF6) (R' = R" = Ph) (4). On the other hand, the 2,6-dimethylphenoxy substituted derivative 2 reacts with (allyl) palladium chloro dimers to give stable allyl palladium complexes, [Pd(&#951;3-1,3-R',R"-C3H3)(2)](PF6) [R' = R" = H (5), Me (7) or Ph (8); R' = H, R" = Me (6)].Detailed NMR studies reveal that the complexes 6 and 7 exist as a mixture of isomers in solution; the relatively less favourable isomer, anti-[Pd(&#951;3-1-Me-C3H4)(2)](PF6) (6b) and syn/anti-[Pd(&#951;3-1,3-Me2-C3H3)(2)](PF6) (7b) are present to the extent of 25% and 40%, respectively. This result can be explained on the basis of the steric congestion around the donor phosphorus atoms in 2. The structures of four complexes (4, 5, 7a and 8) have been determined by X-ray crystallography; only one isomer is observed in the solid state in each case

Palladium(II) allyl complexes of chiral diphosphazane ligands: ambident coordination behaviour and stereodynamic studies in solution

The chemistry of eta(3)-allyl palladium complexes of pyrazolyl substituted diphosphazane ligands, Ph2P(E) N(R) PPh( N2C3HMe2-3,5) [E = lone pair, R = CHMe2 (1); E = lone pair, R = (S)-* CHMePh (2); E = S, R = CHMe2 (3)] bearing a stereogenic phosphorus centre has been investigated and the complexes, [Pd(eta(3)-1,3-R'(2)-C3H3){kappa(2)-Ph2P(E) N( R) PPh(N2C3HMe2-3,5)}](PF6) [E = lone pair or sulfur; R = CHMe2 or (S)-* CHMePh; R' = H, Me or Ph; 4-13], have been isolated. Detailed NMR studies reveal that these complexes exist as a mixture of isomers in solution. The structures of four complexes have been determined by X-ray crystallography and only one isomer is observed in the solid state in each case. The allyl complexes formed by ligands 1 and 2 display a P, N-coordination mode except the 1,3-diphenyl allyl complex, [Pd(eta(3)-1,3-Ph-2-C3H3 {kappa(2)-Ph2PN(CHMe2)PPh(N2C3HMe2-3,5)}](PF6) (8), which shows the presence of both P, N- and P, P-coordinated isomers in solution with the former predominating. On the other hand, the complexes bearing the diphosphazane monosulfide ligand 3 display P,S-coordination. Two-dimensional phase sensitive H-1-H-1 NOESY and ROESY measurements indicate that several of the above allyl palladium complexes undergo syn-anti and/or cis-trans isomerization in solution through an eta(1)-intermediate formed by the opening of the eta(3)-allyl group selectively at the trans position with respect to the phosphorus centre. Preliminary investigations show that the diphosphazanes (1 and (SR)-2) function as efficient auxiliary ligands for catalytic allylic alkylation reactions but lead to only low levels of enantiomeric excess

Stereo- and Regioselective Addition of Arene to Alkyne Using Abnormal NHC Based Palladium Catalysts: Elucidating the Role of Trifluoroacetic Acid in Fujiwara Process

Hydroarylation of alkyne was reported by Fujiwara nearly two decades back. Interestingly, this reaction does not proceed in the absence of trifluoroacetic acid; however, the exact role of TFA has not been unambiguously established, in particular with the support of X-ray crystallography by isolating the TFA-involved catalytically active species. In this work, abnormal N-heterocyclic carbene (<i>a</i>NHC) based Pd catalysts have been used for the efficient hydroarylation of aromatic C–H bonds leading to new C–C bond formation through regio- and stereoselective addition to alkynes. The addition reaction has been realized by a catalytic amount of Pd (II) compound (0.5 mol %) in trifluoroacetic acid (TFA) under ambient conditions. Various arenes undergo transhydroarylation selectively across the triple bond (containing functional groups CO₂Me, CO₂Et, and CO₂H), affording the kinetically controlled cis adduct predominantly in good yields. A simple reaction condition through an intermolecular reaction has been outlined under ambient conditions for the synthesis of coumarin derivatives, which are considered as an important class of bioactive compounds. It was noted that the reaction does not proceed in the absence of TFA. Hence, the major emphasis was given to understand the role of TFA in such hydroarylation reactions. A catalytically active reaction intermediate, [<i>a</i>NHCPd­(CF₃COO)]₂, containing trifluoroacetate anion was characterized as the first solid-state evidence by single-crystal X-ray crystallography, which helps to understand the exact role of TFA in such a reaction. A detailed mechanistic understanding of this fascinating catalytic process has been proposed by tandem experimental and computational experiments