New Dmit-Based Organic Magnetic Conductors (PO-CONH-C2H4N(CH3)3)[M(dmit)2]2 (M = Ni, Pd) Including an Organic Cation Derived from a 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl (PO) Radical

Abstract

Abstract:We have prepared two dmit-based salts with a stable organic radical-substituted ammonium cation, (PO-CONH-C 2 H 4 N(CH 3 ) 3 )[Ni(dmit) 2 ] 2 ·CH 3 CN and (PO-CONH-C 2 H 4 N(CH 3 ) 3 )[Pd(dmit) 2 ] 2 where PO is 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl and dmit is 2-Thioxo-1,3-dithiol-4,5-dithiolate. The salts are not isostructural but have similar structural features in the anion and cation packing arrangements. The acceptor layers of both salts consist of tetramers, which gather to form 2D conducting layers. Magnetic susceptibility measurements indicate that the Ni salt is a Mott insulator and the Pd salt is a band insulator, which has been confirmed by band structure calculations. The cationic layers of both salts have a previously unreported polar structure, in which the cation dipoles order as ÀÄÀÄ along the acceptors stacking direction to provide dipole moments. The dipole moments of nearest neighbor cation layers are inverted in both salts, indicating no net dipole moments for the whole crystals. The magnetic network of the [Ni(dmit) 2 ] layer of the Ni salt is two-dimensional so that the magnetic susceptibility would be expected to obey the 1D or 2D Heisenberg model that has a broad maximum around T ≈ θ. However, the magnetic susceptibility after subtraction of the contribution from the PO radical has no broad maximum. Instead, it shows Curie-Weiss behavior with C = 0.378 emu·K/mol and θ = −35.8 K. The magnetic susceptibility of the Pd salt obeys a Curie-Weiss model with C = 0.329 emu·K·mol −1 and θ = −0.88 K.

Structures and Properties of New Organic Molecule-Based Metals, (D)2BrC2H4SO3 [D = BEDT-TTF and BETS]

“…According to our classification suggested in ref. [44], the crystal has a Type III dipole arrangement (Figure S1) [44,45]. In addition, the dipole moment of the BrC 2 H 4 SO 3 − anion was calculated by MOPAC7 [46] using the geometry observed in 1 to be 9.9 D. Figure 1a shows the crystal structure of 1.…”

“…The molecular arrangement of the anionic layers of 2 is almost the same as 1, and we do not show the structure. All anions in the layer orient along the same direction (//b) and therefore the crystal also has a Type III dipole arrangement [44,45]. In addition, the dipole moment of the BrC 2 H 4 SO 3 − anion was calculated by MOPAC7 [46] using the geometry observed in 2 to be 9.7 D. In addition, a CCDC search indicated that the structures of 72 BETS salts have already been reported, which consist of 21 κ-, 18 θ-, 7 λ-, 7 α-, 4 β-, and 15 other miscellaneous types of salts.…”

Role of the Anion Layer’s Polarity in Organic Conductors β″-(BEDT-TTF)2XC2H4SO3 (X = Cl and Br)

“…We have also prepared magnetic conductors of M(dmit) 2 salts, where M = Ni, Pd, or Pt, with purely organic cationic aminoxyl radicals. 12,13 The resulting salts have not yet shown any clear evidence of the interaction between the localized and itinerant electrons, although some have short contacts between S atoms of the donors and O and/or N of the spin center. 6,8,9 The sulfonates also have relatively large dipole moments, and we have noted that some of these polar ions provide CT salts with unique structural features, which we have classified into four types as shown in Figure 1.…”

“…We also observed self-doping in the type I salts, where the B layers were more positively charged than the A layers. By contrast, type III salts (Figure 1c) 12,13 provide no self-doping because the dipole moments of the ionic layers lie parallel to the conducting layers. Although type III salts are similar to type I, there is no net dipole moment.…”

Magnetism of Molecular Conductors

“…The combination of radical units with electroactive donor networks is another strategy for preparing magnetic conductors, and in this issue Kazuki Horikiri and Hideki Fujiwara describe charge transfer salts of a new EDT-TTF (ethylenedithiotetrathiafulvalene) donor containing a radical through a π-conjugated vinylene spacer, with diamagnetic GaCl 4 and paramagnetic FeCl 4 anions with strong π-d interactions [7]. Another contribution by Hiroki Akutsu et al describes two dmit-based salts with a stable organic radical-substituted ammonium cation, exhibiting magnetic contributions from segregated 2D anionic and cationic sub-lattices [8].…”