C2H3N3











 






























Nitrogen


Nuclear Quadrupole Coupling Constants


in 1H-1,2,4-Triazole


 








 








 








Analysis of the hyperfine structure in the microwave spectrum of 1H-1,2,4-triazole was undertaken by Blackman et al. [1].  Quadrupole coupling constants for each of the three inequivalent 14N nuclei have been obtained.

 








Calculation of the 14N nqcc tensors was made here on molecular structures given by MP2/cc-pVTZ and B3LYP/cc-pVTZ optimization.  These nqcc's are compared with the experimental values in Tables 1 - 3.  Structure parameters are given in Table 4, rotational constants and dipole moments in Table 5, and quartic centrifugal distortion constants in Table 6.

 








In Tables 1 - 3, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  ETA = (Xxx - Xyy)/Xzz, and Ø (degrees) is the angle between its subscripted parameters.

RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of nitrogen efg's/nqcc's.

 








 








   







Table 1.  14N(1) nqcc's in 1H-1,2,4-Triazole (MHz).  Calculation was made on molecular structures given by (1) MP2/cc-pVTZ and (2) B3LYP/cc-pVTZ optimization.
   









Calc. (1)
Calc. (2)
Expt. [1]
   







Xaa
0.795
0.878
0.82(4)

Xbb
2.000
2.031
2.13(4)

Xcc -
 2.795
 -
 2.909
 -
 2.95

Xab
0.414
0.522
0.49

 







RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
0.666
0.677
0.66

Xyy
2.129
2.232
2.29

Xzz -
 2.795
 -
 2.909
 -
 2.95

ETA
0.523
0.535
0.553

Øz,c
  0 *
  0 *



 








 








* z-principal axis lies along c-axis, which is perpendicular to the molecular plane.

 








 








   







Table 2.  14N(2) nqcc's in 1H-1,2,4-Triazole (MHz).  Calculation was made on molecular structures given by (1) MP2/cc-pVTZ and (2) B3LYP/cc-pVTZ optimization.
   









Calc. (1)
Calc. (2)
Expt. [1]
   







Xaa -
 4.270
 -
 4.514
 -
 4.39(4)

Xbb
3.531
3.738
3.79(4)

Xcc
0.739
0.776
0.60

Xab -
 0.974
 -
 0.355
 -
 0.42

 







RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
3.651
3.754
3.81

Xyy
0.739
0.776
0.60

Xzz -
 4.390
 -
 4.530
 -
 4.41

ETA -
 0.663
 -
 0.658
 -
 0.728

Øz,a
  7.01
  2.46
  2.9

Øa,bi *
25.17
21.14



Øz,bi
18.16 **
18.68 **



 








 








* "bi" is the external bisector of the N(1)N(2)C(3) angle.

** The z-principal axis leans away from the external bisector, toward the N(1) atom.

 








 








   







Table 3.  14N(4) nqcc's in 1H-1,2,4-Triazole (MHz).  Calculation was made on molecular structures given by (1) MP2/cc-pVTZ and (2) B3LYP/cc-pVTZ optimization.
   









Calc. (1)
Calc. (2)
Expt. [1]
   







Xaa -
 3.757
 -
 3.554
 -
 3.55(4)

Xbb
1.571
1.372
1.35(4)

Xcc
2.186
2.182
2.20

Xab
1.169
1.610
1.56

 







RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
1.817
1.852
1.80

Xyy
2.186
2.182
2.21

Xzz -
 4.003
 -
 4.034
 -
 4.01

ETA
0.092
0.082
0.102

Øz,a
11.85
16.58
16.2

Øa,bi *
12.19
16.35



Øz,bi
  0.35
  0.23



 








 








* "bi" is the external bisector of the C(3)N(4)C(5) angle.




















 
 

Table 4.  1H-1,2,4-Triazole.  Molecular structure parameters, ropt (Å and degrees).
 



 N
 N,1,B1
 C,2,B2,1,A1
 N,3,B3,2,A2,1,D1,0
 C,1,B4,2,A3,3,D2,0
 H,5,B5,1,A4,2,D3,0
 H,1,B6,5,A5,4,D4,0
 H,3,B7,2,A6,1,D5,0


 MP2/cc-pVTZ B3LYP/cc-pVTZ


 B1=1.34313936
 B2=1.33546334
 B3=1.35788737
 B4=1.34960225
 B5=1.07580732
 B6=1.00604972
 B7=1.07517923
 A1=101.46168484
 A2=115.37505017
 A3=111.00337506
 A4=123.43170407
 A5=129.2458516
 A6=121.18269123
 D1=0.
 D2=0.
 D3=180.
 D4=180.
 D5=180.
  B1=1.35210909
 B2=1.31961595
 B3=1.36082751
 B4=1.3464082
 B5=1.07753502
 B6=1.00543923
 B7=1.07682928
 A1=101.94050725
 A2=115.13354213
 A3=110.28312976
 A4=123.47953198
 A5=129.63636484
 A6=121.64782387
 D1=0.
 D2=0.
 D3=180.
 D4=180.
 D5=180.






 








 














Table 5.  1H-1,2,4-Triazole.  Rotational Constants (MHz) and Dipole Moments * (D).







MP2/cc-pVTZ and B3LYP/cc-pVTZ optimization








  MP2 B3LYP Expt [1]







 A
 10332.8
 10308.2
 10245.058

 B
   9822.1
   9922.4
   9832.056

 C
   5035.5
   5055.8
   5015.161







|µa|   1.06
   0.85


|µb|   2.76
   2.80








* B3PW91/6-311+G(df,pd) calculation on ropt structures.






























Table 4.  1H-1,2,4-Triazole.  MP2/cc-pVTZ and B3LYP/cc-pVTZ Quartic Centrifugal Distortion Constants (kHz).










MP2
B3LYP








Delta_J

 3.56
3.58

Delta_JK-
 5.57
 -
 5.48

Delta_K
2.40
2.29

delta_j -
 0.0431
 -
 0.0469

delta_k -
 0.100
1.46








D_J
3.55
2.61

D_JK -
 5.55
 -
 5.65

D_K
2.39
2.43

d_1
0.0431
0.0468

d_2 -
 0.00127
0.0140


 







 








[1] G.L.Blackman, R.D.Brown, F.R.Burden, and A.Mishra, J.Mol.Spectrosc. 57,294(1975).

 








 








1,2,3-Triazole
Imidazole Pyrazole Pyrrole

 








 








Table of Contents




Molecules/Nitrogen




 








 













124Triazole.html






Last Modified 18 Aug 2015