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Theoretical Study of Metallochlorophylls of Forth Period Elements in Periodic Table

Faramarzi, Sadegh | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42429 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Parsafar, Gholamabbas
  7. Abstract:
  8. In this study, some properties of metallochlorophylls - compounds produced by replacing Mg2+ in tetrapyrrolic ring of chlorophyll b with divalent ions – of the forth period transit elements of the periodic table have been investigated. Using DFT/B3LYP method and DGDZVP basis set, structures of these compounds were optimized and the energy of electronic levels, Gibbs free energy of formation of complex, contribution of atomic orbitals to formation of molecular orbitals and partial charges in these molecules were computed. The results show that some properties of these complexes cannot be justified by the common theories of complexes. Among these properties is the negligible effect of replacing Mg-Zn elements in HOMO and LUMO levels. On the other hand, variation in values of formation free energy in such compounds differs from what is usually seen in square planar complexes. Such a trend is perceptible by separation of electrostatic and covalent interaction between metal and ligand in these compounds. For this set of compounds, complexes in which the electrostatic interaction between metal and ligand is weaker, have more negative values of formation free energy that implies a stronger covalent interaction between metal and ligand. It is also observed that d orbitals of first four elements in the fourth period have important contribution in formation of HOMO and LUMO molecular orbitals while in subsequent elements which are more stable, d orbitals have negligible contribution in formation of these molecular orbitals
  9. Keywords:
  10. Density Functional Theory (DFT) ; Metallochlorophyll ; Square Planar Complex

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