*4.4. JHN*<sup>α</sup> *Spin–Spin Coupling Constant*

The peak-to-peak separation in the absorptive (va) and the dispersive (vd) spectra were measured to derive the *J* coupling constant. The v<sup>a</sup> and v<sup>d</sup> values were obtained using values on the f<sup>2</sup> axis. Equation (3) was used to derive the coupling constants [40].

$$\left(\Box^6 - \upsilon\_\mathbf{d}\,^2\right)^4 + \left(-\frac{9}{4}\upsilon\_\mathbf{a}^4 + \frac{3}{2}\upsilon\_\mathbf{a}^2\,\upsilon\_\mathbf{d}^2 + \frac{3}{4}\upsilon\_\mathbf{d}\,^4\right)\mathfrak{l}^2 + \frac{81}{64}\upsilon\_\mathbf{a}^6 - \frac{9}{16}\upsilon\_\mathbf{a}^4\,\upsilon\_\mathbf{d}^2 - \frac{21}{32}\upsilon\_\mathbf{a}^2\,\upsilon\_\mathbf{d}^4 - \frac{1}{16}\upsilon\_\mathbf{d}^6 - \frac{\upsilon\_\mathbf{d}^8}{64\upsilon\_\mathbf{a}^2} = 0\tag{3}$$
