A photochromic molecule-based magnet

A molecule-based magnet of formula (SP)MnCr(ox)(3).H2O has been synthesized, where SP+ stands for a new N-methylated pyridospiropyran cation and ox(2-) represents the oxalate anion. The compound orders ferromagnetically at 5.5 K and exhibits crystalline-state photochromism. The main spectrokinetic data of the UV-induced open form of SP+ are strongly modified in (SP)MnCr(ox)(3).H2O as compared to those found in (SP)I. The reversible photoreaction of SP+ does not modulate the critical temperature of the long-range ferromagnetic order in (SP)MnCr(ox)(3).H2O but modifies in a significant way its hysteresis loop.