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Organic Nanoparticles Based on Lewis-pair Formation: Observation of Prototropically Controlled Dual Fluorescence

Organic Nanoparticles Based on Lewis-pair Formation: Observation of Prototropically Controlled Dual Fluorescence

Hiroshi Yao, Hikaru Minami, Tomohito Funada

Photochem Photobiol Sci. 2018 Oct 10;17(10):1376-1385.

PMID: 30198040

Abstract:

We successfully synthesize fluorescent organic nanoparticles of a Lewis-pair consisting of an amino-type hydrogen-bonding molecule (Lewis base) and a borinate derivative (Lewis acid). 2-(2'-Aminophenyl)benzothiazole (o-ABT) is chosen as the fluorophore. This molecule has a transferable proton in the amino group, but it does not exhibit ESIPT (excited-state intramolecular proton transfer) reaction in solution and thus shows a single normal emission solely from the enamine form. Organic nanoparticles are prepared by the reprecipitation method in which the fluorophore (o-ABT) in conjunction with a Lewis acid (diphenylborinic anhydride; DPBA) dissolved in a good solvent is rapidly injected into water under sonication. Interestingly, the nanoparticles produced exhibit a characteristic dual fluorescence that can be ascribed to the enamine and imine tautomers of o-ABT generated in the ground-state prototropy, which can be revealed by UV-vis absorption and excitation spectroscopy, IR spectroscopy and computational approaches. In the o-ABT/DPBA Lewis-pair nanoparticles, highly Stokes-shifted emission from the imine tautomer is enhanced in comparison with that from the molecularly dissolved state, suggesting that the present nanofabrication methodology based on Lewis acid-base chemistry (or N-B bonding interaction) plays a key role in tuning the fluorescence colour for the new type of organic nanoparticle.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP4426215	Diphenylborinic anhydride		4426-21-5	Price

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