A novel naphthalene diimide cobalt coordination polymer: synthesis, photo/electric/dehydration discoloration, amine sensing, and magnetism†

A novel naphthalenediimide coordination polymer (CP), [Co₃(BINDI)(μ₃-OH)(μ₂-OH)·6H₂O·2H₂O] (1), was synthesized via a solvothermal method using N,N′-bis(5-isophthalic acid)naphthalenediimide (H₄BINDI), Co(NO₃)₂·6H₂O and isophthalic acid (H₂IPA). Single crystal X-ray diffraction analysis revealed a three-dimensional structure formed by the BINDI⁴⁻ anion and the Co²⁺ cation. CP 1 exhibited rapid color changes: from reddish brown to dark brown under a 300 W xenon lamp within 1 min, colorless to light blue at voltages between −1 V and −0.5 V, and reddish brown to deep purple upon heating at 90 °C for 3 h. Additionally, CP 1 was used to detect ammonia vapor and o-toluidine through color changes and fluorescence quenching, with Stern–Volmer quenching constants (K_SV) of 8.93 × 10² M⁻¹ and 5.895 × 10² M⁻¹, and detection limits (LOD) of 2.23 μM and 2.60 μM, respectively. CP 1 exhibited optical activity and yielded structurally stable product 1@blue upon illumination. It was found that antiferromagnetic interactions can be tuned by light irradiation. Moreover, density functional theory (DFT) was used to furnish theoretical support for the color-changing behavior of CP 1.