BDTA]2[Cu(mnt)2]: an almost perfect one-dimensional magnetic material

[BDTA]2[Cu(mnt)2] (BDTA = benzo-1,3,2-dithiazolyl, mnt = maleonitriledithiolate) was crystallized in the space group P with an inversion center on Cu giving a stacked structure with each metal complex anion sandwiched by two cations. Short intermolecular S...S contacts give rise to a one-dimensional chain lateral to the stacking axis. Variable-temperature magnetic susceptibility and EPR measurements indicate that the salt behaves as an ideal one-dimensional Heisenberg antiferromagnetic material from 2 K < or = T < or = 300 K, with a coupling constant of J/k(B) = 16-17 K; the very low temperature magnetic properties are in quantitative agreement with the predictions of quantum field theory. DFT calculations are consistent with the formation of a one-dimensional magnetic chain with interstack interactions mediated by the BDTA counterions.     

Hexagonal supramolecular architectures from ferrocenium cations incorporating [Ni(mnt)2]- columns: structures and properties of [alkylferrocene][Ni(mnt)2]- charge-transfer complexes (mnt=maleonitriledithiolate)

The crystal architecture, magnetic properties, and thermodynamic properties of [n-butylferrocene][Ni(mnt)2] (1), [tert-butylferrocene][Ni(mnt)2] (2), [1,1'-diethylferrocene][Ni(mnt)2] (3), and [1,1'-diisopropylferrocene][Ni(mnt)2] (4) were investigated (mnt=maleonitriledithiolate). These complexes exhibit a unique supramolecular structure in which the ferrocenium cations constitute honeycomb-like assembled structures surrounding columns of the anions. For 1, the cations form a dimer through a very short intermolecular ferrocene-ferrocene distance of 3.28 A, which mediates an antiferromagnetic interaction with a singlet-triplet energy gap of 5 K. First-order phase transitions occur in 1-3 at 364, 361, and 350 K, respectively, accompanied by thermal hysteresis.     

Biferrocene-M(mnt)2 charge-transfer complexes (M = Ni, Co; mnt = maleonitriledithiolate). structure, valence states, and magnetic properties

Charge-transfer salts of branched-alkyl biferrocenes, (1',1' '-R2-1,1' '-biferrocene)[Ni(mnt)2] (1a, R = isopropyl; 2a, R = dineopentyl) and (1',1' '-R2-1,1' '-biferrocene)2[Co(mnt)2]2 (1b, R = isopropyl; 2b, R = dineopentyl), were prepared. Their valence states were investigated using X-ray crystallography and M?ssbauer spectroscopy. Complexes 1a and 1b show segregated-stack crystal structures that contain columns of acceptors, whereas structures of 2a and 2b, which contain bulky donors, are rather discrete. All of the complexes contain mixed-valent biferrocenium monocations. A two-step valence transition was found in complex 1a. The crystal contains two crystallographically independent cations: one undergoes valence localization below room temperature; the other undergoes valence localization below ca. 130 K. The former transition is derived from asymmetry of the crystal environment around the cation, whereas the latter one is caused by symmetry lowering coupled with a spin-Peierls transition (T(C) = 133.2 K) associated with the dimerization of the acceptors. This compound was found to exhibit a dielectric response based on valence tautomerization. Other complexes (1b, 2a, and 2b) show a valence-trapped state. In all complexes, charge localization was found to occur through local electrostatic interactions between the donor's cationic moiety and the acceptor's electronegative moieties.     

Tracing the Sources of the Different Magnetic Behavior in the Two Phases of the Bistable (BDTA)(2)[Co(mnt)(2)] Compound

A complete computational study of the magnetic properties of the two known phases of the bistable (BDTA)(2)[Co(mnt)(2)] compound is presented. The origin of their different magnetic properties can be traced to a variation in the values of the g tensor, together with a hitherto unknown change in the J(AB) values and their magnetic topology.     

Structural phase transition driven by spin-lattice interaction in a quasi-one-dimensional spin system of [1-(4'-iodobenzyl)pyridinium][Ni(mnt)2

Crystal structures and magnetic properties were determined for two novel compounds, [1-(4'-iodobenzyl)pyridinium][M(mnt)2] (mnt2- = maleonitriledithiolate; M = Ni (1) or Cu (2)). At room temperature, single crystals of 1 and 2 were isostructural, featuring the formation of segregated columnar structures with regular stacks of cations and anions. For crystal 1, a magnetic transition was observed at approximately 120 K; furthermore, its magnetic behavior was consistent with that of a regular Heisenberg antiferromagnetic (AFM) chain of S = 1/2 in the high-temperature phase (HT phase) and that of a spin-gap system in the low-temperature phase (LT phase). Such a phenomenon is similar to the spin-Peierls transition. However, the crystal structure of 1 in the LT phase at 100 K revealed that its structural transition is associated with the magnetic transition. Because crystal 2 (S = 0) did not exhibit a structural transition, the structural transition of 1 is driven by spin-lattice interaction.     

配合物[1-(4′-bromo-2′-fluorobenzyl)pyridinium]2[Ni(mnt)2]和[1-(4′-bromo-2′-fluorobenzyl)pyrazinium]2[Ni(mnt)2](mnt2-=maleonitriledithiolate dianion)的合成及晶体结构

本文报道两个含双(马来二氰基二硫烯)镍(Ⅱ)配合物阴离子的离子对化合物。对阳离子为1-(4′-溴-2′-氟苄基)吡啶 盐时,生成配合物1。晶体数据:三斜晶系,空间P1群,a=0.7086(2)nm,b=1.0968(3)nm,c=1.1775(3)nm,α=69.914(5)°,β=89.495(5)°,γ=74.765(5)°,V=0.8259(4)nm³,Z=1。对阳离子为1-(4′-溴-2′-氟苄基)吡嗪鎓盐时,生成配合物2。晶体数据:单斜晶系,空间群P2₁/n,a=0.71554(17)nm,b=1.4262(3)nm,c=1.6725(4)nm,β=100.396(4)°,V=1.6788(7)nm³,Z=4。两个配合物中,阴离子为拟平面结构,镍原子均位于对称中心。变换对阳离子上的芳环种类对晶体的堆积结构产生影响。     

Unusual spin gap transition observed in two new molecular magnets based on [Ni(mnt)2] monoanion (mnt=maleonitriledithiolate)

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 2via weak π…π stacking interactions, C…C or C…N short interactions between the neighboring anions. Magnetic susceptibility measurements in the temperature range 1.8-300 K indicated that 1 and 2 show unusual spin gap transition around 30 K and 110 K, respectively. The transition for 1 and 2 is the second-order phase transition as determined by the capacity measurement.     

Probing the intrinsic electronic structure of the bis(dithiolene) anions [M(mnt)2]2- and [M(mnt)2]1- (M = Ni, Pd, Pt; mnt = 1,2-S2C2(CN)2) in the gas phase by photoelectron spectroscopy

A detailed understanding of the electronic structure of transition metal bis(dithiolene) complexes is important because of their interesting redox, magnetic, optical, and conducting properties and their relevance to enzymes containing molybdenum and tungsten bis(dithiolene) centers. The electronic structures of the bis(dithiolene) anions [M(mnt)(2)](n-) (M = Ni, Pd, Pt; mnt = 1,2-S(2)C(2)(CN)(2); n = 0-2) were examined by a combination of photodetachment photoelectron spectroscopy (PES) and density functional theory calculations. The combined experimental and theoretical data provide insight into the molecular orbital energy levels of [M(mnt)(2)](2-) and the ground and excited states of [M(mnt)(2)](1-) and [M(mnt)(2)]. Detachment features from ligand-based orbitals of [M(mnt)(2)](2-) occur at similar energies for each species, independent of the metal center, while those arising from metal-based orbitals occur at higher energies for the heavier congeners. Electronic excitation energies inferred for [M(mnt)(2)](1-) from the PES experiments agree well with those obtained in optical absorption experiments in solution, with the PES experiments providing additional insight into the changes in energy of these transitions as a function of metal. The singly charged anions [M(mnt)(2)](1-) were also prepared and studied independently. Electron detachment from the ground states of these doublet anions accessed the lowest singlet and triplet states of neutral [M(mnt)(2)], thereby providing a direct experimental measure of their singlet-triplet splitting.     

Synthesis and Structure of Co(III) Coordination Compounds [Co(DH)2(Anil)2][BF4] and [Co(DH)2(Py)2][BF4]

The complex compounds [Co(DH)₂(Anil)₂][BF₄] and [Co(DH)₂(Py)₂][BF₄] were synthesized from Co(BF₄)₂ · 6H₂O–DH₂–A–alcohol–water systems (DH₂ is dimethylglyoxim and A is pyridine (Py) or aniline (Anil)), and their crystal structures were determined using X-ray diffraction analysis. In octahedral Co(III) complexes, two dimethylglyoxime radicals lie in the equatorial plane and are joined via the intramolecular hydrogen bond O–H···O. The complexes with pyridine and aniline have similar configurations but different crystal structures.     

Peculiar magnetic behavior in ion-pair complex [1-(4'-fluorobenzyl)pyridinium][Ni(mnt)2] (mnt2- = maleonitriledithiolate)

An ion-pair complex [FBzPy][Ni(mnt)2], where [FBzPy]+ = 1-(4'-fluorobenzyl)pyridinium and mnt2- = maleonitriledithiolate, forms a discrete stacking column and shows a peculiar magnetic transition from paramagnetic to diamagnetic around 90 K.     

A hybrid density-functional study of the one-dimensional ferromagnetic ordering of (BDTA)[Ni(mnt)2]

The one-dimensional intermolecular ferromagnetic interaction of a charge-transfer (CT) complex, (BDTA)[Ni(mnt)₂] (BDTA: 1,3,2-benzodithiazolyl, mnt: maleonitriledithiolate), is studied by the Kohn–Sham hybrid density functional method, in order to understand the mechanism of the magnetism. All possible effective exchange integrals, J, between the spin pairs of the system indicate that a ferromagnetic interaction (J = 172 cm⁻¹) exists along the b-axis. Magnetic susceptibility, simulated with the ab initio determined J values by the quantum Monte Carlo (QMC) method, is qualitatively consistent with that measured experimentally.     

One-dimensional (1D) [Ni(mnt)2]−-based spin-Peierls-like complexes: Structural,magnetic and transition properties

1D spin-Peierls-like complexes assembled from [Ni(mnt)₂]^? with Λ-shaped 1-(4′-R-benzyl)pyridinium derivatives (R represents a substituent) are reviewed, with data on their crystal structures, magnetic properties under ambient conditions as well as under pressure, and the nature of the paramagnetic-to-nonmagnetic transition. In this series of 1D spin systems, the correlation between the magnetic exchange and the anion stacking pattern is addressed by application of density functional theory (DFT) combined with a broken-symmetry approach. The qualitative relationship between the transition enthalpy change and the variation of the magnetic susceptibility in the low-temperature phase is determined. The influence of nonmagnetic doping on the structural and magnetic properties and the magnetic transitions are reported. Furthermore, the effect of the substituent group in the phenyl ring of the cation on the transition temperature and the origin of the transition are discussed.     

Studies on the electrochemical growth of (Per)2[Au(mnt)2

The first stages of the electrocrystallization of (Per)(2)[Au(mnt)(2)] salt from dichloromethane on gold, platinum, and highly orientated pyrolytic graphite (HOPG) were investigated by cyclic voltammetry, atomic force microscopy, and X-ray photoelectron spectroscopy in order to understand the determinant factors for nucleation and crystal growth. The crystal growth occurs from adsorbed films of dithiolate on gold or platinum and of perylene on HOPG, after homogeneous nucleation, and it is controlled by the low diffusion of the species toward the growing surface.     

配合物[2-NaPhthMePyNH_2]_2[Ni(mnt)_2]的合成及表征

合成了马来二氰基二硫烯镍(Ⅱ)配合物,[2-Na Phth Me Py NH2]2[Ni(mnt)2]([2-Na Phth Me Py NH2]+为1-(2'-萘苄基)-2-氨基吡啶鎓离子),并用元素分析,UV,IR,单晶X-射线衍射表征了其组成和结构。结果表明,配合物系单斜晶系,空间群P21/c,a=13.335(2),b=7.9458(12),c=17.480(3),α=90°,β=97.646(2)°,γ=90°,V=1835.7(5),Z=2。     

Ferromagnetic anomaly associated with the antiferromagnetic transitions in (donor)[Ni(mnt)2]-type charge-transfer salts

Three newly prepared [Ni(mnt)2] complexes, (HMTTF)[Ni(mnt)2], (ChSTF)[Ni(mnt)2], and (DBTTF)2[Ni(mnt)2], are reported (DBTTF = dibenzotetrathiafulvalene, ChSTF = 2,3-cyclohexylenedithio-1,4-dithia-5,8-diselanafulvalene, HMTTF = bis(trimethylene)-tetrathiafulvalene, and mnt = maleonitrile dithiolate). The former two compounds have usual DA-type (D = donor, A = acceptor) mixed stacks, whereas the DBTTF complex has DDDDAA-type 6-fold columns. These compounds are electrical insulators, but the HMTTF and ChSTF complexes exhibit chiT minima at 16 and 55 K, respectively, followed by chiT peaks at 8 and 16 K. Below these temperatures the ESR signal disappears, indicating antiferromagnetic transitions. The origin of the ferromagnetic interaction is explained either from the difference of the g values between the donor and the anion or from the intrinsic ferromagnetic interaction of the [Ni(mnt)2] anions.     

Order-disorder phase transition with associated cell-tripling in the (octamethylferrocene)(2,3-dichloro-1,4-naphthoquinone)2 charge-transfer complex

The structural change associated with the first-order phase transition (T_C = 155.1 K) in a mixed-stack charge-transfer complex (octamethylferrocene)(2,3-dichloro-1,4-naphthoquinone)₂ was investigated crystallographically. X-ray structure determination at 90 K revealed that the transition is associated with the order-disorder of the C₅Me₄H ring in octamethylferrocene. In the low temperature phase, tripling of the unit cell occurred, accompanied by a change in spacegroup from P2₁/c to P?1, and every third octamethylferrocene molecule twists out of the plane to minimize steric interactions.     

A unique new multiband molecular conductor: [BDTA][Ni(dmit)2]2

A new molecular conducting material, [BDTA][Ni(dmit)2]2, with a novel multiband electronic structure has been prepared by simple mixing of precursor salts of the components.     

Two Ion-pair Complexes Constructed by[M（mnt）2]n- （M=Ni,Co,mnt = Maleonitriledithiolate）:Syntheses,Characterization and Thermal Stability

Two new ion-pair complexes [Co(BBP)2]2[Ni(mnt)2]Cl2·4DMF·2H2O(1, BBP =2,6-bis(benzimidazol-2'-yl) pyridine, mnt = maleonitriledithiolate) and [(Py)2CH2][Co(mnt)2]2·4DMF(2) have been synthesized and characterized by elemental analyses, IR spectroscopy,thermogravimetric analyses and single-crystal X-ray diffraction. X-ray diffraction studies show that complex 1 crystallizes in monoclinic, space group P21/c. The crystal of 2 belongs to a triclinic system with space group P1. Due to the hydrogen bonding interactions, anions and cations formed the mixed packing in complex 1 while the anions and cations formed segregated columns in 2. In addition, thermogravimetric analyses of the two complexes are also investigated.