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

Abstract

Abstract:The aim of the present work is to highlight the unique role of anilato-ligands, derivatives of the 2,5-dioxy-1,4-benzoquinone framework containing various substituents at the 3 and 6 positions (X = H, Cl, Br, I, CN, etc.), in engineering a great variety of new materials showing peculiar magnetic and/or conducting properties. Homoleptic anilato-based molecular building blocks and related materials will be discussed. Selected examples of such materials, spanning from graphene-related layered magnetic materials to intercalated supramolecular arrays, ferromagnetic 3D monometallic lanthanoid assemblies, multifunctional materials with coexistence of magnetic/conducting properties and/or chirality and multifunctional metal-organic frameworks (MOFs) will be discussed herein. The influence of (i) the electronic nature of the X substituents and (ii) intermolecular interactions i.e., H-Bonding, Halogen-Bonding, π-π stacking and dipolar interactions, on the physical properties of the resulting material will be also highlighted. A combined structural/physical properties analysis will be reported to provide an effective tool for designing novel anilate-based supramolecular architectures showing improved and/or novel physical properties. The role of the molecular approach in this context is pointed out as well, since it enables the chemical design of the molecular building blocks being suitable for self-assembly to form supramolecular structures with the desired interactions and physical properties.Keywords: benzoquinone derivatives; molecular magnetism; multifunctional molecular materials; spin-crossover materials; metal-organic frameworks General IntroductionThe aim of the present work is to highlight the key role of anilates in engineering new materials with new or improved magnetic and/or conducting properties and new technological applications. Only homoleptic anilato-based molecular building blocks and related materials will be discussed. Selected examples of para-/ferri-/ferro-magnetic, spin-crossover and conducting/magnetic multifunctional materials and MOFs based on transition metal complexes of anilato-derivatives, on varying the substituents at the 3,6 positions of the anilato moiety, will be discussed herein, whose structural features or physical properties are peculiar and/or unusual with respect to analogous compounds reported in the literature up to now. Their most appealing technological applications will be also reported.

Square Grid Metal–Chloranilate Networks as Robust Host Systems for Guest Sorption

“…The magnetic properties of chloranilate‐bridged framework materials are currently of great interest– not only for those containing diamagnetic can 2− bridges but also, particularly, those containing radical can 3− bridges of the semiquinone type found in d‐block anilato families such as [Fe 2 (can) 3 ] 2− , the latter forming a 6,3‐ hexagonal network structure ,. The present 2D 4,4‐network is an attractive system to explore magnetic properties, including magnetic exchange, as each Ln III centre is bridged by four can 2− groups to neighbouring Ln III centres.…”

Field-Induced Slow Magnetic Relaxation of Mono- and Dinuclear Dysprosium(III) Complexes Coordinated by a Chloranilate with Different Resonance Forms

“…We noticed that chloranilate (Cl2An 2− ) is a promising organic ligand for investigating the above-mentioned Ln III -based SMMs or SIMs. The dianionic form of Cl2An 2− has a delocalized π system with resonance structures that are represented by p-quinone, o-quinone, tetraquinone, and bi-separated delocalized forms (Scheme 1) [24,25]. The coordination geometry and the ligand-field strength of the central Ln III ion can be fine-tuned by combining Cl2An 2− with a suitable ancillary ligand, while maintaining a similar coordination environment.…”

Tuning the Structure and Properties of Lanthanoid Coordination Polymers with an Asymmetric Anilato Ligand

“…The similarities of oxalato and anilato-type ligands can be clearly seen in the classical chiral [M(L)3] 3− monomers [24,25], as well as in the extended 2D and 3D lattices observed for both ligands [22,[26][27][28][29][30]. a b Although anilato-type ligands have been mainly used with transition metal ions [22,23], there are also several examples of anilato-based compounds with lanthanoids (Tables 1-4). These compounds can be formulated as [Ln2(C6O4X2)3(G)n]•mG, and can be grouped into different series depending on X (the anilato-type ligand) and G (the solvent used).…”

“…Other ligands include aromatic amines and quinones, such as the 2,5-dihydroxy-1,4-benzoquinone dianion (C6O4H2) 2− = dhbq, and the corresponding 3,6-disubstituted dianions (C6O4X2) 2− , with X = Cl, Br, NO2, CN, ... (Figure 1) [22,23]. These derivatives of 2,5-dihydroxy-1,4-benzoquinone (anilato-type ligands) are becoming popular ligands, since they resemble the oxalato ligand (Figure 1), although with some advantages.…”

“…Thus, for X = H (i.e., with the ligand C6O4H2 2− = dhbq 2− ) and G = H2O (Table 1), all the Ln(III) ions form isostructural compounds (phase I) formulated as [Ln2(C6O4H2)3(H2O)6]•18H2O, whose structure consists in a (6,3)-2D honeycomb lattice formed by regular (although not planar) hexagons, and where the Ln(III) ions are nona-coordinated with a tri-capped trigonal prismatic geometry [31][32][33]. [31] When X = Cl (i.e., with the ligand C6O4Cl2 2− = chloranilato) and G = H2O (Table 2), up to four different phases, formulated as [Ln2(C6O4Cl2)3(H2O)6]•nH2O, could be prepared, depending Although anilato-type ligands have been mainly used with transition metal ions [22,23], there are also several examples of anilato-based compounds with lanthanoids (Tables 1-4). These compounds can be formulated as [Ln 2 (C 6 O 4 X 2 ) 3 (G) n ]·mG, and can be grouped into different series depending on X (the anilato-type ligand) and G (the solvent used).…”