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COMMUNICATION
DOI: 10.1039/C4CC09857A
dDepartament de Química Física, Universitat de Barcelona, Diagonal 645,
Barcelona 08028, Spain
2 photomerocyanine dye to a wellꢀcharacterized fluidic processor,
namely a vortex fluidic device (VFD23). Here any change in the
decoloration rate of SP-2 arising from the shear present in the
dynamic thin film may reflect perturbations to the HB environment.
The VFD is a flow processor that is likely to become a more
versatile alternative to conventional fluidics schemes, such as the
spinning disk processor. In a VFD (Fig. 3) subꢀmL samples can be
maintained within the tube, hence removing the need for large
volumes of liquid, while the shear in the film is controlled simply by
the speed and the orientation of the tube with the presence of
Stewartson/Ekman layers. Remarkably, kinetic data on the
decoloration of SP-2 solutions reveal a fluidic effect on the apparent
HB balance for this particular system (Table S9, ESI†). For solvents
with either very large or moderate KꢀT β values (DMSO and THF,
Fig. 3a and 3b, respectively) it becomes apparent that under shear
the balance between intraꢀ and interꢀmolecular HB tends to shift in
favour of the former; i.e. the solvents “lose” some of their HBA
†Electronic Supplementary Information (ESI) available. See
DOI: 10.1039/c000000x/
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stationary value. On the other hand, we found no evidence of shear
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,
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will stimulate further research in this area.
Conclusions
We have experimentally confirmed the usefulness of this simple
visual sensor of the HB character of a medium. The concept of
adding a latent intraꢀmolecular HB feature to a spiropyran dye and
the possibility of visually gauging changes to the thermodynamic
cost of this feature is in principle applicable to other families of
photochromic dyes, such as chromenes or spirooxazines. It is
possible to anticipate broader applications of this technique, for
instance changes to the thermal fading rates of SP-2 could be used
for the quick and sensitive determination of water traces in dry
organic solvents or to elucidate controversial issues such as the
nature of intermolecular interactions in ionic liquids24. We have also
shown that in the specific case of SP-2, the intraꢀ/interꢀmolecular
HB balance is altered by a shear stress stimulus in a fluid. Although
still debated,14a but most certainly with broad reaching implications,
the protein literature contains references to the possibility of shearꢀ
14c, 25
related protein denaturation.14b,
Clear insights on the
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A. Pople, Chem. Phys. Lett., 1999, 314, 101ꢀ107.
relationship between shearing forces and the thermodynamic
stability of proteins are still lacking, but our findings for SP-2 have
implication for understanding protein folding under shear stress.
SC acknowledges the University of Wollongong for a Vice
Chancellor Fellowship. CLR acknowledges financial support
from the Government of South Australia. Funding from the
ARC Centre of Excellence Scheme and resources provided
through the National Computational Merit Allocation Scheme
are also gratefully acknowledged.
19 A. V. Marenich, C. J. Cramer and D. G. Truhlar, J. Phys. Chem. A
,
2009, 113, 6378ꢀ6396.
20 Computed solvents effects on the stabilization and destabilization of
TS3 and TS5 indicate a degree of charge separation in these species
(see Figure S14, ESI†).
21 For SP-1 a zwitterionic transition state for the MC/SP relaxation is
generally accepted regardless of the solvent system (see Ref. 6).
22 S. E. Chung, W. Park, S. Shin, S. A. Lee and S. Kwon, Nat. Mater.
,
2008, , 581ꢀ587.
7
23 X. Chen, N. M. Smith, K. S. Iyer and C. L. Raston, Chem. Soc. Rev.
2014, 43, 1387ꢀ1399.
24 S. A. Katsyuba, M. V. Vener, E. E. Zvereva, Z. Fei, R. Scopelliti, G.
,
Notes and references
aARC Centre of Excellence for Electromaterials Science, Intelligent Polymer
Research Institute, University of Wollongong, Wollongong, NSW 2500,
Australia
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bSchool of Chemistry and Physical Sciences, Flinders University, Bedford
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cARC Centre of Excellence for Electromaterials Science, Research School of
Chemistry, Australian National University, Canberra, ACT 2601, Australia
4 | J. Name., 2012, 00, 1-3
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