The structure of N-allyl derivatives of (5-(2′-pyridyl)-[1,3,4]thiadiazol-2-yl) amine in solution and the solid state studied by the 1H, 13C, 15N NMR spectroscopy, X-ray crystallography and DFT computations

The Electronic Structure of the Nitrogen Atoms of Allyl (5- pyridin-2-yl-[1,3,4]-thiadiazol-2-yl)-amine

“…The amino N6 atom is strongly shielded in 1 (about -308 ppm) but in 2 the shielding decreases by a few ppm (to about -304 ppm). The shielding constants for the N3 and N10 atom in the 1,3,4-thiadiazole and pyridine rings, respectively, are almost equal, whereas the N4 atom is much less shielded [10]. The H12 signals at 7.532 ppm -7.395 ppm, 7.517 ppm -7.381 ppm and 7.503 ppm -7.336 ppm (spectra 1 8 ↔ a' 3 A' 3 ↔ a' 0 A' 0 , a' 3 A' 3 ↔ a' A' and a' 3 A' 3 ↔ a' 5 A' 5 ↔ a' 8 A' 8 ↔ a A, The signals of H14 at 7.532 ppm -7.395 ppm, 7.517 ppm -7.381 ppm and 7.503 ppm -7.336 ppm (spectra 1 8 ' 1 A' 1 ↔ a' 2 A' 2 and a' 6 A' 6 ↔ a' 1 A' 1 ↔ a' 3 A' 3 , respectively…”

“…The calculated chemical shifts of the 15 N nitrogen atoms for type a and b tautomers of allyl-(1) and Figure 4) [10]. The amino N6 atom is strongly shielded in 1 (about -308 ppm) but in 2 the shielding decreases by a few ppm (to about -304 ppm).…”

“…The calculated chemical shift of N10 at -86.0 ppm of 2a tautomer (Table 1) [10] point to an amine -type nitrogen atom. (Figures 1-3).…”

“…The intensities of the signals prove the interconversion between these tautomeric forms. According to the XRD data only one tautomer (type a) is present in the crystals of both compounds 1 and 2 [10]. In the solid state the exo-amino form a is stabilized by different H bonds, and the differences in the total energy between tautomers a and b are equal to -35.6 and -34.3 kJ/mol for 1 and 2, respectively, according to DFT level of theory calculations [10].…”

The Studies of Structure of 2N‐(3‐phenyl‐allyl‐)(5‐phenyl‐[1,3,4] Thiadiazol‐2‐yl) Amine in Solution

“…Our previous studies concerning the investigation of structure of 2N‐allyl‐(3‐phenyl‐allyl‐)[5‐(pyridin‐2‐yl)[1,3,4] thiadiazol‐2‐yl] amine in the solid state (X‐ray crystallography), in the solution 1 H (500 MHz), 13 C, 15 N NMR spectra, and DFT computations have shown the presence of the egzo ‐amine tautomers .…”