Structural, optical, dielectric and electrical transport properties of a [Mg(H2O)6]2+-templated proton conducting, semiconducting and photoresponsive 3D hydrogen bonded supramolecular framework

Abstract

Herein, we have presented the crystal structure, supramolecular structure and band structure along with dielectric, electrical transport and optoelectronic properties of a [Mg(H₂O)₆]²⁺ templated 3D hydrogen bonded supramolecular framework (HSF) {[Co(2,5-Pdc)₂,(H₂O)₂]²⁻·[Mg(H₂O)₆]²⁺·4(H₂O)} (where 2,5-pdc = 2,5-pyridinedicarboxylate) synthesized by reflux method. The complex crystallizes in the P space group. The 3D network of the complex has been built up by hydrogen bonding interactions between 2D supramolecular sheets of the complex. The proton conductivity and activation energy of the complex are ∼10⁻⁴ S cm⁻¹ at 40 °C and ∼0.3 eV, respectively, under vacuum. It exhibits anomalous dielectric behavior due to the gradual release of guest water molecules above 40 °C. The complex is a semiconductor with a band gap of 1.626 eV and is capable of absorbing electromagnetic radiation in the range of 355–730 nm. The ITO/complex/Al sandwiched device exhibits Schottky barrier diode (SBD)-like behaviour with a rectification ratio of 13 in the dark and 34 under visible light at 1 V. When exposed to visible light (AM 1.5G) the value of its conductivity enhances 1.35 times, compared to that in the dark. It has been shown that the complex is a semiconducting proton conducting photoresponsive HSF.