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Two new salts, [2-NaMePy]2[Ni(i-mnt)2] (1) and [2-NaMe-4-MePy]2[Ni(i-mnt)2] (2) ([2-NaMePy]+ = 1-(2'-naphthylmethyl)pyridinium, [2-NaMe-4-MePy]+ = 1-(2'-naphthylmethyl)-4-methylpyridinium and i-mnt2- = iso-maleonitriledithiolate), have been prepared and characterized by elemental analyses, UV, IR, molar conductivity, and single crystal X-ray diffraction. The anions in 1 form a 1-D chain through short C ··· N interactions between the anions, while the cations in 2 stack a 1-D column via C-H ··· π and π ··· π stacking interactions between the cations. The effect of weak intramolecular interactions such as C-H ··· N, C-H ··· S, C-H ··· Ni hydrogen bonds, and π ··· π stacking interactions between the cations and the anions further generate a 3-D network structure. The change of the molecular topology of the countercation when the 4-substituted group in the pyridine ring is changed from H atom to CH3 group results in different crystal system, space group, and the stacking mode of the cations and anions of 1 and 2. [ABSTRACT FROM AUTHOR]

Abstract: Two new molecular magnets, [BzPyN(CH3)2][Ni(mnt)2] (1) and [NO2BzPyN(CH3)2][Ni(mnt)2] (2)([BzPyN(CH3)2]+ =1-benzyl-4-dimethylaminopyridinium, [NO2BzPyN(CH3)2]+ =1-(4′-nitrobenzyl)-4-dimethylaminopyridinium, and mnt2− =maleonitriledithiolate) have been prepared and characterized by elemental analyses, IR, MS spectra, single crystal X-ray diffraction and magnetic susceptibility. The Ni(III) ions of both 1 and 2 form a 1D zigzag alternating magnetic chain within a column through Ni⋯S, Ni⋯Ni, Ni⋯N, S⋯S, or π⋯π interactions. Magnetic susceptibility measurements in the temperature range 1.8–300K show that 1 exhibits antiferromagnetic behavior, while 2 shows a spin gap transition around 170K, and antiferromagnetic interaction in the high-temperature phase (HT) and spin gap in the low-temperature phase (LT). The phase transition for 2 is second-order by determination of DSC analyses. [Copyright &y& Elsevier]

Abstract: Two new molecular magnets, [RBzPyN(CH3)2][Ni(mnt)2] [mnt2−=maleonitriledithiolate; [RBzPyN(CH3)2]+=1-(4′-R-benzyl)-4-dimethylaminopyridinium; R=CN(1), F(2)], with unusual magnetic properties have been prepared and characterized. Both 1 and 2 form a 3D network structure in which the [Ni(mnt)2]− anions form a 1D magnetic chain for 1 and a stepwise stack for 2 via weak π…π stacking interactions, C…C or C…N short interactions between the neighboring anions. Magnetic susceptibility measurements in the temperature range 1.8–300K indicated that 1 and 2 show unusual spin gap transition around 30K and 110K, respectively. The transition for 1 and 2 is the second-order phase transition as determined by the capacity measurement. [Copyright &y& Elsevier]

Abstract: Two new molecular solids, [BzPyNH2][Ni(mnt)2](1) and [2-NpCH2PyNH2][Ni(mnt)2](2) (mnt2− =maleonitriledithiolate, [BzPyNH2]+ =1-benzyl-2-aminopyridinium and [2-NpCH2PyNH2]+ =1-(2′-naphthylmethylene)-2-aminopyridinium) have been characterized structurally and magnetically. The Ni(Ш) ions of 1 and 2 form a 1D magnetic chain within a [Ni(mnt)2]− column through Ni⋯N or π⋯π interactions. Some weak interactions observed in 1 and 2 give further rise to a 2D structure. The overlapping fashions of the [Ni(mnt)2]− anions are different when the 2-aminopyridine ring was fixed and the phenyl ring changed into the naphthyl ring of the cation. Magnetic susceptibility measurements in the temperature range 2–300K show that 1 is weak antiferromagnetic coupling, while 2 exhibits a novel and interesting spin-gap transition around 140K with Δ/kb =381.4K. [Copyright &y& Elsevier]