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ABSTRACT: A new fulleride, (K[DB18C6])(4)(C(60))(5)·12THF, was prepared in solution using the "break-and-seal" approach by reacting potassium, fullerene, and dibenzo[18]crown-6 in tetrahydrofuran. Single crystals were grown from solution by the modified "temperature difference method". X-ray analysis was performed revealing a reversible phase transition occurring on cooling. Three different crystal structures of the title compound at different temperatures of data acquisition are addressed in detail: the "high-temperature phase" at 225 K (C2, Z=2, a=49.055(1), b=15.075(3), c=18.312(4) Å, β=97.89(3)°), the "transitional phase" at 175 K (C2 m, Z=2, a=48.436(5), b=15.128(1), c=18.280(2) Å, β=97.90(1)°), and the "low-temperature phase" at 125 K (Cc, Z=4, a=56.239(1), b=15.112(3), c=36.425(7) Å, β=121.99(1)°). On cooling, partial radical recombination of C(60)(·-) into the (C(60))(2)(2-) dimeric dianion occurs; this is first time that the fully ordered dimer has been observed. Further cooling leads to formation of a superstructure with doubled cell volume in a different space group. Below 125 K, C(60) exists in the structure in three different bonding states: in the form of C(60)(·-) radical ions, (C(60))(2)(2-) dianions, and neutral C(60), this being without precedent in the fullerene chemistry, as well. Experimental observations of one conformation exclusively of the fullerene dimer in the crystal structure are further explained on the basis of DFT calculations considering charge distribution patterns. Temperature-dependent measurements of magnetic susceptibility at different magnetic fields confirm the phase transition occurring at about 220 K as observed crystallographically, and enable for unambiguous charge assignment to the different C(60) species in the title fulleride.
Chemistry 02/2011; 17(6):1798-805. · 5.93 Impact Factor
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Advanced Materials 10/2010; 22(48):5483-7. · 13.88 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 08/2009; 2009(26):3900 - 3903. · 2.94 Impact Factor
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ABSTRACT: The “break-and-seal” method known to be used for synthesis of sensitive compounds (alkalides, electrides and for living anionic polymerization) was applied for the first time for fulleride synthesis providing highest purity of the reaction conditions. A new fulleride KC60(THF)5·2THF was prepared in solution by reacting fullerene C60 with potassium and dibenzo-24-crown-8 in tetrahydrofurane. Single crystals were grown from solution by the modified “temperature difference method”, single- crystal X-ray analysis was performed revealing the structure [P21212, Z = 4, a = 17.802(5), b = 30.085(9), c = 9.863(3) Å, R1 = 0.069, wR(all) = 0.191, 5563 independent reflections]. In this compound, the charge of fulleride is –1, the C60– radical-anion being fully ordered. A constitutive structural feature is octahedrally coordinated potassium atoms with five THF and one fullerideas ligands. C60– is functioning as a η3-ligand: [K(η3-C60)(η1-THF)5]·2THF.
Zeitschrift für anorganische Chemie 07/2009; 635(9‐10):1355 - 1361.
