Paper
NJC
respect to the influence of the position of the amido group and
the polarity of the surrounding solvent medium in dictating the
excited state properties of the dyes. Detailed investigation of the
photophysical properties as a function of the solvent polarity
parameter, Df, have revealed interesting similarities as well
as differences in the photophysics of the two series of dyes.
Notably, for both the DPA and TPA dyes, the individual photo-
physical parameters of the derivatives are found to vary depending
on the position of the amido substituent (ortho-, meta- or para-),
although the overall behavior of the dyes as a function of the
solvent polarity remains similar for a particular series, with the
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nature of the emissive S state being governed by the polarity of
1
the solvent medium. Thus, for the TPA series, emission arises
1
from a nonpolar S state in the nonpolar solvent region below
Df B 0.05, and from the ICT state in the moderate to higher
polarity solvent region (Df B 0.05–0.3). For the DPA series, on the 10 A. Mahmood, Sol. Energy, 2016, 123, 127–144.
other hand, the emission is indicated to arise from a nonpolar S
state in the nonpolar solvent region (Df o 0.01), from ICT state in
the intermediate polarity region (Df B 0.01–0.2), and from TICT
1
11 R. Yuan, L. Zhang, L. Chen, H. Zhang, P. Dou, X. Ren,
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intriguing solvent polarity dependent photophysics of DPA and 14 N. Niamnont, N. Kimpitak, K. Wongravee, P. Rashatasakhon,
TPA derivatives is a new observation that has not been reported
earlier for this class of dyes. These results are expected to provide
K. K. Baldridge, J. S. Siegel and M. Sukwattanasinitt, Chem.
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valuable insights for the design and use of TPA and DPA based 15 X. Gan, X. Ge, C. Zhai, J. Zheng, X. Tang, Y. Yang, Y. Tian,
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observations suggest that both the DPA and TPA series of dyes can 16 S. Erdemir, Sens. Actuators, B, 2019, 290, 558–564.
serve as good solvatochromic probes to investigate the polarity of 17 Y. Wang, J. Liu, W. Yuan, Y. Wang, H. Zhou, X. Liu, J. Cao
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derivatives, the para-substituted dyes, TPA-p and DPA-p, by 18 Q. Lu, C. Yang, X. Qiao, X. Zhang, W. Cai, Y. Chen, Y. Wang,
virtue of their higher fluorescence quantum yields, are sug-
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Furthermore, the participation of the TICT state in the photo- 19 Y. Zhang, M. Jiang, G.-C. Han, K. Zhao, B. Z. Tang and
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cence on/off sensors based on the DPA motif, wherein suitable 20 R. Lartia, C. Allain, G. Bordeau, F. Schmidt, C. Fiorini-
binding agents can be employed to reversibly tune the formation
of the TICT state.
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Conflicts of interest
There are no conflicts of interest to declare.
Acknowledgements
24 M. Koenig, G. Bottari, G. Brancato, V. Barone, D. M. Guldi
and T. Torres, Chem. Sci., 2013, 4, 2502–2511.
The authors gratefully acknowledge the generous support
provided by their respective host institutes, Bhabha Atomic
Research Centre (BARC), Mumbai and CSIR-Central Leather
Research Institute, Chennai.
2
5 D. Peckus, T. Matulaitis, M. Franckevi ˇc ius, V. Mimaite,
T. Tamulevi ˇc ius, J. Simokaitiene, D. Volyniuk, V. Gulbinas,
S. Tamulevi ˇc ius and J. V. Gra ˇz uleviius, J. Phys. Chem. A,
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2
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6 A. Kundu, S. Karthikeyan, Y. Sagara, D. Moon and S. P.
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7 J.-H. Wu, W.-C. Chen and G.-S. Liou, Polym. Chem., 2016, 7,
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Notes and references
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