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Course description:
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Application of the molecular-orbital (MO) theory to the description of the ground-state, and ionic and excited states of molecules. The definition and characteristics of the π-electron molecules. The π-electron approximation in the MO theory. The Pariser-Parr-Pople (PPP) model, the problem of empirical parameters. The description of electronic exitations of π-electron molecules within the PPP model. The alternancy symmetry as a hidden symmetry of π-electron hydrocarbons; the alternant and nonalternant hydrocarbons. A hierarchy of the π-electron models: from the PPP model, through the Hubbard one, to the models based on the Huckel model. The introduction of the Hückel-Su-Schrieffer-Heeger (HSSH) model and its application in the description of geometry (the bond lengths) and energy of the π-electron hydrocarbons and carbon molecules (fullerenes and nanotubes). Electric and magnetic properties of π-electron molecules. The application of the HSSH model to the description of the charge distribution in nonalternant hydrocarbons. The interaction of ring-shaped π-electron hydrocarbons with magnetic field (the HSSH model), the ring currents. Chemical reactivity of π-electron molecules, reactivity indices. Wheland's σ-complex model. Pericylic reactions and the conservation of molecular symmetry (the Woodward-Hoffmann rules). The notion of aromaticity of π-eletron molecules - its various aspects.
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