1D Manganese(II) Derivatives of an Imidazole-Substituted Nitronyl Nitroxide. An Approach toward Molecular Magnetic Materials of High Dimensionality

Abstract

Extended linear complexes of manganese(II) with a bis-chelating nitronyl nitroxide ligand, 2-(2-imidazolato)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide-1-oxy (NITIm), have been prepared where metallic and organic spin carriers alternate. Depending on the deprotonating agent, the solvent, and the counteranion, the species [Mn(NITIm)(H(2)O)(2)]CH(3)COO, 1, [Mn(NITIm)(DMSO)(2)]BPh(4), 2, [Mn(NITIm)(H(2)O)(ImH)]NO(3), 3, and [Mn(NITIm)(NITImH)]ClO(4), 4, have been obtained, which differ by the additional ligands completing the metal coordination sphere. Complexes 1-3 are cis isomers and 4 is found as the mer modification; in all compounds, one observes a regular alternation of Lambda and Delta metal environments. Their magnetic properties are similar, with Mn(II)-nitroxide interactions J approximately -45 cm(-)(1) (H = -2JS(i)().S(j)()), and they display weak ferromagnetic properties below 5 K. Canting of the manganese ions is responsible for these properties. Relevant crystallographic parameters are as follows: 1, space group Fdd2, a = 16.713(1), b = 40.111(3), c = 9.735(1), Z = 16; 2, space group Pca2(1), a = 30.328(3), b = 13.422(1), c = 9.589(1), Z = 4; 3, space group P2(1)/c, a = 9.787(2), b = 22.973(5), c = 9.671(2), beta = 117.32(3) degrees, Z = 4; 4, space group P2(1)/c, a = 9.761(2), b = 28.668(5), c = 9.941(2), beta = 96.07(3) degrees, Z = 4.

Quantum phase transitions in alternating spin-($\frac{1}{2}$, $\frac{5}{2}$) Heisenberg chains

“…[13] and of (b) the MnNN compound from Ref. [15]. the FTLM results, the estimation of J is made by using the value of the minimum of the experimental curve: T min = 130 K. We see that both the FTLM and the semiclassical approach agree with the experimental data in the mid-and high-temperature regimes.…”

“…2(b) we present FTLM and semiclassical results [15] for the ssS chain, and experimental data [15] note that the FTLM curve for this chain depart from the experimental one at a higher temperature than the curve for the sS chain. This behavior is in fact a finite size effect since the number of unit cells used in the FTLM calculation for the ssS chain (6 unit cells, with 18 sites) is effectively less than the number used for the sS chain (8 unit cells, with 16 sites).…”

Magnetism and electronic correlations in quasi-one-dimensional compounds

“…In addition, we can also model the alternate spin chains shown in Figure 1(c) by considering in equation (2) S i = S i and S i = s i , with S > s. Such model systems have been used to describe 31,32 a number of organometallic compounds in which, e.g., S = 5/2 or S = 2 and s = 1/2.…”

“…25,26 More recently, the metal-radical hybrid strategy, combined with fabrication of novel polyradicals, 27 has led to the synthesis of a variety of heterospin chain compounds. 28,29 Several of these compounds display 1d ferrimagnetic behavior 30,31 modeled by alternating spin chains 32 such as, for instance, those with the structure shown in Figure 1(c).…”

Two New Nitronyl Nitroxide Radicals and Their Complexes with M(hfac)2 [M=Co(II), Ni(II), Mn(II)]: Syntheses, Crystal Structures, and Magnetic Characterizations

“…This is particularly true if there are potential coordination sites available in the R-group. [4][5][6][7][8][9][25][26][27][28][29][30][31][32][33][34][35] Therefore, modification of the R-group would tune the coordination mode between the nitronyl nitroxides and metal ions and thus alter the magnetic interaction between the nitronyl nitroxides and metal ions. New nitronyl nitroxides with coordination ligands such as pyridyl [27][28][29][30][31] and bipyridyl 9,32,34 have been synthesized, and accordingly a great deal of paramagnetic metal complexes of the nitronyl nitroxides with interesting structures have been reported.…”