Issue 55, 2017, Issue in Progress

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 E1 (mp 107.0 °C) and E2 (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 (ε = 0.9 × 103) and reasonable electrical conductivity in the order ∼5 × 10−6 S m−1. 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 P21/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 λmax absorption (300 nm) in MeOH solution at a concentration of 1 × 10−5 M.

Graphical abstract: 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

Supplementary files

Article information

Article type
Paper
Submitted
15 Mar 2017
Accepted
20 Jun 2017
First published
07 Jul 2017
This article is Open Access
Creative Commons BY license

RSC Adv., 2017,7, 34382-34391

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

U. S. Rai, M. Singh and R. N. Rai, RSC Adv., 2017, 7, 34382 DOI: 10.1039/C7RA03067C

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