Cobalt(II) coordination polymers versus discrete complex with 4,2′:6′,4″-terpyridine ligands: The role of a pyrenyl substituent

A new pyrene-containing 4,2′:6′,4″-terpyridine (4,2′:6′,4″-tpy) ligand (L3) is synthesized. The Co(NCS)2-mediated self-assembly of this ligand along with two known analogues (L1 and L2) was investigated. The reactions of L1 or L2 containing only small aromatic substituents in the 4′-position of 4,2′:6′,4″-tpy with Co(NCS)2 by a layering crystallization procedure give rise to single crystals suitable for X-ray structural analysis and 3-D or 2-D coordination polymers were revealed in their crystals, respectively. Interestingly, going from L1 and L2 to L3 by introducing a relatively bulky 4′-substituent in the ligand results in the observation of the first discrete complex of cobalt(II) with 4,2′:6′,4″-tpy ligands under the same synthetic conditions.

Three divergent 4,2′:6′,4″-terpyridine ligands containing different substituents in the 4′-position were employed to assemble metal–organic architectures with Co(NCS)2. While using small substituents for the self-assembly gives 2D or 3D metal–organic networks as usual, a bulky pyrenyl group is responsible for the formation of the first discrete mononuclear cobalt(II) complex with this type of ligands.Figure optionsDownload as PowerPoint slide