Rational Design of a Copper Cobalt Sulfide/Tungsten Disulfide Heterostructure for Excellent Overall Water Splitting.

Integrating different components into a heterostructure is a novel approach that increases the number of active centers to enhance the catalytic activities of a catalyst. This study uses an efficient, facile hydrothermal strategy to synthesize a unique heterostructure of copper cobalt sulfide and tungsten disulfide (CuCo2S4-WS2) nanowires on a Ni foam (NF) substrate. The nanowire arrays (CuCo2S4-WS2/NF) with multiple integrated active sites exhibit small overpotentials of 202 (299) and 240 (320) mV for HER and OER at 20 (50) mA cm-2 and 1.54 V (10 mA cm-2) for an electrolyzer in 1.0 M KOH, surpassing commercial and previously reported catalysts. A solar electrolyzer composed of CuCo2S4-WS2 bifunctional electrodes also produced significant amounts of hydrogen through a water splitting process. The remarkable performance is accredited to the extended electroactive surface area, reasonable density of states near the Fermi level, optimal adsorption free energies, and good charge transfer ability, further validating the excellent dual function of CuCo2S4-WS2/NF in electrochemical water splitting.

A novel small-molecule IAP antagonist, AZD5582, draws Mcl-1 down-regulation for induction of apoptosis through targeting of cIAP1 and XIAP in human pancreatic cancer.

Inhibitor of apoptosis proteins (IAPs) plays an important role in controlling cancer cell survival. IAPs have therefore attracted considerable attention as potential targets in anticancer therapy. In this study, we investigated the anti-tumor effect of AZD5582, a novel small-molecule IAP inhibitor, in human pancreatic cancer cells. Treating human pancreatic cancer cells with AZD5582 differentially induced apoptosis, dependent on the expression of p-Akt and p-XIAP. Moreover, the knockdown of endogenous Akt or XIAP via RNA interference in pancreatic cancer cells, which are resistant to AZD5582, resulted in increased sensitivity to AZD5582, whereas ectopically expressing Akt or XIAP led to resistance to AZD5582. Additionally, AZD5582 targeted cIAP1 to induce TNF-α-induced apoptosis. More importantly, AZD5582 induced a decrease of Mcl-1 protein, a member of the Bcl-2 family, but not that of Bcl-2 and Bcl-xL. Interestingly, ectopically expressing XIAP and cIAP1 inhibited the AZD5582-induced decrease of Mcl-1 protein, which suggests that AZD5582 elicits Mcl-1 decrease for apoptosis induction by targeting of XIAP and cIAP1. Taken together, these results indicate that sensitivity to AZD5582 is determined by p-Akt-inducible XIAP phosphorylation and by targeting cIAP1. Furthermore, Mcl-1 in pancreatic cancer may act as a potent marker to analyze the therapeutic effects of AZD5582.

On [Fe4S4]2+ -(mu2-SR)-M II bridge formation in the synthesis of an A-cluster analogue of carbon monoxide dehydrogenase/acetylcoenzyme A synthase.

The construction of a synthetic analogue of the A-cluster of carbon monoxide dehydrogenase/acetylcoenzyme synthase, the site of acetylcoenzyme A formation, requires as a final step the formation of an unsupported [Fe(4)S(4)]-(mu(2)-SR)-Ni(II) bridge to a preformed cluster. Our previous results (Rao, P. V.; Bhaduri, S.; Jiang, J.; Holm, R. H. Inorg. Chem. 2004, 43, 5833) and the work of others have addressed synthesis of dinuclear complexes relevant to the A-cluster. This investigation concentrates on reactions pertinent to bridge formation by examining systems containing dinuclear and mononuclear Ni(II) complexes and the 3:1 site-differentiated clusters [Fe(4)S(4)(LS(3))L'](2-) (L' = TfO(-) (14), SEt (15)). The system 14/[{Ni(L(O)-S(2)N(2))}M(SCH(2)CH(2)PPh(2))](+) results in cleavage of the dinuclear complex and formation of [{Ni(L(O)-S(2)N(2))}Fe(4)S(4)(LS(3))]- (18), in which the Ni(II) complex binds at the unique cluster site with formation of a Ni(mu(2)-SR)(2)Fe bridge rhomb. Cluster 18 and the related species [{Ni(phma)}Fe(4)S(4)(LS(3))](3)- (19) are obtainable by direct reaction of the corresponding cis-planar Ni(II)-S(2)N(2) complexes with 14. The mononuclear complexes [M(pdmt)(SEt)]- (M = Ni(II), Pd(II)) with 14 in acetonitrile or Me(2)SO solution react by thiolate transfer to give 15 and [M(2)(pdmt)(2)]. However, in dichloromethane the Ni(II) reaction product is interpreted as [{Ni(pdmt)(mu(2)-SEt)}Fe(4)S(4)(LS(3))](2-) (20). Reaction of Et(3)NH(+) and 15 affords the double cubane [{Fe(4)S(4)(LS(3))}(2)(mu(2)-SEt)](3-) (21). Cluster 18 contains two mutually supportive Fe-(mu(2)-SR)-Ni(II) bridges, 19 exhibits one strong and one weaker bridge, 20 has one unsupported bridge (inferred from the (1)H NMR spectrum), and 21 has one unsupported Fe-(mu(2)-SR)-Fe bridge. Bridges in 18, 19, and 21 were established by X-ray structures. This work demonstrates that a bridge of the type found in the enzyme A-clusters is achievable by synthesis and implies that more stable, unsupported single thiolate bridges may require reinforcement by an additional covalent linkage between the Fe(4)S(4) and nickel-containing components. (LS(3) = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-); L(O)-S(2)N(2) = N,N'-diethyl-3,7-diazanonane-1,9-dithiolate(2-); pdmt = pyridine-2,6-methanedithiolate(2-); phma = N,N'-1,2-phenylenebis(2-acetylthio)acetamidate(4-); TfO = triflate.).

Reactions of arachno-6,8-C2B7H12- with electron deficient olefins: syntheses of cyano-substituted carboranes.

The syntheses of new cyano-substituted derivatives of arachno-6,8-C(2)B(7)H(13) have been achieved through the addition reactions of the arachno-6,8-C(2)B(7)H(12)(-) (1-) anion with cyano-activated olefins. The reaction of PSH+1- with tetracyanoethylene (TCNE) yielded the unusual bridging compound PSH(+)endo-6-endo-7-[micro(2)-(C(CN)(2))(2)]-arachno-6,8-C(2)B(7)H(12)(-) (PSH+2-)) resulting from cycloaddition of the TCNE at the C6-B7 edge of the anion. Consistent with its hypho skeletal electron count, an X-ray crystallographic study and DFT/GIAO calculations confirm 2(-) has a more open structure than 1-. The reaction of 1- with acrylonitrile resulted in the formation of endo-6-(NCCH(2)CH(2))-arachno-6,8-C(2)B(7)H(11)(-) (3-), which, upon acidification, afforded endo-6-(NCCH(2)CH(2))-arachno-6,8-C(2)B(7)H(12) (3) in high yield. X-ray crystallographic and DFT/GIAO studies established that the cyanoethyl fragment in 3 is substituted at the endo-position of the C6 cage-carbon. Heating 3 in THF at 50 degrees C or in toluene at 110 degrees C resulted in the quantitative isomerization of the cyanoethyl-substituent from the endo- to the exo-position at C6 to yield exo-6-(NCCH(2)CH(2))-arachno-6,8-C(2)B(7)H(12) (4). This is the first example of an endo to exo isomerization to be observed at a cage-carbon of a carborane. While heating 3 resulted in isomerization to 4, heating 3- in the presence of a small amount of 3 yielded the new ethylene-bridged 10-vertex tricarbaborane micro(6,9)-(CH(2)CH(2))-arachno-5,6,9-C(3)B(7)H(11) (5) resulting from reduction of the 3- pendant nitrile group, followed by deammination and carbon insertion.

Syntheses, characterizations, and coordination chemistry of the 10-vertex phosphadicarbaboranes 6-R-arachno-6,8,9-PC2B7H11 and 6-R-arachno-6,5,7-PC2B7H11.

The 10-vertex phosphadicarbaboranes, 6-R-arachno-6,8,9-PC(2)B(7)H(11) (1) (R = Ph 1a or Me 1b) and 6-R-arachno-6,5,7-PC(2)B(7)H(11) (2) (R = Ph 2a or Me 2b) have been synthesized using in situ dehydrohalogenation reactions of RPCl(2) (R = Ph or Me) with the arachno-4,5-C(2)B(7)H(13) and arachno-4,6-C(2)B(7)H(13) carboranes, respectively. X-ray crystallographic determinations in conjunction with DFT/GIAO/NMR calculations and NMR spectroscopic studies have established that both 1 and 2 have open cage structures based on an icosahedron missing two vertexes. The two isomeric compounds differ in the positions of the carbons and bridging hydrogens on the open face. Studies of the reactions of 2a with BH(3).THF, S(8), and hydrogen peroxide demonstrated that 2a shows strong donor properties yielding the compounds endo-6-H(3)B-exo-6-Ph-arachno-6,5,7-PC(2)B(7)H(11) (3), endo-6-S-exo-6-Ph-arachno-6,5,7-PC(2)B(7)H(11) (4), and endo-6-O-exo-6-Ph-arachno-6,5,7-PC(2)B(7)H(11) (5) in which the BH(3), S, and O substitutents are bonded to an electron lone pair localized at the phosphorus endo-position. The reaction of 2a with an excess of S(8) results in the loss of a framework boron to produce the unique open-cage compound micro(7,8)-[HS(Ph)P]-hypho-7,8-C(2)B(6)H(11) (6). 2a also formed the donor complexes cis-(eta(1)-[6-Ph-arachno-6,5,7-PC(2)B(7)H(11)])(2)PtBr(2) (7) and trans-(eta(1)-[6-Ph-arachno-6,5,7-PC(2)B(7)H(11)])(2)PdBr(2) (8) in which the metal fragment is bonded in an eta(1)-fashion at the phosphorus endo-position. In these complexes, 2a is functioning as a two-electron sigma donor to the metals and can thus be considered as an analogue of the PR(3) ligands in the classical cis-(PPh(3))(2)PtBr(2) and trans-(PPh(3))(2)PdBr(2) coordination complexes. Although 1a did not show the donor properties exhibited by 2a, its dianion 6-Ph-6,8,9-PC(2)B(7)H(9)(2)(-) (1a(2)()(-)()) readily formed eta(4)-coordinated complexes with late transition metals including 8-Ph-7-(Ph(3)P)(2)-nido-7,8,10,11-PtPC(2)B(7)H(9) (9), 7-Ph-11-(eta(5)-C(5)H(5))-nido-11,7,9,10-CoPC(2)B(7)H(9) (10), and commo-Ni-(7-Ni-8'-Ph-nido-8',10',11'-PC(2)B(7)H(9))(7-Ni-8-Ph-nido-8,10,11-PC(2)B(7)H(9)) (11).