Structural Features of Fréchet-Type Dendrons and Dendrimers in Single Crystals
2010; American Chemical Society; Volume: 10; Issue: 12 Linguagem: Inglês
10.1021/cg100445y
ISSN1528-7505
Autores Tópico(s)Advanced Polymer Synthesis and Characterization
ResumoIn the present systematic study, the solid-state conformational features of widely utilized Fréchet-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′ sequences. Examples of solid-state interactions are discussed in order to analyze their complex and diverse roles in the stabilization of different conformational types. Particular attention is paid to the comparison of structural data, with theoretical results reported in the literature.
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