We present geometric and electronic structures of a model fluoroquinolone (FQ), an antibiotic molecule, computed at the Hartree-Fock and configuration-interaction singles (CIS) levels of ab initio MO theory. Using the electronic structure code GAMESS, we have located the lowest-energy neutral (N-) and zwitterionic (Z-) FQ tautomers, for both ground and excited orbital electronic configurations. Most of the low-lying CIS singlet and triplet excited states are classified as , but several  excited singlet states are presented. Aqueous solvation effects have been studied using both full quantum waters of hydration complexes with FQ and effective fragment potential (EFP) water molecules hydrating the N-FQ and Z-FQ molecules. Up to 55 EFP waters have been included in these studies. In the gas phase, N-FQ is the stable tautomer, but in the aqueous phase Z-FQ is the more stable tautomer.  Structures of low energy solvated excited state transitions were studied, and interpreted.

Computational analysis of molecular fluoroquinolone using GAMESS

245th National Meeting (2013)

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