Two 3D supramolecular frameworks assembled from the dinuclear building block: a crystallographic evidence of carboxylate(O)…π interaction

Abstract

Two new complexes of Mn(II) and Zn(II) have been synthesized using a mixed ligand system and characterized by IR spectroscopy, elemental analysis, single crystal x-ray diffraction and variable temperature magnetic study for one of the compounds. Dimeric coordination structures of [Mn₂(2,4-pyrdc)₂(bpe)(H₂O)₆]·2H₂O (1) and [Zn₂(2,4-pyrdc)₂(azpy)(H₂O)₆]·2H₂O (2) [2,4-pyrdc = 2,4-pyridinedicarboxylate; bpe = 1,2-bis(4-pyridyl)ethane; azpy = 4, 4' azopyridine] are constructed by the bridging of bpe and azpy, respectively and both are extended to a 3D supramolecular structure by non-covalent interactions. In both the cases, unprecedented carboxylate(O)…π interactions played a crucial role in the organization of the 3D supramolecular assembly. The carboxylate(O)… π interactions are controlled by the C-H… π interactions which were accomplished by the proper modulation of the organic linkers. The formation of these supramolecular frameworks revealed that control of weak interactions can be achieved by the interplay of both energetically strong (covalent) and weak forces (non-covalent).