Inducing Structural Diversity in Anionic Metal–Tetraoxolene Coordination Polymers Using Templating Methyl Viologen Countercations

Abstract

Controlling the connectivity of coordination polymers is an important scientific goal, as the physicochemical properties of these compounds are often intimately linked to the network topology. Using redox-active methyl viologen (MeV2+) countercations, a series of one-, two-, and three-dimensional anionic coordination polymers are described in which MnII or CdII centers are bridged with tetraoxolene ligands derived from 3,6-dihalo-2,5-dihydroxy-1,4-benzoquinone (H2Xan, X = F, Cl). Using MeV2+ countercations and either MnII or CdII yields nonporous anionic diamond networks of the general composition (MeV)­[M­(Clan)2] in which eight-coordinate divalent metal centers are linked by Clan2– ligands. Changing the solvent mixture from acetone/water to acetonitrile/water (MeCN/H2O) afforded the same product in the case of CdII, but an anionic 2D honeycomb network with the composition (MeV)­[Mn2(Clan)3]·6MeCN was obtained in the case of MnII. In contrast, the use of Fan2– ligands affords 1D ladder-type anionic coordination polymers (MeV)­[M2(Fan)3(H2O)2] (M = MnII, CdII) despite the chemical and structural similarity of Fan2– and Clan2– ligands. In the case of the diamond and 2D networks, MeV2+ countercations play a key structural role, arising from C–H···O hydrogen bonding extending from the cation to the anionic network. For the 1D ladder-type structures formed with Fan2–, O–H···O hydrogen bonding between anionic [M2(Fan)3(H2O)2]2– ladders is largely responsible for directing the crystal packing. For these compounds, MeV2+ cations play a more nuanced structural role, only occupying the void space between layers of H-bonded anionic [M2(Fan)3(H2O)2]2– ladders.

3,6-Dichlorobenzene-1,2,4,5-tetraol

“…In order to better understand the arrangement of the molecules of 1, it is helpful to remove the water molecules, and the remaining structure of just the tetraol molecules shows a regular two-dimensional network in which each molecule of type 1 is surrounded by and hydrogen bonded to four of type 2 and vice versa (Figure 3). The apparent 20-membered ring cavities bounded only by OH groups, either O (5,6,12,13) or O (2,3,15,16) are those that are filled with two water molecules each, as shown in Figure 2, while the centre of the chlorine-containing rings involving O (2,16,6,12) or O (3,15,5,13) is essentially filled by the chlorine atoms. These are 24-membered rings, R…”

“…More recently, compound 1 has been used as a convenient source of chloranilate, the tetradentate dianion of 2, for the formation of a wide range of metal complexes. In these studies, a solution of compound 1 is simply allowed to undergo air oxidation in the presence of appropriate metals salts, and examples include binuclear complexes of Ga(III) and/or Cr(III) [7], and coordination polymers involving Mn(II) [8], lanthanide(III) complexes [9], zinc and iron complexes with large pore size of interest for gas absorption [10], and similar macrocyclic iron, manganese and cadmium complexes of interest for their magnetic and other properties [11,12].…”

Structure Directing Effects of the Tetraphenylphosphonium Cation upon the Formation of Lanthanoid Anilate Coordination Polymers

“…Control over the topology of lanthanoid anilate CPs is therefore challenging to achieve. The majority of lanthanoid anilate coordination polymers are obtained as 2D (6,3)‐honeycomb structures commonly containing three anilate ligands bound in a bidentate manner to the lanthanoid ion with the remaining coordination sites filled with solvent molecules such as water [13,15,18,19,21,23,28–37] . The honeycomb structures formed from lanthanoids are commonly corrugated due to the facial coordination from the solvent molecules which contrasts with the planar 2D honeycomb obtained with transition metals [8,38] .…”

“…A range of substituents on the anilate ligand have been investigated including chloranilate (Cl), [17,19,21,26,33,34,41–43] bromanilate (Br), [5,12,15,18,21,30,32] dihydroxybenzoquinone (H), [18,21,28,29] and chlorocyananilate (mixed Cl and CN) [12,23,31,37,40,44–46] . Fluoranilic acid (F), however remains significantly underexplored, with the few studies using fluoranilate involving transition metal ions [9,36,38,47–49] . The use of fluoranilate may yield intriguing properties when compared to chloranilate due to the greater electron withdrawing nature of the fluorine, and its ability to form hydrogen bonds with other framework components, counterions and guest molecules within the framework voids.…”

“…The majority of lanthanoid anilate coordination polymers are obtained as 2D (6,3)-honeycomb structures commonly containing three anilate ligands bound in a bidentate manner to the lanthanoid ion with the remaining coordination sites filled with solvent molecules such as water. [13,15,18,19,21,23,[28][29][30][31][32][33][34][35][36][37] The honeycomb structures formed from lanthanoids are commonly corrugated due to the facial coordination from the solvent molecules which contrasts with the planar 2D honeycomb obtained with transition metals. [8,38] One method for obtaining predictable topologies with lanthanoid anilate coordination polymers is the use of a countercation template.…”