C2H2N2Se





 





 























Nitrogen


Nuclear Quadrupole Coupling Constants


in 1,3,4-Selenadiazole


 








 








 








Analysis of the microwave spectrum of 1,3,4-selenadiazole was undertaken by Levine et al. [1].  Rotational constants and the electric dipole moment were determined.

 








Calculation of the 14N nqcc tensor in 1,3,4-selenadiazole was made here on molecular structures given by B3PW91/6-31G(2d,2pd) and B3LYP/cc-pVTZ(G03) optimization.  These are given in Table 1; structure parameters in Table 2; rotational constants and dipole moments in Table 3; and quartic centrifugal distortion constants in Table 4.

 








In Table 1, 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.

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

 








 








   







Table 1.  14N(3,4) nqcc's in 1,3,4-Selenadiazole (MHz).  Calculation was made on molecular structures given by (1) B3PW91/6-31G(2d,2pd) and (2) B3LYP/cc-pVTZ optimization.
   









Calc. (1)
Calc. (2)
Expt.
   







Xaa -
 3.661 -
 3.716



Xbb
1.625
1.749



Xcc
2.036
1.967



Xab ± 2.672 ± 2.600



 







RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
2.740
2.788



Xyy
2.036
1.967



Xzz - 4.776 - 4.755



ETA -
 0.147 -
 0.173



Øz,a
22.66
21.79



Øa,bi *
32.73
32.63



Øz,bi *
10.07
10.84



 








 








* 'bi' is bisector of the NNC angle.

 







 
 


Table 2.  1,3,4-Selenadiazole.  Molecular structure parameters, ropt (Å and degrees).
 


     ropt(1) = B3PW91/6-31G(2d,2pd) optimization.
     ropt(2) = B3LYP/cc-pVTZ(G03) optimization.
 


C2V
ropt(1) ropt(2)





SeC 1.8517 1.8821
CN 1.2945 1.2888
NN 1.3558 1.3670
CH 1.0803 1.0791
CSeC   82.06
   81.03
SeCN 114.43 114.75
CNN 115.54 114.73
SeCH 123.57 122.69



 








 














Table 3.  1,3,4-Selenadiazole.  Rotational Constants (MHz) and Dipole Moments (D).







ropt(1) = B3PW91/6-31G(2d,2pd) optimization.

ropt(2) = B3LYP/cc-pVTZ(G03) optimization.








ropt(1) ropt(2) Expt [1]







A
 8584.6
 8486.2
 8479.55(206)

B
 3408.1
 3324.8
 3342.64(5)

C
 2439.6
 2388.9
 2396.37(4)







|µa| 3.59 *
 3.49 *
 3.40(5)

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






























Table 4.  1,3,4-Selenadiazole.  B3LYP/cc-pVTZ Quartic Centrifugal Distortion Constants (kHz).








Delta_J
0.446
 D_J
0.407

Delta_JK0.240
 D_JK
0.478

Delta_K 2.87
 D_K
2.67

delta_j 0.128
 d_1
 -
 0.128

delta_k 0.957
 d_2
 -
 0.0199









 







 








[1] D.M.Levine, W.D.Krugh, and L.P.Gold, J.Mol.Spectrosc. 30,459(1969).

 








 








1,2,5-Selenadiazole
 1,3,4-Oxadiazole 1,2,5-Oxadiazole

1,2,3-Thiadiazole 1,3,4-Thiadiazole 1,2,4-Thiadiazole

1,2,5-Thiadiazole Thiazole



 








 








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Molecules/Nitrogen




 








 













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Last Modified 14 Nov 2013