Tribenzyl(methyl)ammonium: A Versatile Counterion for the Crystallization of Nanojars with Incarcerated Selenite and Phosphite Ions and Tethered Pyrazole Ligands

One hundred and thirty-five years after its initial discovery, the crystal structure of the tribenzyl­(methyl)­ammonium (TBMA+) cation is reported for the first time (as the nitrate salt). It is shown that TBMA+ is an excellent counterion for the crystallization of large supramolecular assemblies. Thus, single crystals of previously uncrystallizable nanojars with incarcerated selenite and phosphite ions, as well as tethered pyrazole ligands, have been successfully grown by solvent vapor diffusion into solutions with added (TBMA)­NO3. X-ray diffraction studies reveal a variety of possible noncovalent interactions between pairs of TBMA+ cations. Indeed, the structurally adaptable TBMA+ dimer can take on different shapes and sizes to maximize supramolecular interactions with neighboring molecules and to fill up voids in the crystal lattice. The new nanojar crystal structures (TBMA)­(Bu4N)­[SeO3⊂{Cu­(OH)­(pz)}28] and (TBMA)2[HPO3⊂{Cu­(OH)­(pz)}29] (pz = pyrazolate) provide unprecedented examples of noncovalently bound selenite and phosphite ions in supramolecular complexes. The use of TBMA+ counterions has also allowed for the crystallization of a nanojar based on tethered pyrazole ligands, (TBMA)2[SO4⊂{Cu28(OH)28(pzCH2CH2pz)14}]. The synthesis and mass spectrometric studies of the new nanojars are presented along with crystallographic studies detailing the nanojar structure, anion binding, and nanojar–counterion/counterion–counterion supramolecular interactions in the crystal lattice. Finally, the binding of SeO3 2– and SO4 2– ions by the same Cu28 nanojar and the binding of HPO3 2–, CO3 2–, and SO4 2– ions by the same Cu29 nanojar are contrasted, and the δ/λ chelate-ring isomerism in the tethered-ligand nanojar is discussed.