Nuclear Quadrupole Coupling Constants

in Phthalazine


Nitrogen nqcc tensors in phthalazine were calculated on a molecular structure optimized at the B3P86/6-31G(3d,3p) level of theory.  These calculated nqcc's are compared with the experimental values of McNaughton et al. [1] in Table 1.  Structure parameters are given in Table 2, rotational constants and electric dipole moments in Table 3.
In Table 1, subscripts a,b,c refer to principal axes of the inertia tensor, subscripts x,y,z to 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 (percentage of average experimental nqcc).  RSD is the residual stand deviation of calibration of the B3PW91/6-311+G(df,pd) model for calculation of the nqcc's.

Table 1. Nitrogen nqcc's in Phthalazine (MHz).  Calculation was made on the B3P86/6-31G(3d,3p) ropt structure.

Expt. [1]

14N(1,2) Xaa - 4.716 - 4.72845(136)
Xbb 1.723 1.8501 *
Xcc 2.993 2.8783 *
Xab ± 2.470 ± 2.350(94)
RMS 0.099 (3.1 %)
RSD 0.030 (1.3 %)
Xxx 2.561
Xyy 2.993
Xzz - 5.554
ETA 0.0776
Øz,a 18.75
Øa,bi 30.25
Øz,bi** 11.50
* Calculated here from experimental Xaa and Xbb - Xcc = -1.0283(30) MHz.
** The z-axis makes an angle of 11.50o with the external bisector ('bi') of the NNC angle and tilts toward the adjacent nitrogen atom.
Table 2. Phthalazine and Pyridazine.  Selected molecular structure parameters, B3P86/6-31G(3d,3p) ropt (Å and degrees).  The complete structure of phthalazine is given here in Z-matrix format.
Phthalazine Pyridazine
N(1)N(2) 1.3569 1.3251
N(2)C(3) 1.3089 1.3314
N(1)N(2)C(3) 119.49 119.44
Table 3.  Phthalazine, ropt.  Rotational constants (MHz) and B3PW91/6-311+G(df,pd) calculated dipole moments (D).
 Calc.     Expt. [1]
A 3291.67 3263.94094(123)
B 1243.76 1236.018430(35)
C   902.68   896.743486(41)
µa   5.4
[1] D.McNaughton, P.D.Godfrey, M.K.Jahn, D.A.Dewald, and J.-U.Grabow, J.Chem.Phys. 134,154305(2011).



Pyridazine Quinazoline Quinoxaline 1,10-Phenanthroline
Acridine Quinoline Isoquinoline Phenanthridine


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Last Modified 20 April 2011