Imidazole


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Nitrogen


Nuclear Quadrupole Coupling Constants


in Imidazole


 








 








 

 





Nitrogen nqcc's in imidazole were determined by Blackman et al. [1] and Stolze and Sutter [2].  Christen et al. [3] determined a substitution molecular structure, rs.  A semi-experimental equilibrium structure, reSE, was derived by Császár et al. [4].  Calculation of the nqcc's was made here on these structures, and on an ropt  structure given by B3LYP/cc-pVTZ optimization.  These calculated nqcc's are compared with those of Stolze and Sutter in Tables 1 and 2.

 








In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  The nqcc y-axis is chosen coincident with the inertia c-axis, these are perpendicular to the molecular plane.  Ø (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.

RMS is the root mean square difference between calculated and experimental nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation or nitrogen efg's/nqcc's.

 








 








 










Table 1.  14N (Pyrrolic) nqcc's in Imidazole (MHz).  Calculation was made on the rs, reSE, and ropt structures.
 












Calc /rs
Calc /reSE
Calc /ropt
Expt. [2]
 










Xaa
1.294
1.288
1.300
1.281(7)

Xbb
1.254
1.224
1.232
1.278(7)

Xcc - 2.548 -
 2.513
 -
 2.532
 - 2.559

|Xab|
0.142
0.162
0.162














RMS
0.017 (1.0 %)
0.041 (2.4 %)
0.033 (1.9 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)
0.030 (1.3 %)














Xxx
1.130
1.091
1.101



Xyy
1.417
1.422
1.431



Xzz - 2.548 -
 2.513
 -
 2.532



ETA
0.113
0.132
0.130



Øy,a
41.0
39.44
51.01



Øa,NH
28.2
28.02
27.88



Øy,NH
12.8
11.42
11.10















 








 








 










Table 2.  14N (Pyridinic) nqcc's in Imidazole (MHz).  Calculation was made on the rs, reSE, and ropt structures.
 












Calc /rs
Calc /reSE
Calc /ropt
Expt. [2]
 










Xaa - 3.945 -
 3.961
 -
 4.003
 - 3.981(5)

Xbb
1.732
1.726
1.733
1.753(8)

Xcc
2.214
2.234
2.270
2.228

|Xab|
0.794
0.802
0.810














RMS
0.025 (1.0 %)
0.019 (0.7 %)
0.029 (1.1 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)
0.030 (1.3 %)














Xxx
1.840
1.837
1.845



Xyy
2.214
2.234
2.269



Xzz - 4.054 -
 4.072
 -
 4.115



ETA
0.092
0.098
0.103



Øz,a
  7.8
  7.88
  7.89



Øa,bi
10.0
  9.97
  9.91



Øz,bi *
  2.2
  2.09
  2.02















 








* Angle between the z-axis and the bisector ( 'bi' ) of the CNC angle.

 







 
 



Table 3. Molecular structure parameters,  rs [3], reSE [4], and B3LYP/cc-pVTZ ropt (Å and degrees).





 
   rs  reSE   ropt






N(1)H(1) 0.99801.0013(1)
 1.0048

N(1)C(2) 1.36431.3594(3)
 1.3624

C(2)N(3) 1.31351.3114(2)
 1.3098

N(3)C(4) 1.38221.3774(3)
 1.3746

C(4)C(5) 1.36381.3663(3)
 1.3670

C(5)N(1) 1.37741.3758(3)
 1.3760

C(2)H(2) 1.07881.0761(1)
 1.0774

C(4)H(4) 1.07751.0749(2)
 1.0766

C(5)H(5) 1.07851.0734(3)
 1.0747

N(1)C(2)N(3) 111.99111.90(2)
 111.56

C(2)N(3)C(4) 104.93105.08(2)
 105.49

N(3)C(4)C(5) 110.69110.69(2)
 110.57

C(4)C(5)N(1) 105.48105.16(3)
 105.14

C(5)N(1)C(2) 106.90107.18(1)
 107.24

C(2)N(1)H(1) 126.22126.44(4)
 126.51

N(1)C(2)H(2) 122.51122.39(3)
 122.42

N(1)C(5)H(5) 121.92122.29(3)
 122.31

N(3)C(4)H(4) 121.36121.48(3)
 121.48



 








 








[1] G.L.Blackman, R.D.Brown, F.R.Burden, and I.R.Elsum, J.Mol.Spectrosc. 60,63(1976).

[2] M.Stolze and D.H.Sutter,  Z.Naturforsch. 42a,49(1987).

[3] D.Christen, J.H.Griffiths, and J.H.Sheridan, Z.Naturforsch. 37a,1378(1982).

[4] A.G.Császár, J.Demaison, and H.D.Rudolph, J.Phys.Chem. A, 119(9),1731(2015).

 








 








Pyrrole Pyrazole Oxazole



Pyridine Isoxazole Thiazole



 








 








Table of Contents




Molecules/Nitrogen




 








 













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Last Modified 30 Oct 2014