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)

Abstract

A new family of six paramagnetic metals, namely, κ-(BDH-TTP)4­CoCl4­·(H2O)5 (I), κ-(BDH-TTP)4­Co0.54Mn0.46Cl4­·(H2O)5 (II), κ-(BDH-TTP)4­MnCl4­·(H2O)5 (III), κ⊥-(BDH-TTP)4­CoBr4­·(CH2Cl2) (IV), κ⊥-(BDH-TTP)4­MnBr4­·(CH2Cl2) (V), and κ⊥-(BDH-TTP)4­MnBr4­·(CH2Br2) (VI), 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 I–VI form two isostructural groups: I–III (κ) and IV–VI (κ⊥). Salts I–III are isostructural to the previously discovered κ-(BDH-TTP)2­FeIIIX4 (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 I–III but completely ordered in IV–VI. The type of included solvent molecule is solely determined by the anion size. The paramagnetic subsystem is effectively spin diluted either by anion disorder (I–III) or by spatial separation (IV–VI). The Weiss constants are virtually zero for all compounds (e.g., θ­(III) = 0.0056 K, θ­(V) = −0.076 K). Curie constants are dominated by anion paramagnetic centers indicating high spin states 5/2 for MnII and 3/2 for CoII with large spin–orbital coupling. All compounds retain metallic properties down to 4.2 K. There is a magnetic breakdown gap of width (w) in the chiral salts IV–VI: w(IV) > w(V) ≈ w(VI) but no gap in the centrosymmetric salts I–III. Electronic structure calculations at room temperature revealed a nearly isotropic triangular lattice in I–III and a honeycomb lattice in IV–VI with an extreme geometric spin frustration exceeding the level reported for the quantum “spin liquid” κ-(BEDT-TTF)2­Cu2(CN)3.

Spectrally-resolved third-harmonic generation and the fundamental role of O–H⋯Cl hydrogen bonding in Oh, Td-cobalt(ii) tetraphenylmethane-based coordination polymers

“…To investigate the influence of the halide counter-ion on spectroscopic and THG properties, we also tried to synthesize 2-Cl analogues using CoBr 2 and CoI 2 salts; however, we consistently obtained non-centrosymmetric phases (1-Br and 1-I, respectively) instead of isomorphous 2-Br and 2-I. We suppose that larger lengths of Co-Br (2.41-2.43 Å at room temperature) 38 and Co-I bonds (2.59-2.62 Å, at 150 K) 39 result in a much bigger size of CoBr 4 2− and CoI 4 2− which can induce the mismatch of those anions within the hydrogen-bonded cavity. Moreover, larger ionic radii of Br − and I − compared to Cl − , combined with lower electronegativity may cause O-H⋯Br and O-H⋯I hydrogen bonds to be weaker and therefore will not be strong enough to sustain the structure of 2-Cl (a detailed analysis of hydrogen-bonding below).…”

New Radical Cation Salts Based on BDH-TTP Donor: Two Stable Molecular Metals with a Magnetic [ReF6]2− Anion and a Semiconductor with a [ReO4]− Anion

“…The terminal ethylene groups in 1 are disordered. The central C=C bond length of the radical cation, as well as two terminal C=C bond lengths in the TTP fragments, have almost the same values (1,353-1.357 Å), which correspond well to the charge +0.5 [18][19][20][21]. The anionic layer, formed by isolated anions with the incomplete population of Re (Figure 2b), is highly disordered.…”

“…In the present work, we investigated the electrochemical oxidation of 2,5-bis (1,3dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene donor, C 10 S 8 H 8 , (BDH-TTP, Scheme 1) in the presence of (PPh 4 ) 2 [ReF 6 ] 2H 2 O, electrolyte. Our choice of the BDH-TTP donor, as in the case of BEDO, is determined by the fact that it forms radical cation salts with counterions of a different nature, size and shape, which retain metallic conductivity up to the temperature of liquid helium (4.2 K) [18,19].…”

“…The donor molecules are arranged into "face-to-face" dimers by a "ring-over-bond" type (Figure S2, Supplementary Materials) [19]. This configuration, in which two neighboring donor molecules are shifted in relation to each other along the long molecular axis by approximately a length of the C=C double bond (~1.4 Å), is typical for the BEDT-TTF and BDH-TTP κ-salts [18][19][20]. The terminal ethylene groups in 1 are disordered.…”

A New Charge-Ordered Molecular Conductor: κ-(BEDT-TTF)2K+(18-crown-6)[CoII(NCS)4]∙(H2O)

“…In the current report, we update the rational nomenclature for ET κ-salts by thorough analysis of mutual arrangements and repeating motifs of ET radical cations in the dimension that is perpendicular to the layer expansion one. Previously, we performed a similar update for the conductive κ salts of another organic single electron donor-BDH (vide infra) [6].…”