The Theoretical Studies On The Novel Molecules With Poly-cage And Hetero-cage Like Structure

Molecular devices are the organised structural systems formed by molecules and supramolecules which have been shown the remarkable structural, electronic, optical, hot, mechanical, ionic, and magnetic properties. Molecular devices are the chemical and physical systems which will fulfil storage, transfer, detection, conversion, and treatment of information and energy on the molecular or supramolecular level. Since the molecular-based materials which have been shown the remarkable structural, electronic, optical, hot, mechanical, ionic, and magnetic properties are required for preparing molecular devices, they have been the focus of attention for chemical researches.Because they have the special srtuctues and properties, the molecules with cage-like structure could be the molecular-based materials for molecular devices. In the past two decades, a great number of achievements have been acquired for fullerenes, carbon nano-tubes, carbon nano-onions, and endohedral complexes, which are the molecules with cage-like structure.There are many researches on the molecules with cage-like structure, but few studies are about the molecules as follows. The first is the studies of poly-cage molecules. The second is the heterofullerene molecule containing the odd number of atoms assembling a cage, which is a novel type molecules with cage-like structure. The third is the cage-like molecule contains many oxygen atoms, which has more hydrophilicity. We have done the work on above three aspects.This thesis contains three aspects asfollows:1. The studies of the bi-cage fullerenesWe studied the C114 molecule by using the density functional method (DFT) at the B3LYP/6-31G* level of theory, and found that it has four isomers, which structures are two intact C60 cages sharing the same hexagon. The results show that isomer 1 of C114 is the most stable among the four isomers and more stable than C60.We studied the C120 molecule by using the density functional method at the B3LYP/6-31G* level of theory, and found that it has two isomers, which structures are two intact C60 cages linked by six carbon-carbon single bonds. The results show that the two isomers are all less stable than C60, but the pathways for decomposition to C60 are forbidden by orbital symmetry. Therefore, it is possible that they can be observed experimentally as metastable molecules.2. The studies of cage-like molecules contains many oxygen atomsWe studied a cage-like molecule C24O12 containing 24 carbon atoms and 12 oxygen atoms, whcich contains 2 hexagons and 12 heptagons, and every heptagon has 5 carbon atoms and 2 oxygen atoms, by using the DFT method at the B3LYP/6-31G* level of theory, and found that it is chiral molecule. Heat of formation, vibrational frequencies, NMR spectral signals, and other properties of C24O12 are reported here. Heat of formation shows that C24O12 is very stable. We also studied the the molecule C40O10 with cage-like structure, 10 oxygen atoms linking two corannulene, by using the DFT method at the B3LYP/6-31G* level of theory, and found it has two isomers. Heat of formation, vibrational frequencies, NMR spectral signals, and other properties of C40O10 are reported here. Heat of formation shows that C40O10 is more stable than C60 only from the thermodynamic points of view.3. The studies of heterofullerenes C58X(X=S,Se,Te) containing the odd number of atomsWe think that if an atomhas suitable size and can form four bonds in near plane, it can substitute a C-C bond on the surface of fullerene cage, and thus the heterofullerene with odd number of atoms on the skeleton of cage can be formed. We think that S, Se, Te atoms are the suitable atom. When a S or Se or Te atom substitutes a 6-6 C-C bond (hexagon-hexagon) of C60, a molecule of C58X(X=S,Se,Te) with odd number of atoms assembling a cage has been obtained. Heat of formations, vibrational frequencies, NMR spectral signals, and other properties of C58X(X=S,Se,Te) are studied by sing the DFT method at the B3LYP/3-21G* level of theory. Because the absence of imaginary vibrational frequency, every C58X(X=S,Se,Te) molecule corresponds to a true minimum on the potential energy hypersurface.