TY - JOUR

T1 - Aminonitrone–iminohydroxamic acid tautomerism

T2 - Theoretical and spectroscopic study

AU - Il'in, Mikhail V.

AU - Novikov, Alexander S.

AU - Bolotin, Dmitrii S.

PY - 2019/1/15

Y1 - 2019/1/15

N2 - The comprehensive theoretical study of the tautomerism of aminonitrone species employing the С-methylaminonitrone MeC(NH2) = N+(Me)O− and the С-phenylaminonitrone PhC(NH2) = N+(Me)O− species as models and direct experimental observation of the tautomeric forms in a chloroform solution by infrared spectroscopy have been reported. All possible tautomeric forms including different (E)/(Z)-configurations of each species and the nature of solvent on their relative energies have been considered at the M06-2X/6-311 + G(d,p) level of theory. Results of theoretical calculations reveal that the most stable tautomeric form in chloroform, dimethyl sulfoxide, and methanol solutions is the (Z)-aminonitrone. The protic solvent (MeOH) significantly stabilizes both zwitter-ionic (E)- and (Z)-aminonitrone forms, whereas all tautomers related to the iminohydroxamic acid remain almost unaffected upon variation of the solvent nature. The phenomenon of intramolecular N–H⋯O and O–H⋯N hydrogen bonding in (Z)-aminonitrone and (E,Z)-iminohydroxamic acid tautomeric forms was studied by the topological analysis of the electron density distribution (QTAIM method), and estimated energies of these non-covalent interactions vary from 6 to 10 kcal/mol.

AB - The comprehensive theoretical study of the tautomerism of aminonitrone species employing the С-methylaminonitrone MeC(NH2) = N+(Me)O− and the С-phenylaminonitrone PhC(NH2) = N+(Me)O− species as models and direct experimental observation of the tautomeric forms in a chloroform solution by infrared spectroscopy have been reported. All possible tautomeric forms including different (E)/(Z)-configurations of each species and the nature of solvent on their relative energies have been considered at the M06-2X/6-311 + G(d,p) level of theory. Results of theoretical calculations reveal that the most stable tautomeric form in chloroform, dimethyl sulfoxide, and methanol solutions is the (Z)-aminonitrone. The protic solvent (MeOH) significantly stabilizes both zwitter-ionic (E)- and (Z)-aminonitrone forms, whereas all tautomers related to the iminohydroxamic acid remain almost unaffected upon variation of the solvent nature. The phenomenon of intramolecular N–H⋯O and O–H⋯N hydrogen bonding in (Z)-aminonitrone and (E,Z)-iminohydroxamic acid tautomeric forms was studied by the topological analysis of the electron density distribution (QTAIM method), and estimated energies of these non-covalent interactions vary from 6 to 10 kcal/mol.

KW - Aminonitrone

KW - DFT

KW - Hydroxamic acid

KW - Nitrone

KW - QTAIM

KW - Tautomerism

KW - HYDROGEN-BOND

KW - NITROXIDES

KW - COMPLEXES

KW - NONCOVALENT INTERACTIONS

KW - HALOGEN

KW - CRYSTALS

KW - RADICALS

KW - CHARGE-TRANSFER

KW - ENERGIES

KW - DERIVATIVES

UR - http://www.scopus.com/inward/record.url?scp=85054794156&partnerID=8YFLogxK

U2 - 10.1016/j.molstruc.2018.09.020

DO - 10.1016/j.molstruc.2018.09.020

M3 - Article

AN - SCOPUS:85054794156

VL - 1176

SP - 759

EP - 765

JO - Journal of Molecular Structure

JF - Journal of Molecular Structure

SN - 0022-2860

ER -