H4C4(CN)2
	Nitrogen
	Nuclear Quadrupole Coupling Constants
		in 1,2-Dicyanocyclobutene
	Calculation of the nitrogen nqcc's in 1,2-dicyanocyclobutene was made on the ro, rs, and re molecular structures of Petitprez et al. [1].  These are compared with the experimental nqcc's in Tables 1 - 3.  Structure parameters are compared in Table 4.
	In Tables 1 - 3, 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.
	RMS is the root mean square difference between calculated and experimental nqcc's (percent of the average absolute experimental nqcc).  RSD is the residual standard deviation of calibation of the  B3PW91/6-311+G(df,pd) model for calculation of the nqcc's.
	Table 1.  Nitrogen nqcc's in 1,2-Dicyanocyclobutene (MHz).  Calcuation was made on the effective ro molecular structure [1].       Calc. Expt. [1]       14N Xaa - 1.026 - 1.079(1) Xbb - 1.272 - 1.148(1) Xcc 2.298 2.227(1) Xab ± 3.330     RMS 0.088 (5.9 %) RSD 0.030 (1.2 %)   Xxx 2.183 Xyy 2.298 Xzz - 4.482 ETA 0.026 Øz,a 46.06 Øa,CN 45.40 Øz,CN   0.66
	Table 2.  Nitrogen nqcc's in 1,2-Dicyanocyclobutene (MHz).  Calcuation was made on the substitution rs molecular structure [1].       Calc. Expt. [1]       14N Xaa - 1.163 - 1.079(1) Xbb - 1.143 - 1.148(1) Xcc 2.306 2.227(1) Xab ± 3.310     RMS 0.066 (4.5 %) RSD 0.030 (1.2 %)   Xxx 2.157 Xyy 2.306 Xzz - 4.463 ETA 0.033 Øz,a 44.92 Øa,CN 44.67 Øz,CN   0.25
	Table 3.  Nitrogen nqcc's in 1,2-Dicyanocyclobutene (MHz).  Calcuation was made on the equilibrium re molecular structure [1].       Calc. Expt. [1]       14N Xaa - 1.006 - 1.079(1) Xbb - 1.282 - 1.148(1) Xcc 2.289 2.227(1) Xab ± 3.314     RMS 0.095 (6.4 %) RSD 0.030 (1.2 %)   Xxx 2.173 Xyy 2.289 Xzz - 4.461 ETA 0.026 Øz,a 46.19 Øa,CN 45.51 Øz,CN   0.68
	Table 4.  Molecular structure parameters; ro, rs, and re [1] (Å and degrees).  These structures are also given here in Z-matrix format.     ro   rs   re C(1)C'(1) 1.361 1.326(2) 1.354 C(1)C(2) 1.515 1.522(3) 1.516 C(2)C'(2) 1.567 1.578(2) 1.566 C(1)C(3) 1.420 1.426(2) 1.421 C(3)N 1.157 1.159(1) 1.159 C(2)H 1.088 1.088 * 1.088 C'(1)C(1)C(2)   93.9   94.7(2)   93.9 C(1)C(2)C'(2)   86.1   85.3(1)   86.1 C(2)C(1)C(3) 133.3 133.3 C'(1)C(1)C(3) 133.9(2) C(1)C(3)N 178.2 178.6(12) 178.2 C(1)C(2)H 114.7 114.7 * 114.7 C'(1)C(1)C(2)H 115.8 115.8 * 115.8 * ro value.
	[1] D.Petitprez, G.Wlodarczak, H.Lignier, J.Demaison, A.DeMeijere, A.G.Steiniz, and H.Møllendal, J.Mol.Struct. 612,315(2002).
	S(CN)2		H2C(CN)2		H2C=C(CN)2		O=C(CN)2
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	Molecules/Nitrogen
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						Last Modified 1 April 2006