Optimization of the geometry and calculation of the normal vibrations of the dendrimer with amine terminal groups

The structure of the first generation dendrimer Gi constructed from a hexafunctional cyclotriphosphazene core with six branches -O-C6H4-CH=N-N(CH3)-P(S)< and twelve 4-hydroxyphenethylamine end groups O-C6H4-(CH2)2-NH2 was studied. Structural optimization and analysis of normal vibrations were performed for the Gi dendrimer. The Gi dendrimer molecule has a convex lens structure with flat -O-C6H4-CH=N-N(CH3)-P(S)< fragments and a slightly nonplanar cyclotriphosphazene core. Full optimization shows that the conformation of terminal 4-hydroxyphenethylamine groups O-C6H4-(CH2)2-NH2 with dihedral angles C(13)-C(22)-C(23)-N(6) and C(22)-C(23)-N(6)-H(23): 63.7 and 46.8° is predominant. The flat and anisotropic form of the cyclotriphosphazene core determines the ability of dendrimers to pack with each other in the most likely disk-like form. The spatial distribution of electron density for the core and end groups allows estimating the magnitude of electrostatic interactions on the surface of the dendrimer in the guest-host complexes.