C4H4N2OS



















 




 








Nitrogen

Nuclear Quadrupole Coupling Constants

in 2-Thiouracil

 








 








 








Nitrogen nqcc's in uracil, as well as a best estimate ab initio equilibrium structure, were determined by Puzzarini et al. [1].  Calculation of the nqcc tensors was made here on this re structure and on a ropt structure given by B3LYP/cc-pVTZ optimization.  Calculated and experimental nqcc's are compared in Tables 1 - 4.  Structure parameters are given in Z-matrix format in Table 5.

 








Calculation was made with both B3PW91/6-311+G(df,pd) and B3PW91/6-311+G(d,p) models, the latter shown to perform better than the former for modeling conjugated pi-electron systems [2].

 








In Tables 1 - 4, 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 experimental diagonal nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation model for calculation of nitrogen efg's/nqcc's.

 








 








   







Table 1.  14N(1) nqcc's in 2-Thiouracil (MHz).  Calculation was made on the re molecular structure with both (1) B3PW91/6-311+G(df,pd) and (2) B3PW91/6-311+G(d,p) models.
   









Calc (1)
Calc (2)
Expt. [1]
   







Xaa
1.574
1.650
1.634(10)

Xbb
1.706
1.795
1.777(12)

Xcc -
 3.280 - 3.445
 - 3.411(12)

|Xab|
0.272
0.297



 







RMS
0.092 (4.1 %)
0.024 (1.1 %)


RSD
0.030 (1.3 %)
0.086 (3.8 %)


 







Xxx
1.360
1.416



Xyy
1.920
2.029



Xzz -
 3.280 - 3.445



ETA
0.171
0.096



 








 








 







   







Table 2.  14N(1) nqcc's in 2-Thiouracil (MHz).  Calculation was made on the ropt = B3LYP/cc-pVTZ molecular structure with both (1) B3PW91/6-311+G(df,pd) and (2) B3PW91/6-311+G(d,p) models.
   









Calc (1)
Calc (2)
Expt. [1]
   







Xaa
1.557
1.634
1.634(10)

Xbb
1.731
1.819
1.777(12)

Xcc -
 3.288 - 3.453
 - 3.411(12)

|Xab|
0.201
0.307



 







RMS
0.088 (3.9 %)
0.034 (1.5 %)


RSD
0.030 (1.3 %)
0.086 (3.8 %)


 







Xxx
1.350
1.406



Xyy
1.938
2.047



Xzz -
 3.288 - 3.453



ETA
0.179
0.186



 








 








 








   







Table 3.  14N(3) nqcc's in 2-Thiouracil (MHz).  Calculation was made on the re molecular structure with both (1) B3PW91/6-311+G(df,pd) and (2) B3PW91/6-311+G(d,p) models.
   









Calc (1)
Calc (2)
Expt. [1]
   







Xaa
1.690
1.787
1.726(10)

Xbb
1.377
1.437
1.399(13)

Xcc -
 3.067 - 3.224
 - 3.125(13)

|Xab|
0.320
0.344



 







RMS
0.041 (2.0 %)
0.071 (3.4 %)


RSD
0.030 (1.3 %)
0.086 (3.8 %)


 







Xxx
1.177
1.226



Xyy
1.890
1.998



Xzz -
 3.067 - 3.224



ETA
0.232
0.239



 


















 








   







Table 4.  14N(3) nqcc's in 2-Thiouracil (MHz).  Calculation was made on the ropt = B3LYP/cc-pVTZ molecular structure with both (1) B3PW91/6-311+G(df,pd) and (2) B3PW91/6-311+G(d,p) models.
   









Calc (1)
Calc (2)
Expt. [1]
   







Xaa
1.723
1.818
1.726(10)

Xbb
1.351
1.411
1.399(13)

Xcc -
 3.074 - 3.229
 - 3.125(13)

|Xab|
0.323
0.347



 







RMS
0.040 (1.9 %)
0.080 (3.9 %)


RSD
0.030 (1.3 %)
0.086 (3.8 %)


 







Xxx
1.164
1.212



Xyy
1.909
2.017



Xzz -
 3.074 - 3.229



ETA
0.242
0.249



 








 








 














Table 5.  2-Thiouracil.  Structure parameters, best estimate ab initio equilibrium structure, re [1] and ropt = B3LYP/cc-pVTZ (Å and degrees).
 








 N
 C,1,R1
 N,2,R2,1,A1
 C,3,R3,2,A2,1,D1,0
 C,4,R4,3,A3,2,D2,0
 C,1,R5,2,A4,3,D3,0
 S,2,R6,1,A5,6,D4,0
 O,4,R7,3,A6,2,D5,0
 H,1,R8,2,A7,3,D6,0
 H,3,R9,4,A8,5,D7,0
 H,5,R10,6,A9,1,D8,0
 H,6,R11,1,A10,2,D9,0







     re
     ropt


 R1=1.3654
 R2=1.3631
 R3=1.4017
 R4=1.4522
 R5=1.3714
 R6=1.6496
 R7=1.2130
 R8=1.0058
 R9=1.0098
 R10=1.0768
 R11=1.0796
 A1=113.78
 A2=127.78
 A3=113.84
 A4=123.69
 A5=122.53
 A6=119.99
 A7=115.18
 A8=116.16
 A9=122.19
 A10=115.29
 D1=0.
 D2=0.
 D3=0.
 D4=180.
 D5=180.
 D6=180.
 D7=180.
 D8=180.
 D9=180.
 R1=1.37356398
 R2=1.36463607
 R3=1.41356546
 R4=1.45335732
 R5=1.37002833
 R6=1.65934243
 R7=1.21171605
 R8=1.00688533
 R9=1.01042093
 R10=1.07684659
 R11=1.08041653
 A1=113.40161438
 A2=128.04468613
 A3=113.35984116
 A4=123.82652174
 A5=122.29482256
 A6=120.03237973
 A7=115.18482861
 A8=115.76446271
 A9=122.02803941
 A10=115.27375758
 D1=0.
 D2=0.
 D3=0.
 D4=180.
 D5=180.
 D6=180.
 D7=180.
 D8=180.
 D9=180.








 








 








[1] C.Puzzarini, M.Biczysko, V.Barone, I.Peña, C.Cabezas, and J.L.Alonso, PCCP, 15, 16965(2013).

[2] R.Kannengießer, W.Stahl, H.V.L.Nguyen, and W.C.Bailey, J.Mol.Spectrosc. 317,50(2015).

 








 








Pyrimidine Uracil
 Thymine 2-Pyridone

N-Vinylformamide
 N-Methyldiacetamide



 








 








Table of Contents




Molecules/Nitrogen




 








 













2Thiouracil.html






Last Modified 28 March 2016