Proton Transfer in the Molecular Complexes of Phosphorus Acids with DMSO
Irina V. Fedorova and Lyubov P. Safonova
G. A. Krestov Institute of Solution Chemistry of Russian Academy of Sciences, 1 Akademicheskaya Street,
Ivanovo 153045, Russia
Supplementary Materials
Fig. S1 Various types of H-bonded complexes formed by phosphorus acids (where acid is H3PO4, H3PO3 and
H2MePO3) and DMSO molecules [24]
Table S1 The depths of the second minima (V in kJ/mol) on the PES for proton transfer
complexes of H3PO4, H3PO3 and H2MePO3 with DMSO at the B3LYP/6-31++G(d,p) level
model (R in angstroms)
V
Complex
R=2.5
R=2.6
R=2.7
H3PO4–DMSO
1.42
9.92 (0.10)
24.12 (8.43)
H3PO3–DMSO
0.16
7.15 (0.08)
20.38 (8.17)
H2MePO3–DMSO
4.50
16.14 (3.72)
(H3PO4)2–DMSO
2.24 (1.43)
11.03 (13.66)
27.06 (25.63)
(H3PO3)2–DMSO
1.02
8.48 (3.14)
21.93 (14.76)
(H2MePO3)2–DMSO
5.49
17.64 (10.06)
H3PO4–(DMSO)2
6.57
19.60 (4.29)
H3PO3–(DMSO)2
5.39
17.98 (2.71)
H2MePO3–(DMSO)2
3.22
14.63 (2.08)
H3PO4–(DMSO)3
4.08
16.06 (3.91)
In parentheses are given data for the gas phase.
in the H-bonded
using the CPCM
R=2.8
41.01 (22.88)
36.70 (22.56)
31.25 (15.06)
47.35 (41.44)
38.66 (25.80)
33.07 (23.53)
36.83 (17.12)
34.33 (14.46)
30.54 (13.47)
32.48 (25.06)
There are some important similarities between the proton transfer processes in the initial dimeric
complexes of H3PO4, H3PO3 and Н2MeРО3, namely:
 The PES for proton transfer has a character of a double minimum well with two equivalent energy
minima at the mid-point of the H-bond (δ  0). As an example, the potential energy curves for proton transfer in
the (H3PO4)2 are shown in Fig. S2.
 The energy barrier heights for proton transfer in the fully relaxed structure of (acid) 2 are lower than
those found for this process at fixed R.
 With increasing intermolecular O…O distance the energy barrier increases.
 The solvent effect (the CPCM-DMSO model) favors a proton transfer.
It is worth noting that the height of the barrier for proton transfer in (acid)2 slightly decreases when
1
passing from H3PO4 to H3PO3 and Н2MeРО3 (Table S2). These results correlate with the obtained data from ab
initio MD simulations of pure liquid phosphoric and phosphorous acids (Vilčiauskas L (2012) Proton Transport
Mechanisms of Phosphoric Acid and Related Phosphorus Oxoacid Systems: A First Principles Molecular
Dynamics
Study.
Ph.D.
Thesis,
Universität
Stuttgart,
(http://elib.unistuttgart.de/opus/volltexte/2012/7158/pdf/thesisv2.0.pdf)).
Fig. S2 Energies for proton transfer in the (H3PO4)2 at various R in the gas phase (filled symbols) and DMSO
modeled by the CPCM (open symbols) calculated at the B3LYP/6-31++G(d,p) level. The curves for each
distance (Å) are assigned in the legend
Table S2 The energy barrier heights (ETS in kJ/mol) for proton transfer in phosphorus acid dimers at the
B3LYP/6-31++G(d,p) level using the CPCM model (R in angstroms)
ETS
Complex
Rfreea
R=2.5
R=2.6
R=2.7
(Н3РО4)2b
13.93 (14.92)
18.70 (19.36)
32.19 (33.83)
49.74 (51.69)
(Н3РО3)2
13.58 (14.31)
18.28 (18.64)
32.07 (33.01)
49.65 (50.81)
(H2MePO3)
12.98 (13.63)
17.63 (17.81)
31.62 (32.09)
49.21 (50.02)
In parentheses are given data for the gas phase.
a
Rfree=2.570 (2.579), 2.570 (2.578) and 2.567 (2.586) for the fully relaxed structure of the (H 3PO4)2, (H3PO3)2
and (H2MePO3)2, respectively.
b
ETS=15.48 kJ/mol, if no constraints are imposed on the system (B3LYP/6-311G(d,p)) [20].
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