Exploring the structural landscape of 2-(thiophen-2-yl)-1,3-benzothiazole: high-Z′ packing polymorphism and cocrystallization with calix[4]tube

We report here for the first time a cocrystal of the so-called neutral calix[4] tube, which is two tail-to-tail-arranged and partially deprotonated tetrakis(carboxymethoxy) calix[4] arenes, including three sodium ions, with 2-(thiophen-2-yl)-1,3benzothiazole, namely trisodium bis(carboxymethoxy) bis(carboxylatomethoxy)calix[4] arene tris(carboxymethoxy)(carboxylatomethoxy) calix[4] arene-2-(thiophen- 2-yl)-1,3-benzothiazole-dimethyl sulfoxide-water (1/1/2/2), 3Na + C36H30O12 2 C36H31O12 C11H7NS2 2C2H6OS 2H2O, which provides a new approach into the host-guest chemistry of inclusion complexes. Three packing polymorphs of the same benzothiazole with high Z0 (one with Z0 = 8 and two with Z0 = 4) were also discovered in the course of our desired cocrystallization. The inspection of these polymorphs and a previously known polymorph with Z0 = 2 revealed that Z0 increases as the strength of intermolecular contacts decreases. Also, these results expand the frontier of invoking calixarenes as a host for nonsolvent small molecules, besides providing knowledge on the rare formation of high-Z0 packing polymorphs of simple molecules, such as the target benzothiazole.