Rationalization of Noncovalent Interactions within Six New M-II/8-Aminoquinoline Supramolecular Complexes (M-II = Mn, Cu, and Cd): A Combined Experime

Abstract

<p> <span lang="EN-US" style="font-size: 12pt; font-family: &quot;Arial&quot;,&quot;sans-serif&quot;; mso-fareast-font-family: &quot;MS Mincho&quot;; mso-fareast-theme-font: minor-fareast; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font color="#000000">To examine the influence of the metal ions and their counterions on crystalline networks, we have designed and synthesized six MX2/8-aminoquinoline (8-aq) (M = Mn-II, Cu-II, Cd-II and X = Cl-, Br-, I-, NO3-, SCN-) complexes, having the formulas [Mn(8-aq)(2) I-2].(1), [Mn(8-aq)(2)(H2O)(2)](8-aq)(3).Br-2 (2), [Mn(8-aq)(2)(SCN)(2)] (3), [Cu(8-aq)(2)Cl(H2O)].Cl.H2O (4), [Cu(8-aq)(2)(NO3)(H2O)].NO3 (5), and Cd(8-aq)(2)I-2 (6). Single-crystal X-ray diffraction analyses showed that all of the complexes have a distorted octahedral geometry, in which each 8-aq molecule acts as a bidentate ligand and coordinates to the central metal ion with its common coordination mode, to form an N,N&#39; chelating motif. Remarkably, the influence of the counterion on the geometry of the complex is very significant since both I- and SCN- anions are coordinated to the metal ion in compounds 1, 3, and 6, adopting a cis configuration, while a single anion occupies an axial position in compounds 4 and 5 (Cl- and NO3-, respectively) and the other counterion is not coordinated. Finally, both Br anions are not coordinated in the cationic complex 2 (Mn metal center). In all cases, there are extended supramolecular networks due to cooperativity hydrogen-bonding and pi-pi stacking interactions that play an essential role in the formation and stability of the crystalline materials. The binding energies attributed to the different interactions have been evaluated using DFT calculations.</font></span></p>