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Phenol–Quinone Tautomerism in (Arylazo)naphthols and the Analogous Schiff Bases: Benchmark Calculations

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journal contribution
posted on 30.01.2014, 00:00 by S. Tahir Ali, Liudmil Antonov, Walter M. F. Fabian
Tautomerization energies of a series of isomeric [(4-R-phenyl)­azo]­naphthols and the analogous Schiff bases (R = N­(CH3)2, OCH3, H, CN, NO2) are calculated by LPNO-CEPA/1-CBS using the def2-TZVPP and def2-QZVPP basis sets for extrapolation. The performance of various density functionals (B3LYP, M06-2X, PW6B95, B2PLYP, mPW2PLYP, PWPB95) as well as MP2 and SCS-MP2 is evaluated against these results. M06-2X and SCS-MP2 yield results close to the LPNO-CEPA/1-CBS values. Solvent effects (CCl4, CHCl3, CH3CN, and CH3OH) are treated by a variety of bulk solvation models (SM8, IEFPCM, COSMO, PBF, and SMD) as well as explicit solvation (Monte Carlo free energy perturbation using the OPLSAA force field).