Synthesis, structure, and dynamic behavior in solution of arylamino-1,3,5-triazines

Abstract

Ten unsymmetrically substituted arylamino 1,3,5 triazines were synthesized and studied by dynamic NMR spectroscopy. The free energies of the hindered rotation ∆G ≠ are in 59-77 kJ mol -1 range. Using difference mode NOE NMR experiments, the structures of the major and minor rotation isomers were proved. The DFT B3LYP/6 31G* calculations were performed. The difference between the calculated rotation barriers and the experimental values obtained by line shape analysis is less than 7.6 kJ mol -1 . The height of the rotation barrier varies in a 18 kJ mol -1 range depending on the substituents in the triazine ring.

Structure and Conformational Mobility of OLED-Relevant 1,3,5-Triazine Derivatives

“…The rotational barriers in our compounds fall in the range of reported values for arylamino1,3,5-triazines (59–77 kJ mol −1 ) (14–18 kcal/mol) [ 81 ], for 2-chloro-4,6-bis(pyrazolylamino)-1,3,5-triazines (50–76 kJ mol −1 ) (12–18 kcal/mol) [ 54 ], and for N 2 , N 4 , N 6 -tris(1 H -pyrazolyl)-1,3,5-triazine-2,4,6-triamines (49–79 kJ mol −1 ) (12–19 kcal/mol) [ 83 ]. The rotational barriers of 2,4-diamino-1,3,5-triazine derivatives were estimated by coalescent methods and are in the range of 53–63 kJ mol −1 (13–15 kcal/mol) [ 84 ].…”

“…The experimentally determined rotational barriers of the studied compounds in DMF-d7 are within the interval from 11.7 to 14.7 kcal/mol ( Table 3 ). It is known that arylamino-1,3,5-triazines show hindered rotation about the partially double exocyclic C–N bond, due to the n–πconjugation of the amine lone pair with the triazine ring [ 81 ]. The substituents that enhance the double character of the C–N bond increase the barrier to hindered rotation.…”