Fluorescence sensor for water based on PET (photo-induced electron transfer): Anthracene-bis(aminomethyl)phenylboronic acid ester

• A fluorescence PET-type sensor for water based on anthracene have been developed.
• Introduction of two phenylboronic acid ester on fluorophore activates the PET.
• To enhance the Lewis acidity of boronic acid ester is effective for the PET sensor.

In order to provide a direction in molecular design toward creating a highly-sensitive fluorescence PET (photo-induced electron transfer) sensor for a trace amount of water in organic solvents, we have designed and synthesized anthracene-bis(aminomethyl)phenylboronic acid ester OA-1 and OA-2, without substituent and with cyano group, respectively, on the phenylboronic acid ester. It was found that the introduction of bis(aminomethyl)phenylboronic acid ester on the fluorophore such as anthracene activates significantly the PET compared with that of an (aminomethyl)phenylboronic acid ester. On the basis of the proposed mechanisms of fluorescence PET sensors for detection of water, a key point for creating a highly-sensitive fluorescence PET sensor based on fluorophore–phenylboronic acid ester for a trace amount of water is to effectively facilitate the formation of fluorescent ionic structure by the addition of water molecules.

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