Two methods are described for doping of fullerite C 60 with molecular oxygen at a pressure of ~10 4 Pa and at temperature 20-30 °C. It was found by mass spectrometry using oxygen 18 O as dopant that a portion of molecular oxygen absorbed by the pre decontaminated fullerite (first method) is removed as CO and CO 2 at the heating temperature ≤200 °C. Doping during fullerite precipitation from the liquid phase (second method) makes it possible to prepare samples with the oxygen content ≥1.2 at.%. The fullerite doped with oxygen to this level is diamagnetic. The paramagnetic properties of an O 2 molecule disappear when O 2 is incorpo rated into the fullerene lattice. This is interpreted on the basis of quantum chemical calcula tions as a sequence of equilibrium formation of the adduct C 60 O 2 . Calculations showed that the subsequent chemical transformation of C 60 O 2 resulting in the O-O bond cleavage is energeti cally favorable, enabling prerequisites for the formation of products of incomplete (CO) and deep (CO 2 ) oxidation of fullerene under mild conditions. It is known 1,2 that fullerite C 60 with the face centered cubic (fcc) lattice has one octopore (average radius R oh = 2.06 Å) and two tetrapores (average radius R th = 1.13 Å) per fullerene molecule. Atoms of some elements (Ar, Kr, and others) 3 and small molecules, viz., CO, 4 CO 2 , 5 and N 2 O 6 , can be located in these holes as "guests" in rather high concentrations without decomposition of the "host" lattice. Such a doping can sharply change the prop erties of fullerite. The appearance of superconductivity of compounds A 3 C 60 (A is an alkaline metal) with the fcc lattice is an example of the nontrivial result of such a doping (see, e.g., review 7 ). It was found 3,8 that the pres ence of atoms of inert gases in holes of the fullerite lattice affects the temperature of the phase transition fcc → SC (SC lattice is the simple cubic lattice) or changes the value of the pressure inducing this transition at room temperature. Filling of holes in fullerite can be consid ered as a convenient method for storage of rare gases, because filling of all octopores only (one gas molecule in each pore) corresponds to the volume concentration ob served at a gas pressure of 5 MPa. 1 At the same time, gas doping of solid fullerene result ing in filling of all its octopores requires high pressures and temperatures. For example, an inert gas pressure of 170-200 MPa and the temperature interval from 200 to 500 °C were used 3 to obtain compounds Ar 1.0 C 60 , Kr 0.9 C 60 , and Xe 0.66 C 60 . However, this method does not allow one to dope crystalline fullerite with reactive mol ecules, such as O 2 . It was found 9 that a powder of the pure fullerite, which was stored in air, absorbed several per cents of molecular oxygen. The 13 C NMR spectrum of this sample contains the main peak at δ 143.6 and a new peak at δ 144.3, whose appearance can be related 9 to the presence of paramagnetic oxygen molecules in the fullerite lattice. The appearance of the new peak in the 13 C NMR ...
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