Cd(II) Based Coordination Polymer Series: Fascinating Structures, Efficient Semiconductors, and Promising Nitro Aromatic Sensing

Three Cd(II) based coordination polymers (CPs) (1-3) are designed using 3-aminoquinoline and 5-aminoquinoline based Schiff base ligands and thiocyanate and dicyanamide as bridging ligands. Pseudohalide linkers play a crucial role in the architecture of the CPs. These compounds are prepared under an ambient condition with high yield. The I-V characteristics of the 1-3 based thin film devices (Al/complex interface) under dark and illumination conditions are nonlinear rectifying nature, which is the signature of a Schottky barrier diode (SBD). The rectification ratio (I-on/I-off) of the SBDs under dark condition at +/- 2 V has been obtained as 16.41, 15.48, and 14.73 and under illumination conditions; the same has been evaluated as 67.18, 46.23, and 37.69 for 1, 2, and 3, respectively. The photoresponsivity of the device is found to be 5.52, 2.89, and 2.54 for 1, 2, and 3 based SBDs, respectively. The enhancement of conductivity under photoilluminated conditions depends on pi-electron donor capacity of Schiff base ligands and the length of pseudohalide linkers of 1-3. Again, depending on the binding fashion of the coordinating ligands, three CPs (1-3) exhibit different selectivity toward nitroaromatic sensing. In 2,4,6-trinitrophenol (TNP) sensing, CPs follow the order 3 > 2 > 1. CP 3 has the highest quenching constant among the other two CPs along with a prominent selectivity and lowest detection limit in response to TNP.