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Donors and Acceptors Based on Triangular Dehydrobenzo[12]annulenes: Formation of a Triple-Layered Rosette Structure by a Charge-Transfer Complex

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posted on 29.10.2008, 00:00 by Kazukuni Tahara, Takumi Fujita, Motohiro Sonoda, Motoo Shiro, Yoshito Tobe
We present here the results of studies of the synthesis and properties of donors and acceptors based on triangular dehydrobenzo[12]annulene ([12]DBA) system as a π core. These studies were aimed at controlling the supramolecular crystal structure. Toward this end, the tricyano[12]DBA 2 and dodecafluoro[12]DBA (3) were synthesized as acceptors (A) and the tris(dialkylamino)[12]DBAs 4a−d as donors (D), and their electronic properties were determined by electronic absorption spectroscopy and electrochemical measurements. The main focus, though, was the formation of supramolecular structures in crystals. These compounds form distinct packing patterns as a result of the different intermolecular interactions. Tricyano[12]DBA 2 forms a two-dimensional (2D) sheet structure via hydrogen-bonding interactions, whereas a tilted-stack structure was found for 3 because of the lack of significant intermolecular interactions. Tris(dibutylamino)[12]DBA 4b exhibits a ladder-type 2D structure, probably because of van der Waals interactions between the butyl groups. The most significant finding is that charge-transfer interactions between donor 4a and acceptor 3 combined with their triangular molecular shapes and lateral CH···F hydrogen bonding result in the formation of a 2D rosette structure consisting of two different trimeric (DAD- and ADA-type) sandwich structures with 1:2 and 2:1 A/D ratios, respectively.