Nuclear Quadrupole Coupling Constants

in Vinylcyanodiacetylene


Calculation of the nitrogen nqcc's in vinylcyanodiacetylene was made on a rc molecular structure derived ab initio as discussed here.  These are compared with the experimental nqcc's of Thornwirth et al. [1] in Table 1.  Structure parameters are given in Table 2, rotational constants in Table 3.
In Table 1, subscripts a,b,c refer to the principal axes of the inertia tensor, subscripts 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 plane of the molecule.  Ø (degrees) is the angle between its subscripted parameters. ETA = (Xxx - Xyy)/Xzz.
RSD is the residual stand deviation of calibration of the B3PW91/6-311+G(df,pd) model for calculation of the nqcc's, which may be taken as an estimate of the uncertainty in the calculated nqcc's.

Table 1. Nitrogen nqcc's in vinylcyanodiacetylene (MHz).  Calculation was made on the rc structure given below in Table 2.

Expt. [1]

14N Xaa - 4.227 - 4.2(1)
Xbb 2.107 2.1(2)
Xcc 2.120 2.1 *
|Xab| 0.547
RSD 0.030 (1.3 %)
Xxx 2.154
Xyy 2.120
Xzz - 4.274
ETA 0.008
Øz,a 4.90
Øa,CN 4.68
Øz,CN 0.22
* Calculated here from zero trace condition..
Table 2.  Vinylcyanodiacetylene (Cs).  Heavy atom structure parameters, rc (Å and degrees).  The complete structure is given here in Z-matrix format.
For calculation of the CH, C-C, and C=C bond lengths, see here.   For calculation of the CC triple bonds, see here.  Interatomic angles are those given by MP2/6-311+G(d,p) optimization.
Angles are exaggerated. Parameter     rc
C(1)C(2) 1.3340
C(2)C(6) 1.4206
C(6)C(7) 1.2144
C(7)C(8) 1.3594
C(8)C(9) 1.2145
C(9)C(10) 1.3680
C(10)N 1.1622
C(1)C(2)C(6) 123.40
C(2)C(6)C(7) 176.62
C(6)C(7)C(8) 177.05
C(7)C(8)C(9) 177.35
C(8)C(9)C(10) 177.46
Click on image to enlarge. C(9)C(10)N 179.67

Table 3.  Rotational Constants (MHz).
Calc. rc    Expt. [1]
A 36 482.7 36 061.(41)
B      568.9      569.198 74(5)
C      560.1      560.089 14(5)
[1] S.Thorwirth, M.C.McCarthy, J.B.Dudek, and P.Thaddeus, J.Chem.Phys. 122,184308(2005).



H2C=CHCN Vinylcyanoacetylene

HCCCN t-Cyanovinylacetylene


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Last Modified 1 Nov 2007