A novel multicolor viologen-derived Zn-organic coordination polymer for environment friendly ink free erasable printing

Highlights: • CP 1 was synthesized using viologen ligand 1,1′-bis-((3-carboxylatobenzyl)-4,4′-bipyridinium) dichloride (H₂bcbpy·2Cl). • CP 1 exhibited photochromic properties under xenon lamp and blue light irradiation. • CP 1 obtaining a structurally stable light product 1T after irradiation. • CP 1 can be used as a good ink-free printing medium. A novel multifunctional coordination polymer {[Zn(HCOO) (bcbpy)Cl]·H₂O}_n (1) with multiple colour-changing has been synthesized from Zn(NO₃)₂·6H₂O, and viologen ligand 1,1′-bis-((3-carboxylatobenzyl)-4,4′-bipyridinium) dichloride (H₂bcbpy·2Cl). In coordination polymer (CP) 1, bcbpy ligands bridge Zn²⁺ cations to form a 1D wave-like chain. CP 1 exhibited photochromic properties under xenon lamp and blue light irradiation while obtaining a structurally stable light product 1T. CP 1 thermochromic properties can also be observed during heating. 1 showed photo-controlled fluorescence properties during color rendering and decolorization, and its properties were studied. Interestingly, CP 1 can be deposited in filter paper by coating it with a solution of H₂O. The filter paper can be used as a printing medium without ink.