Aggregates of trans-4-Alkoxy-4′-carboxystilbenes
J. Phys. Chem. B, Vol. 101, No. 3, 1997 329
to CHEMX using the CHEMLIB software development tools.22
The interaction potential between the packing unit and all the
other molecules was then computed using the nonbonded and
electrostatic terms of the CFF91 force field given by eqs 1 and
2. The lattice energy for each stage was then computed using
eq 3.
Supporting Information Available: Atomic coordinates for
all atoms, bond lengths, and angles, anisotropic displacement
parameters, torsion angles, and least-squares planes (39 pages).
Ordering information is given on any current masthead page.
References and Notes
(1) Kuhn, H. In Light Induced Charge Separation in Biology and
Chemistry; Gerischer, H., Katz, J. J., Eds.; Dahlem Konferenzen: West
Berlin, 1979; pp 151-169.
(2) Gilman, P. B. In Photographic SensitiVity; Cox, R. J., Ed.; Academic
Press: London, 1973; p 187.
(3) Sturmer, D. M. In Special Topics in Heterocyclic Chemistry;
Weissburger, A., Taylor, E. C., Eds.; Wiley: New York, 1977; p 540.
(4) Furman, I.; Geiger, H. C.; Whitten, D. G.; Penner, T. L.; Ulman,
A. Langmuir 1994, 10, 837-843.
(5) Song, X.; Geiger, C.; Furman, I.; Whitten, D. G. J. Am. Chem.
Soc. 1994, 116, 4103-4104.
(6) Song, X.; Perlstein, J.; Whitten, D. G. J. Am. Chem. Soc. 1995,
117, 7816.
(7) Chen, H.; Law, K. Y.; Perlstein, J.; Whitten, D. G. J. Phys. Chem.
1994, 98, 5138.
9
6
Bij
Bij
Enb
)
A 2
- 3
(1)
∑
ij
( )
∑
( )
[
]
rij
rij
i,j
qiqj
Eel )
(2)
(3)
i,j ꢀ0rij
Elattice ) (1/2)(Enb + Eel)
In eq 1 Enb is the nonbonded van der Waals dispersive and
repulsive term with parameters Aij and Bij given by the force
field, and rij is the atom-atom distance. In eq 2 Eel is the
Coulomb electrostatic term with a dielectric constant ꢀ0 ) 1.0.
The summation in eqs 1 and 2 is over all atoms, i, in the packing
unit interacting with all atoms, j, in all the other molecules of
the crystal. The partial atomic charges, q, in eq 2 are those
given by the force field. Interestingly, the presence of H-
bonding in any KAP stage becomes readily apparent by
extracting the H atom contribution to eq 1. We make the
following assertion about the presence of H-bonding.
(8) Farahat, C. W.; Penner, T. L.; Ulman, A.; Whitten, D. G. J. Phys.
Chem. 1996, 100, 12616.
(9) Geiger, C. Unpublished results.
(10) Chen, H.; Farahat, M.; Law, K. Y.; Whitten, D. G. J. Am. Chem.
Soc. 1996, 118, 2584.
(11) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A29, 158-166.
(12) Cromer, D. T.; Waber, J. T. International Tables for X-ray
Crystallography; The Kynoch Press: Birmingham, England, 1974; Vol.
IV, Table 2.2 A.
(13) Cromer, D. T. International Tables for X-ray Crystallography; The
Kynoch Press: Birmingham, England, 1974; Vol. IV, Table 2.3.1.
(14) TEXSAN-TEXRAY Structure Analysis Package. Molecular Struc-
ture Corporation, 1985.
(15) Spooner, S. P. Ph.D. Thesis, University of Rochester, 1993.
(16) Finder, C. J.; Newton, M. G.; Allinger, N. L. Acta Crystallogr.
1974, B30, 411.
(17) Song, X.; Geiger, C.; Leinhos, U.; Perlstein, J.; Whitten, D. J. Am.
Chem. Soc. 1994, 116, 10340.
(18) Kitaigorodskii, A. I. Organic Chemical Crystallography; Consult-
ants Bureau: New York, 1961. Chapter 3, pp 65-112.
(19) (a) Hwang, M. J.; Stockfisch, T. P.; Hagler, A. T. J. Am. Chem.
Soc. 1994, 116, 2515-2525. (b) Maple, J. R.; Hwang, M.-J.; Stockfisch,
T. P.; Dinur, U.; Waldman, M.; Ewig, C. S.; Hagler, A. T. J. Comput.
Chem. 1994, 15, 162-182. (c) DiscoVer User Guide, Version 2.8 Part 2;
Biosym Technologies, San Diego, March 1992. A complete set of
parameters for the CFF91 force field are listed in this version.
(20) (a) Perlstein, J. J. Am. Chem. Soc. 1994, 116, 11420. (b) Perlstein,
J. J. Am. Chem. Soc. 1994, 116, 455.
For H atom donors (O or N) in the packing unit, Enb for the
hydrogen atom is always greater than 0 if the donor is inVolVed
in a hydrogen bond and less than or equal to 0 otherwise.
In another paper this is demonstrated with several examples.23
In the current case, for both 2 and 3, Enb for the donor hydrogen
on the carboxyl group is only greater than 0 in stage 3 of KAP.
We represent this as a type 13 hydrogen bond. In this notation
type 1 refers to the fact that the hydrogen bond only occurs in
a single KAP stage and the subscript indicates which one. There
are 16 H-bond types, which are detailed elsewhere.23
The lattice energy of each stage is finally given by eq 3, where
the 1/2 is inserted to avoid double counting of the energy. If
the packing unit contains more than one molecule, then the
lattice energy is computed by adding the energy of the packing
unit (stage 0 energy different from 0) to eq 3 and then dividing
by the number of molecules in the packing unit (for 2, this means
dividing by 2).
(21) Chen, H.; Law, K. Y.; Perlstein, J.; Whitten, D. G. J. Am. Chem.
Soc. 1995, 117, 7257-7258.
(22) CHEM-X is a molecular modeling program developed and distrib-
uted by Chemical Design Ltd., Roundway House, Cromwell Park, Chipping
Norton, Oxfordshire OX7 5SR, U.K. CHEMLIB is a CHEMX interface
that allows the user to link his own subroutines to CHEMX.
(23) Perlstein, J.; Steppe, K.; Vaday, S.; Ndip, E. M. J. Am. Chem. Soc.
1996, 118, 8433.