Issue 21, 2019

On/off fluorescence emission induced by encapsulation, exchange and reversible encapsulation of a BODIPY-guest in self-assembled organometallic cages

Abstract

A dynamic guest-binding study of BODIPY-derivative 3 (3 = 1,3,5,7,8-pentamethyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) with two Cp*RhIII-based organometallic cages [Cp*6Rh6(μ-CA)3(tpt)2](OTf)61 (H2CA = chloranilic acid, tpt = 2,4,6-tripyridyl-1,3,5-triazine) and [Cp*6Rh6(μ-DHNA)3(tpt)2](OTf)62 (H2DHNA = 6,11-dihydroxynaphthacene-5,12-dione) have been demonstrated. While guest 3 displays a strong green fluorescence emission, the host–guest complexes 31 and 32 exhibit almost no emission. However, fluorescence emission can be again ‘turned on’ by adding coronene (4) or pyrene (5) into the solution of 31 and 32. Guests 4 and 5 show stronger binding affinities toward the organometallic cages 1 and 2 due to the strong electrostatic interactions between the electron-rich guest and electron-deficient tpt resulting in the displacement of 3 by 4 or 5, which eventually helps the fluorescence enhancement. Further guest-binding studies using a Job's plot experiment illustrate the formation of discrete 1 : 1 host–guest complexes which are also supported by 1H NMR spectroscopy and ESI mass spectrometry. The anion-exchange study with sodium chloride reveals that the chloride ion can effectively disassemble the host frameworks of 1 and 2 releasing the fluorescent guest 3 which can be again encapsulated into the cavity of reassembled cages promoted by the addition of silver triflate.

Graphical abstract: On/off fluorescence emission induced by encapsulation, exchange and reversible encapsulation of a BODIPY-guest in self-assembled organometallic cages

Supplementary files

Article information

Article type
Paper
Submitted
24 Ker. 2018
Accepted
21 Gen. 2019
First published
22 Gen. 2019

Dalton Trans., 2019,48, 7236-7241

On/off fluorescence emission induced by encapsulation, exchange and reversible encapsulation of a BODIPY-guest in self-assembled organometallic cages

X. Gou, J. Peng, R. Das, Y. Wang and Y. Han, Dalton Trans., 2019, 48, 7236 DOI: 10.1039/C8DT05103H

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