Multiresponsive Photo‑, Solvato‑, Acido‑, and Ionochromic Schiff Base Probe
- Publication date
- 2015
- Publisher
Abstract
Nonclassical
protomeric tautomerism in Schiff bases have the advantage of controlling
and differentiating specific interactions in the −CN–
linkage since its interactions are not governed by keto–enol
tautomerism. Here, we report about the optical properties of a Schiff
base probe (<b>P1</b>). X-ray structure analysis evidenced the
existence of an intramolecular hydrogen bond which is responsible
of a photochromic-fluorescent behavior. The properties of <b>P1</b> were investigated by UV–vis and fluorescence spectroscopy
in solution and solid state. A positive solvatochromism resulting
from specific interactions taking place in <b>P1</b> was studied
by three different solvent scales, namely Lippert–Mataga, Kamlet–Taft,
and Catalán, finding consistent results. Moreover, a strong
acidochromic behavior was detected and the p<i>K</i><sub>a</sub> and p<i>K</i><sub>a</sub>* values were determined,
finding a photobasic character. Further, an ionochromic behavior was
stablished. <b>P1</b> exhibits a λ-ratiometric fluorescence
response toward Sn(IV) giving a luminescence color change from blue
to green, displaying also a chromogenic response. Finally, theoretical
calculations were conducted to analyze the probe mechanism in terms
of natural transition orbitals (NTOs) and spatial extent of charge
transfer excitations. The present contribution focused on the factors
determining the ability of a single Schiff base probe to present photo-,
solvato-, acido-, and ionochromism