Supporting information
Figure S1: A: The two-step topological methodology previously proposed for the search of the
different isomers of a 1:1 complex, and B: the structures that were determined from this
methodology in the case of the 1/1 DAC/H2O complex. For each of the three isomer (P1, P2 and
π_like), the relative energy to the most stable isomer is given (based on MP2/aug-cc-pVTZ
calculations). On the molecular graphs, the bond critical points (BCP's) and ring critical points
(RCP's) are indicated with green and red circles, respectively. 40
Figure S2: Topological characterization of the initial compounds considered for the construction
of the 1/2 DAC/H2O isomers. A: Contour map of the Laplacian of the electron density ∇2ρ. The
green and red small circles correspond to the BCP’s and RCP’s, respectively. B: Computed
electrostatic potentials mapped on the 0.001 a. u. molecular surface of the DAC, H2O, (H2O)2,
P1, P2 and π_like species. The blue color corresponds to the maximum electrostatic potentials,
and the red to the minimum.
Figure S3: Relative energies of the ten isomers of the 1/2 DAC/H2O complex, as calculated at the
MP2/aug-cc-pVDZ level of theory. The confidence ranges correspond to the uncertainty of the
energies calculated at this level.
Figure S4: Computed electrostatic potentials mapped on the 0.001 a. u. molecular surface of the
1/2 DAC/H2O isomers. The blue color corresponds to the maximum electrostatic potentials, and
the red to the minimum.
SI_1: Optimized structures (MP2/aug-cc-pVDZ) for the water dimer and the 1/2 DAC/H2O
isomers. For the 1/2 DAC/H2O isomers, the theoretical IR frequencies are also given
(wavenumbers in cm-1 and relative intensities in km/mol.).
SI_2: ESP at the 0.001 isosurface of the building blocks presented in Figure S2.
SI_3: Comparisons of the topological characterizations of the 1/2 DAC/H2O isomers with the
ones of the 1/1 isomers
A: Two steps of the topological methodology
B: 1/1 DAC/H2O isomers
ΔE = 0.00 kJ/mol
2 hydrogen bondings
Topological characterization
Energetical characterization
2 intermolecular BCP
1 RCP
Planar_Side_1
(P1)
1. Of the isolated monomers
ΔE = 0.11 kJ/mol
Identification of specific interaction sites
and construction of guessed complexes
SAPT analysis
Full optimization of the isomers.
Determination of the
 relative energies
 dissociation energies
 nature of the stabilization
3 hydrogen bondings
3 intermolecular BCP
2 RCP
Planar_Side_2
(P2)
ΔE = 2.98 kJ/mol
π-hole like interaction
(C=ODAC--OH2O)
1 hydrogen bonding
2. Of the isomers
(BCP, RCP in the QTAIM
framework)
2 intermolecular BCP
1 RCP
π-hole like interaction
(π_like)
Figure S1: A: The two-step topological methodology previously proposed for the search of the different
isomers of a 1:1 complex, and B: the structures that were determined from this methodology in the case of
the 1/1 DAC/H2O complex. For each of the three isomer (P1, P2 and π_like), the relative energy to the
most stable isomer is given (based on MP2/aug-cc-pVTZ calculations). On the molecular graphs, the bond
critical points (BCP's) and ring critical points (RCP's) are indicated with green and red circles,
respectively. Error! Bookmark not defined.
A
B
Species
DAC
H 2O
(H2O)2
A
B
P1 isomer
π_like isomer
P2 isomer
Figure S2: Topological characterization of the initial compounds considered for the construction of the 1/2
DAC/H2O isomers. A: Contour map of the Laplacian of the electron density ∇2ρ. The green and red small
circles correspond to the BCP’s and RCP’s, respectively. B: Computed electrostatic potentials mapped on
the 0.001 a. u. molecular surface of the DAC, H2O, (H2O)2, P1, P2 and π_like species. The blue color
corresponds to the maximum electrostatic potentials, and the red to the minimum.
Species
ΔE (kJ/mol)
30
25
20
π_like _ π_like _trans
15
P2_P1_trans
10
5
P1_(H2O)2
0
π_like _(H2O)2_side_P1
-5
π_like _(H2O)2_side_P2
-10
Figure S3: Relative energies of the ten isomers of the 1/2 DAC/H2O complex, as calculated at the
MP2/aug-cc-pVDZ level of theory. The confidence ranges correspond to the uncertainty of the energies
calculated at this level.
π_like_(H2O)2_side_P2
π_like_(H2O)2_side_P1
P2_P2_trans
P1_(H2O)2
P2_π_like_trans
P2_P1_tra
ns
P1_P1_trans
P1_π_like_trans
P2_P1_bifide
π_like_π_like_trans
Figure S4: Computed electrostatic potentials mapped on the 0.001 a. u. molecular surface of the 1/2
DAC/H2O isomers. The blue color corresponds to the maximum electrostatic potentials, and the red to the
minimum.
SI_1: Optimized structures (MP2/aug-cc-pVDZ) for the water dimer and the 1/2 DAC/H2O
isomers. For the 1/2 DAC/H2O isomers, the theoretical IR frequencies are also given
(wavenumbers in cm-1 and relative intensities in km/mol.).
Energy = -152.530207 Hartree
H2O dimer
O 0.000076 1.521960 0.000000
H -0.097975 0.554087 0.000000
H -0.906284 1.852757 0.000000
O 0.000076 -1.394625 0.000000
H 0.501520 -1.712763 0.762685
H 0.501520 -1.712763 -0.762685
Energy = -458.2231925
π_like_(H2O)2_side_P2
C -0.621087 -0.625825
C -1.020784 0.789189
O 0.359162 -0.771007
O -2.079201 0.933335
C -1.491952 -1.760911
C -0.104026 1.924523
H -1.134532 -2.699879
H -2.538733 -1.565575
H -1.448995 -1.806107
H 0.001535 1.964955
H 0.898263 1.755075
H -0.523332 2.865551
H 2.132372 -0.184331
O 2.831455 0.065534
H 3.577781 -0.506408
H 1.703766 -0.266974
O 0.855895 -0.402256
H 1.020479 -0.123007
Hartree
Energy = -458.2229449
π_like_(H2O)2_side_P1
C -1.745780 -1.407428
C -1.525834 -0.053428
O -2.330283 0.516224
C -0.202627 0.657306
O 0.482345 0.232920
C 0.150770 1.869090
O 2.998055 -0.185851
H 1.158298 2.215519
H -0.590840 2.659623
H 0.085224 1.621312
H -2.734119 -1.785631
H -0.949241 -2.081629
H -1.659467 -1.336683
H 2.337907 0.055937
H 3.670476 -0.688173
H 1.711415 -0.954942
O 0.836518 -1.153864
H 1.018082 -1.373994
Energy = -458.2188349
P1_(H2O)2
C 2.857219 1.166719
C 2.133733 -0.156197
O 2.695805 -1.250940
C 0.588916 -0.107763
O 0.046401 1.003591
C -0.140381 -1.418681
O -2.751186 1.579809
H -1.227655 -1.272347
H 0.181980 -2.003667
Hartree
-0.552447
-0.085636
-1.289903
0.525080
-0.096044
-0.464256
-0.536348
-0.373873
1.002837
-1.559986
-0.044689
-0.086792
-0.848655
-0.215997
-0.435683
1.281108
1.747747
2.656963
-0.697929
-0.078609
0.658922
-0.419024
-1.355879
0.397921
-0.192454
0.134869
0.200087
1.466483
-0.408183
-0.347060
-1.793066
-0.868947
-0.669454
0.976472
1.365311
2.287441
Hartree
0.003304
0.002902
0.010470
-0.007938
-0.013089
-0.010902
-0.088443
-0.019719
-0.887165
55
99
139
201
311
367
597
709
1011
1309
1445
1464
1715
3080
3204
3675
0,7
3,1
12,2
2,7
100,1
3,8
36,5
0,5
0,2
0,1
14,1
8,1
141,0
1,5
3,5
327,8
64
118
172
230
352
527
612
928
1053
1369
1450
1630
1717
3168
3208
3887
4,6
3,3
29,0
97,9
24,5
0,1
89,1
13,3
0,2
58,6
19,1
80,1
25,1
1,9
6,5
105,6
89
134
178
246
362
538
666
954
1143
1396
1456
1650
3077
3170
3616
3888
4,4
4,6
70,7
12,3
105,8
21,1
96,4
6,5
56,7
0,8
7,1
69,6
2,2
0,9
184,3
124,3
42
99
145
199
330
380
605
712
1012
1312
1445
1462
1714
3077
3205
3666
1,0
6,9
2,5
1,5
126,1
56,4
80,4
0,3
0,1
0,2
13,7
7,2
138,6
1,0
3,3
344,5
50
111
167
217
340
531
608
928
1054
1368
1449
1632
1716
3167
3206
3886
2,0
5,2
5,0
101,0
6,6
1,0
22,0
14,6
0,4
63,2
12,9
93,5
12,7
0,6
5,8
94,5
83
139
184
245
367
538
669
958
1145
1397
1455
1655
3075
3170
3606
3889
3,0
19,6
72,3
18,1
49,7
25,1
99,6
8,0
60,1
1,0
7,2
72,3
2,8
1,8
206,9
133,2
22
55
134
193
340
378
614
739
1008
1311
1446
0,2
7,9
0,8
49,5
17,6
60,2
2,4
85,4
0,5
0,1
10,2
37
95
142
217
360
532
625
926
1057
1376
1452
0,9
18,1
3,0
41,6
64,7
2,1
125,0
14,4
0,0
53,4
20,4
51
133
170
260
373
538
708
952
1145
1398
1455
4,2
96,8
10,1
37,6
13,3
38,1
1,1
3,7
60,9
3,7
15,1
H
H
H
H
H
H
H
O
H
0.167830
3.939477
2.556183
2.563706
-1.786535
-2.930553
-3.428697
-3.536049
-4.312438
-1.999915 0.872910
0.988131 0.008645
1.755083 0.884256
1.751714 -0.882380
1.431472 -0.051173
2.197375 0.631453
-0.149034 0.009445
-1.117905 0.085978
-1.319720 -0.449801
Energy = -458.2161577
P2_P2_trans
C 1.142675 1.619341
C -0.095028 0.768031
O -1.240316 1.226927
C 0.094976 -0.767982
O 1.240291 -1.226816
C -1.142687 -1.619335
O 3.905925 -0.026129
H -0.854657 -2.677435
H -1.763451 -1.385257
H -1.763226 -1.385323
H 0.854682 2.677451
H 1.762536 1.385543
H 1.764085 1.385009
H 3.083766 -0.544034
H 4.607535 -0.688664
O -3.905833 0.026007
H -3.083802 0.544115
H -4.607611 0.688366
Hartree
Energy = -458.2159756
P2_π_like_trans
C -0.488124 -0.519566
C -0.259615 0.911959
O 0.863917 1.247977
O -1.594253 -0.806906
C 0.671239 -1.473701
H 1.013221 -1.559373
H 1.523537 -1.084966
H 0.359771 -2.451681
C -1.446658 1.835309
H -1.132307 2.833218
H -1.896260 1.873949
H -2.205980 1.423187
H -1.734841 -1.175641
O -1.619934 -0.846807
H -2.240982 -1.364660
H 2.613274 0.417523
O 3.442504 -0.090854
H 4.101645 0.537156
Hartree
Energy = -458.2158624
P1_P1_trans
C 1.297715 1.495776
C 0.767384 0.088718
O 1.471232 -0.925771
C -0.767377 -0.088704
O -1.471224 0.925786
C -1.297705 -1.495764
O -4.246724 0.079762
H -2.394236 -1.487218
H -0.909809 -2.028586
H -0.908404 -2.029219
H 2.394246 1.487225
H 0.910081 2.028422
H 0.908155 2.029408
H -3.420271 0.592968
H -4.948820 0.741564
H 3.420245 -0.592988
O 4.246706 -0.079793
Hartree
0.000413
0.001064
0.001739
0.000974
0.000885
0.000933
-0.002065
0.000985
0.879918
-0.878247
0.000935
-0.879305
0.878872
-0.001107
-0.002803
-0.002484
-0.000788
-0.003363
-0.740714
-0.208317
0.173768
-1.202822
-0.666781
0.375607
-1.245735
-1.054522
-0.201747
0.127664
-1.205512
0.480032
2.660852
1.759590
1.227578
0.326762
0.338752
0.658324
-0.000133
-0.000166
-0.000357
0.000171
0.000327
0.000211
-0.000143
0.000974
-0.882382
0.881781
-0.001178
0.882687
-0.881476
0.000470
-0.000922
-0.000571
0.000080
1463
1706
3076
3208
3647
2,4
114,0
0,3
12,0
509,1
1642
1711
3153
3208
3888
74,0
60,8
1,0
7,1
141,2
1659
3069
3162
3599
3894
34,2
9,7
2,1
439,2
87,9
8
73
145
180
310
372
523
709
1016
1308
1443
1462
1709
3077
3209
3726
1,0
13,5
2,4
1,1
305,1
0,0
0,0
0,0
0,0
0,0
0,0
0,0
216,6
0,1
0,0
0,0
22
98
173
185
320
505
549
934
1050
1372
1445
1640
1711
3159
3209
3903
0,0
0,0
0,0
0,0
0,0
0,0
39,6
9,9
0,0
62,0
62,0
131,4
0,0
0,3
10,5
309,7
59
143
176
248
348
511
612
941
1148
1396
1456
1642
3077
3159
3724
3904
0,1
0,0
259,0
15,2
3,0
115,8
0,0
3,8
51,9
0,0
22,7
0,0
5,3
0,0
520,3
0,0
13
85
140
166
247
352
533
709
1013
1308
1447
1463
1713
3079
3204
3778
0,7
9,2
3,0
92,4
16,1
3,3
61,9
0,1
0,1
0,4
4,3
2,0
129,5
1,8
5,3
9,6
47
90
145
183
265
370
544
930
1053
1369
1448
1615
1716
3164
3207
3901
4,0
11,3
3,6
44,6
47,6
1,0
40,9
11,7
0,2
60,7
37,2
116,1
56,8
0,7
5,9
141,2
66
132
161
214
327
526
609
950
1145
1396
1458
1647
3078
3170
3706
3916
4,3
0,2
135,5
62,1
133,2
1,0
0,7
7,0
53,1
0,5
15,4
55,7
1,7
0,5
321,6
73,0
20
61
133
145
349
376
535
713
1015
1317
1448
1459
1707
3074
3212
3702
1,6
11,9
0,3
0,0
0,4
0,0
0,0
0,0
0,0
0,0
0,0
0,0
136,0
3,7
0,0
0,0
39
97
134
148
358
525
550
929
1059
1379
1449
1640
1708
3158
3213
3903
0,0
0,0
0,0
274,2
264,9
0,0
34,5
13,3
0,0
62,5
16,8
202,5
0,0
2,3
3,8
273,9
45
130
142
265
364
528
615
954
1153
1398
1453
1641
3073
3158
3699
3903
0,0
0,0
0,7
116,7
0,0
108,9
0,0
4,7
72,5
0,0
18,2
0,0
0,0
0,0
559,9
0,0
H 4.948794 -0.741604
Energy = -458.2158441
P1_π_like_trans
C 1.236972 -0.526286
C -0.271903 -0.210767
O 1.942500 0.076108
O -0.977327 -0.883584
C 1.749504 -1.576986
C -0.785851 0.891689
H 2.826239 -1.716815
H -1.875640 0.974608
H 1.545759 -1.255323
H -0.298158 1.831357
H 1.206471 -2.521488
H -0.491479 0.693718
O 1.394085 1.681088
H 2.119904 1.924320
H 1.425478 2.336329
H -2.858077 -0.410485
O -3.711936 0.018337
H -4.351418 -0.457712
0.000865
Hartree
Energy = -458.2155094
P2_P1_trans
C -0.280831 -1.245224
C -0.460410 0.244757
O -1.552449 0.823009
C 0.810751 1.125201
O 1.922388 0.592246
C 0.605439 2.616368
O 2.812693 -2.200674
H 1.579596 3.119883
H 0.015926 2.903330
H 0.013416 2.911684
H -1.258974 -1.741053
H 0.310903 -1.544365
H 0.309658 -1.552265
H 2.640554 -1.244686
H 3.775052 -2.271649
O -3.649285 -1.185448
H -3.132163 -0.361572
H -4.570432 -0.898985
Hartree
Energy = -458.2148966
P2_P1_bifide
C -2.174790 0.739968
C -1.527738 -0.618273
O -2.145815 -1.683058
C 0.017987 -0.676753
O 0.662329 0.380029
C 0.647822 -2.039930
O -0.125465 3.221978
H 1.740948 -1.958204
H 0.292623 -2.603828
H 0.293712 -2.592668
H -3.264720 0.617045
H -1.854478 1.322653
H -1.849361 1.311371
H 0.239398 2.322067
H 0.648460 3.798319
O 3.503042 -0.316285
H 2.650864 0.151133
H 4.170130 0.380719
Hartree
0.384968
0.319304
1.195376
-0.439139
-0.563789
1.202355
-0.406169
1.109659
-1.596387
0.901737
-0.405451
2.244547
-1.242060
-0.649792
-1.951508
-0.458841
-0.268337
-0.811542
0.010788
0.004368
0.001281
0.001556
0.005304
-0.005699
-0.007437
-0.006727
-0.890433
0.874585
0.013667
0.890520
-0.867065
-0.000040
-0.012441
-0.008487
-0.002579
0.009148
0.012106
0.001623
-0.006073
0.000361
0.005749
-0.007651
-0.010105
-0.006542
0.869286
-0.892130
0.014394
-0.865818
0.895534
-0.002029
-0.019546
0.003269
0.006903
0.018591
Energy = -458.2144036 Hartree
π_like_π_like_trans
C -0.190816 -0.679038 0.311723
C 0.191169 0.679806 -0.311727
O -0.698014 -0.703193 1.434982
O 0.698969 0.703948 -1.434729
C -0.075951 1.905973 0.517548
21
77
127
143
251
371
544
712
1013
1313
1446
1461
1710
3078
3205
3779
1,3
7,6
3,3
9,1
11,5
0,5
38,5
0,0
0,0
0,2
12,2
2,9
87,5
1,0
6,1
10,1
48
85
138
184
256
377
560
928
1056
1371
1451
1616
1717
3167
3210
3901
3,4
7,8
69,8
168,9
55,8
138,6
57,8
13,3
0,1
63,2
11,8
118,8
57,5
1,1
0,7
125,3
71
120
140
223
352
532
609
956
1148
1396
1457
1648
3077
3167
3673
3917
7,0
3,5
52,7
60,5
2,3
1,1
0,4
8,0
62,9
0,2
10,5
85,4
1,2
1,6
368,0
72,4
14
61
137
169
307
374
529
711
1015
1312
1445
1461
1704
3077
3210
3729
0,0
2,3
8,0
149,0
152,8
1,1
0,4
0,0
0,1
1,6
9,7
2,4
83,7
0,2
4,7
241,3
31
96
140
180
348
500
549
931
1054
1374
1449
1639
1713
3154
3211
3903
0,3
13,4
108,7
0,8
1,6
47,7
37,7
11,6
0,0
61,6
25,9
122,1
92,7
0,2
3,3
189,8
52
133
141
257
358
526
613
947
1150
1396
1454
1642
3073
3162
3702
3905
0,0
0,4
5,9
51,5
128,1
61,8
1,0
4,3
61,5
1,6
18,0
43,9
2,5
1,0
278,1
101,0
8
65
132
159
318
374
528
711
1015
1311
1446
1461
1705
3076
3207
3732
1,2
7,7
0,0
246,9
122,0
0,3
2,1
0,2
0,0
0,3
17,3
2,8
140,5
1,3
5,0
210,1
6,9
4,6
1,5
0,4
1,5
3,5
36,7
11,6
0,0
59,1
19,3
49,5
31,9
0,6
2,4
83,0
53
109
137
256
360
511
613
947
1150
1397
1454
1646
3075
3160
3713
3906
0,6
11,3
3,6
53,4
145,7
100,4
0,2
4,2
61,2
1,8
17,7
111,9
1,5
0,5
243,6
212,2
21
75
123
157
233
305
525
12,5
0,0
9,7
13,9
1,9
0,1
0,0
1,6
43,3
82,8
100,4
28,7
8,7
46,0
40
120
140
229
294
364
607
0,0
0,2
100,1
148,5
87,9
0,0
0,0
33
100
134
183
348
472
549
931
1054
1376
1449
1632
1708
3158
3216
3903
37
90
138
158
244
361
538
C
H
H
H
H
H
H
H
O
H
H
O
H
0.075068
-1.157415
0.425532
0.285855
-0.284785
1.155984
-0.429468
2.810744
2.830003
3.762063
-2.810667
-2.830006
-3.762282
-1.905096
1.982435
1.802855
2.793458
-2.792757
-1.980934
-1.802310
0.232402
-0.145121
-0.137212
-0.233674
0.142967
0.137059
-0.518093
0.705740
1.491896
-0.016702
0.017194
-0.709529
-1.490941
-0.537066
0.354469
0.607494
0.537632
-0.354244
-0.606248
708
1011
1306
1448
1461
1718
3078
3203
3773
0,0
0,0
0,0
24,1
0,0
120,0
4,0
0,0
9,4
928
1055
1366
1448
1612
1718
3171
3204
3916
14,2
0,0
65,7
0,1
272,7
10,5
1,4
12,1
76,9
954
1143
1395
1457
1614
3078
3171
3773
3917
9,6
55,9
0,0
15,5
0,4
0,2
0,2
6,3
79,0
SI_2: ESP at the 0.001 isosurface of the building blocks presented in Figure S2.
1. Two positive regions can be identified on the isosurface of the DAC molecule, on both sides
of the Ccarboxylic-Ccarboxylic bond, with an ESP value of +25.9 kcal/mol. These are the two most
electron-deficient regions of the DAC molecule. Each hydrogen atom is also characterized by
a positive value of the ESP: the two hydrogen atoms that are coplanar with the carbon and
oxygen atoms are characterized by a less electron-deficient ESP value (+15.6 kcal/mol ) than
the four other hydrogen atoms (+18.0 kcal/mol). An electron-rich region is located in the
vicinity of each oxygen of the ketone group, and the minimum ESP value is -27.8 kcal/mol.
2. The water molecule presents an electron rich region located around the oxygen atom, with a
minimum ESP of 43.4 kcal/mol, whereas the hydrogen atoms are associated with an electrondeficient region, with a maximum ESP of +29.4 kcal/mol.
3. In the water dimer, the charges bearing by the atoms of the two water molecules are different
from each others. If we define a P plan with the two oxygen atoms and two hydrogen atoms,
the water molecule that belongs to this plan is more electron-rich than the other water
molecule. The oxygen atom of the first water molecule is characterized by an ESP value of 39.8 kcal/mol, whereas the other oxygen atom has an ESP of -20.3 kcal/mol. The hydrogen
atom located in the P plan and not involved in the hydrogen bonding has an ESP value of
+32.5 kcal/mol, whereas the two hydrogen atoms of the other water molecule have an ESP
value of +51.3 kcal/mol.
4. The P1 isomer of the 1/1 DAC/H2O complex presents two particularly electron-rich regions
that correspond to the two lone pairs of electron of the oxygen atom of the water molecule,
with a minimum ESP of -32.0 kcal/mol. Another electron-rich region is located close to the
oxygen atom of the DAC molecule that is not involved in the interaction with the water
molecule, on the methyl side, diametrically opposed to the water molecule. The minimum ESP
value at this region is -24.6 kcal/mol. The third electron-rich region of this 1/1 DAC/H2O
isomer is located on the other oxygen atom and corresponds to the lone pair of electrons that is
not involved in the hydrogen bonding with the water molecule. Height electron-poor regions
can be identified on this isomer. The most electron depleted region is located on the hydrogen
of the water molecule that is not involved in the hydrogen bonding, and the maximum of the
ESP value is +36.7 kcal/mol. The two next electron-deficient regions are located on both sides
of the Ccarboxylic-Ccarboxylic bond, with an ESP value of +26.8 kcal/mol. The five remaining
electron-deficient regions correspond to the hydrogen atoms of the DAC molecules that are
not involved in a hydrogen-bonding. The two hydrogen atoms of the final free methyl group
that are located on each side of the plan defined by the carbon and oxygen atoms bear a
positive electrostatic potential, of +20.3 kcal/mol. The third hydrogen atom of this methyl
group is characterized by a positive ESP value, of +18.9 kcal/mol. The two remaining
hydrogen atoms that are not involved in a hydrogen bonding with the water molecules have a
positive ESP value of +17.4 kcal/mol.
5. In the case of the P2 isomer of the 1/1 DAC/H2O complex, an electron-rich region with an
ESP value of -32.6 kcal/mol is located on the oxygen atom of the water molecule, opposite to
the direction of the DAC molecule. Another electron-rich region is located closed to the
oxygen atom of the DAC molecule that is not involved in the hydrogen bonding (-25.3
kcal/mol), whereas the other oxygen atom of the DAC molecule is characterized by a
minimum ESP value of -16.6 kcal/mol. The most acidic hydrogen atom is the one of the
water molecule that is not involved in the hydrogen bonding; this hydrogen atom is
characterized by a maximum ESP value of +36.6 kcal/mol. Perpendicularly to the plane
defined by the oxygen and carbon atoms, there are on both sides of the Ccarboxylic-Ccarboxylic bond
an electron-depleted region with a maximum ESP value of +27.0 kcal/mol. The hydrogen
atoms located on both sides of the plan and not involved in the hydrogen bondings are
associated with an electron-depleted region with a maximum ESP value of +20.4 kcal/mol.
The third hydrogen atom of this methyl group is less acidic, with a maximum ESP value of
+18.3 kcal/mol. The remaining hydrogen atom that is not involved in a hydrogen bonding is
characterized by a maximum ESP value of +13.3 kcal/mol.
6. The π_like isomer of the 1/1 DAC/H2O complex presents two particularly electron-rich
regions close to the oxygen atoms of the DAC molecule: the oxygen atom that is not involved
in the interaction with the water molecule has a minimum electrostatic potential of -30.7
kcal/mol whereas the other one has a minimum electrostatic potential of -25.0 kcal/mol.
Opposite to the hydrogen atom involved in the interaction with the DAC molecule, the
minimum ESP beared by the oxygen atom of the water molecule is of -16.8 kcal/mol. Four
electron-deficient regions are as follows: the hydrogen of the water molecule that is not
involved in the interaction with the DAC molecule (+46.0 kcal/mol), the hydrogen of the
water molecule that is involved in the interaction with the DAC molecule (+39.0 kcal/mol),
the side of the Ccarboxylic-Ccarboxylic bond opposite to the water molecule (+18.0 kcal/mol), and
the hydrogen in the plan of the carbon and oxygen atoms of the methyl group that is not
involved in the interaction with the water molecule (+12.7 kcal/mol).
SI_3: Comparisons of the topological characterizations of the 1/2 DAC/H2O isomers with the
ones of the 1/1 isomers
Critical Points
HH2O OC=O
ρBCP
2ρ
ε
BCP
RCP
OH2O HCH3
ρBCP
2ρ
ε
ρRCP
2ρ
P1
P1_(H2O)2
P1_P1_trans
0.023
0.08
0.0
0.03
0.10
0.0
0.023 |
0.023
0.08 | 0.08
0.0 |0.0
0.009
0.04
0.2
0.01
0.04
0.1
0.007
0.03
0.002
0.01
0.009 |
0.009
0.03 |
0.03
0.1
| 0.1
0.007 |
0.007
0.03 |
0.03
P1_π_like_trans P2_P1_trans P2_P1_bifide
0.025
0.09
0.0
0.023
0.08
0.0
0.02
0.07
0.0
0.008
0.03
0.3
0.008
0.03
0.2
0.009
0.04
0.2
0.007
0.03
0.006
0.03
0.003
0.04
Table SI_3-1: The QTAIM parameters of the P1 interaction in the 1/2 DAC/H2O isomers compared with
the ones for the P1 1/1 DAC/H2O isomer.
BCP
RCP
Critical Points
HH2O - OC=O
ρBCP
 2ρ
ε
OH2O - HCH3
ρBCP
 2ρ
ε
(1st cycle)
ρRCP
 2ρ
(2nd cycle)
ρRCP
 2ρ
P2
P2_P2_trans
P2_P1_trans P2_P1_bifide
0.022
0.09
0.0
0.021 | 0.021
0.08 | 0.08
0.0 | 0.0
0.022
0.08
0.0
0.021
0.08
0.0
0.006
0.03
1.6
0.006 | 0.006
0.03 | 0.03
1.7 | 1.7
0.006
0.03
3.4
0.006
0.03
1.0
0.005
0.03
0.006 | 0.006
0.03 | 0.03
0.005
0.03
0.006
0.03
None
0.006
0.03
0.006 | 0.006
0.03 | 0.03
0.006
0.03
Table SI_3-2: The QTAIM parameters of the P2 interaction in the 1/2 DAC/H 2O isomers compared with
the ones for the P2 1/1 DAC/H2O isomer.
Critical
Points
BCP OH2O
OC=O
ρBCP
2ρ
ε
OH2O
HCH3
ρBCP
2ρ
ε
RCP ρRCP
2ρ
π_like
π_like_(H2O)2_ π_like_(H2O)2_ P2_π_like_trans P1_π_like_trans π_like_π_like_trans
side_P2
side_P1
0.011
0.05
2.0
0.013
0.05
1.2
0.012
0.05
0.2
0.012
0.05
0.7
0.012
0.05
0.5
0.012 | 0.012
0.05 | 0.05
1.1 | 1.1
0.007
0.03
0.8
0.007
0.03
0.8
0.07
0.03
1.4
0.007 | 0.007
0.02 | 0.02
0.6 | 0.6
0.007
0.03
0.007
0.03
0.007
0.03
0.006 | 0.006
0.03 | 0.003
None BCP
0.007
0.03
0.3
0.006
0.02
None RCP
Table SI_3-3: The QTAIM parameters of the π_like interaction in the 1/2 DAC/H2O isomers compared
with the ones for the π_like 1/1 DAC/H2O isomer.