7/28/2019 Mutual influence of water/benzene interactions
1/1
a b a a
aDepartment of Chemistry, University of Belgrade, Studentski trg
16, 11000 Belgrade, SerbiabIHTM, University of Belgrade, Njegoeva
12, 11000 Belgrade, Serbia
INTRODUCTION
Interactions of water molecule with aromatic systems are of
great importance in fields of supramolecular chemistry, biological
systems,
crystal-engineering and materials science. During the last two
decades, water/benzene dimer has been intensively studied. It has
been
determined that the minimum energy structure of water/benzene
dimer is a structure with OH/ interaction (-3.19 kcal/mol)[1].
Water andbenzene can also form CH/O interaction (-1.38 kcal/mol)[2]
and parallel alignment interaction (-2.45 kcal/mol)[3].
METHODS
In order to investigate the mutual influence of water/benzene
interactions, ab initio
calculations were performed on water/benzene/water
model-systems. The most stable
geometries for OH/, CH/O and parallel alignment interactions
were used for constructionof water/benzene/water trimers. All
quantum chemical calculations were done using
Gaussian03 program. Potential energy surfaces of trimers were
investigated using MP2
method and cc-pVTZ basis set. For the most stable trimer
geometries single point energies
were calculated at MP2/cc-pVQZ level and corrected for BSSE
error. Interaction energies of
water/benzene dimers with another water molecule (ETRIMER) were
compared withenergies of corresponding water-benzene dimers
(EDIMER). The overall effect was then
judged by using the E value (E=ETRIMER-EDIMER).
REFERENCES
[1] B. D. Ostoji, G. V. Janji, S. D. Zari, Chem. Commun. 28,
6546 (2008)[2] D. . Veljkovi, G. V. Janji, S. D. Zari, CrystEngComm
13, 5005 (2011)[3] G. V. Janji, D. . Veljkovi, S. D. Zari, Cryst.
Growth Des. 11, 2680 (2011)
RESULTS
It was found that two OH/ interactions (Figure 1) weaken each
other by 0.40 kcal/mol as
the result of both water molecules competing for the negative
charge on benzene. Theeffect is similar with two simultaneous CH/O
interactions, where both water molecules
compete for the positive charge on benzene, resulting in mutual
weakening by 0.31
kcal/mol. However, when system contains one OH/ and one CH/O
interaction (Figure 2),there is no competition for the same charge
and E value is -0.44 kcal/mol. It was alsofound that all E values
for systems with parallel alignment interactions are in the
rangefrom +0.04 to -0.07 kcal/mol (Table 1).
CONCLUSIONS
As the result of both water molecules competing
for the charge of the same type, two interactions
of the same type (OH/ or CH/O) weaken eachother. Opposite to
that, two interactions of the
different types strengthen each other, since there
is no competition for the same charge. Parallel
aligned water molecule does not have significant
influence on other water/benzene interactions.
Figure 1.
Trimer containing two simultaneous OH/interactions
Figure 2.
Trimer containing OH/ and CH/Ointeraction
Figure 3.
Trimer containing two parallel alignment
interactions
OH/ CH/O parallel
OH/ +0.40 -0.42 +0.04
CH/O -0.44 +0.31 -0.06
parallel +0.02 -0.07 -0.03
Table 1. E values (in kcal/mol) for all combinations of
water/benzene interactions in the most stabletrimer geometries;
interaction in the first column was fixed, while interaction in the
first row was varied
E=ETRIMER-EDIMERETRIMER=E123(123)-[E12(123)+E3(123)]
EDIMER=E12(12)-[E1(12)-E2(12)]
