Remarkable dielectric properties of 1 : 2 inter-molecular compound of 2-(4-(dimethylamino) benzylideneamino) benzoic acid and urea due to excited-state intramolecular proton transfer

Abstract

The phase diagram of 2-(4-(dimethylamino) benzylideneamino) benzoic acid (DMABAB)-urea (U) gives two eutectics E 1 (mp 107.0 C) and E 2 (mp 138.0 C) with 0.01 and 0.86 mole fractions of urea, respectively, and a 1 : 2 inter-molecular compound (IMC) with a congruent melting point of 219.0 C, which has a high dielectric constant (3 ¼ 0.9 Â 10 3 ) and reasonable electrical conductivity in the order $5 Â 10 À6 S m À1. This is due to the remarkable packing of U molecules in the IMC, where it shows coupling of two different types of cyclic hydrogen-bonded motifs alternating to form a corrugated sheet or chain of rings extending along the b axis via N-H/O hydrogen bonding interactions. In the presence of an electric field, an inter-molecular proton transfer process occurs in the NH/O bonds of the chain of the U molecules, which leads to disproportionate defects and the formation of polar domains on the macroscopic scale. An appropriate quantity of the IMC is synthesized via a green synthetic method, which has a monoclinic crystal system with the P2 1 /c centrosymmetric space group. Additionally, its crystal data and hydrogen bonding parameters are determined. According to powder X-ray diffraction, spectral and thermal characterization, the eutectics are a mechanical mixture of the IMC and pure components, although the IMC behaves as a pure compound. The IMC shows a broad emission band in the range of 350 to 580 nm with a quantum yield of almost 1 (0.99) upon excitation at the l max absorption (300 nm) in MeOH solution at a concentration of 1 Â 10 À5 M.

Forecast of Phase Diagram for the Synthesis of a Complex for the Detection of Cr6+ Ions

“…Interestingly, the novel complex (ANNBA) displays selective behavior toward chromium (Cr 6+ ) ions present in the water samples and have been used as a turn-off fluorescent sensor. This significant finding of the complex in the present work is likely to open a new pathway to synthesize more novel complexes and to study other known organic biodegradable fluorescent materials , to be used as sensors.…”