Electronic, Optical, and Computational Studies of a Redox-Active Napthalenediimide-Based Coordination Polymer

The new one-dimensional coordination framework (Zn(DMF)NO3)(2)(NDC)(DPMNI), where NDC = 2,6-naphthalenedicarboxylate and DPMNI = N,N'-bis(4-pyridyl-methyl)-1,4,5,8-naphthalenetetracarboxydiimide, which has been crystallographically characterized, exhibits two redox-accessible states due to the successive reduction of the naphthalenediimide (NDI) ligand core. Solid-state electrochemical and vis near-IR spectroelectrochemical measurements coupled with density functional theory (DFT) calculations enabled the origins of the optical transitions in the spectra of the monoradical anion and dianion states of the material to be assigned. Electron paramagnetic resonance (EPR) spectroscopy revealed that the paramagnetic radical anion state of the DPMNI core could be accessed upon broad-spectrum white light irradiation of the material, revealing a long-lived excited state, possibly stabilized by charge delocalization which arises from extensive pi-pi r* stacking interactions between alternating NDC and NDI aromatic cores which are separated by a distance of 3.580(2) angstrom.