Spectroscopic Response of Ferrocene Derivatives Bearing a BODIPY Moiety to Water: A New Dissociation Reaction

Ferrocence and its derivatives have long been known to be a class of stable organometallic compounds, and their dissociation usually occurs under harsh conditions. Here we report a new type of ferrocene derivatives, 4,4‐difluoro‐8‐ferrocenyl‐1,3,5,7‐tetramethyl‐4‐bora‐3a,4a‐diaza‐ s ‐indacene and 4,4‐difluoro‐2,6‐diethyl‐8‐ferrocenyl‐1,3,5,7‐tetramethyl‐4‐bora‐3a,4a‐diaza‐ s ‐indacene, which surprisingly can hydrolyze under mild conditions. These two derivatives, initially developed as donor–acceptor probes for reactive oxygen species by incorporating the electron donor of ferrocene as a quencher into the fluorophore of BODIPY (boron dipyrromethene difluoride), barely emit fluorescence. Upon reaction with H 2 O under the irradiation of natural light at room temperature, however, both of the probes display a dramatic color change and fluorescence retrievement. Detailed experimental results reveal that the reaction of the probes with H 2 O leads to the removal of a cyclopentadiene unit and iron(II), yielding a BODIPY derivative that retains the other cyclopentadiene unit and shows a large fluorescence enhancement (over 100‐fold). Moreover, the increase in fluorescence intensity is directly proportional to microamount of water, and the presence of both light and H 2 O is indispensable in the reaction, which makes the present system of great potential not only for determining water but also for forming a AND logic gate. Most importantly, the present mild dissociation reaction may give a new insight into the stability of ferrocene and its derivatives.