Stable nitronyl nitroxide radical was incorporated into the benzene ring of novel photochromic bis(3-ethyl-3-hydroxy-6-methyl-1-oxoindan-2-ylidene), leading to the synthesis of novel multifunctional compound 1-((3,3'-diethyl-3,3'-dihydroxy-6'-methyl-1,1'-dioxo-[2,2']-biindanylidene)-6-ylmethyl)-4-(4",4", 5",5"-tetramethylimidazoline-2"-yl) pyridinium bromide 3"-oxide 1"-oxyl (3). The photochromic property, ESR spectroscopy and magnetic property of the title compound were investigated. Compound 3 possesses visible photochromism upon photoirradiation, and its ESR signal undergoes secular broadening after photoirradiation. The magnetic susceptibility measurement shows that the antiferromagnetic interaction in 3 becomes stronger after photoirradiation. The results demonstrated that both the colour and the magnetic property of compound 3 could be modulated by photoirradiation.

Key words: bis(indanon-2-ylidene), photomodulation magnetism, photochromism, organic solid multi- functional material