10.1021/ja052108q.s005 Cristian Saul Campos-Fernández Cristian Saul Campos-Fernández Brandi L. Schottel Brandi L. Schottel Helen T. Chifotides Helen T. Chifotides Jitendra K. Bera Jitendra K. Bera John Bacsa John Bacsa John M. Koomen John M. Koomen David H. Russell David H. Russell Kim R. Dunbar Kim R. Dunbar Anion Template Effect on the Self-Assembly and Interconversion of Metallacyclophanes American Chemical Society 2005 Anion Template Effect BF 4 anion bptz SbF 6 Ni presence CH 3 CN Zn IO ClO 4 2005-09-21 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Anion_Template_Effect_on_the_Self_Assembly_and_Interconversion_of_Metallacyclophanes/3266968 Reactions of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) with solvated first-row transition metals M(II) (M(II) = Ni, Zn, Mn, Fe, Cu) have been explored with emphasis on the factors that influence the identity of the resulting cyclic products for Ni(II) and Zn(II). The relatively small anions, namely [ClO<sub>4</sub>]<sup>-</sup> and [BF<sub>4</sub>]<sup>-</sup>, lead to the formation of molecular squares [{M<sub>4</sub>(bptz)<sub>4</sub>(CH<sub>3</sub>CN)<sub>8</sub>}⊂X][X]<sub>7</sub>, (M = Zn(II), Ni(II); X = [BF<sub>4</sub>]<sup>-</sup>, [ClO<sub>4</sub>]<sup>-</sup>), whereas the larger anion [SbF<sub>6</sub>]<sup>-</sup> favors the molecular pentagon [{Ni<sub>5</sub>(bptz)<sub>5</sub>-(CH<sub>3</sub>CN)<sub>10</sub>}⊂SbF<sub>6</sub>][SbF<sub>6</sub>]<sub>9</sub>. The molecular pentagon easily converts to the square in the presence of excess [BF<sub>4</sub>]<sup>-</sup>, [ClO<sub>4</sub>]<sup>-</sup>, and [I]<sup>-</sup> anions, whereas the Ni(II) square can be partially converted to the less stable pentagon under more forcing conditions in the presence of excess [SbF<sub>6</sub>]<sup>-</sup> ions. No evidence for the molecular square being in equilibrium with the pentagon was observed in the ESI-MS spectra of the individual square and pentagon samples. Anion-exchange reactions of the encapsulated ion in [{Ni<sub>4</sub>(bptz)<sub>4</sub>(CH<sub>3</sub>CN)<sub>8</sub>}⊂ClO<sub>4</sub>][ClO<sub>4</sub>]<sub>7</sub> reveal that a larger anion such as [IO<sub>4</sub>]<sup>-</sup> cannot replace [ClO<sub>4</sub>]<sup>-</sup> inside the cavity, but that the linear [Br<sub>3</sub>]<sup>-</sup> anion is capable of doing so. ESI-MS studies of the reaction between [Ni(CH<sub>3</sub>CN)<sub>6</sub>][NO<sub>3</sub>]<sub>2</sub> and bptz indicate that the product is trinuclear. Mass spectral studies of the bptz reactions with Mn(II), Fe(II), and Cu(II), in the presence of [ClO<sub>4</sub>]<sup>-</sup> anions, support the presence of molecular squares. The formation of the various metallacyclophanes is discussed in light of the factors that influence these self-assembly reactions, such as choice of metal ion, anion, and solvent.