C6H9N3O2











 


























 









Nitrogen


Nuclear Quadrupole Coupling Constants

in Histidine

 








 








 

 





Calculation of the 14N nuclear quadrupole coupling constant tensors in Histidine was made here on ropt molecular structures given by MP2/6-311++G(d,p) [1] and B3P86/6-31G(3d,3p) optimization.

 








Calculated and experimental [1] nitrogen nqcc's are compared in Tables 1 - 3.  Structure parameters are given here in Z-Matrix format.  Rotational constants are given 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.  RMS is the root mean square difference between calculated and experiment diagonal nqcc's (percent of average magnitude of experimental nqcc's).  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the efg's/nqcc's. 


 








 








   







Table 1.  14N(1) nqcc's in Histidine (MHz).  Atomic numbering is shown in the above figure.  Calculation was made on (1) MP2/6-311++G(d,p) and (2) B3P86/6-31G(3d,3p) ropt structures.
   









Calc (1)
Calc (2)
Expt [1]
   







Xaa -
 0.218
 -
 0.131
 -
 0.17933(26)

Xbb
1.146
1.093
1.12207(87)

Xcc -
 0.928
 -
 0.961
 -
 0.94273(87)

Xab
0.382
0.422



Xac
1.747
1.765



Xbc -
 0.256
-
 0.321


 







RMS
0.028 (3.7 %)
0.034 (4.6 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
1.073
1.078



Xyy
1.338
1.356



Xzz -
 2.411
 -
 2.434



ETA
0.110
0.114



 








 








 








   







Table 2.  14N(4) nqcc's in Histidine (MHz).  Atomic numbering is shown in the above figure.  Calculation was made on (1) MP2/6-311++G(d,p) and (2) B3P86/6-31G(3d,3p) ropt structures.
   









Calc (1)
Calc (2)
Expt [1]
   







Xaa
1.669
1.487
1.6113(17)

Xbb -
 3.560
 -
 3.361
 -
 3.4973(16)

Xcc
1.891
1.874
1.8860(16)

Xab -
 0.960
 -
 1.423



Xac
0.011
 -
 0.085



Xbc
0.040
-
 0.209


 







RMS
0.049 (2.1 %)
0.107 (4.6 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
1.839
1.850



Xyy
1.892
1.906



Xzz -
 3.731
 -
 3.756



ETA
0.014
0.015



 








 








 








   







Table 3.  14N(10) nqcc's in Histidine (MHz).  Atomic numbering is shown in the above figure.  Calculation was made on (1) MP2/6-311++G(d,p) and (2) B3P86/6-31G(3d,3p) ropt structures.
   









Calc (1)
Calc (2)
Expt [1]
   







Xaa
0.577
 -
 0.154
0.0052(22)

Xbb
1.890
2.368
2.0982(43)

Xcc -
 2.467
 -
 2.214
 -
 2.1034(43)

Xab
0.660
0.497



Xac
1.976
2.458



Xbc -
 2.119
-
 1.316


 







RMS
0.409 (29. %)
0.192 (14. %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
1.466
1.406



Xyy
2.762
2.733



Xzz -
 4.228
 -
 4.139



ETA
0.307
0.321



 








 







 
 



Table 4.  Histidine. Rotational Constants (MHz).  ropt(1) = MP2/6-311++G(d,p), ropt(2) = B3P86/6-31G(3d,3p).

 




ropt(1) ropt(2)      Expt [1]

 



A
  1817.
  1887.
 1847.53472(52)

B
    862.
    813.
   831.71551(16)

C
    772.
    732.
   745.94445(18)



 








 








[1] C.Bermùdez, S.Mata, C.Cabezas, J.L.Alonso, Angew.Chem.Int.Ed. 53,11015(2014).

 








 








N-Acetyl-prolinamide
 Imidazole




 








 








Table of Contents




Molecules/Nitrogen




 








 













Histidine.html






Last Modified 24 May 2016