Issue 14, 2018

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

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

Supplementary files

Article information

Article type
Paper
Submitted
07 Pun 2017
Accepted
31 Phe 2018
First published
31 Phe 2018

J. Mater. Chem. C, 2018,6, 3762-3773

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, 6, 3762 DOI: 10.1039/C7TC05051H

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