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Two novel lanthanide coordination polymers, [Eu2(EBTC)(DMF)5(NO3)2]·DMF (1) and [Eu2(BBTC)1.5(CH3OH)2(H2O)2]·7DMF·HNO3(2) (EBTC4−= 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylate; BBTC4−= 1,1′-butadiynebenzene-3,3′,5,5′-tetracarboxylate), were successfully synthesized from conjugated ligands of EBTC4−and BBTC4−. Although the two tetracarboxylate ligands have similar structures, their different rigidity/flexibility results in quite different networks upon complexation. Complex 1has a two-dimensional (2-D) layered structure with two crystallographically independent Eu3+ions, one in a distorted monocapped square-antiprism and the other in a distorted square-antiprism coordination geometry. Complex 2exhibits a three-dimensional (3-D) porous framework, with one type of Eu3+in a distorted square-antiprism and the other in a trigondodecahedron environment. Both 1and 2emit the intensely red characteristic luminescence of Eu3+ion at room temperature, with a long lifetime of up to 1.3 and 0.7 ms, respectively, during which the ligand emission of EBTC4−/BBTC4−was quenched by the Eu3+ion, indicating the existence of efficient energy transfer between the conjugated ligand of EBTC4−/BBTC4−and the Eu3+ion. Thus, both EBTC4−and BBTC4−are ideal ligands with an “antenna” effect for the Eu3+ion. The two complexes show the single-ion magnetic behaviors of Eu3+with strong spin–orbit coupling interactions even if there are shorter distances (5.714 Å for 1versus4.275 and 5.360 Å for 2) between the neighboring Eu3+ions connected by oxygen atoms of the tetracarboxylates. [ABSTRACT FROM AUTHOR]

A low-dimensional compound [C6-Apy][Ni(mnt)2] (1, where mnt2−= maleonitriledithiolate, C6-Apy+= 4-amino-1-hexylpyridinium) has been designed and synthesized, which has layer arrangement of anions and cations and shows two steps of magnetic transitions. The low temperature magnetic transition has an uncommon hysteresis loop, while the crystal structure investigations disclosed no structural transition with the magnetic transition. The high temperature magnetic transition exhibits two remarkable features: (1) it synchronously occurs with a crystalline-to-mesophase transition in the first heating process and (2) the structural changes that accompany the solid-mesophase transition are irreversible. A diamagnetic and isostructural compound, [C6-Apy][Cu(mnt)2], is further characterized by structure, DSC and POM techniques, which revealed also the existence of an irreversible crystalline-to-mesophase transition in the same temperature interval of [C6-Apy][Ni(mnt)2]. Therefore, the high-temperature magnetic transition in 1is driven by release of the structural strains, but not magnetoelastic interactions. The mesophase exhibits the characteristic of smectic A phase, and the alkyl chain melting in the cation layers probably lead to the formation of mesophase. It is noticeable that the finding of a mesophase occurring in a hexyl hydrocarbon chain molecular system is in contrast to a suggested rule that at least a dodecyl chain is required. Our results will shed a light on the design and preparation of a new low-dimensional molecular system combining magnetic transition and liquid crystal properties. [ABSTRACT FROM AUTHOR]

Three novel coordination polymers, [Mn(TPB)0.5(IPA)(H2O)2]n (1), [Zn1.5(TPB)0.5(TMA)(H2O)·(H2O)]n (2), and [Co(TPB)0.5(PMA)0.5(H2O)2·(H2O)]n (3) (TPB = 1,2,3,4-tetra-(4-pyridyl)-butane; H2IPA = isophthalic acid; H3TMA = trimesic acid; and H4PMA = pyromellitic acid), have been synthesized under hydrothermal conditions and structurally characterized. Complex 1 features a 2D infinite layer framework consisting of bi-manganese clusters, which is further stacked along the [1&cmb.macr;11] direction via strong interlayer π⋯π interactions to form a 3D supramolecular architecture. Complex 2 has a 3D complicated framework comprised of two kinds of infinite 1D chains. The 3D framework of complex 3 possesses three topologically nonequivalent 4-connected nodes synchronously and exhibits an unprecedented (64·102)(42·84)(4·65)2 topology. The magnetic susceptibility data of complex 1 show strong antiferromagnetic interactions in the dinuclear Mn(ii) units. Complex 2 exhibits strong fluorescent emissions in the solid state at room temperature and may be suitable as a candidate of blue-fluorescent material. [ABSTRACT FROM AUTHOR]

The synthesis, molecular structure and spectroscopic and magnetic properties of (NH4)2(15-crown-5)3[Ni(mnt)2]2 (mnt  =  maleonitriledithiolate dianion) are reported. The most notable structural feature of (NH4)2(15-crown-5)3[Ni(mnt)2]2 is that the ions form a stacked structure with well-separated columns along the c and a axes. Variable temperature magnetic susceptibility measurements indicate strong antiferromagnetic interactions in the complex. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: A novel coordination polymer 1 {[Zn5(MDIP)2(H2O)6(μ3-OH)2]·2H2O} n has been synthesized using methylenediisophthalic acid (H4MDIP) under hydrothermal conditions. Single-crystal X-ray diffraction analysis indicates that 1 shows a 3D porous framework with two types of 1D channel. The structure is further simplified by topology analysis which indicates a (4, 8)-connected net with a Schläfli symbol of (44.62)2(416.612) topology. Moreover, compound 1 displays a strong blue photoluminescent property. [Copyright &y& Elsevier]

Abstract: Three new interesting coordination polymers, [Zn(PDCO)(H2O)·H2O]n (1), [Co(PDCO)(H2O)3]n (2) and [Mn(PDCO)(H2O)2]n (3), (H2PDCO=pyridine-2,4-dicarboxylic acid N-oxide), have been prepared under hydrothermal conditions and structurally characterized. Polymer 1 exhibits 0D Zn units, polymer 2 features 1D infinite zigzag Co chains. In polymer 3, four Mn atoms and four PDCO ligands form a 24-member ring and these rings are interlocked to form a 2D infinite layer. Compounds 1–3, with systematic variation in dimensionality from 0D to 1D to 2D, are the first examples of metal coordination polymers into which pyridine-2,4-dicarboxylic acid N-oxide has been introduced. In addition, the photoluminescent properties of 1 as well as the magnetic behavior of 2 have been investigated. [Copyright &y& Elsevier]

Abstract: Two new molecular solids, [1-NaMePid][Ni(mnt)2] (1) and [2-NaMePid][Ni(mnt)2] (2) (mnt2− =maleonitriledithiolate, [1-NaMePid]+ =1-(1′-naphthylmethyl)piperidinium and [2-NaMePid]+ =1-(2′-naphthylmethyl)piperidinium) have been characterized structurally and magnetically. Both [Ni(mnt)2]− anions and the cations of 1 and 2 form segregated column stacks, and the Ni(III) ions form a 1D zigzig alternating magnetic chain within a [Ni(mnt)2]− column through Ni···S, S···S, Ni···Ni, or π···π interactions. Some conformational features in two isomeric cations and the geometry of the individual [Ni(mnt)2]− anion for 1 and 2 remain similar, while the changes of the space filling properties, the packing requirements and the existence of the water molecule in 2 result in the difference of the stacking mode of the [Ni(mnt)2]− anions. Magnetic susceptibility measurements in the temperature range 2–300K show that 1 is diamagnetism, while 2 exhibits a novel and interesting spin–gap transition around 16.8K with antiferromagnetic interaction (J =−4.6cm−1) in the high-temperature phase (HT) and the spin–gap (Δ/k b =68.5K) in the low-temperature phase (LT). [Copyright &y& Elsevier]

Abstract: Employing the tetrapodal compound 1,2,3,4-tetra(4-pyridyl)thiophene (TPT) as a bridging ligand, a new metal–organic framework was obtained and characterized by single crystal X-ray diffraction, [Cd(TPT)(N3)2·(H2O)] (1). This polymer exhibits a 2D layer network and an unprecedented 3,4-connected topology, which is constructed from the three-connector TPT and EE azido bridges. It also displays good thermal stability and strong photoluminescence in the blue regionband thus may serve as a candidate of thermally stable blue-light-emitting electroluminescence material. The nature of electronic transitions in the photoluminescent process has also been investigated by means of time-dependent density functional theory (TDDFT) calculations and molecular orbital analyses, which shows that the luminescent property is ligand-based. [Copyright &y& Elsevier]

Abstract: Employing the symmetrical ligand 1,2,3,4-tetra-(4-pyridyl)-butane (TPB) as bridges, two novel Zn(II) coordination polymers were obtained and characterized by single crystal X-ray diffraction: [Zn(TPB)0.5(NCS)2] (1) and [Zn(TPB)(N3)2] (2). Polymer 1 features a 2D network with herringbone structural motif constructed by TPB, while polymer 2 shows a dense 3D network connected by TPB and μ1,3-N3- bridges. In the former, the TPB ligand acts as a four-connector, while in the latter it acts as four-connector and linear bridge. Both 1 and 2 exhibit strong fluorescent emissions in the solid state, which may be of significance in the field of photoactive materials. [Copyright &y& Elsevier]

Abstract: Syntheses, structural characterizations, magnetic behaviors and theoretical analyses of two new ion-pair complexes, [IFBzIQl][Ni(mnt)2](1) and [IClBzIQl]2[Ni(mnt)2]2 ·MeCN(2) [IFBzIQl][Ni(mnt)2] ([IFBzIQl]+ =1-(2′-fluoro-4′-iodobenzyl)isoquinolinium, [IClBzIQl]+ =1-(2′-chloro-4′-iodobenzyl)isoquinolinium, mnt2− =maleonitriledithiolate), have been investigated. In crystal of 1, the [Ni(mnt)2]− anions and the [IFBzIQl]+ cations stack into an alternating column through π⋯π stacking interactions. The anions of both 1 and 2 form a dimer via π⋯π stacking and S⋯S short interactions between the [Ni(mnt)2]− anions. The overlapping mode of two neighboring [Ni(mnt)2]− anions in the dimer is the Ni-ring fashion with a Ni⋯Ni distance of 4.076Å for 1, and ring–ring fashion with the Ni⋯Ni and S⋯S distances being 4.395 and 3.593Å for 2. Some weak interactions such as π⋯π, C⋯N, C–H⋯F or C–H⋯N in 1 and 2 play a crucial role in stacking and stabilizing the crystal lattice, and give a 3D network structure and exchange pathways of the magnetic interaction for 1 and 2. Magnetic susceptibility measurements for 1 and 2 in the temperature range 1.8–300K show that the overall magnetic behavior indicates the presence of antiferromagnetic interaction, while 2 exhibits an activated magnetic behavior in the high-temperature region (HT) together with a Curie tail in the low-temperature region (LT). [Copyright &y& Elsevier]

Abstract: Two new molecular magnets, based on [Ni(mnt)2]− monoanion, [DiBrBzPy][Ni(mnt)2] (1) and [DiBrBzIQl][Ni(mnt)2] (2) ([DiBrBzPy]+ =1-(3′,5′-dibromobenzyl)pyridinium, [DiBrBzIQl]+ =1-(3′,5′-dibromobenzyl)isoquinolinium and mnt2− =maleonitriledithiolate), were prepared and characterized by elemental analyses, IR, ESI-MS spectra, single crystal X-ray diffraction and magnetic measurements. The [Ni(mnt)2] anions and the cations of 1 and 2 are alternately stacked and form 1D column via π⋯π stacking interactions between the [Ni(mnt)2] anions and the neighboring cations. Some weak Ni⋯N, C⋯N interactions and CBr, CN hydrogen bonds between the adjacent columns further generate a 3D network structure. Magnetic susceptibility measurements show that both 1 and 2 exhibit the typical magnetic behavior of a spin gap system with an energy gap of 1151.9K for 1 and 73.9K for 2. [Copyright &y& Elsevier]

Abstract: A charge-transfer compound, [NO2BzPz][Ni(mnt)2] (NO2BzPz+ =1-(4′-nitrobenzyl)pyrazinium and mnt2− =maleonitriledithiolate), has been structurally characterized, which shows rare noncovalently intermolecular interactions between lone-pair electron and electron-deficient pyrazine rings (NO2⋯π and CN⋯π), theoretical analysis reveals that such intermolecular interactions can be attributed to Coulomb interaction. The paramagnetic [Ni(mnt)2]− anions in [NO2BzPz][Ni(mnt)2] form a dimerized stack and strong antiferromagnetic coupling interaction is observed in such a spin dimer which lead to weak paramagnetic feature in this compound. [Copyright &y& Elsevier]