P a g e | S1
Supporting Information
Submitted to the Journal of Computational Chemistry
On the mechanism of intramolecular nitrogen-atom hopping in
̂
the carbon chain of C6N radical: A plausible 3c-4e crossover 𝝅
long-bond
Gurpreet Kaur and Vikas*
Quantum Chemistry Group, Department of Chemistry & Centre of Advanced Studies in Chemistry, Panjab
University, Chandigarh-160014, INDIA.
Contents
Page Nos.
I. Non-linear Isomers of C6N ……………………………………………………………S2
II. Supporting Information Figures S1-S3………………………………………………S6
III. Supporting Information Tables S1-S12…………………………………………….S11
P a g e | S2
I. Non-linear Isomers of C6N
EQ1, the first non-linear isomer above EQ0, has a three-membered CCC (cyclopropane-like)
ring with an exocyclic CCCN fragment. It is C2v symmetrized and possesses 2Aʹ ground state,
lying only 2.32 kcal/mol above EQ0 at ZPE corrected CCSD/6-311++G(d,p)//DFT/B3LYP/6311++G(d,p) level of the theory. However, at CASSCF(13,13)/aug-cc-pVTZ level of the theory,
EQ1 is observed to be lying 22.65 kcal/mol above EQ0. As evident in Table S2, the vibrational
modes associated with C-N stretch and C-C stretch in ring were observed with highest intensity,
whereas highest Raman activity was found to be associated with C-C and C-N stretch in the
chain. In EQ1, bond-distance C4-C5 and C6-N7 resembles triple bond whereas C1-C3 bond lies
between C-C single and double-bond. Further, the natural charge distribution in EQ1, listed in
Table S12, and the NBO analysis justifies the structure of EQ1 by two resonating geometries:
C2
C3
C1
•
C4
C5
C6
•
N7
C2
•
C3
C4
C5
C6
•
N7
C1
EQ2, also contains a cyclopropane-like ring but with two exocyclic C-N and C-C fragments. It
is C1 symmetrized and possesses 2Aʹ electronic ground state. However, EQ2 is observed to by
lying even above EQ4 (as evident in Table 1) at CASSCF(13,13)/aug-cc-pVTZ and
DFT/B3LYP/6-311++G(d,p) level of the theory. For EQ2, highest IR intensity corresponds to
the C-C stretch whereas highest Raman activity was found to be associated with C-N stretch
and C-C stretch adjacent to the N-atom with an isotopic shift of 27.9 cm-1. In EQ2, C2-C4 and
C1-C2 bonds are closer to C-C single bond, and the bond-distance C5-C6 lies between that of
P a g e | S3
C=C and C≡C bond. Furthermore, the natural charge distribution in EQ2, listed in Table S12,
and further NBO calculations suggested two resonating forms of EQ2 as:
C3
C3
C2
•
C2
C4
•
C5
C1
•
•
C6
N7
C4
•
C1
C5
•
C6
N7
EQ4 is a four-membered bicyclic ring isomer with a kite like geometry having exocyclic CCN
fragment. It has C2v symmetry and 2Aʹ
electronic ground state. EQ4 features a transannular
bond in the ring which is formed by fusion of two three-membered cyclopropane-like rings. In
case of EQ4 (as evident in Table S5), highest IR intensity was observed with C-C stretch in the
four-membered ring while highest
Raman activity was found
associated with stretching
vibrations in CCN fragment showing an isotopic shift of 20.2 cm-1. Further, the computed C-C
bond-lengths in the ring lies closer to C-C bond, whereas that of C4-C5 is comparable to C=C
bond. Moreover, the natural charge distribution in EQ2, listed in Table S12, and NBO analysis
supported the structure by two resonating forms:
•
C1
| C2
C4
C3
•
•
C5
C6
•
N7
C1
| C2
C4
•
C5
C6
•
N7
C3
EQ5 contains a three membered CCN ring and a one exocyclic C-C-C fragment. For EQ5,
highest IR intensity corresponds to the C-C stretch in chain whereas highest Raman activity was
found to be associated with stretching motion in ring as well as chain with an isotopic shift of
2.8 cm-1 as evident in Table S6. In EQ5, bond-distance C1-C2, C2-C3, C3-C4, C4-C5 and C6-N7
P a g e | S4
bond lies closer to C=C. Moreover, the natural charge distribution in EQ5, listed in Table S12,
and the NBO analysis justifies the structure by two resonating geometries:
N7
N7
C5
C4
C3
C2
C5
C1
C4
C3
C2
C1
C6
C6
Out of the remaining high-lying isomers, EQ6-EQ17, we were mainly interested in the nonlinear isomers (EQ7, EQ8, EQ9, EQ14 and EQ15) involved in the isomerisation pathways of the
linear isomers. In this view, for the sake of brevity, the details of only these non-linear isomers
are further provided below, whereas the linear isomers, EQ0, EQ3, EQ8 and EQ15, are discussed
in the main article.
EQ7 is a bicyclic isomer having a fused a six membered pyridine-like and a three membered
cyclopropane-like rings. In case of EQ7, highest intensity and Raman scattering was observed at
1767.07 and 1022.47 cm-1, respectively, with corresponding isotopic frequency shift of 0.3 and
3.5 cm-1 respectively, as evident in Table S7. In EQ7, bond-distances C6-N7 and C1-N7 lay
between C-C and C=C whereas C4-N5 bond-length
lies between C=C and C≡C. EQ7 is
observed to have strongly delocalized geometry with natural charge distribution listed in Table
S12. NBO analysis supported the structure by two resonating forms:
N7
C6
C5
C1
C3
C4
N7
C2
C6
C5
C1
C2
C3
C4
.
EQ9 has similar structure as that of EQ7 but differing in position of N-atom in the pyridine-like
ring. As evident in Table S9, highest IR intensity was observed with bending motion while
P a g e | S5
highest Raman activity was found associated with stretching vibrations. Further, computed C1C2 and C4-C5 is comparable to C=C bond. Moreover, the natural charge distribution in EQ9,
listed in Table S12, and NBO analysis supported the structure by two resonating forms:
C1
N7
C2
C6
C1
C3
C4
N7
C6
C5
C2
C3
C4
C5
The high-energy isomer, EQ14 is a seven-membered ring isomer. As evident in Table S10,
highest IR intensity was observed with vibrations with no movement of N-atom while highest
Raman activity was found associated with stretching motion in the ring. Further, looking at the
calculated bond-distances: C2-C3 and C5-C6 lies between C=C and C≡C bond whereas C3-C4
bond resembles C-C bond. Moreover, the natural charge distribution in EQ14, listed in Table
S12, and NBO analysis supported the structure by two resonating forms:
—
C3
C2
C5
C1
C6
N7
—
C3
C4
C4
C2
C5
C1
C6
N7
P a g e | S6
II. Supporting Information Figures
Figure S1. Optimized geometries of isomers (EQ0-EQ17) of C6N at the DFT/B3LYP/6311++G(d,p) level, with bond lengths depicted in Å and angles in degrees. The
values in parenthesis alongwith symmetry refer to ZPE corrected relative energies
(in kcal/mol) with respect to the lowest–lying isomer (EQ0) obtained at the
CCSD(T)/6-311++G(d,p)//DFT/B3LYP/6-311++G(d,p) level of the theory.
Figure S2. Same as Figure S1, but for the optimized geometries of transition states, TSm/n(k),
where, k denotes the kth transition state connecting mth isomer with nth isomer.
Figure S3. CASSCF/aug-cc-pVTZ optimized geometries of a few relevant isomers of C6N, with
bond lengths depicted in Å and angles in degrees. The value in parenthesis
represents total energy in a.u. (EQ0, EQ1, EQ2, and EQ4, are computed using
CASSCF(13,13) whereas CASSCF(13,12) is employed for EQ3, EQ8).
P a g e | S7
EQ0 (C∞v) (0.0)
EQ1 (C2v) (2.32)
EQ2 (C1) (23.28)
EQ3 (C∞v) (24.72)
EQ4 (C2v) (29.93)
EQ5 (Cs) (42.23)
EQ6 (Cs) (45.37)
EQ7 (Cs) (52.84)
EQ8 (C∞v) (57.48)
EQ9 (Cs) (62.56)
EQ10 (Cs) (67.58)
EQ11 (C2v) (68.15)
EQ12 (C1) (70.41)
EQ13 (C2v) (70.47)
EQ14 (Cs) (70.85)
EQ15 (C∞v) (73.92)
EQ16 (C2) (78.82)
EQ17 (Cs) (116.15)
Figure S1. Optimized geometries of isomers (EQ0-EQ17) of C6N at the DFT/B3LYP/6-311++G(d,p)
level, with bond lengths depicted in Å and angles in degrees. The values in parenthesis alongwith
symmetry refer to ZPE corrected relative energies (in kcal/mol) with respect to the lowest–lying isomer
(EQ0) obtained at the CCSD(T)/6-311++G(d,p)//DFT/B3LYP/6-311++G(d,p) level of the theory.
P a g e | S8
TS0/1 (Cs) (17.76)
TS0/2(Cs) (44.80)
TS0/2 (2) (C1) (93.56)
TS0/4 (Cs) (63.19)
TS0/5 (C1) (53.78)
TS0/7(C1) (96.57)
TS0/14(Cs) (65.70)
TS1/7(Cs) (88.10)
TS2/9(Cs) (67.46)
TS3/5 (Cs) (48.07)
TS3/7(Cs) (76.62)
TS6/7(Cs) (72.23)
TS6/12(Cs) (79.69)
TS7/9(Cs) (69.84)
TS7/9 (2) (C1) (140.19)
Figure S2. Same as Figure S1, but for the optimized geometries of transition states, TSm/n(k),
where, k denotes the kth transition state connecting mth isomer with nth isomer.
Figure S2 continued………
P a g e | S9
Figure S2 continued………
TS7/14(Cs) (70.22)
TS8/9(C1) (91.24)
TS9/15(Cs) (112.89)
TS10/16 (C1) (72.60)
TS11/17(Cs) (135.35)
TS12/13 (C1) (88.60)
TS12/16(C1) (79.63)
TS12/12(C1) (80.57)
TS14/15(Cs) (125.56)
TS8/ C3 + C3N (107.56)
TS13/ C5 + CN (112.64)
P a g e | S10
EQ0 (-281.6555)
EQ1(-281.6189)
EQ2(-281.5864)
EQ3 (-281.5973)
EQ4(-281.5881)
EQ8( -281.5337)
Figure S3. CASSCF/aug-cc-pVTZ optimized geometries of a few relevant isomers of C6N, with
bond lengths depicted in Å and angles in degrees. The value in parenthesis
represents total energy in a.u. (EQ0, EQ1, EQ2, and EQ4, are computed using
CASSCF(13,13) whereas CASSCF(13,12) is employed for EQ3, EQ8).
P a g e | S11
III. Supporting Information Tables
Table S1. Unscaled harmonic vibrational frequencies (in cm-1), IR intensities (in km/mol), Raman
scattering activities (in Å/a.m.u. ), rotational constants and corresponding isotopic (15N) shift
calculated for EQ0 at DFT/B3LYP/aug-cc-pVTZ. The values compared in the parenthesis are
from Ref.[1] computed at DFT/B3LYP/6-311G(d,p) level of the theory.
Table S2. Same as Table S1, but for isomer EQ1.
Table S3. Same as Table S1, but for isomer EQ2.
Table S4. Same as Table S1, but for isomer EQ3.
Table S5. Same as Table S1, but for isomer EQ4.
Table S6. Same as Table S1, but for isomer EQ5.
Table S7. Same as Table S1, but for isomer EQ7.
Table S8. Same as Table S1, but for isomer EQ8.
Table S9. Same as Table S1, but for isomer EQ9.
Table S10.Same as Table S1, but for isomer EQ14.
Table S11.Same as Table S1, but for isomer EQ15.
Table S12.NBO charge distribution on different atoms of relevant isomers, at DFT/B3LYP/6311++G(d,p) level of the theory (for atom labels, refer to NBO structures in the
supporting information text).
P a g e | S12
Table S1. Unscaled harmonic vibrational frequencies (in cm-1), IR intensities (in km/mol),
Raman scattering activities (in Å/a.m.u. ), rotational constants and corresponding isotopic
(15N) shift calculated for EQ0 at DFT/B3LYP/aug-cc-pVTZ. The values compared in the
parenthesis are from Ref.[1] computed at DFT/B3LYP/6-311G(d,p) level of the theory.
15
EQ0
Ae = 0.8800 GHz
N-substituted EQ0
Ae = 0.8600 GHz
Rotational
Constants
Mode
Frequency
IR Intensity
Raman
Scattering activity
Frequency
shift
IR Intensity
change
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
ν16
2241.7(2249)
2091.6(2079)
1954.0(1962)
1558.5(1559)
1068.2(1068)
603.4(722)
558.8(558)
535.7(557)
476.4(553)
436.3(458)
362.2(352)
316.4(329)
181.3(184)
178.3(183)
78.4(80)
76.6(80)
78.69(65)
18.8(8)
757.7(730)
129.0(120)
10.4(9)
0.6(1)
2.1(2)
2.1(2)
6.3(4)
0.0(2)
3.0(2)
7.5(5)
0.6(0)
0.2(1)
11.1(10)
7.8(10)
1838.5
1007.6
929.5
67.0
31.3
11.1
33.7
0.0
3.9
1.0
0.1
0.4
0.1
0.0
1.0
1.6
-22.1
-2.5
-1.4
-2.2
-6.0
-0.2
-5.5
-0.8
-1.9
-0.3
-0.2
-1.0
-0.5
-0.5
-0.6
-0.7
11.5
-6.4
-4.3
-0.8
-0.2
0.0
-0.1
-0.1
-0.3
0.0
0.0
-0.2
0.0
0.0
-0.2
-0.1
Raman
activity
change
42.7
-104.4
17.9
5.1
-1.6
-0.1
-0.3
0.0
-0.2
0.0
0.0
-0.1
0.0
0.0
0.2
0.3
Table S2. Same as Table S1, but for isomer EQ1.
Rotational
constants
Mode
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
EQ1
Ae = 46.1881 GHz, Be = 1.0750 GHz,
Ce = 1.0506 GHz
Frequency
IR Intensity
Raman
Scattering
activity
2318.2(2326) 0.3(0)
2554.1
2203.8(2203) 31.4(30)
847.2
1657.6(1660) 55.1(60)
614.4
1320.8(1312) 42.3(30)
296.7
1052.6(1051) 8.8(8)
95.7
586.9(592)
1.5(0)
9.1
556.9(573)
58.0(3)
13.2
539.0(539)
0.1(0)
10.0
525.4(524)
8.7(6)
0.3
524.9(517)
146.9(55)
4.8
469.9(452)
245.8(345)
20.8
282.3(282)
0.8(0)
0.0
234.0(230)
20.4(30)
9.3
103.2(103)
7.3(6)
0.1
91.0(89)
18.7(20)
4.0
15
N-substituted EQ1
Ae = 46.1880 GHz, Be = 1.0480 GHz,
Ce = 1.0248 GHz
Frequency
IR Intensity Raman
shift
change
activity
change
-18.6
-0.3
268.2
-8.7
0.5
-299.7
-0.5
-0.4
3.4
-1.5
0.5
7.2
-5.8
-0.4
-5.4
-0.3
0.1
-0.1
-0.2
1.0
-0.1
-5.1
0.0
-0.1
-0.9
-0.3
0.0
-0.7
3.3
0.2
-0.8
-4.5
-0.4
-1.3
-0.1
0.0
-1.0
0.2
0.3
-0.9
-0.1
0.0
-0.7
-0.4
-0.3
P a g e | S13
Table S3. Same as Table S1, but for isomer EQ2.
Rotational
constants
Mode
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
EQ2
Ae = 7.2834 GHz, Be = 1.7362 GHz,
Ce = 1.4020 GHz
Frequency
IR Intensity
Raman
Scattering
activity
2325.0
2.7
679.6
2007.6
972.1
194.4
1710.7
10.7
134.3
1332.1
8.4
564.4
922.5
119.6
50.1
754.6
36.4
21.4
688.8
34.5
20.5
617.8
2.1
0.6
587.7
2.5
22.3
477.4
0.2
2.3
403.8
11.0
18.5
230.9
11.2
2.3
208.2
6.4
20.4
164.1
10.2
1.3
91.6
7.6
11.2
15
N-substituted EQ2
Ae = 7.1932GHz, Be = 1.6944 GHz,
Ce = 1.3714 GHz
Frequency
IR Intensity Raman
shift
change
activity
change
-27.9
0.1
-6.3
-0.1
0.2
-0.6
-2.0
-0.3
-4.5
-0.8
-0.1
-0.9
-2.8
1.9
-0.5
-0.2
1.3
0.2
-6.1
-3.1
-0.5
-0.3
-0.1
0.0
-0.4
-0.1
0.1
-0.7
0.0
0.0
-1.3
-0.2
0.1
-1.9
-0.3
-0.1
-1.2
0.0
-0.5
0.0
0.0
0.0
-1.0
-0.1
0.0
Table S4. Same as Table S1, but for isomer EQ3.
15
EQ3
Ae = 0.9169 GHz
Rotational
Constants
Mode
Frequency
IR Intensity
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
ν16
2132.8(2141)
2066.8(2069)
1900.9(1910)
1579.6(1578)
1112.1(1111)
581.1(601)
573.8(573)
486.5(491)
411.1(398)
356.0(358)
345.1(340)
280.6(283)
180.4(182)
170.0(172)
80.6(82)
79.5(81)
2.2(1)
0.1(2)
1070.3(975)
95.0(90)
7.2(7)
3.2(6)
2.2(2)
1.0(1)
0.5(0)
1.3(0)
1.4(1)
4.8(4)
0.6(1)
0.3(0)
9.3(9)
6.6(9)
N-substituted EQ3
Ae = 0.9068 GHz
Raman
Scattering
activity
2848.1
38.6
1903.7
142.6
16.4
9.2
31.7
1.1
0.7
5.4
0.5
1.2
0.2
0.0
0.3
0.6
Frequency
shift
IR Intensity
change
-7.6
-19.3
-12.7
0.0
-1.8
-0.2
-4.2
-3.9
-0.2
-7.4
0.0
-3.0
-0.7
-0.2
0.0
0.0
4.9
15.5
-30.0
-0.8
-0.5
0.0
0.1
0.1
0.0
-0.1
0.0
-0.1
0.0
0.0
0.0
0.0
Raman
activity
change
-383.8
59.8
214.1
2.2
2.7
0.0
-1.8
0.1
0.1
0.2
0.0
0.2
0.1
0.0
0.0
0.0
P a g e | S14
Table S5. Same as Table S1, but for isomer EQ4.
Rotational
constants
EQ5
Ae = 36.8511 GHz, Be = 1.2985 GHz,
Ce = 1.2543 GHz
Mode
Frequency
IR Intensity
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
2081.6
1912.6
1423.0
1253.4
964.3
911.3
580.3
568.6
565.9
516.9
414.7
357.6
274.8
118.1
42.3
1.1
58.4
192.9
6.1
7.9
12.1
0.2
25.7
35.2
5.5
2.3
7.4
1.2
12.3
7.3
Raman
Scattering
activity
876.3
133.9
189.3
13.6
19.4
9.7
4.3
13.6
13.2
3.9
0.1
0.9
1.2
0.0
0.8
15
N-substituted EQ5
Ae = 36.8510 GHz, Be = 1.2635
Ce = 1.2216 GHz
Frequency
shift
IR Intensity
change
-20.2
-4.7
-0.6
-5.1
-1.7
0.0
0.0
-1.2
-4.5
-1.7
-2.6
-0.2
-0.6
-1.1
-0.4
0.9
-0.1
-1.2
0.6
-0.2
0.0
0.0
31.8
-31.9
-0.2
-0.3
0.0
0.1
-0.2
-0.1
Raman
activity
change
15.7
-34.2
2.4
-1.2
-0.2
0.0
0.0
-6.6
6.5
-0.2
0.1
0.0
0.1
0.0
-0.1
Table S6. Same as Table S1, but for isomer EQ5.
Rotational
constants
Mode
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
EQ5
Ae = 48.2860 GHz, Be = 1.0896 GHz,
Ce = 1.0655 GHz
Frequency
IR Intensity
Raman
Scattering
activity
2104.2
1401.0
320.8
1974.0
8.9
949.6
1680.5
259.3
26.4
1360.0
4.2
158.0
961.5
4.4
411.4
779.4
6.5
277.6
559.4
8.3
0.1
534.4
0.4
10.1
515.4
0.1
7.5
485.0
4.2
1.1
411.1
2.5
5.0
219.1
1.6
7.5
211.6
2.3
0.2
93.0
7.5
2.2
87.1
6.2
0.2
15
N-substituted EQ5
Ae = 46.6632 GHz, Be = 1.0740 GHz,
Ce = 1.0498 GHz
Frequency
IR Intensity Raman
shift
change
activity
change
-0.2
-2.6
-3.2
-2.8
0.8
23.5
-12.5
-1.4
-9.4
-8.4
-1.4
-13.9
-5.1
0.0
12.1
-8.9
0.1
-13.9
0.0
0.0
0.0
-3.4
-0.1
-0.6
-1.3
0.0
0.7
-0.4
0.0
0.0
-1.0
0.0
-0.3
-0.5
0.0
0.0
-0.1
0.0
0.0
-0.4
0.0
0.1
-0.3
0.0
0.0
P a g e | S15
Table S7. Same as Table S1, but for isomer EQ7.
Rotational
constants
Mode
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
EQ7
Ae = 7.4157 GHz, Be = 4.0875 GHz,
Ce = 2.6351 GHz
Frequency
IR Intensity
Raman
Scattering
activity
1767.1(1770.04)
210.7(190)
19.5
1611.9(1615.34)
26.6(25)
11.1
1397.0(1399.76)
65.8(65)
4.6
1363.6(1362.86)
18.8(20)
44.3
1139.2(1139.60)
60.6(55)
6.8
1022.5(1020.34)
7.7(7)
67.8
838.3(839.10)
45.8(45)
5.7
736.0(734.34)
3.0(2)
3.0
679.9(677.46)
0.1(0)
12.3
644.2(638.47)
3.7(4)
0.1
527.0(521.55)
0.7(0)
0.0
512.8(512.82)
8.2(8)
12.5
482.4(484.03)
2.4(2)
36.3
410.7(408.64)
0.2(0)
2.3
215.1(209.82)
23.8(20)
0.1
15
N-substituted EQ7
Ae = 7.2327 GHz, Be = 4.0844 GHz,
Ce = 2.6103 GHz
Frequency
IR Intensity Raman
shift
change
activity
change
-0.3
-0.5
0.1
-3.3
0.4
0.6
-9.3
-4.4
12.0
-13.2
5.4
-12.8
-2.6
-2.7
0.8
-3.5
0.7
0.0
-10.5
-1.3
-0.8
-6.1
0.1
0.0
-4.4
0.0
-0.2
-5.4
-0.1
0.0
-2.9
0.1
0.0
-0.2
-0.1
0.1
-0.2
0.0
-0.1
-0.2
0.0
0.0
-0.3
-0.1
0.0
Table S8. Same as Table S1, but for linear isomer EQ8.
15
EQ8
Ae = 0.9540 GHz
Rotational
Constants
Mode
Frequency
IR Intensity
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
ν16
2155.3(2165)
1964.5(1974)
1835.7(1849)
1610.5(1609)
1067.4(1065)
609.6(608)
514.8(534)
511.4(521)
347.8(361)
328.1(343)
264.8(274)
219.6(223)
180.3(180)
157.7(161)
83.5(69)
67.9(69)
0.0(23)
2.3(2)
1711.2(1500)
0.0(0)
26.6(20)
0.0(0)
10.4(16)
0.0(0)
0.0(0)
0.6(0)
2.9(3)
8.0(7)
0.0(0)
0.0(0)
14.0(12)
14.1(12)
N-substituted EQ8
Ae = 0.9540 GHz
Raman
Scattering
activity
655.8
9.0
0.0
420.2
0.0
149.3
0.0
3.8
0.9
0.0
0.0
0.0
0.2
0.3
0.0
0.0
Frequency
shift
IR Intensity
change
0.0
-32.1
-0.5
0.0
-12.6
0.0
-3.4
-0.5
0.0
0.0
-5.6
-2.4
0.0
0.0
-0.6
-0.7
0.0
8.1
-9.8
0.0
-0.2
0.0
-10.4
10.2
0.0
0.0
0.2
0.4
0.0
0.0
-0.2
-0.3
Raman
activity
change
0.0
-9.0
0.0
0.0
0.0
0.0
3.8
-3.8
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
P a g e | S16
Table S9. Same as Table S1, but for isomer EQ9.
Rotational
constants
Mode
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
EQ9
Ae = 7.2146 GHz, Be = 4.1110 GHz,
Ce = 2.6188 GHz
Frequency
IR Intensity
Raman
Scattering
activity
1708.3
19.7
78.1
1663.1
36.3
89.4
1346.0
62.4
4.2
1321.1
94.4
24.0
1109.4
9.2
27.1
1010.7
9.3
67.7
798.4
44.7
6.5
615.3
0.7
1.2
613.5
27.1
8.9
605.0
10.6
11.3
524.3
1.4
0.6
508.5
101.0
10.9
431.9
0.9
0.5
381.6
6.3
31.0
246.1
22.5
0.9
15
N-substituted EQ9
Ae = 7.1792 GHz, Be = 4.0386 GHz,
Ce = 2.5846 GHz
Frequency
IR Intensity Raman
shift
change
activity
change
-0.3
-0.5
2.3
-2.0
-1.3
-2.8
-10.8
-30.0
5.3
-3.6
28.4
-6.0
-10.8
-0.4
-0.2
-2.7
1.0
-1.1
-2.7
-0.1
0.3
-2.7
-0.1
0.1
-5.1
3.3
4.0
-8.0
-2.7
-4.4
-1.1
0.1
0.0
-0.3
-1.2
0.2
-3.2
-0.2
0.0
-0.1
0.0
-0.1
-0.8
-0.1
0.1
Table S10. Same as Table S1, but for isomer EQ14.
Rotational
constants
Mode
EQ14
Ae = 6.3081 GHz, Be = 4.2238 GHz,
Ce = 2.5299 GHz
Frequency
IR Intensity Raman Scattering
activity
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
1875.8(1977.04)
1722.8(1854.19)
1396.6(1825.60)
1325.2(1286.31)
1105.4(1172.48)
1012.5(1005.62)
801.8(828.02)
622.9(494.02)
593.4(483.58)
593.2(448.41)
460.7(396.17)
436.4(391.45)
310.5(211.17)
251.7(-301.66)
171.5(-415.16)
81.3
138.8
13.2
7.5
36.3
16.8
4.4
44.9
4.7
22.2
6.5
63.1
3.2
23.5
25.5
15.2
21.5
4.3
10.2
12.6
45.2
2.1
7.1
3.5
15.7
0.5
24.2
2.6
1.6
18.1
15
N-substituted EQ14
Ae = 6.2995 GHz, Be =4.1292 GHz,
Ce = 2.4943 GHz
Frequency
IR Intensity Raman
shift
change
activity
change
-3.1
0.3
0.4
0.0
0.0
0.0
-8.2
2.2
0.2
-0.7
-0.7
-0.5
-2.7
-1.7
1.6
-10.7
0.0
-1.8
-15.4
0.1
-0.3
-0.5
-2.2
0.4
-2.7
18.9
11.7
-3.3
-17.8
-12.1
-0.7
0.2
0.0
-0.1
0.0
0.1
0.0
0.0
0.0
-2.3
-0.5
0.2
-0.7
-0.2
-0.2
P a g e | S17
Table S11. Same as Table S1, but for linear isomer EQ15.
15
EQ15
Ae = 0. 9436GHz
Rotational
Constants
Mode
Frequency
IR Intensity
ν1
ν2
ν3
ν4
ν5
ν6
ν7
ν8
ν9
ν10
ν11
ν12
ν13
ν14
ν15
ν16
2125.5(2134)
2072.5(2086)
1844.9(1858)
1560.9(1559)
1104.8(1103)
600.1(599)
539.1(549)
487.2(488)
410.3(409)
362.6(369)
324.5(324)
270.9(272)
183.7(180)
171.1(172)
83.6(80)
79.1(80)
19.8(20)
309.6(371)
3679.2(3300)
0.0(0)
80.1(70)
0.5(0)
0.2(1)
0.0(0)
0.5(0)
1.1(1)
1.5(1)
5.7(5)
0.0(0)
0.0(0)
13.3(15)
16.4(15)
N-substituted EQ15
Ae = 0.9410 GHz
Raman
Scattering
activity
101.4
163.0
76.2
425.2
7.7
157.2
1.5
9.3
2.6
1.6
0.3
0.4
0.5
0.1
0.2
0.2
Frequency
shift
IR Intensity
change
-6.8
-19.2
-5.8
-10.7
-4.7
-1.1
-3.1
-6.7
-0.1
-4.7
-0.1
0.0
-1.6
-0.8
-0.4
-0.2
61.5
-139.2
49.7
2.7
-6.3
0.0
0.0
0.0
0.0
0.1
-0.1
0.0
0.0
0.0
-0.1
-0.1
Raman
activity
change
-45.9
46.6
25.3
-28.2
1.0
-0.9
0.6
-0.5
-0.1
0.1
0.0
0.0
0.1
0.0
0.0
0.0
Table S12. NBO charge distribution on different atoms of relevant isomers, at
DFT/B3LYP/6-311++G(d,p) level of the theory (for atom labels, refer to NBO structures in
the supporting information text).
Isomers
EQ0
EQ1
EQ2
EQ3
EQ4
EQ5
EQ7
EQ8
EQ9
EQ14
EQ15
Natural charge distribution on different atoms
C1
C2
C3
C4
0.194
-0.352
0.169
-0.062
0.012
0.012
-0.120
0.139
0.228
-0.100
0.147
0.077
0.172
-0.367
0.174
-0.126
0.081
-0.087
0.081
-0.118
0.168
-0.313
0.234
-0.119
0.228
0.46
-0.104
0.090
0.187
-0.439
0.433
0.449
0.243
-0.070
0.049
0.037
0.138
0.004
-0.066
0.103
0.198
-0.400
0.183
0.204
C5
0.336
-0.356
-0.362
0.327
0.068
0.148
-0.160
-0.462
-0.165
-0.164
-0.066
C6
0.255
0.194
0.187
0.378
0.156
0.242
0.362
0.199
0.332
0.381
0.083
N7
-0.221
-0.193
-0.176
-0.558
-0.180
-0.322
-0.461
-0.366
-0.425
-0.395
-0.194