Effect of Hydrogen Bonding on the Luminescence Lifetime and Device Resistance: A Case Study Based on Two New Related Cd-Based Coordination Polymers

Abstract

Two new coordination polymers of formulas [Cd2(2,3-pzdc)­(tz)2] (1) and [Cd2(2,3-pzdc)­(dtz)2] (2) {2,3-pzdc = 2,3-pyrazine dicarboxylate, tz = 1,2,4-triazolate, dtz = 3,5-diamino-1,2,4-triazolate)} were synthesized via hydrothermal techniques. Both the compounds were characterized by single-crystal X-ray analysis, powder X-ray diffraction, Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). Single-crystal X-ray analysis shows that both the structures are three-dimensional in nature and connectivity-wise they are similar to each other. In compound 2, the presence of N–H···O hydrogen-bond interactions further stabilized the structure. Aqueous dispersion of both the compounds showed a strong dual emissionone at around 353 nm and another at 369 nm upon excitation at 280 nm. Lifetime studies from time-resolved spectra show 0.82 and 0.60 ns for compound 1 and 2.02 and 1.78 ns for compound 2. The higher lifetimes of the excited states in the case of compound 2 establish the role of hydrogen-bond interactions in reducing the nonradiative decay processes. To explore the junction properties at the Al/material interface of these Schottky barrier diodes, the dark J–V characteristics of both of the devices (ITO/PEDOT/compound 1/Al and ITO/PEDOT/compound 2/Al) were analyzed using the well-known Shockley diode equation. In both the devices (with compound 1 and compound 2), asymmetric behavior is observed under forward and reverse bias, indicating rectification. However, in the compound 2 device, the overall current magnitude is 10 times higher than that of the compound 1 device. The series resistance extracted for the compound 2 device is ≈ 22 times lower than that of the compound 1 device, indicating the higher conductivity of compound 2. This behavior indicates a probable role of hydrogen-bond interactions in the lower resistance and higher conductivity of compound 2 compared to compound 1.

Differential supercapacitor and Schottky diode behaviours in two new isostructural coordination polymers based on redox active metal ions

“…46,47 Furthermore, the impact of distinct functional groups and hydrogen bonding within coordination polymers, along with their photosensitive properties, on conductivity and device manufacturing has been established as a well-explored area of research. [48][49][50][51][52] The study of Schottky diodes in the context of isostructural coordination polymers, with the only difference in the metal ions used, has not been explored yet.…”