Solid-state electronic absorption, fluorescence and C-13 CPMAS NMR spectroscopic study of thermo- and photo-chromic aromatic Schiff bases

Alarcon, S H and Olivieri, A C and Nordon, A and Harris, R K (1996) Solid-state electronic absorption, fluorescence and C-13 CPMAS NMR spectroscopic study of thermo- and photo-chromic aromatic Schiff bases. Journal of the Chemical Society, Perkin Transactions 2 (11). pp. 2293-2296. ISSN 1472-779X (https://doi.org/10.1039/P29960002293)

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Abstract

Solid-state electronic absorption, fluorescence emission and C-13 CPMAS spectroscopies have been applied to a series of aromatic Schiff bases displaying both ground and excited state intramolecular proton transfer phenomena. All the results can be explained on the basis of a thermal equilibrium between enolimine and keto-enamine tautomeric forms in the crystalline state. Most of the studied compounds are thermochromic. However, a few are photochromic. The carbon-13 NMR data in the solid state show, in general, residual (C-13,N-14) dipolar coupling effects. In certain cases, however, where fast proton transfer occurs in the ground state, these effects are shown to be self-decoupled.