Structural, proton-transfer, thermodynamic and nonlinear optical studies of (E)-2-((2-hydroxyphenyl)iminiomethyl)phenolate

Recently, the study of imine-bridged organics is interested in proton-transfer and photo-responsive material fields. Herein, we make a investigation on the structural, thermodynamic and nonlinear optical properties of (E)-2-((2-hydroxyphenyl)iminiomethyl)phenolate (HPIMP). The structural varieties of the studied compound are characterized by the X-ray single crystal diffraction and vibrational spectral techniques, as well as the vibrational spectral bands are precisely ascribed to the studied structure with the aid of DFT theoretical calculations. The experimental results of the FT-IR and X-ray measurements supply good proofs to reveal the proton-transfer procedures of HPIMP, and exhibit that the studied compound is a good proton-transfer model. In addition, the thermodynamic properties are obtained from the theoretical vibrations of the optimized HPIMP. The linear polarizability (α0) and first-order hyperpolarizabilities (β0) respectively present the values of 26.28 Å3 and 7.41 × 10−30 cm5/esu predicated theoretically by the DFT-B3lYP method at 6-31G(d) level, which indicates that the studied compound is a promising nonlinear optical material candidate.

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► The title compound (HPIMP) was synthesized in one step by an amine-formaldehyde reaction.
► The HPIMP molecule adopt trans configuration about CN bond with intramolecular hydrogen bonding.
► A proton-transfer characteristic of HPIMP is proved by experimental results of X-ray and FT-IR.
► The vibrational spectra have been precisely ascribed to molecular structure.
► The thermodynamic properties have been obtained by the theoretical vibrational analysis.
► The theoretical first-order hyperpolarizabilities is 19.9 times magnitude of urea.