Unusual Magnetic Properties of One-Dimensional Molecule-Based Magnets Associated with a Structural Phase Transition

Abstract

Three ion-pair complexes, [RbzPy](+)[Ni(mnt)(2)](-) (mnt(2)(-) = maleonitriledithiolate; [RbzPy](+) = 4-R-benzylpyridinium; R = Br (1), Cl (2), and NO(2) (3)), with unusual magnetic properties have been synthesized and characterized. The crystal structures of 1 and 2 have been solved. The two complexes belong to the P2(1)/c space group with Z = 4 and C(20)H(11)BrN(5)NiS(4), a = 12.0744(17) A, b = 26.369(4) A, c = 7.440(3) A, and beta = 102.63(3) degrees for 1 and C(20)H(11)ClN(5)NiS(4), a = 12.105(2) A, b = 26.218(4) A, c = 7.374(2) A, and beta = 102.55(2) degrees for 2, respectively. The [Ni(mnt)(2)](-) anions in 1-3 form uniformly spaced one-dimensional (1-D) magnetic chains of s = 1/2 at room temperature. The temperature dependences of the susceptibility for 1-3 show that they undergo phase transitions. All three complexes are paramagnetic in their high-temperature (abbreviation HT) phase and diamagnetic in the low-temperature (abbreviation LT) phase because of strong dimerization along the stacking direction. The results of thermal analysis (DSC) further confirm that the phase transition for 1 and 2 is first-order but maybe second-order for 3. The phenomena observed in this study are similar to those of the 1-D radical systems.

An intriguing NO2⋯π and CN⋯π interactions in [1-(4′-nitrobenzyl)pyrazinium][Ni(mnt)2]: Crystal structure, magnetic property and DFT calculation

“…1a, an asymmetric unit contains two pairs of independent anions and cations. Two [Ni(mnt) 2 ] À anions possess approximated planar geometry and most of the bond lengths and angles are in good agreement with various [Ni(mnt) 2 ] À compounds [13,14,16,17,21]. Two inequivalent [NO 2 BzPz] + cations exhibit similar molecular conformations, in which the benzene and pyrazine make the dihedral angles of 80.2°/77.1°and 83.9°/89.9°, respectively, with the reference plane of C(benzene)-C(H 2 )-N(pyrazine).…”

“…In this field, the elegant theoretical investigations by Dougherty and co-workers have presented strong proof for the existence of such an interaction [6]. On the other hand, more and more crystallographic data have evidenced the presence of lpÁ Á Áp interactions between the electrondeficient aromatic ring and the lone-pair electrons of O-atom in water [7-9], ether [10], or carbonyl [11,12] moieties.In our previous studies, we have utilized the paramagnetic and planar tecton, [Ni(mnt) 2 ] À (mnt 2À = maleonitriledithiolate), with the pyridinium derivative to fabricate a series of quasi-one-dimensional (quasi-1D) spin systems which exhibit novel spin-Peierlslike transition [13,14]. It is worthy noting that the transition is sensitive to the weakly intermolecular interaction patterns, such as SÁ Á ÁS, SÁ Á ÁNi contacts between the paramagnetic [Ni(mnt) 2 ] À anions or H-bonding interactions between the anions and the cations [15,16].…”

Two New Salts Based on Bis(1,2,5-thiadiazole-3,4-dithiolate)nickelate Anion with Substituted Benzyl 4-ethylpyridinium: Syntheses, Crystal Structures and Properties

“…([RBzPy] ? = benzylpyridinium derivative) etc., originates from versatile magnetic properties such as ferromagnetic ordering at low temperature [7,8], magnetic transition from ferromagnetic coupling to diamagnetism [9], meta-magnetism [10], spin-gap transitions [11,12] and spin-Peierls-like transitions [13][14][15]. In these complexes, [RBzPy] ?…”

Syntheses, weak interactions, 3D network structures and magnetic properties of two salts based on bis(maleonitriledithiolate)copper(II) anion and substituted triphenylphosphonium cation

“…The maleonitriledithiolate (mnt) ligand and relevant complexes have been investigated in order to prepare novel and advanced molecular solids [9][10][11][12][13]. Introduction of some inorganic or organic cations as counterions of [M(mnt) 2 ] x-(where M is Ni, Pd, Pt, and x is 1 or 2) cation not only tunes the stacking pattern of the [M(mnt) 2 ] xanions but also obtains some molecular materials [14][15][16][17][18][19][20][21]. However, the salts containing [Cu(mnt) 2 ] 2-anion have been rarely investigated [22][23][24][25].…”