Sakamoto, Youichi Miyoshi, Naomi Hirakida, Mihoko Kusumoto, Shirou Kawase, Haruo Rudzinski, Jerzy M. Shinmyozu, Teruo Syntheses, Structures, and Transannular π−π Interactions of Multibridged [3<i><sub>n</sub></i>]Cyclophanes<sup>1</sup> The syntheses, conformational study, and transannular π−π interaction of multibridged [3<i><sub>n</sub></i>]cyclophanes including the ultimate member of this series, [3<sub>6</sub>](1,2,3,4,5,6)cyclophane <b>1</b>, are described. The stepwise construction of trimethylene bridges starting from [3<sub>3</sub>](1,3,5)cyclophane <b>6 </b>led to the synthesis of <b>1</b> by way of four- and five-bridged cyclophanes <b>7</b> and <b>8</b>. The variable-temperature (VT) <sup>1</sup>H NMR study (CD<sub>2</sub>Cl<sub>2</sub>) and molecular mechanics calculations (MM3) of five-bridged <b>8 </b>revealed the most stable conformer, the relative stability order of the three stable isomers, and energy barriers for the trimethylene bridge inversion. A similar VT <sup>1</sup>H NMR study (toluene-<i>d</i><sub>8</sub>) of <b>1 </b>suggests the presence of the trimethylene bridge inversion process between two <i>C</i><sub>6</sub><i><sub>h</sub></i> conformers. The charge transfer (CT) bands of the complexes of multibridged [3<i><sub>n</sub></i>]cyclophanes with tetracyanoethylene (TCNE) show significant bathochromic shifts with the increase in the number of the bridges, and this is mainly attributed to the effective hyperconjugation between the benzyl hydrogens and the benzene rings. The CT band of the TCNE−<b>1</b> complex (728 nm) is the longest wavelength among those of the TCNE complexes of [<i>m</i>.<i>n</i>]cyclophanes and multibridged benzenophanes. Cyclophanes 1;charge transfer;bathochromic shifts;trimethylene bridge inversion process;cyclophane;MM;1 H NMR study;trimethylene bridges;CD 2 Cl 2;benzene rings;TCNE complexes;energy barriers;trimethylene bridge inversion;multibridged benzenophanes;mechanics calculations;VT 1 H NMR study;benzyl hydrogens;C 6 h conformers;CT band;stability order 1996-12-11
    https://acs.figshare.com/articles/journal_contribution/Syntheses_Structures_and_Transannular__Interactions_of_Multibridged_3_i_sub_n_sub_i_Cyclophanes_sup_1_sup_/3661902
10.1021/ja961944k.s001