192
M. K. Bilonda and L. Mammino
Table 4 Vibrational frequencies (harmonic approximation) of the O–H bonds in the calculated
conformers of shuangancistrotectorine A HF/6-31G(d,p) results in vacuo
Conformers
Vibrational frequency
(cm −1 )
Conformers
Vibrational frequency
(cm −1 )
O43 H52 O44 H54
O43 H52 O44 H54
1-a-b-g-h-i-u-q-v-x 3729.36
3727.41
3729.36
3727.41
10-a-d-g-h-i-u-q-t-x
3723.53
3744.89
11-b-c-g-h-i-u-q-t-x
3744.89
3723.53
2-a-b-g-h-i-u-q-t-y
3733.28
3738.63
12-b-c-g-h-i-u-q-t-y
3751.12
3732.73
3-a-b-g-h-i-u-p-v-y 3740.48
3738.52
3740.48
3738.52
13-c-d-g-h-i-u-p-v-y 3728.99
3723.11
3728.99
3723.11
4-a-b-g-h-i-u-q-t-x
3735.05
3733.12
3735.05
3733.12
14-b-c-g-h-i-u-q-t-x
3730.13
3724.54
3730.13
3724.54
5-b-c-g-h-i-u-p-v-y 3745.25
3728.32
15-c-d-g-h-i-u-q-v-x 3731.23
3730.66
3731.23
3730.66
6-a-d-g-h-i-u-q-t-y
3722.89
3743.03
7-a-d-g-h-i-u-p-v-y 3728.43
3745.36
16-c-d-g-h-i-u-q-t-y
3734.85
3724.29
3734.85
3724.29
8-b-c-g-h-i-u-q-v-x 3747.96
3718.66
9-a-d-g-h-i-u-q-v-x 3718.75
3748.06
The frequency values have been scaled by 0.9024, recommended for HF/6-31G(d,p) calculations
[13]. When two values are reported for the same conformers, the vibrations of the two OHs are
coupled, and one frequency corresponds to symmetric coupling and the other to antisymmetric
coupling
Fig. 3 Model structure used
to calculate a reference
frequency for the vibrations
of the OHs attached to the
naphthalene moieties of SHA
(O43–H52 and O44–H54).
The atom numbering of the
D,C naphthalene moiety is
selected for this model
13
12
11
20
19
14
18
17
16
15
43
O
42
O
52
H
51
CH 3
H 3
53
C
C
D
CH 3
CH 3
red shifts of the OHs in SHA. The red shifts of the vibrations of O43–H52 and O44–
H54 when they are engaged in O–H···O IHBs are reported in Table 5, while table S4
reports the red shifts when these OHs are engaged in O–H···π IHBs. The values of the
red shifts for O–H···O IHBs and O–H···π IHBs are basically comparable, although
the latter are slightly smaller. It is not easy to make straightforward inferences on
the strength of the IHBs in SHA from the red shifts. The strength of an IHB and,
M. K. Bilonda and L. Mammino
Table 4 Vibrational frequencies (harmonic approximation) of the O–H bonds in the calculated
conformers of shuangancistrotectorine A HF/6-31G(d,p) results in vacuo
Conformers
Vibrational frequency
(cm −1 )
Conformers
Vibrational frequency
(cm −1 )
O43 H52 O44 H54
O43 H52 O44 H54
1-a-b-g-h-i-u-q-v-x 3729.36
3727.41
3729.36
3727.41
10-a-d-g-h-i-u-q-t-x
3723.53
3744.89
11-b-c-g-h-i-u-q-t-x
3744.89
3723.53
2-a-b-g-h-i-u-q-t-y
3733.28
3738.63
12-b-c-g-h-i-u-q-t-y
3751.12
3732.73
3-a-b-g-h-i-u-p-v-y 3740.48
3738.52
3740.48
3738.52
13-c-d-g-h-i-u-p-v-y 3728.99
3723.11
3728.99
3723.11
4-a-b-g-h-i-u-q-t-x
3735.05
3733.12
3735.05
3733.12
14-b-c-g-h-i-u-q-t-x
3730.13
3724.54
3730.13
3724.54
5-b-c-g-h-i-u-p-v-y 3745.25
3728.32
15-c-d-g-h-i-u-q-v-x 3731.23
3730.66
3731.23
3730.66
6-a-d-g-h-i-u-q-t-y
3722.89
3743.03
7-a-d-g-h-i-u-p-v-y 3728.43
3745.36
16-c-d-g-h-i-u-q-t-y
3734.85
3724.29
3734.85
3724.29
8-b-c-g-h-i-u-q-v-x 3747.96
3718.66
9-a-d-g-h-i-u-q-v-x 3718.75
3748.06
The frequency values have been scaled by 0.9024, recommended for HF/6-31G(d,p) calculations
[13]. When two values are reported for the same conformers, the vibrations of the two OHs are
coupled, and one frequency corresponds to symmetric coupling and the other to antisymmetric
coupling
Fig. 3 Model structure used
to calculate a reference
frequency for the vibrations
of the OHs attached to the
naphthalene moieties of SHA
(O43–H52 and O44–H54).
The atom numbering of the
D,C naphthalene moiety is
selected for this model
13
12
11
20
19
14
18
17
16
15
43
O
42
O
52
H
51
CH 3
H 3
53
C
C
D
CH 3
CH 3
red shifts of the OHs in SHA. The red shifts of the vibrations of O43–H52 and O44–
H54 when they are engaged in O–H···O IHBs are reported in Table 5, while table S4
reports the red shifts when these OHs are engaged in O–H···π IHBs. The values of the
red shifts for O–H···O IHBs and O–H···π IHBs are basically comparable, although
the latter are slightly smaller. It is not easy to make straightforward inferences on
the strength of the IHBs in SHA from the red shifts. The strength of an IHB and,