Gram-Scale Synthesis and Multifunctional Properties of a Two-Dimensional Layered Copper(II) Coordination Polymer

Accomplishing an inexpensive and industrially scalable, robust multifunctional material exhibiting a range of technologically significant phenomena is apparently essential for its projected use in a wide range of device applications. Herein we report on the extremely simple, gram-scale synthesis, electrical conductivity, redox behavior, thermoelectric properties, and magnetism of a two-dimensional (2D) layered copper­(II) coordination polymer (COP) formed by treating the ligand 3,3′-diaminobenzidine (DAB) with copper­(II) acetate monohydrate, Cu­(OAc)2·H2O. The experimental observations show that the COP synthesized, hereafter termed Cu­(DAB), and stored under ambient conditions remains intact, exhibiting resistance to air, light, heat, water, and alkaline aqueous solution. FTIR spectroscopy, Raman spectral analyses, microanalytical data, SEM-EDX imaging, surface analysis by XPS/AFM, powder X-ray diffraction, and HRTEM suggest a neutral 2D COP with Cu­(DAB) repeating units. While the AC experiments completely rule out ionic conductivity, two-probe DC electrical conductivity measurements on a pellet (bulk sample) as a function of temperature (150–320 K) evidence the electrical conductivity of the COP. Notably, at room temperature (298 K) the conductivity was found to be 0.01 S/m. The inherent p-type conduction was revealed by Hall effect experiments. Apart from being redox-active, it shows thermoelectric behavior, and magnetic susceptibility vs temperature measurements reveal the spin crossover from diamagnetic to the paramagnetic state upon cooling the bulk sample.