Coordination Polymers of 2,5-Dihydroxybenzoquinone and Chloranilic Acid with the (10,3)-a Topology

Abstract

b S Supporting Information 2,5-D ihydroxybenzoquinone (I, hereafter H 2 dhbq) and chloranilic acid (II, hereafter H 2 can) upon deprotonation provide dianionic ligands capable of chelating a single metal center to give mononuclear complexes.They are capable also of bridging two metal centers to yield binuclear and oligomeric complexes as well as 1D, 2D, and 3D polymers. A feature of major interest in these systems is their ability to exist, after deprotonation, not only as the À2 anion but also as the relatively stable À1 or À3 radical anions, as well as the À4 anion. Electrochemical studies of dhbq-bridged and canbridged binuclear complexes reveal that radical oxidation states of the organic bridges are easily achieved. 1 Some of the longer term objectives of our group are to discover dhbq-based or canbased coordination polymers in which (a) some or all of the bridging ligands are in a radical state, or (b) both the metal centers and the bridging ligands carry unpaired electrons, or (c) both metal and ligand components are amenable to facile electron transfer. These various circumstances may lead to interesting and possibly useful electronic/magnetic properties.On the basis of the many structural studies of dhbq 2À -based and can 2À -based coordination polymers in the literature, we present here a very brief overview of the major structural types known at present. A number of 1D polymers (generally M 2+ / can 2À or M 2+ /dhbq 2À ) are known in which the octahedral metal components of the chain carry two monodentate ligands such as H 2 O. If these two ligands are trans, a linear polymer results in which the dhbq 2À or can 2À components are essentially coplanar, 2 whereas if the two are cis, a zigzag conformation is adopted. 2c,3 Related zigzag polymers are formed when a single bidentate ligand occupies two cis positions. 4 In some cases, neutral bridging ligands (other than can 2À or dhbq 2À ) link M/can or M/dhbq ABSTRACT: Crystalline compounds of general composition (NBu 4 ) 2 [M II 2 (dhbq) 3 ] (where M = Mn, Fe, Co, Ni, Zn, and Cd and dhbq 2À is the dianion of 2,5-dihydroxybenzoquinone) are obtained by reaction of the divalent metal acetate (or the sulfate in the case of Fe) with 2,5-diaminobenzoquinone and an excess of NBu 4 Br in aqueous solution at 115°C in sealed tubes. The dhbq 2À ligand is generated in situ by hydrolysis of the 2,5-diaminobenzoquinone. We have been unable to obtain these compounds in a crystalline form suitable for single crystal X-ray diffraction studies directly from H 2 dhbq itself. A structural feature common to this series is the presence of two interpenetrating [M II 2 (dhbq) 3 ] 2À coordination networks, each with the chiral (10,3)-a topology, with the two independent nets being of opposite hand-unprecedented circumstances for dhbq-based coordination polymers. Crystals of the same zinc compound as that obtained above from 2,5-diaminobenzoquinone can alternatively be obtained by in situ aerial oxidation of 1,2,4,5-tetrahydroxybenzene in the presence of Zn(OAc) 2 and NBu 4 Br in aq...

Investigating the Case of Titanium(IV) Carboxyphenolate Photoactive Coordination Polymers

“…The structure consists of isolated TiO 6 octahedra, with the oxygen atoms arising solely from DOBDC ligands ( Figure 2a), connected to each other by the ditopic linkers through chelating six-membered rings involving both phenolic and carboxylic oxygen atoms (Figure 2a) to afford a 3D chiral network exhibiting 10,3-a topology ( Figure 2b). 44 Two enantiomeric networks are then interpenetrated to afford the final MIL-167 solid (Figure 2b), which holds cavities of about 6−7 Å free diameter.…”

Recent Advances on Anilato-Based Molecular Materials with Magnetic and/or Conducting Properties

“…The layers formed with two M II ions contain a 2-charge per formula, [ [47]. Further interest for the anilate ligands is related to their ability to form 3D structures with the (10,3)-a topology, similar to the one observed with the oxalate [111]; these structures are afforded when all the ML 3 units show the same chirality, in contrast with the 2D honeycomb layer, which requires alternating Λ-ML 3 and ∆-ML 3 units. This 3D structure with a (10,3)-a topology has been recently reported for the [(n-Bu) 4 3 ] − type, would afford ferrimagnetic coupling and ordering.…”

From mononuclear to linear one-dimensional coordination species of copper(ii)–chloranilate: design and characterization

“…2 The magnetic properties can be designed and ne-tuned by choice of the bridging ligand; small ligand strongly affects exchange interaction and spin coupling, whereas some ligands with conjugated p-electron systems are able to mediate exchange interactions at long distances. 11-20 They are prone to form a variety of coordination modes [19][20][21][22][23][24] and to mediate electronic effects between paramagnetic metal ions via their four oxygen donors and p-electron systems, respectively. Generally, the use of nitrogen-and oxygen-donor ligands prevails in the construction of coordination polymers.…”