Showing papers by "Emma Jakab published in 2006"
TL;DR: In this article, the rotor-stator phases of fullerenes with cubane were described, and the polymerization was followed by HPLC, IR and UV-VIS spectroscopy, and determined the thermal stability by TG-MS analysis.
Abstract: A new family of heteromolecular crystals has been described recently: the rotor-stator phases of fullerenes with cubane. Cubane (CgHg), the stator component of these materials is a highly strained molecule which decomposes to higher stability CgHg hydrocarbons at 200 °C. This unimolecular isomerization takes also place in the rotor-stator phases, inducing a single phase topochemical reaction with the surrounding fullerenes. The resulting material is a random copolymer, percolating in the primitive cubic sublattices of the parent crystals. We followed the polymerization by HPLC, IR and UV-VIS spectroscopy, and determined the thermal stability by TG-MS analysis. The polymers are insoluble, and stable up to 400 °C. At this temperature they start to decompose while preserving their crystalline appearance. The influence of the side groups of substituted cubanes on the polymerization will also be discussed.
18 citations
TL;DR: In this article, the formation, structure and properties of a new family of molecular crystals of distinct rotating and static components: the derivatives of fullerenes with cubane are presented. But their properties are not discussed.
Abstract: We present the formation, structure and properties of a new family of molecular crystals of distinct rotating and static components: the derivatives of fullerenes with cubane. The new crystals consist of alternating arrays of the constituents, stabilized by the recognition of the complementary molecular surfaces. The concave cubanes match six rotating fullerenes in octahedral configuration, while the six nearest neighbours of the convex fullerenes may form either octahedral or trigonal prismatic configurations. Fullerenes rotate freely in the 'molecular bearing' of cubanes. Lower symmetry crystals of similar properties form when cubane is replaced by 1,4-diethynyl cubane. The following properties will be discussed: (i) The significant size and shape recognition makes possible the design of the crystal structure of new higher fullerenes and substituted cubane derivatives. (ii) The phase diagram of the rotor-stator crystals can be constructed in terms of the ball diameter of rotating fullerenes. (iii) The molecular geometry of the constituents has an influence on the structure and dynamics of the lower symmetry variants. (iv) At elevated temperatures the decomposition of cubane or diethynyl cubane induces topochemical copolymerization with the surrounding fullerenes.
14 citations
TL;DR: Among the known three pyridine complexes of silver permanganate, i.e. [Agpy2]MnO4 (1), [Agπ2.25]MmO4 or 7[Agπ 2]mNO4[Agpy4]mnH-bonded structures are responsible for a thermally induced low-temperature intramolecular redox reaction observed for the first time.
Abstract: Among the known three pyridine complexes of silver permanganate, i.e. [Agpy2]MnO4 (1), [Agpy2.25]MnO4 or 7[Agpy2]MnO4[Agpy4]MnO4 (2) and [Agpy2]MnO40.5py (3), compounds (1) and (2) were studied by means of thermal analysis and TG-MS methods. Presuming identical structural motifs for the Agpy2MnO4 blocks in (1) as it has been found in its solvate (3) by single-crystal diffraction, α-C–H...O–Mn H-bonded structures are responsible for a thermally induced low-temperature intramolecular redox reaction observed for the first time between the [Agpy2]+ cation and permanganate anion.
10 citations