Four Thermochromic o-Hydroxy Schiff Bases of α-Aminodiphenylmethane: Solution and Solid State Study

Abstract

More than a hundred years after the first studies of the photo-and thermochromism of o-hydroxy Schiff bases (imines), it is still an intriguing topic that fascinates several research groups around the world. The reasons for such behavior are still under investigation, and this work is a part of it. We report the solution-based and mechanochemical synthesis of four o-hydroxy imines derived from α-aminodiphenylmethane. The thermochromic properties were studied for the single crystal and polycrystalline samples of the imines. The supramolecular impact on the keto-enol tautomerism in the solid state was studied using SCXRD and NMR, while NMR spectroscopy was used for the solution state. All four imines are thermochromic, although the color changes of the single crystals are not as strong as of the polycrystalline samples. One of the imines shows negative thermochromism, and that one is in keto-amine tautomeric form, both in the solid state as in solution.

Ultrasonic assisted preparation of some new zinc complexes of a new tetradentate Schiff base ligand: thermal analyses data, antimicrobial and DNA cleavage potential

“…[ 3–5 ] The azomethine group, planarity of the π‐bonding orbitals and electrons from the attached electronegative atoms afford them the great opportunity for coordination to metal ions. [ 6 ] Study of the coordination chemistry of transition metal with different types of the ligands has been increased by the current developments in the fields of bioinorganic chemistry, medicine, dye, and industry. [ 7–10 ] The sustained attempts in the study of the Schiff base complexes with several transition metals generally in (II) oxidation states arises from the ease of their preparation, high stability, versatility, and good solubility in common solvents.…”

Tautomeric Study of Schiff Bases Derived from o‐Dihydroxybenzaldehyde by UV‐Vis, IR, 1H NMR, 13C NMR Spectroscopy and Computational Modeling.

“…[36] It has been reported by Zbacnik et al that the lengthening of the CÀ O bond and the shortening of the NÀ C bonds correlates with a significant elongation of N(1)À C(7) bond by the transfer of a OÀ H phenolic hydrogen atom to the nitrogen atom of the C=N group. [37] Consequently, the contraction of the C(1)À O(1) bond length on the ka tautomers is produced. The 1 and 3 crystalline phase, previously reported, also showed the ka/ei tautomeric equilibrium is displaced towards the ka tautomers.…”

“…[22,24] 2 has only one strong intramolecular hydrogen bond NÀ H⋅⋅⋅O (O(1 , as reported in its analog. [37] The NÀ H⋅⋅⋅O hydrogen-bonded rings in 2 and 3 ka tautomers were almost planar-coupled with the cyclohexadiene ring, which showed C(1)À C(6)À C(7)À N(1) torsion angles of À 2.0(3)°for 2 and 3.5(2)°for 3 (Supporting Information, Table S5) Figure 10b). Finally, in Figure 11a, b, the crystal packing of 2 and 3 is shown, built by molecules linked through intermolecular hydrogen bonds.…”

Amino-Modified Hollow Mesoporous Silica Microspheres Loaded with Cresol Red-Boric Acid for Potent Reversible Thermochromic Performance

“…Compared with inorganic substances, the simple mechanism and easy preparation lead to the organic thermochromic dyes well developed. They included polymer 8 , Schiff bases 9 , spiropyran and spirooxazine 10 , lactone derivatives 11 and liquid crystals 12 . Mainly organic substance's thermochromic mechanisms were achieved by chemical structural change, included the opening and closing of ring structures or conformation transition of chemical bonds during heating, and after cooling and the original structure is restored.…”