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

Abstract

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.