Metal(II) Complexes Derived from Conformation Flexible Cyclic Imide Tethered Carboxylic Acids: Syntheses, Supramolecular Structures, and Molecular Properties

A series of mononuclear M­(II) complexes, namely, [Mn­(L1)₂(H₂O)₄] (<b>1</b>), [Cu­(L1)₂(pyr)₂(H₂O)₂] (<b>2</b>), [Zn­(L1)₂(pyr)₂(H₂O)₂] (<b>3</b>), [Cd­(L1)₂(pyr)₂(H₂O)₂] (<b>4</b>), [Co­(L2)₂(pyr)₂(H₂O)₂].pyr (<b>5</b>), [Cu­(L2)₂(pyr)₂].2pyr.2H₂O (<b>6</b>), and [Cd­(L2)₂(pyr)₂(H₂O)₂].pyr (<b>7</b>) (where <b>L1H</b> = 4-(1,3-dioxo-1,3-dihydro-isoindol-2-ylmethyl)-cyclohexanecarboxylic acid, <b>L2H</b> = 4-(1,3-dioxo-1<i>H</i>,3<i>H</i>-benzo­[<i>de</i>]­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 <b>L1H</b>, <b>1</b> 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 <b>5</b> and <b>7</b>; 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 <b>6</b> is sustained by helical channels, which are filled by lattice water and pyridine molecules. Solid state fluorescence emission properties of <b>L1H</b> and its M­(II) complexes show resemblance to each other, whereas they have different characteristics in the case of <b>L2H</b> and its M­(II) complexes. Cyclic voltammetry of redox-active ligand <b>L2H</b> and its complexes <b>5</b> and <b>6</b> are also studied