Exploration of semiconducting properties of Zn(ii)- and Cd(ii)-based coordination polymers with dicarboxylate of a chair-type backbone

Abstract

A new Cd(II)-based two-dimensional coordination polymer (2D CP) [{Cd₂(cis-1,4-chdc)₂(1,10-phen)₂}·5H₂O]_n (1) has been synthesized at room temperature by a slow diffusion technique using a 1,4-cyclohexanedicarboxylic acid (1,4-H₂chdc) and 1,10-phenanthroline (1,10-phen) mixed-ligand system. CP 1 was characterized by elemental analysis, infrared (IR) spectroscopy, powder X-ray diffraction (PXRD) analysis, single crystal X-ray diffraction (SCXRD) and thermogravimetric analysis (TGA) techniques. The structural analysis has revealed that CP 1 forms a 2D layer structure with guest water molecules encapsulated in the cavity generated by the Cd(II) centers and 1,4-chdc anions. Interestingly, CP 1 shows electrical conductivity in the semiconductor region and behaves as a Schottky barrier diode. In order to compare the conductivity with a similar type of CP made of another d¹⁰ metal ion Zn(II), a reported CP {Zn(cis-1,4-chdc)(1,10-phen)(H₂O)}_n (2) with a 1D helical structure was synthesized and its conductivity was compared. CP 2 also exhibits electrical conductivity and reveals Schottky barrier diode behavior. However, it has been found that CP 1 shows better properties for electronic device application as compared to CP 2.