The crystal structure of a solid controls the interactions between the electronically active units and thus its electronic properties. In the high-temperature superconducting copper oxides, only one spatial arrangement of the electronically active Cu(2+) units-a two-dimensional square lattice-is available to study the competition between the cooperative electronic states of magnetic order and superconductivity. Crystals of the spherical molecular C(60)(3-) anion support both superconductivity and magnetism but can consist of fundamentally distinct three-dimensional arrangements of the anions. Superconductivity in the A(3)C(60) (A = alkali metal) fullerides has been exclusively associated with face-centred cubic (f.c.c.) packing of C(60)(3-) (refs 2, 3), but recently the most expanded (and thus having the highest superconducting transition temperature, T(c); ref. 4) composition Cs(3)C(60) has been isolated as a body-centred cubic (b.c.c.) packing, which supports both superconductivity and magnetic order. Here we isolate the f.c.c. polymorph of Cs(3)C(60) to show how the spatial arrangement of the electronically active units controls the competing superconducting and magnetic electronic ground states. Unlike all the other f.c.c. A(3)C(60) fullerides, f.c.c. Cs(3)C(60) is not a superconductor but a magnetic insulator at ambient pressure, and becomes superconducting under pressure. The magnetic ordering occurs at an order of magnitude lower temperature in the geometrically frustrated f.c.c. polymorph (Néel temperature T(N) = 2.2 K) than in the b.c.c.-based packing (T(N) = 46 K). The different lattice packings of C(60)(3-) change T(c) from 38 K in b.c.c. Cs(3)C(60) to 35 K in f.c.c. Cs(3)C(60) (the highest found in the f.c.c. A(3)C(60) family). The existence of two superconducting packings of the same electronically active unit reveals that T(c) scales universally in a structure-independent dome-like relationship with proximity to the Mott metal-insulator transition, which is governed by the role of electron correlations characteristic of high-temperature superconducting materials other than fullerides.

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In view of its unique photocatalytic properties, decatungstate (W(10)O(32)(4-)) is rapidly emerging as a promising tool in organic chemistry. This tutorial review surveys recent developments in the chemistry of decatungstate, including mostly synthetic, and to a lesser extent mechanistic aspects. We have chosen to present several representative examples that illustrate the diverse uses of decatungstate in organic synthesis. Thus, the decatungstate-mediated radical functionalization of several classes of organic compounds such as alkanes, alkenes, alcohols, aldehydes and sulfides, under both aerobic and anaerobic conditions, represents reactions of fundamental and practical interest in academia and industry. Several new discoveries concerning the heterogenization of decatungstate for the development of sustainable methods with broad applications in catalysis, such as the photooxidation or photodegradation of various organic substrates, are also presented.

A versatile and highly efficient photochemical methodology for the direct acylation of C(60) has been developed. This approach utilizes a wide variety of acyl radicals derived from aldehydes through a hydrogen atom abstraction process mediated by tetrabutylammonium decatungstate [(n-Bu(4)N)(4)W(10)O(32)]. The single addition reaction of these acyl radicals to [60]fullerene proceeded selectively to afford a novel class of previously unexplored fullerene-based materials. Product analysis of this reaction showed that decarbonylation and acylation pathways compete when a tertiary or phenylacetyl aldehyde is the starting material. However, a decrease of the reaction temperature was found to be effective in overcoming the decarbonylation encountered in certain acyl radical additions to C(60); the carbonyl radical addition precedes decarbonylation even in the cases where the decarbonylation rate constant exceeds 10(6) s(-1) (i.e., phenylacetaldehyde). The regiochemistry of the t-butyl radical addition was also found to be thermally controlled. The present methodology is directly applicable even in the cases of the cyclopropyl-substituted aldehydes, where rapid rearrangement of the cyclopropyl acyl radical intermediate can potentially occur. A mechanistic approach for this new reactivity of C(60) has been also provided, based mainly on intra- and intermolecular deuterium isotope effect studies.

A series of donor-acceptor-substituted alkynes, 2 a-f, was synthesized in which the length of the π-conjugated polyyne spacer between the N,N-diisopropylanilino donor and the 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) acceptor was systematically changed. The effect of this structural change on the optoelectronic properties of the molecules and, ultimately, their third-order optical nonlinearity was comprehensively investigated. The branched N,N-diisopropyl groups on the anilino donor moieties combined with the nonplanar geometry of 2 a-f imparted exceptionally high solubility to these chromophores. This important property allowed for performing INADEQUATE NMR measurements without (13) C labeling, which, in turn, resulted in a complete assignment of the carbon skeleton in chromophores 2 a-f and the determination of the (13) C-(13) C coupling constants. This body of data provided unprecedented insight into characteristic (13) C chemical shift patterns in push-pull-substituted polyynes. Electrochemical and UV/Vis spectroscopic studies showed that the HOMO-LUMO energy gap decreases with increasing length of the polyyne spacer, while this effect levels off for spacers with more than four acetylene units. The third-order optical nonlinearity of this series of molecules was determined by measuring the rotational averages of the third-order polarizabilities (γrot ) by degenerate four-wave mixing (DFWM). These latter studies revealed high third-order optical nonlinearities for the new chromophores; most importantly, they provided fundamental insight into the effect of the conjugated spacer length in D-A polyynes, that can be exploited in the future design of suitable charge-transfer chromophores for applications in optoelectronic devices.

Easy crowning for [60]fullerene: The simplest and hitherto elusive C60/crown ether conjugates have been prepared through an effective free‐radical approach. This approach includes the activation of the otherwise unreactive α‐CH bond in a series of structurally diverse mono‐ or polyethers and sulfides. This facile method provides an expedient entry into a novel class of fullerene‐based materials.

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A convenient, highly efficient, decatungstate-mediated chemical methodology to functionalize fullerenes is demonstrated. A variety of radicals have been generated by the photochemical interaction of tetrabutylammonium decatungstate [(n-Bu4N)4W10O32] and para-substituted toluenes, anisoles, and thioanisole and effectively trapped by the [60]fullerene affording the corresponding 1,2-dihydro[60]fullerene monoadducts in moderate to good yields.