Aminoisophthalate Bridged Cd(II)-2D Coordination Polymer: Structure Description, Selective Detection of Pd²⁺ in Aqueous Medium, and Fabrication of Schottky Diode

Photoluminescence activity of coordination polymers (CPs)has evokedintricate applications in the field of materials science, especiallysensing of ions/molecules. In the present study, 2,3,5,6-tetrakis(2-pyridyl)pyrazine(tppz) and 5-aminoisophthalate (HAIPA(-)) coordinatedto Cd(II) to architect a coordination polymer, {[Cd(HAIPA)(tppz)(OH)]& BULL;3H(2)O}( n ) (CP1) which unveilsblue emission in an aqueous acetonitrile (98% aqueous) suspension.The emission is selectively quenched by Pd2+ only withoutinterference in the presence of as many as 16 other cations. The structureof CP1 shows the presence of a free -COOH group,and the interlayer (-CO)O(2)& BULL;& BULL;& BULL;O(7) (OC-)distance, 4.242 & ANGS;, along with the & pi;& BULL;& BULL;& BULL;& pi;interactions (3.990, 3.927 & ANGS;), may make a cavity which suitablyaccommodates only Pd2+ (van der Waal's radius, 1.7 & ANGS;) through the Pd(II)-carboxylato (-COO-Pd) coordination.The stability of the composite, [CP1 + Pd2+] may be assessed from the fluorescence quenching experiment, andthe Stern-Volmer constant (K (SV))is 7.2 x 10(4) M-1. Therefore, thecompound, CP1, is a promising sensor for Pd(II) in aselective manner with limit of detection (LOD), 0.08 & mu;M. TheXPS spectra of CP1 and [CP1 + Pd2+] have proven the presence of Pd2+ in the host and theexistence of a coordinated -COO-Pd bond. Interestingly,inclusion of Pd2+ in CP1 decreases the bandgap from 3.61 eV (CP1) to 3.05 eV ([CP1 +Pd2+]) which lies in the semiconducting region and hasexhibited improved electrical conductivity from 7.42 x 10(-5) (CP1) to 1.20 x 10(-4) S m(-1) ([CP1 + Pd2+]).Upon light irradiation, the electrical conductivities are enhancedto 1.45 x 10(-4) S m(-1) (CP1) and 3.81 x 10(-4) S m(-1) ([CP1 + Pd2+]); which validates the highlydesired photoresponsive device applications. Therefore, such typeof materials may serve as SDG-army (sustainable development goal)to battle against the environmental issues and energy crisis. 5-Aminoisophthalic acid and 2,3,5,6-tetrakis(2-pyridyl)pyrazineconstruct a highly luminescent 2D coordination polymer with Cd(II)which is quenched by Pd2+ only in an aqueous (98%) medium(LOD, 0.08 & mu;M). The 2D CP- and Pd2+-loaded materialsexhibit electrical conductivities which are enhanced by light irradiation.