Anthracene-boronic acid ester as a new class of fluorescence PET sensors for detection of a trace amount of water in organic solvents has been designed and developed.

A series of anthracene-boronic acid ester OM-1, OM-2, OU-1, and OU-2 have been designed and synthesized as a new class of fluorescence PET (photo-induced electron transfer) sensors for detection and quantification of a trace amount of water in organic solvents. OM-1 and OM-2 have a boronic acid ester and bisboronic acid ester, respectively, located at the proximity of a tertiary amino group as an electron donor via a methylene spacer at the 9-position on the anthracene fluorophore. In OU-1, on the 10 other hand, a boronic acid ester is directly connected to the 10-position on the anthracene fluorophore. OU-2 has bisboronic acid ester, which are located at the same positions as those of OM-1 and OU-1. It was found that OM-1 and OM-2 show enhancement of fluorescence with the increase in water content for various solvents (polar, less polar, protic and aprotic solvents), which can be attributed to the suppression of PET due to the formation of fluorescent ionic structure OM-1a or OM-2a by hydrolysis. 15For OU-1 and OU-2, on the other hand, there is no appreciable change in fluorescence intensity upon addition of water to the solution. We propose that a key point for creating a highly-sensitive fluorescence PET sensor for detection of a trace amount of water is to design molecular structures capable of forming stable fluorescent ionic structure between the protonated tertiary amino group and the hydroxylated boronic acid ester by hydrolysis. 20 65 range of application to various solvents, we have designed and synthesized anthracene-boronic acid ester OU-1 and anthracenebisboronic acid ester OU-2 (Scheme 3). In OU-1, a boronic acid ester is directly connected to the 10-position on the anthracene fluorophore. On the other hand, OU-2 has bisboronic acid ester, 70 which are located at the same positions as those of OM-1 and OU-1. This work indicates that a key point for creating a highly-Journal Name, [year], [vol], 00-00 | 5 5 10 15 20 25 Fig. 6 Fluorescence peak intensity of OM-2 at around 415 nm (λ ex = 366 nm) as a function of water content in (a) 1,4-dioxane, (b) THF, (c) acetonitrile and (d) ethanol.

No abstract

No abstract