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4,5-Diazafluorene co-oligomers as electron-deficient light-emitting materials and selective fluorescence sensors for mercury(II) cations

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Abstract

A series of 4,5-diazafluorene-based (N) conjugated co-oligomers with 9,9-dialkylfluorene (F) or electron-deficient dibenzothiophene-S,S-dioxide (S) has been synthesized by Pd-catalyzed coupling reaction (FNF, FFNFF, FNoF, SNS, NSN). Cyclic voltammetry studies reveal their improved electron affinity compared to oligofluorene. SNS and NSN co-oligomers showed a decrease of their LUMO energies by 0.37–0.38 eV compared to FNF co-oligomer. Absorption/emission studies showed that all oligomers, except FNoF, are blue-emitting materials (λPL ∼ 400–450 nm) with high quantum yields of their photoluminescence (ΦPL = 84–100% in solution and 24–42% in the solid state). FNoF trimer emits in the yellow region with a very low ΦPL ∼ 1% in dichloromethane solution, but the emission efficiency is substantially increased to ΦPL = 10–17% in the solid state. FNF co-oligomer was studied as a metal cation responsive colorimetric and fluorescent sensor using a series of mono- and divalent cations and it showed high sensitivity and selectivity toward mercury cations. Upon addition of Hg2+, the blue emission of FNF (λPL = 404 nm) was quenched and a new, bathochromically shifted (to the green region, λPL = 507 nm) emission band appeared, which allows this compound to be used as both an “ON → OFF” and “OFF → ON” fluorescent sensor.

Graphical abstract: 4,5-Diazafluorene co-oligomers as electron-deficient light-emitting materials and selective fluorescence sensors for mercury(ii) cations

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Publication details

The article was received on 07 Nov 2017, accepted on 31 Jan 2018 and first published on 31 Jan 2018


Article type: Paper
DOI: 10.1039/C7TC05051H
Citation: J. Mater. Chem. C, 2018, Advance Article
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    4,5-Diazafluorene co-oligomers as electron-deficient light-emitting materials and selective fluorescence sensors for mercury(II) cations

    S. Ghosh, A. S. Alghunaim, M. H. Al-mashhadani, M. P. Krompiec, M. Hallett and I. F. Perepichka, J. Mater. Chem. C, 2018, Advance Article , DOI: 10.1039/C7TC05051H

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