Magnetic and photoluminescent properties of three new organic radical cation salts

Three new organic radical cation salts were prepared by exchanging perchlorate anion of 2,3′-biimidazo[1,2-a]pyridin-2′-one radical perchlorate salt with metal coordination anions. These cation salts, [H (Hbipo–)]+2· [FeCl4]2–·H2O (1), [H (Hbipo–)]+2· [MnCl4]2–(2) and [H (Hbipo–)]+·[Zn(SCN)3] –·H2O (3), were characterized by EPR and IR spectra, and their composition was demonstrated by the elemental analyses and TGA analyses. Salts 1, 2 and 3 mainly exhibit antiferromagnetic properties, however, salts 2 and 3 reveal interesting magnetic phase transition at 243 K and 65 K, respectively. Compared to 2,3′-biimidazo[1,2-a]pyridin-2′-one radical itself (green emission), salts 1, 2 and 3 display obviously blue shifted to blue emission, attributable to their low HOMO energy level caused by the protonation of N atom at imidazo[1,2-a]pyridine ring. Present work will provide new organic radical cation for the preparation of molecular materials with combination of different physical properties by using various metal coordination anions.