Tautomerization, molecular structure, transition state structure, and vibrational spectra
of 2-aminopyridines: A combined computational and experimental study.
Jamelah S. Al-Otaibi
Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University,
Riyadh 11951, Saudi Arabia
1
Table S1
Optimized geometrical parameters for 2A3MP molecule (bond lengths in Å, angles in
degrees) at two computational methods.
Parameters
R(1,2)
R(1,6)
R(1,9)
R(2,3)
R(2,7)
R(3,4)
R(3,10)
R(4,5)
R(4,11)
R(5,6)
R(6,8)
R(8,12)
R(8,13)
R(9,14)
R(9,15)
R(9,16)
A(2,1,6)
A(2,1,9)
A(6,1,9)
A(1,2,3)
A(1,2,7)
A(3,2,7)
A(2,3,4)
A(2,3,10)
A(4,3,10)
A(3,4,5)
A(3,4,11)
A(5,4,11)
A(4,5,6)
A(1,6,5)
A(1,6,8)
A(5,6,8)
A(6,8,12)
A(6,8,13)
A(12,8,13)
A(1,9,14)
A(1,9,15)
A(1,9,16)
A(14,9,15)
A(14,9,16)
A(15,9,16)
D(6,1,2,3)
D(6,1,2,7)
D(9,1,2,3)
D(9,1,2,7)
D(2,1,6,5)
HF
B3LYP
6-31++G(d,p)
6-311++G(d,p) 6-31++G(d,p)
6-311++G(d,p)
1.377
1.411
1.508
1.394
1.077
1.376
1.074
1.326
1.076
1.317
1.380
0.996
0.994
1.086
1.088
1.084
116.4
122.4
121.2
120.8
119.4
119.8
117.3
121.6
121.1
123.5
120.8
115.8
118.8
123.3
120.5
116.2
113.6
117.5
114.1
111.3
111.9
110.6
107.7
107.9
107.3
-0.3
-180.0
179.0
-0.6
0.2
1.374
1.410
1.508
1.393
1.077
1.374
1.074
1.325
1.077
1.315
1.381
0.995
0.994
1.087
1.089
1.084
116.4
122.4
121.2
120.8
119.4
119.8
117.3
121.6
121.1
123.5
120.7
115.8
118.7
123.3
120.4
116.2
113.4
117.1
113.8
111.3
111.8
110.6
107.6
108.0
107.4
-0.3
-180.0
179.1
-0.6
0.2
1.388
1.417
1.505
1.397
1.086
1.388
1.083
1.337
1.086
1.336
1.386
1.010
1.008
1.096
1.097
1.092
116.6
122.4
121.0
120.7
119.2
120.1
117.6
121.5
120.9
123.5
120.8
115.8
118.3
123.3
120.7
115.9
113.9
118.1
114.9
111.4
111.9
110.9
107.2
107.9
107.3
-0.3
180.0
179.1
-0.6
0.1
2
1.392
1.420
1.507
1.400
1.088
1.392
1.085
1.340
1.088
1.34
1.387
1.011
1.009
1.097
1.099
1.094
116.6
122.4
121.0
120.7
119.2
120.2
117.6
121.5
120.9
123.5
120.8
115.7
118.3
123.4
120.8
115.8
113.9
118.2
114.8
111.4
112.0
110.9
107.2
107.9
107.2
-0.4
180.0
179.1
-0.6
0.2
D(2,1,6,8)
D(9,1,6,5)
D(9,1,6,8)
D(2,1,9,14)
D(2,1,9,15)
D(2,1,9,16)
D(6,1,9,14)
D(6,1,9,15)
D(6,1,9,16)
D(1,2,3,4)
D(1,2,3,10)
D(7,2,3,4)
D(7,2,3,10)
D(2,3,4,5)
D(2,3,4,11)
D(10,3,4,5)
D(10,3,4,11)
D(3,4,5,6)
D(11,4,5,6)
D(4,5,6,1)
D(4,5,6,8)
D(1,6,8,12)
D(1,6,8,13)
D(5,6,8,12)
D(5,6,8,13)
177.8
-179
-1.61
-123.0
116.7
-2.9
56.5
-64.0
176.5
0.1
-180.0
179.7
-0.2
0.4
-180.0
-180.0
-0.0
-0.5
179.7
0.2
-177.0
167.6
30.7
-14.6
-151.0
177.7
-179.2
-1.7
-122.7
116.9
-2.7
56.6
-63.8
176.7
0.1
-179.8
179.7
-0.2
0.4
-179.9
-179.8
-0.1
-0.5
179.8
0.3
-177.4
167.2
31.4
-15.1
-150.9
3
177.5
-179.0
-2.0
-122.0
117.7
-2.1
57.2
-62.9
177.4
0.1
-180.0
179.8
-0.2
0.4
-180.0
-180.0
-0.0
-0.6
179.7
0.3
-177.0
167.8
28.5
-14.6
-154.0
177.5
-179.4
-1.9
-122.0
117.9
-1.8
57.4
-62.6
177.6
0.1
-179.8
179.8
-0.1
0.4
-180.0
-179.7
-0.0
-0.6
179.7
0.3
-177.2
167.7
28.4
-14.7
-154.0
Table S2
Optimized geometrical parameters for 2A4MP molecule (bond lengths in Å, angles in
degrees) at two computational methods.
Parameters
HF
6-31++G(d,p)
R(1,2)
R(1,6)
R(1,9)
R(2,3)
R(2,7)
R(3,4)
R(3,10)
R(4,5)
R(4,11)
R(5,6)
R(6,8)
R(7,12)
R(7,13)
R(7,14)
R(8,15)
R(8,16)
A(2,1,6)
A(2,1,9)
A(6,1,9)
A(1,2,3)
A(1,2,7)
A(3,2,7)
A(2,3,4)
A(2,3,10)
A(4,3,10)
A(3,4,5)
A(3,4,11)
A(5,4,11)
A(4,5,6)
A(1,6,5)
A(1,6,8)
A(5,6,8)
A(2,7,12)
A(2,7,13)
A(2,7,14)
A(12,7,13)
A(12,7,14)
A(13,7,14)
A(6,8,15)
A(6,8,16)
A(15,8,16)
D(6,1,2,3)
D(6,1,2,7)
D(9,1,2,3)
D(9,1,2,7)
D(2,1,6,5)
1.377
1.405
1.076
1.402
1.508
1.375
1.075
1.328
1.077
1.317
1.376
1.086
1.085
1.083
0.995
0.994
119.1
121
119.8
117.9
121.5
120.6
118.2
121.3
120.5
124.4
120.2
115.5
117.7
122.8
120.5
116.7
110.5
110.5
111.5
107.6
108.3
108.3
114.4
117.2
114.7
0.186
180
-179
0.689
0.029
B3LYP
6311++G(d,p)
1.374
1.404
1.075
1.400
1.507
1.373
1.075
1.327
1.077
1.315
1.378
1.086
1.086
1.083
0.995
0.994
119.1
121
119.8
117.9
121.5
120.6
118.2
121.3
120.5
124.4
120.1
115.5
117.6
122.8
120.4
116.8
110.4
110.4
111.5
107.6
108.4
108.4
114.1
116.8
114.4
0.2
-180.0
-179.0
0.6
0.01
4
6-31++G(d,p)
1.391
1.412
1.087
1.408
1.509
1.390
1.086
1.342
1.088
1.340
1.385
1.096
1.096
1.094
1.011
1.009
119.4
120.5
120.0
117.7
121.4
120.9
118.6
121.1
120.4
124.3
120.3
115.5
117.3
122.7
121.0
116.2
110.9
110.9
111.6
107.1
108.1
108.0
114.5
117.8
115.2
0.2
-180.0
-179.0
0.6
0.0
6-311++G(d,p)
1.387
1.409
1.085
1.405
1.507
1.387
1.084
1.338
1.087
1.337
1.384
1.094
1.094
1.092
1.009
1.008
119.5
120.5
120.0
117.7
121.4
120.9
118.6
121.1
120.4
124.2
120.2
115.5
117.4
122.7
121.0
116.3
110.9
110.8
111.6
107.2
108.1
108.1
114.5
117.7
115.1
0.2
-179.9
-179.2
0.6
0.0
D(2,1,6,8)
D(9,1,6,5)
D(9,1,6,8)
D(1,2,3,4)
D(1,2,3,10)
D(7,2,3,4)
D(7,2,3,10)
D(1,2,7,12)
D(1,2,7,13)
D(1,2,7,14)
D(3,2,7,12)
D(3,2,7,13)
D(3,2,7,14)
D(2,3,4,5)
D(2,3,4,11)
D(10,3,4,5)
D(10,3,4,11)
D(3,4,5,6)
D(11,4,5,6)
D(4,5,6,1)
D(4,5,6,8)
D(1,6,8,15)
D(1,6,8,16)
D(5,6,8,15)
D(5,6,8,16)
-178.0
179.3
1.4
-0.1
179.9
-180.0
0.1
120.5
-120
0.023
-59.7
59.34
179.8
-0.21
-180.0
179.8
0.051
0.422
-180.0
-0.33
177.7
-166.0
-27
16.37
154.9
-178.0
179.4
1.4
-0.1
179.9
-180.0
0.1
120.7
-120
0.2
-59.5
59.4
179.9
-0.2
-180.0
179.8
0.1
0.4
-180.0
-0.3
177.7
-165.0
-27.8
16.9
154.1
5
-178.0
179.5
1.8
-0.1
179.9
-180.0
0.1
120.8
-120
0.2
-59.4
59.5
-180.0
-0.2
-180.0
179.7
0.0
0.5
-180.0
-0.4
177.4
-166.0
-25.9
16.1
156.3
-177.7
179.5
1.8
-0.1
179.9
-180.0
0.1
120.8
-120.3
0.2
-59.4
59.5
-180.0
-0.2
-179.9
179.7
0.0
0.5
-179.8
-0.3
177.4
-166.1
-26.0
16.1
156.2
Table S3
Optimized geometrical parameters for 2A3MP molecule (bond lengths in Å, angles in
degrees) using Møller–Plesset perturbation theory (MP2/6-31G(d) and MP2/631++G(d,p) methods.
Parameters
R(1,2)
R(1,6)
R(1,9)
R(2,3)
R(2,7)
R(3,4)
R(3,10)
R(4,5)
R(4,11)
R(5,6)
R(6,8)
R(8,12)
R(8,13)
R(9,14)
R(9,15)
R(9,16)
A(2,1,6)
A(2,1,9)
A(6,1,9)
A(1,2,3)
A(1,2,7)
A(3,2,7)
A(2,3,4)
A(2,3,10)
A(4,3,10)
A(3,4,5)
A(3,4,11)
A(5,4,11)
A(4,5,6)
A(1,6,5)
A(1,6,8)
A(5,6,8)
A(6,8,12)
A(6,8,13)
A(12,8,13)
A(1,9,14)
A(1,9,15)
A(1,9,16)
A(14,9,15)
A(14,9,16)
A(15,9,16)
D(6,1,2,3)
D(6,1,2,7)
D(9,1,2,3)
D(9,1,2,7)
MP2
6-31G(d)
6-31++G(d,p)
1.392
1.413
1.502
1.397
1.089
1.390
1.086
1.346
1.089
1.342
1.397
1.016
1.014
1.095
1.097
1.093
116.9
122.7
120.4
120.2
119.4
120.4
118.1
121.3
120.6
123.5
121.0
115.5
117.6
123.8
120.2
115.9
110.7
115.0
111.8
110.6
111.7
110.8
107.5
108.6
107.6
-1.2
179.7
178.6
-0.4
1.394
1.414
1.502
1.399
1.085
1.392
1.082
1.347
1.084
1.343
1.396
1.012
1.010
1.092
1.094
1.089
116.9
122.5
120.6
120.2
119.3
120.4
118.0
121.4
120.6
123.4
121.1
115.6
117.7
123.7
120.3
115.9
111.8
115.7
112.5
110.7
111.6
110.6
107.7
108.4
107.7
-1.4
179.7
178.9
0.0
6
D(2,1,6,5)
D(2,1,6,8)
D(9,1,6,5)
D(9,1,6,8)
D(2,1,9,14)
D(2,1,9,15)
D(2,1,9,16)
D(6,1,9,14)
D(6,1,9,15)
D(6,1,9,16)
D(1,2,3,4)
D(1,2,3,10)
D(7,2,3,4)
D(7,2,3,10)
D(2,3,4,5)
D(2,3,4,11)
D(10,3,4,5)
D(10,3,4,11)
D(3,4,5,6)
D(11,4,5,6)
D(4,5,6,1)
D(4,5,6,8)
D(1,6,8,12)
D(1,6,8,13)
D(5,6,8,12)
1.255
176.8
-178.6
-3.0
-126.6
113.7
-6.2
53.2
-66.5
173.7
0.4
-179.6
179.4
-0.6
0.6
-179.8
-179.5
0.2
-0.6
179.7
-0.3
-176.1
168.7
40.8
-15.4
1.4
176.6
-179.0
-3.7
-126.0
114.1
-5.8
54.3
-65.7
174.5
0.6
-180.0
179.5
-0.7
0.3
-180.0
-180.0
0.3
-0.3
179.9
-0.6
-176.0
167.7
37.1
-16.8
7
Table S4
Optimized geometrical parameters for 2A4MP molecule (bond lengths in Å, angles in
degrees) using Møller–Plesset perturbation theory (MP2/6-31G(d) and MP2/631++G(d,p) methods.
Parameters
R(1,2)
R(1,6)
R(1,9)
R(2,3)
R(2,7)
R(3,4)
R(3,10)
R(4,5)
R(4,11)
R(5,6)
R(6,8)
R(7,12)
R(7,13)
R(7,14)
R(8,15)
R(8,16)
A(2,1,6)
A(2,1,9)
A(6,1,9)
A(1,2,3)
A(1,2,7)
A(3,2,7)
A(2,3,4)
A(2,3,10)
A(4,3,10)
A(3,4,5)
A(3,4,11)
A(5,4,11)
A(4,5,6)
A(1,6,5)
A(1,6,8)
A(5,6,8)
A(2,7,12)
A(2,7,13)
A(2,7,14)
A(12,7,13)
A(12,7,14)
A(13,7,14)
A(6,8,15)
A(6,8,16)
D(6,1,2,3)
D(6,1,2,7)
D(9,1,2,3)
D(9,1,2,7)
D(2,1,6,5)
MP2
6-31G(d)
6-31++G(d,p)
1.390
1.406
1.089
1.403
1.505
1.389
1.087
1.347
1.089
1.342
1.395
1.095
1.094
1.093
1.015
1.014
119.5
120.5
119.9
117.6
121.4
121.0
118.9
120.8
120.3
124.1
120.6
115.3
116.9
123.0
120.9
116.0
110.9
110.9
111.2
107.5
108.0
108.2
111.4
114.9
0.7
-179.0
-179.0
1.9
-0.5
1.392
1.407
1.085
1.404
1.505
1.391
1.083
1.348
1.084
1.343
1.395
1.092
1.090
1.090
1.011
1.010
119.6
120.5
119.9
117.6
121.2
121.2
118.9
120.9
120.2
124.0
120.6
115.4
117.0
123.0
120.8
116.1
110.8
110.8
111.0
107.8
108
108.3
112.4
115.4
112.8
0.8
-178.0
-179.0
2.3
8
D(2,1,6,8)
D(9,1,6,5)
D(9,1,6,8)
D(1,2,3,4)
D(1,2,3,10)
D(7,2,3,4)
D(7,2,3,10)
D(1,2,7,12)
D(1,2,7,13)
D(1,2,7,14)
D(3,2,7,12)
D(3,2,7,13)
D(3,2,7,14)
D(2,3,4,5)
D(2,3,4,11)
D(10,3,4,5)
D(10,3,4,11)
D(3,4,5,6)
D(11,4,5,6)
D(4,5,6,1)
D(4,5,6,8)
D(1,6,8,15)
D(1,6,8,16)
D(5,6,8,15)
D(5,6,8,16)
-177.0
178.9
2.8
-0.3
179.6
179.0
-1.1
106.7
-134.0
-13.4
-72.5
46.9
167.4
-0.4
179.9
179.7
0.0
0.5
-180.0
-0.1
176.3
-165.0
-36.0
18.6
147.6
-0.6
-176.0
178.9
3.0
-0.5
179.5
178.5
-1.4
95.8
-145.0
-24.2
-83.2
36.4
156.8
-0.1
-180.0
179.9
-0.1
0.3
-180.0
0.0
176.0
-165.0
-33.9
18.8
9
Table S5
Optimized geometrical parameters of transition state structures for 2A4MP molecule
(bond lengths in Å , angles in degrees) using B3LYP/6-311++G(d,p) method.
Proton transfer TS
R(1,2)
R(1,6)
R(1,9)
R(2,3)
R(2,7)
R(3,4)
R(3,10)
R(4,5)
R(4,11)
R(5,6)
R(5,15)
R(6,8)
R(6,15)
R(7,12)
R(7,13)
R(7,14)
R(8,15)
R(8,16)
A(2,1,6)
A(2,1,9)
A(6,1,9)
A(1,2,3)
A(1,2,7)
A(3,2,7)
A(2,3,4)
A(2,3,10)
A(4,3,10)
A(3,4,5)
A(3,4,11)
A(5,4,11)
A(4,5,6)
A(4,5,15)
A(1,6,5)
A(1,6,8)
A(1,6,15)
A(5,6,8)
A(2,7,12)
A(2,7,13)
A(2,7,14)
A(12,7,13)
A(12,7,14)
A(13,7,14)
A(6,8,16)
A(5,15,8)
D(6,1,2,3)
1.387
1.415
1.083
1.417
1.507
1.384
1.082
1.333
1.084
1.375
1.306
1.328
1.695
1.094
1.094
1.091
1.395
1.01
118.4
121.1
120.5
120.1
120.6
119.3
119.2
120.8
120.1
120.4
122.4
117.2
122.4
159.2
119.5
138.3
168.4
102.3
110.7
110.7
111.7
107.1
108.3
108.3
123.1
102.4
-0.0
10
Inversion at N TS
R(1,2)
R(1,6)
R(1,9)
R(2,3)
R(2,7)
R(3,4)
R(3,10)
R(4,5)
R(4,11)
R(5,6)
R(6,8)
R(7,12)
R(7,13)
R(7,14)
R(8,15)
R(8,16)
A(2,1,6)
A(2,1,9)
A(6,1,9)
A(1,2,3)
A(1,2,7)
A(3,2,7)
A(2,3,4)
A(2,3,10)
A(4,3,10)
A(3,4,5)
A(3,4,11)
A(5,4,11)
A(4,5,6)
A(1,6,5)
A(1,6,8)
A(5,6,8)
A(2,7,12)
A(2,7,13)
A(2,7,14)
A(12,7,13)
A(12,7,14)
A(13,7,14)
A(6,8,15)
A(6,8,16)
A(15,8,16)
D(6,1,2,3)
D(6,1,2,7)
D(9,1,2,3)
D(9,1,2,7)
1.386
1.411
1.085
1.405
1.507
1.387
1.084
1.338
1.087
1.338
1.371
1.094
1.094
1.092
1.006
1.003
119.4
120.5
120.0
117.8
121.3
120.9
118.5
121.1
120.4
124.4
120.2
115.5
117.3
122.6
121.2
116.2
110.8
110.8
111.6
107.2
108.1
108.1
118.4
122.0
119.6
-0.0
180.0
180.0
-0.0
D(6,1,2,7)
D(9,1,2,3)
D(9,1,2,7)
D(2,1,6,5)
D(2,1,6,8)
D(2,1,6,15)
D(9,1,6,5)
D(9,1,6,8)
D(9,1,6,15)
D(1,2,3,4)
D(1,2,3,10)
D(7,2,3,4)
D(7,2,3,10)
D(1,2,7,12)
D(1,2,7,13)
D(1,2,7,14)
D(3,2,7,12)
D(3,2,7,13)
D(3,2,7,14)
D(2,3,4,5)
D(2,3,4,11)
D(10,3,4,5)
D(10,3,4,11)
D(3,4,5,6)
D(3,4,5,15)
D(11,4,5,6)
D(11,4,5,15)
D(4,5,6,1)
D(4,5,6,8)
D(4,5,15,8)
D(1,6,8,16)
D(5,6,8,16)
180.0
-180.0
-0.0
-0.0
-180.0
0.0
180.0
0.0
180.0
0.0
-180.0
-180.0
0.0
120.7
-121.0
0.0
-59.3
59.3
-180.0
-0.0
-180.0
180.0
0.00
0.0
180.0
180.0
0.0
0.0
180.0
-180.0
0.0
180.0
11
D(2,1,6,5)
D(2,1,6,8)
D(9,1,6,5)
D(9,1,6,8)
D(1,2,3,4)
D(1,2,3,10)
D(7,2,3,4)
D(7,2,3,10)
D(1,2,7,12)
D(1,2,7,13)
D(1,2,7,14)
D(3,2,7,12)
D(3,2,7,13)
D(3,2,7,14)
D(2,3,4,5)
D(2,3,4,11)
D(10,3,4,5)
D(10,3,4,11)
D(3,4,5,6)
D(11,4,5,6)
D(4,5,6,1)
D(4,5,6,8)
D(1,6,8,15)
D(1,6,8,16)
D(5,6,8,15)
D(5,6,8,16)
0.0
180.0
180.0
0.0
0.0
-180.0
-180.0
0.0
120.6
-121.0
0.0
-59.4
59.4
-180.0
0.0
180.0
180.0
0.0
0.0
180.0
0.0
-180.0
180.0
0.0
0.0
180.0
Table S6
Wiberg bond index matrix in the natural atomic orbital basis (NAO) for 2A4MP1 computed at B3LYP/6-311+G(d,p).
Atom
C1
C2
C3
C4
N5
C6
C7
N8
H9
H10
H11
H12
H13
H14
H15
H16
C1
0.000
1.458
0.016
0.104
0.030
1.307
0.011
0.048
0.925
0.010
0.001
0.014
0.014
0.002
0.011
0.002
C2
1.458
0.000
1.347
0.016
0.087
0.016
1.036
0.013
0.005
0.004
0.008
0.003
0.003
0.002
0.000
0.000
C3
0.016
1.347
0.000
1.463
0.036
0.085
0.011
0.036
0.011
0.925
0.003
0.005
0.005
0.008
0.001
0.001
C4
0.104
0.016
1.463
0.000
1.397
0.013
0.010
0.010
0.001
0.004
0.925
0.000
0.000
0.000
0.000
0.001
N5
0.030
0.087
0.036
1.397
0.000
1.369
0.002
0.076
0.011
0.010
0.019
0.004
0.004
0.000
0.005
0.011
C6
1.307
0.016
0.085
0.013
1.369
0.000
0.009
1.145
0.003
0.001
0.009
0.000
0.000
0.000
0.002
0.002
C7
0.011
1.036
0.011
0.010
0.002
0.009
0.000
0.000
0.003
0.002
0.001
0.927
0.927
0.945
0.000
0.000
N8
0.048
0.013
0.036
0.010
0.076
1.145
0.000
0.000
0.001
0.001
0.000
0.001
0.001
0.000
0.831
0.844
12
H9
0.925
0.005
0.011
0.001
0.011
0.003
0.003
0.001
0.000
0.000
0.001
0.000
0.000
0.001
0.000
0.000
H10
0.010
0.004
0.925
0.004
0.010
0.001
0.002
0.001
0.000
0.000
0.002
0.000
0.000
0.000
0.000
0.000
H11
0.001
0.008
0.003
0.925
0.019
0.009
0.001
0.000
0.001
0.002
0.000
0.000
0.000
0.000
0.000
0.000
H12
0.014
0.003
0.005
0.000
0.004
0.000
0.927
0.001
0.000
0.000
0.000
0.000
0.001
0.001
0.000
0.000
H13
0.014
0.003
0.005
0.000
0.004
0.000
0.927
0.001
0.000
0.000
0.000
0.001
0.000
0.001
0.000
0.000
H14
0.002
0.002
0.008
0.000
0.000
0.000
0.945
0.000
0.001
0.000
0.000
0.001
0.001
0.000
0.000
0.000
H15
0.011
0.000
0.001
0.000
0.005
0.002
0.000
0.831
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
H16
0.002
0.000
0.001
0.001
0.011
0.002
0.000
0.844
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
13