Supramolecular assembly driven by hydrogen-bonding and π–π stacking interactions based on copper(II)-terpyridyl complexes

Six 2D and 3D supramolecular complexes [Cu(L1)(O2CCH3)2] · H2O (1), [Cu2(L2)2(μ2-O2CCH3)2](BF4)2 (2), [Cu2(L1)2(BDC)(NO3)2] · 0.5H2O (3) [Cu2(L2)2(BDC)(NO3)2] (4), [Cu2(L3)2(BDC)(NO3)2] · 0.5H2O (5) and [Cu2(L2)2(BDC)(H2O)2](BDC) · 8H2O (6) (L1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, L2 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine, L3 = 4′-phenyl-2,2′:6′,2″-terpyridine, BDC = 1,4-benzenedicarboxylate), have been prepared and structurally characterized by X-ray diffraction crystallography. In complexes 1, 3, and 4, 1D channels are formed through C–H⋯O and C–H⋯N hydrogen-bonding interactions, and further linked into 3D structure via C–H⋯O and O–H⋯O interactions. Complex 2 is a 2D layer constructed from intermolecular C–H⋯F and π–π stacking interactions. In the structure of 6, the BDC2− ions and solvent water molecules form a novel 2D layer containing left- and right-handed helical chains via hydrogen-bonds, and an unusual discrete water octamer is formed within the layer. In 2, 4, 6 and [Ag2(L2)2](PF6)2 (7) the bonding types of pendent pyridines of L2 depending on the twist about central pyridines are involved in intramolecular (2 and 4), intermolecular (6) or coordination bonds (7) in-twist-order of 5.8°, 3.7°, 28.2° and 38.0°, respectively. Differently, the pendent pyridines of L1 in 1 and 3 form intermolecular hydrogen bonds despite of distinct corresponding twist angles of 25.1° (1) and 42.6°(3). Meanwhile, π–π stacking interactions are present in 1–6 and responsible for the stabilization of these complexes.

Six novel 2D and 3D supramolecular frameworks were constructed by C–H⋯O, C–H⋯N, C–H⋯F, O–H⋯O and O–H⋯N hydrogen bonds and π–π stacking interactions based on copper(II)-terpyridyl complexes incorporating carboxylate groups. Uniquely, a discrete (H2O)8 chain was formed in complex [Cu2(L)2(BDC)(H2O)2](BDC) · 8H2O via Ow–H⋯Ow hydrogen bonds (L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine, BDC = 1,4-benzenedicarboxylate), which was further hydrogen bonded to BDC2− counter ions into 2D layer containing left- and right-handed helical chains.Figure optionsDownload as PowerPoint slide