Elucidating structure–property relationships in Cd(ii) coordination polymers for enhanced charge transport properties and Schottky device fabrication

Abstract

Herein, we report the synthesis of two isostructural one-dimensional (1D) Cd(II) coordination polymers (CPs) based on the monodentate 4-[2-(9-anthryl)vinyl]pyridine (4-avp) ligand, namely, [Cd(DCTP)(4-avp)₂(CH₃OH)₂] (CP1) and [Cd(DBTP)(4-avp)₂(CH₃OH)(H₂O)] (CP2), using bidentate O-donor linkers 2,5-dichloroterephthalic acid (H₂DCTP) and 2,5-dibromoterephthalic acid (H₂DBTP), respectively. CP1 and CP2 are synthesized and characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy and single-crystal X-ray diffraction (SCXRD). Structural analyses reveal that both CP1 and CP2 form 1D chain polymers via the bridging of the ditopic linkers H₂DCTP/H₂DBTP. Interestingly, both CPs exhibit electrical conductivity and Schottky behavior. However, CP1 exhibits superior conductivity (7.55 × 10⁻⁴ S m⁻¹) over CP2 (3.78 × 10⁻⁴ S m⁻¹). This difference in conductivity is rationalized by solid-state density functional theory (DFT) calculations, which reveal that the frontier orbitals (HOMO and LUMO) are exclusively localized on the conjugated 4-avp linkers. Consequently, the superior charge transport in CP1 is attributed to the parallel π⋯π stacking of these active 4-avp units, which provides a more efficient orbital overlap than the crossed arrangement observed in CP2. These results highlight the critical role of ligand arrangement in modulating the electronic properties of d¹⁰ metal-based CPs for electronic device fabrication.