Improved electrical conductivity of Co(ii) and Cu(ii) ladder polymers in the fabrication of photoresponsive Schottky devices

Abstract

In this work, two new Cu(II) and Co(II) based coordination polymers (CPs), [Co₂(bpd)₂(nac)₂]·2CH₃OH·H₂O (Co-CP) and [Cu₂(bpd)₂(nac)₂]·2CH₃CN·2H₂O (Cu-CP) respectively, have been synthesized using a bidentate pyridyl ligand, N,N′-bis(1-pyridine-4-yl-ethylidene) (bpd), linker with the less explored 3-(1-naphthyl)acrylic acid (nac) ligand appended at the metal centre to fulfil the molecular geometry. Here, Co-CP forms a one-dimensional (1D) ladder polymer, whereas Cu-CP consists of a combination of 1D chains and 1D ladder polymers. Interestingly, both the CPs exhibit semiconducting behaviour with increased conductivity upon illumination, signifying the photosensitive nature. However, Cu-CP reveals better conductivity as compared to Co-CP. This is obvious from the field emission electron microscopy (FESEM) study, where Cu-CP with flower-like morphology shows a higher surface area with respect to the rod-shaped morphology of Co-CP, resulting in higher charge transport. To the best of our knowledge, Co/Cu based CPs showing photosensitivity seem to be scarce. Thus, this study opens a new avenue in the fabrication of photoresponsive electronic devices.