Metal(II) Complexes Derived from Conformation Flexible Cyclic Imide Tethered Carboxylic Acids: Syntheses, Supramolecular Structures, and Molecular Properties
datasetposted on 2012-04-04, 00:00 authored by Devendra Singh, Jubaraj B. Baruah
A series of mononuclear M(II) complexes, namely, [Mn(L1)2(H2O)4] (1), [Cu(L1)2(pyr)2(H2O)2] (2), [Zn(L1)2(pyr)2(H2O)2] (3), [Cd(L1)2(pyr)2(H2O)2] (4), [Co(L2)2(pyr)2(H2O)2].pyr (5), [Cu(L2)2(pyr)2].2pyr.2H2O (6), and [Cd(L2)2(pyr)2(H2O)2].pyr (7) (where L1H = 4-(1,3-dioxo-1,3-dihydro-isoindol-2-ylmethyl)-cyclohexanecarboxylic acid, L2H = 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-cyclohexanecarboxylic acid, and pyr = pyridine) were synthesized and structurally characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, powder X-ray diffraction, and single crystal X-ray diffraction. Coordination environments around the metal centers and subtle differences in weak interactions affect the dimensionality and features of supramolecular architectures of these complexes. In the case of M(II) complexes of L1H, 1 shows a zigzag 3D architecture, whereas other complexes exhibit 3D channel-like structures containing the coordinated pyridine rings inside these channels. The coordination environments around the M(II) centers are the same in the complexes 5 and 7; however, the former is composed of 3D architecture containing channels and voids, whereas the latter reveals a 2D sheet structure. The 3D supramolecular architecture of complex 6 is sustained by helical channels, which are filled by lattice water and pyridine molecules. Solid state fluorescence emission properties of L1H and its M(II) complexes show resemblance to each other, whereas they have different characteristics in the case of L2H and its M(II) complexes. Cyclic voltammetry of redox-active ligand L2H and its complexes 5 and 6 are also studied.