Paper
RSC Advances
H(1) atom position in 1 and 2, the difference between cation– lengthening can be also caused by other interactions with
anion interaction energies calculated for the whole carboxylate oxygen atoms, though the inuence even of rather strong
group seems to be more demonstrative since the difference interactions with alkali metal ions is lower. Isotropic ADP of the
between EO(1) and EO(4) values in 1 at 300 K becomes nearly the hydrogen atom involved in SSHB can also serve as a disorder
same as in 2 estimated at 100 K (Table 3). In its turn, it implies indicator, particularly when evaluated at different tempera-
the inuence of charge distribution within carboxylate group on tures. However, it can also increase due to unrelated low-
2
˚
the DWP of SSHB and on the possible disorder of the H atom. frequency vibrations. We suggest the Uiso values of <0.04 A at
2
˚
Taking into account that the energy estimations and 100 K and <0.07 A at room temperature as the indication of the
geometric characteristics can both be helpful to elucidate the H-atom ordering (for protium) for the SSHBs with O/O sepa-
disorder of hydrogen atom involved in SSHB we have tried to ration less than 2.5 A˚ .
verify given above power ts approximating energy/distance
Another useful metric is the difference in energy between
relation and simultaneously to conrm declared importance cation–anion interaction involving the H-donor and H-acceptor
of ECOO/ECOOH difference for the DWP analysis using two fragments. Our work demonstrates the strong inuence of the
examples from the CSD: sodium hydrogen trans-1-propene-1,3- charge distribution within the carboxylate group on the DWP of
dicarboxylate (refcode CARVAS) and potassium hydrogen SSHB; here we present a numeric approximation for the alkali
diformiate (refcode KHDFRM05). Of course, this sample is very metal—carboxylate group interaction energy using the M–O
narrow and cannot be considered as a representative one, distance for a given metal type as a predictor.
however it fully coincides with the data discussed above espe-
Sufficient difference in the total M–O interaction energy
cially in the sense of the correlation between energy difference between carboxylate fragments participating in the SSHB leads
ꢂ1
and geometric characteristics. Thus, in the CARVAS structure to hydrogen ordering. We suggest ECOO ꢂ E
< 3 kcal mol
COOH
˚
the hydrogen atom involved in the SSHB (O/O 2.484 A) was as a cutoff value of the DWP asymmetry indicating the H-atom
˚
˚
rened at 0.884 A from one oxygen atom (CO 1.303 A) and at disorder. Such estimations of the cation–anion interaction
˚
˚
1
.604 A from the another (CO 1.285 A), which implies ordering energy can be used to forecast a hydrogen atom disorder and to
of the hydrogen atom. The sodium cation (coordination tune possible proton transfer in related compounds by varying
number ¼ 6) forms four interactions with the COO group and the cation nature. Similar approach can also be adapted to other
only two ones with the COOH group (see Table S6†); the cor- structural tasks in which the analysis of M/O interactions
responding ECOO/ECOOH difference calculated according to plays crucial role, example being incomplete isomorphous
ꢂ1
power ts is 3.7 kcal mol , while the EO(4)/EO(1) difference (with replacement in crystals of alkali metals carboxylates.
the corresponding labeling of oxygen atoms) is only 0.3 kcal
ꢂ1
mol that is even smaller than in the disordered crystal of 2 at
3
Acknowledgements
00 K (Table 3). On the contrary, in KHDFRM05 the lengths of
˚
CO bond involved in the SSHB (O/O 2.442 A) are very close to Authors gratefully thank Dr I. V. Fedyanin for periodic DFT
˚
each other (1.281 and 1.279 A) and the hydrogen atom is closer calculations. This study was nancially supported by the
to the middle of the O/O separation (O–H 1.173 and 1.269 A˚ ). Russian Science Foundation (Project No. 14-13-00884).
Although the coordination number of the potassium ion is
formally eight in this case the energy estimations (Table S6†) are
Notes and references
in line with the possible hydrogen atom disorder: EO(4)/EO(1)
ꢂ1
difference in this case is 3.0 kcal mol while the ECOO/ECOOH
1 S. Horiuchi and Y. Tokura, Nat. Mater., 2008, 7, 357;
I. Prigogine, S. Rice, V. Krasnoholovets, P. Tomchuk and
S. Lukyanets, Adv. Chem. Phys., 2003, 125.
ꢂ1
one is 3.4 kcal mol that is slightly larger than this value for the
disordered crystal of 2 at 100 K and smaller than this value for
the ordered crystal of 1 at 300 K (Table 3).
2 P. Li, Y. Bu, H. Ai, S. Yan and K. Han, J. Phys. Chem. B, 2004,
108, 16979; P. Hobza and J. Sponer, Chem. Rev., 1999, 99,
3
247; C. Viragh, T. Harris, P. Reddy, M. Massiah,
Conclusions
A. Mildvan and I. Kovach, Biochemistry, 2000, 39, 16200;
K. Kim, D. Kim, J. Lee, P. Tarakeshwar and K. Oh,
Biochemistry, 2002, 41, 5300.
The XRD-based descriptors of the DWP features considered in
our study complement each other and show that the DWP
asymmetry caused by cation/anion interactions cause
hydrogen atom disorder in 2, in contrast to its ordering in 1 (in
the 100–300 K temperature range).
We consider it useful to summarize the peculiarities of each
derived parameter and to provide several additional comments.
While the hydrogen atom position rened against XRD data
should be always analyzed with caution, the inequality of the
participating C–O bonds can serve as sign of the H-atom
ordering within SSHB between hydrodicarboxylate anions
3 J. Brickmann and H. Zimmermann, J. Chem. Phys., 1969, 50,
1608; N. Sokolov and M. Vener, Chem. Phys., 1992, 168, 29;
V. Sakun, M. Vener and N. Sokolov, J. Chem. Phys., 1996,
105, 379; Hydrogen-Transfer Reactions, 4 Volume Set, ed. J.
Hynes, J. Klinman, H. Limbach and R. L. Schowen, 2006.
4 L. Remer and J. Jensen, J. Phys. Chem., 2000, 104, 9266.
5 R. Nelmes and W. Kuhs, Acta Crystallogr., 1984, A40, C135.
6 K. Lyssenko, D. Lyubetsky and M. Antipin, Mendeleev
Commun., 2003, 13, 60; D. Golovanov, A. Tokareva,
A. Uraev, Y. Ryabukhin, A. Pyshchev, T. Kovaleva,
M. Antipin and K. A. Lyssenko, Russ. Chem. Bull., 2006, 55,
˚
even when their difference is only a few hundredths A. On the
other hand, one should keep in mind that the C–O bond
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RSC Adv., 2015, 5, 97495–97502 | 97501