Interplay between Magnetism and Photochromism in Spiropyran−MnPS₃ Intercalation Compounds

Abstract

N-Methylated pyridospiropyran cations SP-R+ (R= Me, Ph) have been inserted into MnPS3 by ion exchange to yield Mn1-xPS3(SP-R)2x intercalates. Thin transparent films of these materials have been processed, which exhibit photochromism due to spiropyran−merocyanin transformation. Intercalation considerably stabilizes the merocyanin form. When R = Me, the films are stable in the dark over months. Such a strong stabilization may be due to the formation of J-aggregates within the weakly polar interlayer medium of the MnPS3 host lattice. The modifications of the basal spacing associated with photochromism have been characterized. One of the two intercalates (R = Me) acquires a spontaneous magnetization below about 40 K. Irradiation does not change Tc but considerably affects the hysteresis loop, increasing remanence and coercitivity.