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Spectroscopic and quantum chemical study on electronic and geometric properties of free and embedded dithizone molecules
Author(s) -
Schönherr T.,
Linder R.,
Rosellen U.,
Schmid V.
Publication year - 2001
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.1609
Subject(s) - chemistry , dithizone , tautomer , enol , supermolecule , molecule , intermolecular force , computational chemistry , ab initio , electron paramagnetic resonance , density functional theory , chemical shift , nuclear magnetic resonance , physics , inorganic chemistry , stereochemistry , organic chemistry , catalysis
The molecular and electronic structure of the three tautomeric forms of dithizone has been calculated by using semiempirical, density functional theory (DFT), and ab initio methods. Comparison of ground‐state energies shows the symmetric form most stabilized, but there is only a small barrier (<3 kcal/mol) for the hydrogen transfer from NH toward HS (enol form). For understanding the origin of the optical transitions intermolecular interactions have to be taken into account. By using the supermolecule method, the absorption band pattern can be rationalized already on the level of the PM3 model. The nuclear magnetic resonance (NMR) solution spectrum is interpreted in terms of an equilibrium between the symmetric and the enol forms of dithizone. The appearance of strong EPR signals only for the solid state reflects a considerable lowering of the triplet state (symmetric form). Experimental features are discussed in view of calculated energies (stabilization), chemical shifts (NMR), and SOMO orbitals (EPR). © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001