C3N2H3I


















 





 





Iodine and Nitrogen

Nuclear Quadrupole Coupling Constants


in 4-Iodopyrazole


 








 








Iodine and nitrogen nuclear quadrupole coiupling constants in 4-iodopyrazole were determined by Cooper et al. [1].

 








Calculation of the 127I and 14N nqcc's was made here on molecular structures given by B3LYP/cc-pVTZ (cc-pVTZ-PP for I) and B3PW91/6-311G(2d,2pd) optimization.  Calculated nqcc's are compared with experimental values in Tables 1 and 2.  Structure parameters are given in Table 3, rotational constants in Table 4.











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.  ETA = (Xxx - Xyy)/Xzz.  Ø (degrees) is the angle between its subscripted parameters.  RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation of the B1LYP/TZV(df,p) model for calculation of iodine efg's/nqcc's; and in Tables 2 and 3, of the B3PW91/6-311+G(df,pd) model for nitrogen.





















   








Table 1.  Iodine nqcc's in 4-Iodopyrazole (MHz).  Calculation was made on (1) B3LYP/cc-pVTZ and (2) B3PW91/6-311G(2d,2pd) optimized molecular structures.
   











Calc (1)
Calc (2)
   Expt [1]
   








127I Xaa -
 2012.5
 -
 1992.1
 -
 2007.8620(93)


Xbb - cc
    - 4.1
    - 0.9
  - 13.0640(96)


Xbb
1004.2
  995.6
  997.3990(67) *


Xcc
1008.3
  996.5
1010.4630(67) *


|Xab|
    15.0
    10.4
    18.96(44)












RMS
  4.9 (0.37 %)
12.2 (0.91 %)




RSD
15.2 (1.23 %)
15.2 (1.23 %)



 









Xxx
1004.3
  995.6
  997.5186(87)


Xyy
1008.3
  996.5
1010.4630(67)


Xzz -
 2012.6
 -
 1992.1
 -
 2007.982(11)


ETA
0.0020
0.0005




Øz,a
0.28
0.20




Øa,CI
0.21
0.18




Øz,CI
0.07
0.02














 








* Calculated here from experimental Xaa and Xbb - cc

 








 








   








Table 2.  Nitrogen nqcc's in 4-Iodopyrazole (MHz).  Calculation was made on (1) B3LYP/cc-pVTZ and (2) B3PW91/6-31G(2d,2pd) optimized molecular structures.  N(1) is pyrrolic, N(2) pyridinic.
   











Calc (1)
Calc (2)
Expt [1]
   








14N(1) Xaa
0.822
0.805
0.774(10)


Xbb - cc
5.261
5.179
5.3560(64)


Xbb
2.219
2.187
2.291(6) *


Xcc -
 3.041
 -
 2.992
 -
 3.065(6) *


|Xab|
0.187
0.183
0.35(21)












RMS
0.052 (2.5 %)
0.075 (3.7 %)




RSD
0.030 (1.3 %)
0.030 (1.3 %)













14N(2) Xaa -
 3.628
 -
 3.619
 -
 3.6787(80)


Xbb - cc
2.032
2.003
2.1088(64)


Xbb
2.830
2.811
2.8938(51)


Xcc
0.798
0.808
0.7849(51)


|Xab|
2.379
2.359
2.14(23)


 








RMS
0.047 (1.9 %)
0.060 (2.5 %)




RSD
0.030 (1.3 %)
0.030 (1.3 %)



 









 








* Calculated here from experimental Xaa and Xbb - cc

 








 


Table 3.  4-Iodopyrazole: Optimized structure parameters ropt(1) = B3LYP/cc-pVTZ, ropt(2) = B3PW91/6-31G(2d,2pd) (Å and degrees).
 



 N
 N,1,B1
 C,2,B2,1,A1
 C,3,B3,2,A2,1,D1,0
 C,1,B4,2,A3,3,D2,0
 H,1,B5,2,A4,3,D3,0
 H,3,B6,2,A5,1,D4,0
 H,5,B7,1,A6,2,D5,0
 I,4,B8,3,A7,2,D6,0





     ropt(1)      ropt(2)
 



 B1=1.34399991
 B2=1.32628861
 B3=1.40938003
 B4=1.352656
 B5=1.00476459
 B6=1.07651124
 B7=1.07515599
 B8=2.08814117
 A1=104.68748257
 A2=111.10280707
 A3=113.28291668
 A4=119.03932601
 A5=120.43235844
 A6=122.76472095
 A7=127.8541811
 D1=0.
 D2=0.
 D3=180.
 D4=180.
 D5=180.
 D6=180.
  B1=1.33909699
 B2=1.32741243
 B3=1.41083521
 B4=1.34967482
 B5=1.00559989
 B6=1.07952058
 B7=1.07827344
 B8=2.07236354
 A1=104.59203681
 A2=111.12033011
 A3=113.71771056
 A4=118.90144352
 A5=120.47963773
 A6=122.85709074
 A7=128.05182002
 D1=0.
 D2=0.
 D3=180.
 D4=180.
 D5=180.
 D6=180.


 








 








 



Table 4.  4-Iodopyrazole: Rotational Constants (MHz), ropt(1) = B3LYP/cc-pVTZ, ropt(2) = B3PW91/6-31G(2d,2pd).
 





 ropt(1) ropt(2)     Expt [1]






A
  9567.
  9570.
 9495.62203(88)

B
    944.
    952.
   955.21854(54)

C
    860.
    865.
   867.75762(49)


 








 








[1]  G.A.Cooper, C.Medcraft, J.D..Littlefair, T.J.Penfold, and N.Walker, J.Chem.Phys. 147,214303(2017).

 








G.A.Cooper, C.Medcraft, A.Legon, N.Walker, Abstract FB04, 72nd ISMS, Champaign-Urbana, Illinois, 2017.

 








 








4-Bromopyrazole Iodobenzene 3-Iodothiophene
 Pyrazole

4-Iodoimidazole







 








 








Table of Contents




Molecules/Iodine







Molecules/Nitrogen




 








 













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Last Modified 3 Dec 2017