Crystal Growth & Design
Article
The first is indicative of a heterogeneous one-dimensional
linear growth, and the second is indicative of heterogeneous
two-dimensional growth, with a decreasing nucleation rate over
time. The chemical system in the present work consists of light-
sensitive guest molecules that are almost isolated within cavities
formed by light-stable host molecules; therefore, we expected
different behavior. We have found that n = 0.95(6), indicating
that the growth mechanism is similar to the kinetics of o-
methoxy cinnamic acid.25 A very different Avrami exponent of
0.55(8) was recently reported for the [4 + 4] photo-
dimerization of 9-anthracene-carboxylic acid.26 An Avrami
exponent of 0.55 would lead to a negative dimensionality,
which might suggest an auto inhibition step in the reaction. It is
important to note that in this particular case the two monomers
are related by crystallographic translation leading to head-to-
head orientation (β-type packing); therefore, the carboxylic
acid groups have to adjust their conformations to enable
dimerization with minimal interference between them. This
might lead to additional disorder in the crystal, as suggested by
the authors.
ACKNOWLEDGMENTS
This work was supported by the Israel Science Foundation, no.
499/08.
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5. CONCLUSION
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ASSOCIATED CONTENT
* Supporting Information
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X-ray crystallographic information files (CIF) for compounds I-
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material is available free of charge via the Internet at http://
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AUTHOR INFORMATION
Corresponding Author
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Present Addresses
‡State Key Laboratory of Coordination Chemistry, Coordina-
tion Chemistry Institute, Nanjing University, Nanjing 210093,
People’s Republic of China.
§Structural Dynamics of (Bio)Chemical Systems, Max-Planck-
Institute for Biophysical Chemistry, Am Fassberg 11, 37077
Gottingen, Germany.
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Notes
The authors declare no competing financial interest.
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dx.doi.org/10.1021/cg3016707 | Cryst. Growth Des. 2013, 13, 936−941