The cardiovascular effects of inorganic arsenic have been documented, but the dose-response relationship between ischemic heart disease (ISHD) and long-term arsenic exposure remains to be elucidated. Mortality rates from ISHD among residents in 60 villages of the area in Taiwan with endemic arseniasis from 1973 through 1986 were analyzed to examine their association with arsenic concentration in drinking water. Based on 1 355 915 person-years and 217 ISHD deaths, the cumulative ISHD mortalities from birth to age 79 years were 3.4%, 3.5%, 4.7%, and 6.6%, respectively, for residents who lived in villages in which the median arsenic concentrations in drinking water were <0.1, 0.1 to 0.34, 0.35 to 0.59, and > or = 0.6 mg/L. A cohort of 263 patients affected with blackfoot disease (BFD), a unique arsenic-related peripheral vascular disease, and 2293 non-BFD residents in the endemic area of arseniasis were recruited and followed up for an average period of 5.0 years. There was a monotonous biological gradient relationship between cumulative arsenic exposure through drinking artesian well water and ISHD mortality. The relative risks were 2.5, 4.0 and 6.5, respectively, for those who had a cumulative arsenic exposure of 0.1 to 9.9, 10.0 to 19.9, and > or = 20.0 mg/L-years compared with those without the arsenic exposure after adjustment for age, sex, cigarette smoking, body mass index, serum cholesterol and triglyceride levels, and disease status for hypertension and diabetes through proportional-hazards regression analysis. BFD patients were found to have a significantly higher ISHD mortality that non-BFD residents, showing a multivariate-adjusted relative risk of 2.5 (95% CI, 1.1 to 5.4).

The first atomically and structurally precise silver-nanoclusters stabilized by Se-donor ligands, [Ag {Se P(O Pr) } ] (3) and [Ag {Se P(OEt) } ] (4), were isolated by ligand replacement reaction of [Ag {S P(O Pr) } ] (1) and [Ag {S P(O Pr) } ] (2), respectively. Furthermore, doping reactions of 4 with Au(PPh )Cl resulted in the formation of [AuAg {Se P(OEt) } ] (5). Structures of 3, 4, and 5 were determined by single-crystal X-ray diffraction. The anatomy of cluster 3 with an Ag core having C symmetry is very similar to that of its dithiophosphate analogue 1. Clusters 4 and 5 exhibit an Ag and Au@Ag core of O symmetry composed of eight silver capping atoms in a cubic arrangement and encapsulating an Ag and Au@Ag centered icosahedron, respectively. Both ligand exchange and heteroatom doping result in significant changes in optical and emissive properties for chalcogen-passivated silver nanoparticles, which have been theoretically confirmed as 8-electron superatoms.

A novel discrete [Ag21{S2P(OiPr)2}12](PF6) nanocluster has been synthesized and characterized by single-crystal X-ray diffraction and also NMR spectroscopy ((1)H, (31)P), ESI mass spectrometry, and other analytic techniques (XPS, EDS, UV/Vis spectroscopy). The Ag21 skeleton has an unprecedented silver-centered icosahedron that is capped by eight additional metal atoms. The whole framework is protected by twelve dithiophosphate ligands. According to the spherical Jellium model, the stability of monocationic nanocluster can be described by an 8-electron superatom with 1S(2) 1P(6) configuration, as confirmed by DFT calculations.

An air- and moisture-stable nanoscale polyhydrido copper cluster [Cu32 (H)20 {S2 P(OiPr)2 }12 ] (1H ) was synthesized and structurally characterized. The molecular structure of 1H exhibits a hexacapped pseudo-rhombohedral core of 14 Cu atoms sandwiched between two nestlike triangular cupola fragments of (2×9) Cu atoms in an elongated triangular gyrobicupola polyhedron. The discrete Cu32 cluster is stabilized by 12 dithiophosphate ligands and a record number of 20 hydride ligands, which were found by high-resolution neutron diffraction to exhibit tri-, tetra-, and pentacoordinated hydrides in capping and interstitial modes. This result was further supported by a density functional theory investigation on the simplified model [Cu32 (H)20 (S2 PH2 )12 ].

The syntheses of the first rhombicuboctahedral copper polyhydride complexes [Cu28 (H)15 (S2 CNR)12 ]PF6 (NR=N(n) Pr2 or aza-15-crown-5) are reported. These complexes were analyzed by single-crystal X-ray and one by neutron diffraction. The core of each copper hydride nanoparticle comprises one central interstitial hydride and eight outer-triangular-face-capping hydrides. A further six face-truncating hydrides form an unprecedented bridge between the inner and outer copper atom arrays. The irregular inner Cu4 tetrahedron is encapsulated within the Cu24 rhombicuboctahedral cage, which is further enclosed by an array of twelve dithiocarbamate ligands that subtends the truncated octahedron of 24 sulfur atoms, which is concentric with the Cu24 rhombicuboctahedron and Cu4 tetrahedron about the innermost hydride. For these compounds, an intriguing, albeit limited, H2 evolution was observed at room temperature, which is accompanied by formation of the known ion [Cu8 (H)(S2 CNR)6 ](+) upon exposure of solutions to sunlight, under mild thermolytic conditions, and on reaction with weak (or strong) acids.

The synthesis and structural determination of a silver nanocluster [Ag20 {S2 P(OiPr)2 }12 ] (2), which contains an intrinsic chiral metallic core, is produced by reduction of one silver ion from the eight-electron superatom complex [Ag21 {S2 P(OiPr)2 }12 ](PF6 ) (1) by borohydrides. Single-crystal X-ray analysis displays an Ag20 core of pseudo C3 symmetry comprising a silver-centered Ag13 icosahedron capped by seven silver atoms. Its n-propyl derivative, [Ag20 {S2 P(OnPr)2 }12 ] (3), can also be prepared by the treatment of silver(I) salts and dithiophosphates in a stoichiometric ratio in the presence of excess amount of [BH4 ](-) . Crystal structure analyses reveal that the capping silver-atom positions relative to their icosahedral core are distinctly different in 2 and 3 and generate isomeric, chiral Ag20 cores. Both Ag20 clusters display an emission maximum in the near IR region. DFT calculations are consistent with a description within the superatom model of an 8-electron [Ag13 ](5+) core protected by a [Ag7 {S2 P(OR)2 }12 ](5-) external shell. Two additional structural variations are predicted by DFT, showing the potential for isomerism in such [Ag20 {S2 P(OR)2 }12 ] species.

Dinitrosyl iron complex [(-SC(7)H(4)SN)(2)Fe(NO)(2)](-) (1) was prepared by reaction of [S(5)Fe(NO)(2)](-) and bis(2-benzothiozolyl) disulfide. In synthesis of the analogous dinitrosyl iron compounds (DNICs), the stronger electron-donating thiolates [RS](-) (R = C(6)H(4)-o-NHCOCH(3), C(4)H(3)S, C(6)H(4)NH(2), Ph), compared to [-SC(7)H(4)SN](-) of complex 1, trigger thiolate-ligand substitution to yield [(-SC(6)H(4)-o-NHCOCH(3))(2)Fe(NO)(2)](-) (2), [(-SC(4)H(3)S)(2)Fe(NO)(2)](-) (3), and [(SPh)(2)Fe(NO)(2)](-) (4), respectively. At 298 K, complexes 2 and 3 exhibit a well-resolved five-line EPR signal at g = 2.038 and 2.027, respectively, the characteristic g value of DNICs. The magnetic susceptibility fit indicates that the resonance hybrid of {Fe(+)((*)NO)(2)}(9) and {Fe(-)((+)NO)(2)}(9) in 2 is dynamic by temperature. The IR nu(NO) stretching frequencies (ranging from (1766, 1716) to (1737, 1693) cm(-)(1) (THF)) of complexes 1-4 signal the entire window of possible electronic configurations for such stable and isolable {Fe(NO)(2)}(9) [(RS)(2)Fe(NO)(2)](-). The NO-releasing ability of {Fe(NO)(2)}(9) [(RS)(2)Fe(NO)(2)](-) is finely tuned by the coordinated thiolate ligands. The less electron-donating thiolate ligands coordinated to {Fe(NO)(2)}(9) motif act as better NO-donor DNICs in the presence of NO-trapping agent [Fe(S,S-C(6)H(4))(2)](2)(2-). Interconversion between {Fe(NO)(2)}(9) [(RS)(2)Fe(NO)(2)](-) and {Fe(NO)(2)}(10) [(Ph(3)P)(2)Fe(NO)(2)] was verified in the reaction of (a) [(RS)(2)Fe(NO)(2)](-), 10 equiv of PPh(3) and sodium-biphenyl, and (b) 2 equiv of thiol, [RS](-), and [(Ph(3)P)(2)Fe(NO)(2)], respectively. The biomimetic reaction cycle, transformation between {Fe(NO)(2)}(9) [(RS)(2)Fe(NO)(2)](-) and {Fe(NO)(2)}(9) [(R'S)(2)Fe(NO)(2)](-), reversible interconversion of {Fe(NO)(2)}(9) and {Fe(NO)(2)}(10) DNICs, and degradation/reassembly of [2Fe-2S] clusters may decipher and predict the biological cycle of interconversion of {Fe(NO)(2)}(9) DNICs, {Fe(NO)(2)}(10) DNICs, and the [Fe-S] clusters in proteins.

The first structurally characterized copper cluster with a Cu centered cuboctahedral arrangement, a model of the bulk copper fcc structure, was observed in [Cu (S CN Bu ) (C≡CR) ](PF ) (R=C(O)OMe, C H F) nanoclusters. Four of the eight triangular faces of the cuboctahedron are capped by acetylide groups in μ fashion, and each of the six square faces is bridged by a dithiolate ligand in μ ,μ fashion, which leads to a truncated tetrahedron of twelve sulfur atoms. DFT calculations are fully consistent with the description of these Cu clusters as two-electron superatoms, that is, a [Cu ] core passivated by ten monoanionic ligands, with an a HOMO containing two 1S jellium electrons.