Adamantane-based Bidendate Metal Complexes in Crystalline and Solution State

Bidentate organic molecules with imidazole or benzimidazole moieties connected to a rigid 1,3-diphenyladamantane spacer are simple and unique building blocks that facilitate the assembly of supramolecular architectures in the solid state via metal-coordination. Single-crystal X-ray analysis revealed that the complexation of bidentate ligand-bearing imidazole moieties with cobalt(II) or cadmium(II) ions in methanol/chloroform produced complexes that showed doubly interpenetrated two-dimensional (2D) sheets through the formation of coordination bonds between the cobalt or cadmium metal centers and the nitrogen atoms of the imidazole groups. In the complexation of another ligand bearing a bulky benzimidazole group with cobalt(II) ion generated in methanol/chloroform, extended zigzag one-dimensional (1D) chains were formed, indicating that the molecular shape and bulkiness of the ligand design are crucial in the control of coordination polymers. The crystallization solutions were subjected to cold-spray ionization mass spectrometry (CSI-MS), and ion peaks derived from complexes with metal-ligand 1:2 and 1:1 were observed in complexation with ligands bearing the imidazole and benzimidazole moieties, respectively. The metal-ligand ratio in the CSI-MS analysis was identical to that found in the single-crystal X-ray analysis of an independent molecule. In addition, coordination oligomers with large molecular weight were detected as part of the obtained coordination polymers observed by CSI-MS/MS.