Molecular Conductors from Neutral-Radical Charge-Transfer Salts:Preparation and Characterization of an Iodine-Doped Hexagonal Phase of 1,2,3,5-Dithiadiazolyl ([HCN2S2]∙)

Sublimation of 1,2,3,5-dithiadiazolyl in vacuo affords a triclinic phase of the dimer [HCN2S2]2. The crystals belong to the space group P¯1, a = 6.816(3), b = 13.940(2), c = 14.403(3) Å, α = 116.830(14), β = 98.64(3), γ = 99.18(3)°, FW = 212.4 (for [HCN2S2]2·[N2]0.08) Z = 6. The crystal structure consists of stacked dimers, with three dimers per asymmetric unit. Pairs of asymmetric units, related by an inversion center, generate a pinwheel motif consisting of six dimers. The columnar structure associated with these pinwheels forms close-packed sets of “molecular tubes”. Cosublimation of the radical in the presence of iodine in the mole ratio (HCN2S2:I = 5:1) yields an iodine-doped hexagonal phase of composition [HCN2S2]6[I]1.1. Crystals of this material belong to the space group P61, a = b = 14.132(16), c = 3.352(5) Å, FW = 128.20, Z = 6. The crystal structure consists of sixfold pinwheels in which the now evenly spaced HCN2S2 rings form a spiral about the 61 axis. The iodine atoms lie within the columnar cavity of the pinwheels in a disordered array wrapped tightly about the sixfold screw axis. The single-crystal conductivity of the doped material is 15 S cm-1 at room temperature. Raman spectroscopic and magnetic susceptibility measurements on the doped material are reported

Global surveillance of cancer survival 1995-2009: analysis of individual data for 25,676,887 patients from 279 population-based registries in 67 countries (CONCORD-2)

BACKGROUND: Worldwide data for cancer survival are scarce. We aimed to initiate worldwide surveillance of cancer survival by central analysis of population-based registry data, as a metric of the effectiveness of health systems, and to inform global policy on cancer control. METHODS: Individual tumour records were submitted by 279 population-based cancer registries in 67 countries for 25·7 million adults (age 15-99 years) and 75,000 children (age 0-14 years) diagnosed with cancer during 1995-2009 and followed up to Dec 31, 2009, or later. We looked at cancers of the stomach, colon, rectum, liver, lung, breast (women), cervix, ovary, and prostate in adults, and adult and childhood leukaemia. Standardised quality control procedures were applied; errors were corrected by the registry concerned. We estimated 5-year net survival, adjusted for background mortality in every country or region by age (single year), sex, and calendar year, and by race or ethnic origin in some countries. Estimates were age-standardised with the International Cancer Survival Standard weights. FINDINGS: 5-year survival from colon, rectal, and breast cancers has increased steadily in most developed countries. For patients diagnosed during 2005-09, survival for colon and rectal cancer reached 60% or more in 22 countries around the world; for breast cancer, 5-year survival rose to 85% or higher in 17 countries worldwide. Liver and lung cancer remain lethal in all nations: for both cancers, 5-year survival is below 20% everywhere in Europe, in the range 15-19% in North America, and as low as 7-9% in Mongolia and Thailand. Striking rises in 5-year survival from prostate cancer have occurred in many countries: survival rose by 10-20% between 1995-99 and 2005-09 in 22 countries in South America, Asia, and Europe, but survival still varies widely around the world, from less than 60% in Bulgaria and Thailand to 95% or more in Brazil, Puerto Rico, and the USA. For cervical cancer, national estimates of 5-year survival range from less than 50% to more than 70%; regional variations are much wider, and improvements between 1995-99 and 2005-09 have generally been slight. For women diagnosed with ovarian cancer in 2005-09, 5-year survival was 40% or higher only in Ecuador, the USA, and 17 countries in Asia and Europe. 5-year survival for stomach cancer in 2005-09 was high (54-58%) in Japan and South Korea, compared with less than 40% in other countries. By contrast, 5-year survival from adult leukaemia in Japan and South Korea (18-23%) is lower than in most other countries. 5-year survival from childhood acute lymphoblastic leukaemia is less than 60% in several countries, but as high as 90% in Canada and four European countries, which suggests major deficiencies in the management of a largely curable disease. INTERPRETATION: International comparison of survival trends reveals very wide differences that are likely to be attributable to differences in access to early diagnosis and optimum treatment. Continuous worldwide surveillance of cancer survival should become an indispensable source of information for cancer patients and researchers and a stimulus for politicians to improve health policy and health-care systems

Iodine Charge-Transfer Salts of Benzene-Bridged Bis(1,2,3,5-diselenadiazolyl) Diradicals. Electrocrystallization and Solid-State Characterization of 1,3- and 1,4-[(Se2N2C)C6H4(CN2Se2)][I]

Electroreduction of 1,3- and 1,4-benzene-bridged bis(diselenadiazolium) salts [1,4-Se][SbF6]2 and [1,4-Se][SbF6]2 in acetonitrile, at a Pt wire and in the presence of iodine affords the 1:1 charge-transfer salts [1,4-Se][I] and [1,3-Se][I]. Crystals of [1,4-Se][I] belong to the monoclinic space group C2/m, with FW = 598.9, a = 10.586(2), b = 16.713(2), c = 3.5006(14) Å, β = 104.26(2)°, V = 600.2(3) Å3, Z = 2. Crystals of [1,3-Se][I] belong to the orthorhombic space group Ima2, with FW = 598.9, a = 28.489(7), b = 3.543(2), c = 12.283(2) Å, V = 1239.8(8) Å3, Z = 4. In the presence of an excess of iodine, electrocrystallization of [1,4-Se]2+ affords the mixed iodide/triiodide salt [1,4-Se][I][I3], space group C2/c, FW = 979.59, a = 12.862(3), b = 15.063(2), c = 9.028(3) Å, β = 100.62(2)°, V = 1719.1(7) Å3, Z = 4. The structures of the two 1:1 compounds consist of perfectly superimposed stacks of molecular units interspersed by columns of disordered iodines. Interstack contacts in both structures are limited, indicative of 1-dimensional electronic structures. Variable-temperature single-crystal conductivity measurements on [1,4-Se][I] reveal weakly metallic behavior at room temperature, with a phase transition to a semiconducting state occurring at about 240 K. Magnetic susceptibility measurements on [1,4-Se][I] are consistent with the conductivity data; the magnetic susceptibility of [1,3-Se][I] behaves similarly. The crystal structures and transport properties are discussed in light of extended Hückel band structure calculations.

Preparation and Characterization of the Disjoint Diradical 4,4'-Bis(1,2,3,5-dithiadiazolyl) [S2N2C-CN2S2] and Its Iodine Charge Transfer Salt [S2N2C-CN2S2][I]

Condensation of oxamidrazone with sulfur dichloride in acetonitrile affords 4,4'-bis(1,2,3,5-dithiadiazolium) dichloride in moderate yield. Reduction of this salt with triphenylantimony yields the diradical 4,4'-bis(1,2,3,5-dithiadiazolyl) [S2N2C-CN2S2], which has been isolated and characterized in the solid state as its dimer [S2N2C-CN2S2]2. The diradical is disjoint, and ab initio molecular orbital methods confirm a very small energy gap (<0.5 kcal/mol) between the triplet and diradical singlet states, regardless of the torsion angle about the central C-C bond. In accord with these theoretical predictions the ESR spectrum of the diradical consists (in CHCl3 at 273 K) of a simple five-line pattern (aN = 0.50 mT, g = 2.011), i.e., there is no observable exchange coupling between the two centers. In the solid state, the dimer [S2N2C-CN2S2]2 forms a slipped stack structure, with a mean intradimer S-S distance of 3.078 Å and mean interdimer S- - -S contact of 3.761 Å. Cosublimation of the diradical with iodine produces the charge-transfer salt [S2N2C-CN2S2][I], orthorhombic space group Ccmm, a = 11.909(3) Å, b = 3.271(2) Å, c = 19.860(6) Å, Z = 4 (at 293 K). In this structure the heterocyclic rings form perfectly superimposed and evenly spaced stacks along the y direction, with channels of disordered iodines. The iodine-doped material is metallic at ambient temperatures, with a single-crystal conductivity of 460 S cm-1 at 300 K; variable temperature conductivity and magnetic measurements reveal a phase transition near 270 K, with the onset of semiconducting behavior. Transport data for the neutral and doped materials are discussed in the light of Extended Hückel band calculations.

Charge Transfer Salts of Benzene-Bridged 1,2,3,5-Dithiadiazolyl Diradicals. Preparation, Structures, and Transport Properties of 1,3- and 1,4-[(S2N2C)C6H4(CN2S2)][X] (X = I, Br)

Cosublimation of 1,3- and 1,4-benzene-bis(1,2,3,5-dithiadiazolyl) and iodine/bromine affords crystals of the mixed valence salts 1,3- and 1,4-[(S2N2C)C6H4(CN2S2)][X] (X = I, Br). The crystal structures of the two iodide salts consist of perfectly superimposed stacks of molecular units with interannular spacing along the stacks of 3.487(3) and 3.415(2) Å, for the 1,3- and 1,4-derivatives. In both compounds the iodines are disordered along the stacking direction. The 1,3-derivative has a highly one-dimensional structure; there are no short intercolumnar S-S interactions. In the 1,4-derivative, however, lateral S-S contacts of 3.911 Å, afford some measure of three-dimensionality. The bromide salt of the 1,4-derivative consists of ribbons of alternating 1,4-[(S2N2C)C6H4(CN2S2)]+ units and bromide ions. Within each molecule one heterocyclic ring is closed shell, i.e., a [CN2S2]+ cation, while the other is a discrete radical. The ribbons are layered in zigzag fashion that maximizes ion pairing and isolates the radical centers. The bromide salt of the 1,3-derivative also forms ribbon-like arrays, but the unit cell repeat consists of four layers of ribbons. Within these layers the [CN2S2] rings are approximately stacked. The four rings within the repeat unit along each stack consists of three rings clustered into a trimeric [CN2S2]3+ cation, while the remaining ring is a discrete [CN2S2]+ cation. Magnetic susceptibility and conductivity measurements on the two iodide salts indicate weakly metallic behavior at room temperature, with a charge density wave (CDW) driven metal-insulator phase transition occurring near 270 and 190 K for the 1,3- and 1,4-derivatives, respectively. For the 1,4-derivative, analysis of the CDW wavevector associated with the transition affords a degree of charge transfer of 1/4 of electron per radical, i.e., an overall formulation of [(S2N2C)C6H4(CN2S2)]0.5+[I]0.5-. The bromide salt of the 1,3-derivative is a closed shell insulator, while in the 1,4-bromide the isolated radical centers are antiferromagnetically coupled.