Aminoisophthalate Bridged Cd(II)-2D Coordination Polymer: Structure Description, Selective Detection of Pd<sup>2+</sup> in Aqueous Medium, and Fabrication of Schottky Diode
Suprava Bhunia, Dipankar Sahoo, Suvendu Maity, Basudeb Dutta, Satyabrata Bera, Nabin Baran Manik, Chittaranjan Sinha
Abstract
Photoluminescence activity of coordination polymers (CPs) has evoked intricate applications in the field of materials science, especially sensing of ions/molecules. In the present study, 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) and 5-aminoisophthalate (HAIPA – ) coordinated to Cd(II) to architect a coordination polymer, {[Cd(HAIPA)(tppz)(OH)]·3H 2 O} n (CP 1 ) which unveils blue emission in an aqueous acetonitrile (98% aqueous) suspension. The emission is selectively quenched by Pd 2+ only without interference in the presence of as many as 16 other cations. The structure of CP 1 shows the presence of a free –COOH group, and the interlayer (–CO)O(2)···O(7) (OC–) distance, 4.242 Å, along with the π···π interactions (3.990, 3.927 Å), may make a cavity which suitably accommodates only Pd 2+ (van der Waal’s radius, 1.7 Å) through the Pd(II)-carboxylato (–COO–Pd) coordination. The stability of the composite, [CP 1 + Pd 2+ ] may be assessed from the fluorescence quenching experiment, and the Stern–Volmer constant ( K SV ) is 7.2 × 10 4 M –1 . Therefore, the compound, CP 1, is a promising sensor for Pd(II) in a selective manner with limit of detection (LOD), 0.08 μM. The XPS spectra of CP 1 and [CP 1 + Pd 2+ ] have proven the presence of Pd 2+ in the host and the existence of a coordinated –COO–Pd bond. Interestingly, inclusion of Pd 2+ in CP 1 decreases the band gap from 3.61 eV (CP 1 ) to 3.05 eV ([CP 1 + Pd 2+ ]) which lies in the semiconducting region and has exhibited improved electrical conductivity from 7.42 × 10 –5 (CP 1 ) to 1.20 × 10 –4 S m –1 ([CP 1 + Pd 2+ ]). Upon light irradiation, the electrical conductivities are enhanced to 1.45 × 10 –4 S m –1 (CP 1 ) and 3.81 × 10 –4 S m –1 ([CP 1 + Pd 2+ ]); which validates the highly desired photoresponsive device applications. Therefore, such type of materials may serve as SDG-army (sustainable development goal) to battle against the environmental issues and energy crisis.