New Family of Six Stable Metals with a Nearly Isotropic Triangular Lattice of Organic Radical Cations and Diluted Paramagnetic System of Anions: κ(κ_⊥)‑(BDH-TTP)₄MX₄·Solv, where M = Co^II, Mn^II; X = Cl, Br, and Solv = (H₂O)₅, (CH₂X₂)

A new family of six paramagnetic metals, namely, κ-(BDH-TTP)₄­CoCl₄­·(H₂O)₅ (<b>I</b>), κ-(BDH-TTP)₄­Co_0.54Mn_0.46Cl₄­·(H₂O)₅ (<b>II</b>), κ-(BDH-TTP)₄­MnCl₄­·(H₂O)₅ (<b>III</b>), κ_⊥-(BDH-TTP)₄­CoBr₄­·(CH₂Cl₂) (<b>IV</b>), κ_⊥-(BDH-TTP)₄­MnBr₄­·(CH₂Cl₂) (<b>V</b>), and κ_⊥-(BDH-TTP)₄­MnBr₄­·(CH₂Br₂) (<b>VI</b>), has been synthesized and characterized by X-ray crystallography, four-probe conductivity measurements, SQUID magnetometry, and calculations of electronic structure. The newly discovered κ_⊥-type packing motif of organic layers differs from the parent κ-type by a series of longitudinal shifts of BDH-TTP radical cations in the crystal structure. Salts <b>I</b>–<b>VI</b> form two isostructural groups: <b>I</b>–<b>III</b> (κ) and <b>IV</b>–<b>VI</b> (κ_⊥). Salts <b>I</b>–<b>III</b> are isostructural to the previously discovered κ-(BDH-TTP)₂­Fe^IIIX₄ (X = Cl, Br) even though the charge of FeX₄^– anions is half that of the MX₄^2– (M = Co, Mn) anions. The tetrahedral anions are disordered in <b>I</b>–<b>III</b> but completely ordered in <b>IV</b>–<b>VI</b>. The type of included solvent molecule is solely determined by the anion size. The paramagnetic subsystem is effectively spin diluted either by anion disorder (<b>I</b>–<b>III</b>) or by spatial separation (<b>IV</b>–<b>VI</b>). The Weiss constants are virtually zero for all compounds (e.g., θ­(<b>III</b>) = 0.0056 K, θ­(<b>V</b>) = −0.076 K). Curie constants are dominated by anion paramagnetic centers indicating high spin states 5/2 for Mn^II and 3/2 for Co^II with large spin–orbital coupling. All compounds retain metallic properties down to 4.2 K. There is a magnetic breakdown gap of width (<i>w</i>) in the chiral salts <b>IV</b>–<b>VI</b>: <i>w</i>(<b>IV</b>) > <i>w</i>(<b>V</b>) ≈ <i>w</i>(<b>VI</b>) but no gap in the centrosymmetric salts <b>I</b>–<b>III</b>. Electronic structure calculations at room temperature revealed a nearly isotropic triangular lattice in <b>I</b>–<b>III</b> and a honeycomb lattice in <b>IV</b>–<b>VI</b> with an extreme geometric spin frustration exceeding the level reported for the quantum “spin liquid” κ-(BEDT-TTF)₂­Cu₂(CN)₃