Structural Features of Fréchet-Type Dendrons and Dendrimers in Single Crystals

In the present systematic study, the solid-state conformational features of widely utilized Frechet-type dendrimers and dendrons derived from 3,5-di(benzyloxy)benzene are discussed on the basis of X-ray structures reported up now. Their conformations are described in terms of the six-torsion-angle sequences u1-u2-u3-u3′-u2′-u1′ of the 3,5-di(benzyloxy)benzene moiety, and of the conformational descriptors Ap (antiperiplanar), Ac (anticlinal), Sc (synclinal), and Sp (synperiplanar). Of the 10 possible conformational types of u3-u3′ sequences, only six types were observed in single crystals, and out of 136 possible types of conformations of u2-u3-u3′-u2′ sequences, only 14. Ap-Sp and Ap-Ap are the preferred conformations of sequences u3-u3′, and Ap-Ap-Sp-Ap and Ap-Ap-Ap-Ap those of the sequences u2-u3-u3′-u2′. The presence of a substituent at position 2 of the focal phenyl ring generally induces a preference for the Ap-Sp conformation of u3-u3′ sequences and for the Ap-Ap-Sp-Ap conformation of u2-u3-u3′-u2′ ...