Ion-pair complexes with strong near infrared absorbance: syntheses, crystal structures and spectroscopic properties

Insight into understanding magnetic transition quite sensitive to nonmagnetic impurity in a one-dimensional S = ½ regular linear chain system

Herein, we demonstrate that the antiferromagnetic couplings in a [Ni(mnt)2]− stack are realized mainly through spatial dipole–dipole type interactions.

Spin-crossover phenomena of the mononuclear Mn(III) complex tuned by metal dithiolene counteranions

Three ion-pair complexes based on spin-crossover [Mn(5-Br-sal-N-1,5,8,12)]ClO4 with TBA2[Ni(mnt)2], TBA2[Pt(mnt)2] (mnt = maleonitriledithiolate) and TBA[Ni(dmit)2] respectively (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato) have been synthesized and structurally characterized. Complexes [Mn(5-Br-sal-N-1,5,8,12)]2[Ni(mnt)2] and [Mn(5-Br-sal-N-1,5,8,12)]2[Pt(mnt)2] are isomorphic and show the axial compression of the octahedral coordination environment of Mn(III) ions. With the temperature increasing the equatorial metal-ligand bond lengths show significant elongation, but the axial bond lengths remain unchanged. Complex [Mn(5-Br-sal-N-1,5,8,12)][Ni(dmit)2]·CH3CN contains π-π, p-π and H-bonds weak interactions. Magnetic investigation shows the spin-crossover phenomena for and , and T1/2 has been increased by 230 K comparing with the reactant complex. However, no spin-crossover was observed in complex , and theoretical calculations show that there are weak antiferromagnetic couplings mediated through π-π interactions.

Bis(1-ethyl-4,4′-bipyridin-1-ium) bis(1,2-dicyanoethene-1,2-dithiolato-κ2S,S′)nickelate(II)

In the anion of the title compound, (C₁₂H₁₃N₂)[Ni(C₄N₂S₂)₂], the Ni^II atom is coordinated by four S atoms from two 1,2-di­cyano­ethene-1,2-di­thiol­ate (mnt) ligands in a suqare-planar geometry. Weak C—H⋯N and C—H⋯S hydrogen bonds between the 1-ethyl-4,4′-bipyridin-1-ium cations and mnt anions and weak π–π inter­actions between the pyridine rings of the cations [centroid–centroid distances = 3.808 (3) and 3.972 (3) Å] lead to a two-dimensional network parallel to (010).

Observation of divergent isotope effects as well as metal ion-modulated T(C) and spin-canting nature in isostructural supramolecular magnets

The ion-pair complexes of [4-NH(2)-PyH][M(mnt)(2)] (M = Pt for 1 and Ni for 3) and their deuterated analogues [4-NH(2)-PyD][M(mnt)(2)] (M = Pt for 2 and Ni for 4) are isostructural with each other. Four complexes crystalline in monoclinic space group C2/c, whose asymmetric unit consists of two halves of [M(mnt)(2)](-) anions and one cation, show quite similar cell parameters and almost identical packing structures as well. In the crystals of 1-4, two types of crystallographically inequivalent [M(mnt)(2)](-) anions construct individual layers, which are separated by the cation layer; the supramolecular networks are formed via the H-bonding interactions between the [M(mnt)(2)](-) and 4-NH(2)-PyH(+) (or 4-NH(2)-PyD(+)) ions as well as the weakly ππ stacking interactions between the [M(mnt)(2)](-) anions. The four isostructural complexes exhibit canted antiferromagnetism, arising from the non-collinearity of the magnetic moments between the crystallographically inequivalent anion layers, with T(C) ≈ 14.8 K for 1, 13.6 K for 2, 7.7 K for 3 and 8.8 K for 4, respectively. Ac magnetic susceptibility measurements revealed that 1 and 2 show spin canting, while 3 and 4 show hidden-spin canting characteristics. The isostructural 1 and 3 were deuterated to give the divergent isotope effects on the cell volume and T(C).

Bis(3,5,7-triaza-1-azoniatricyclo-[3.3.1.1]deca-ne) bis-(1,2-dicyano-ethene-1,2-dithiol-ato)nickelate(II)

The asymmetric unit of the title complex, (C₆H₁₃N₄)₂[Ni(C₄N₂S₂)₂], comprises one 1-azonia-3,5,7-triaza­tricyclo­[3.3.1.1^3,7]decane cation and one half of an [Ni(mnt)₂]²⁻ (mnt²⁻ is maleonitrile­dithiol­ate or 1,2-dicyano­ethene-1,2-dithiol­ate) dianion. The Ni²⁺ ion is located on a center of inversion and is coordinated by four S atoms from two mnt²⁻ ligands in a square-planar coordination mode. Inter­molecular N—H⋯N hydrogen-bond inter­actions link one anion and two cations in the crystal structure.