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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.

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In order to provide a direction in molecular design of catechol (Cat) dyes for type II dye-sensitized solar cells (DSSCs), the dye-to-TiO2 charge-transfer (DTCT) characteristics of Cat dyes with various substituents and their photovoltaic performance in DSSCs are investigated. The Cat dyes with electron-donating or moderately electron-withdrawing substituents exhibit a broad absorption band corresponding to DTCT upon binding to TiO2 films, whereas those with strongly electron-withdrawing substituents exhibit weak DTCT. This study indicates that the introduction of a moderately electron-withdrawing substituent on the Cat moiety leads to not only an increase in the DTCT efficiency, but also the retardation of back electron transfer. This results in favorable conditions for the type II electron-injection pathway from the ground state of the Cat dye to the conduction band of the TiO2 electrode by the photoexcitation of DTCT bands.

Effective and convenient co-sensitization to enhance dye coverage on TiO 2 electrodes for dye-sensitized solar cells have been achieved successfully by employing two kinds of D-p-A dyes with a pyridyl group capable of adsorbing at the Brønsted acid sites and the Lewis acid sites on a TiO 2 surface.Scheme 1 Chemical structures of D-p-A dye sensitizers NI-5, NI-6, YNI-2 and SAT-1.