6.4.1. N–H VibrationsAs shown in th

6.4.1. N–H Vibrations
As shown in the IR absorption spectra of secondary amines, a single
weak band due to the N–H stretching vibration usually occurs around
3500–3000 cm−1. [56–58] This weak band is observed experimentally
at 3270, 3256 and 3271 cm−1 for compounds 6a–g, respectively while
calculated at 3493, 3528 and 3542 cm−1, respectively. The experimental
values are lower than the calculated ones probably due to the presence
of intermolecular H-bonding interactions in the solid crystal lattice. The
calculated data are for single molecule and in gas phase where no
intermolecular interactions take place. On other hand, tertiary amines
(R3N) such as 6i do not show any band in this region since they do
not have any N–H bonds.
Also, the in-plane N–H bending vibrations of the amine group are
calculated in the range 1579–1523 cm−1 (exp. 1628–1558 cm−1),
1576–1554 cm−1 (exp. 1621–1581 cm−1) and 1576–1557 cm−1
(exp. 1628–1604 cm−1) for compounds 6a–g, respectively. The inplane
N–H bending vibrationswere found to be overlappedwith the triazine
C_N stretching modes, both were found to have very high