Ag(I) and Cu(I) [2 × 2] Chiral Grids Containing Pyrimidine Ligands with Camphor Moieties. Arene Encapsulation

The C2 symmetric chiral ligand 4,6-bis[(4S,7R)-7,8,8′-trimethyl-4,5,6,7-tetrahydro-4,7-methaneindazol-2-yl]pyrimidine (bpzCampm) was synthesized and reacted with Cu(I) and Ag(I) salts to give four chiral [2 × 2] grid-type structures: [M4(bpzCampm)4]X4, M = Cu(I), Ag(I); X = BF4−, PF6−. The structures of the two BF4− derivatives were determined by X-ray diffraction. The grids contain facing ligands that are not parallel and, in contrast to the situation found in previous examples, the anions are not hosted within the cavities but toluene molecules are. In the case of the copper derivative, π-stacking interactions are established between the pyrimidine rings and these toluene molecules and others situated in the intercationic regions, giving rise to the formation of π-stacked columns with alternating pyrimidine and toluene molecules. Due to the chirality of bpzCampm, chiral cavities are generated in the crystalline structure. From NMR studies, it was concluded that the copper grids are maintained in solution but this is not the case for the silver derivatives. The UV−vis spectra of the copper complexes show an MLCT band, higher for the PF6− derivative. Some derivatives exhibit fluorescence with a high influence of the solvent and counteranion in the intensity of the emission.