Magnetic Semiconductor:  Structural, Magnetic, and Conducting Properties of the Salts of the 6-Oxoverdazyl Radical Cation with M(dmit)₂ Anions (M = Ni, Zn, Pd, and Pt, dmit = 1,3-dithiol-2-thione-4,5-dithiolate)

Abstract

Five kinds of (1:1), (1:3), and (2:1) salts of 3-[4-(diethylmethylammonio)phenyl]-1,5-diphenyl-6-oxoverdazyl radical cation [V](+) with M(dmit)(2) anions (M = Ni, Zn, Pd, and Pt, dmit = 1,3-dithiol-2-thione-4,5-dithiolate) ([V](+)[Ni(dmit)(2)](-) (1), [V](+)[Ni(dmit)(2)](3)(-) (2), [V](+)(2)[Zn(dmit)(2)](2-) (3), [V](+)(2)[Pd(dmit)(2)](2-) (4), and [V](+)(2)[Pt(dmit)(2)](2-) (5)) and an iodide salt of [V](+) ([V](+)[I](-) (6)) have been prepared, and the magnetic susceptibilities (chi(M) values) have been measured between 1.8 and 300 K. The chi(M) of the (1:1) Ni salt (1) can be well reproduced by the sum of the contributions from (i) a Curie-Weiss system with a Curie constant (C) of 0.376 K emu/mol and a negative Weiss constant (theta) of -1.5 K and (ii) the one-dimensional Heisenberg antiferromagnetic alternating chain system with 2J(A-B)/k(B) = -274 K (alternation parameter alpha = J(A-C)/J(A-B) = 0.2). The chi(M) of the (1:3) Ni salt (2) can be well explained by the two-term contributions from (i) the Curie-Weiss system with C = 0.376 K emu/mol and theta = -5.0 K and (ii) the dimer system with 2J/k(B) = -258 K. The magnetic properties of 1 and 2 were discussed based on the results obtained by crystal structure analysis and ESR measurements of 1 and 2. The chi(M) values of the (2:1) Zn, Pd, Pt salts 3, 4, and 5 and [V](+)[I](-) salt 6 follow the Curie-Weiss law with C = 0.723, 0.713, 0.712, and 0.342 K emu/mol and theta = -2.8, -3.1, -2.6, and +0.02 K, respectively, indicating that only the spins of the verdazyl radical cation contribute to the magnetic property of these salts. The salts 1, 3, and 5 are insulators. On the other hand, the conductivity (sigma) of the Ni salt 2 and Pd salt 4 at 20 degrees C was sigma = 8.9 x 10(-2) and 1.3 x 10(-4) S cm(-)(1) with an activation energy E(A) = 0.11 and 0.40 eV, respectively. The salts 2 and 4 are new molecular magnetic semiconductors.

A novel BEDT-TTF-based purely organic magnetic conductor, α - (BEDT - TTF)2(TEMPO - N(CH3)COCH2SO3) ⋅ 3H2O

“…Therefore many researchers have introduced organic radicals in organic conducting salts. For example, charge-transfer (CT) salts of free radical substituted organochalcogen donors [7][8][9][10][11][12][13][14][15][16], CT complexes of free radicals and acceptors [17][18], CT salts of free radical substituted cations and acceptors [19][20][21][22][23], have been reported.…”

Three ion–pair complexes containing bis(maleonitriledithiolate)copper(II) anion and substituted 2-aminopyridinium cations: Syntheses, crystal structures, and magnetic properties

“…Inorganic complex anions [M(mnt) 2 ] n-(M = Ni, Pd, Pt, Cu, Fe; mnt 2− = maleonitriledithiolate, n = 1 or 2) are especially interesting because they have been proved to be very useful and potential building block over the past few years and the overlapping of the neighboring anions are influenced by the size and configuration of the organic couter-cation as well as some non-covalent interactions such as weak p⋅⋅⋅π or π⋅⋅⋅π stacking interactions and H-bonding interactions [7][8][9][10][11][12][13]. In this area, one important branch is the design and synthesis of molecular solids containing the [Ni(mnt) 2 ] − anion and some organic cations due to their versatile magnetic properties such as ferromagnetism, magnetic transition from ferromagnetic to diamagnetic coupling, spin-Peierls-like transitions, and meta-magnetism [14][15][16][17][18][19].…”

Syntheses, weak interactions, and 3-D network structures of two salts based on [Ni(i-mnt)2]2− (i-mnt2−=iso-maleonitriled-ithiolate) anion with substituted pyridinium cation

“…Transition metal complexes of 1,2-dithiolenes are of interest in materials science owing to their application as building blocks in molecular-based materials showing magnetic, superconducting, and optical properties [1][2][3][4][5][6][7]. A number of maleonitriledithiolate (mnt) complexes have been investigated to prepare advanced molecular solids [8][9][10][11][12] Ni(III), Pd(III), or Pt(III) ion) tunes the stacking pattern of the [M(mnt) 2 ] À anions giving molecular materials with unusual magnetic properties [13][14][15][16][17].…”