One-dimensional Metal Complexes Research Articles

One-dimensional coordination polymers with 4-(2-aminoethyl)pyridine: Synthesis, crystal structures and spectroscopic properties

Two new one-dimensional polymeric metal complexes, namely [Zn(NH3)(μ-4aepy)Ni(μ-CN)(CN)3]n (1) and [Cu(H2O)(μ-4aepy)Pd(μ-CN)(CN)3]n (2) [4aepy=4-(2-aminoethyl)pyridine], were synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. The complexes crystallize in the monoclinic system, P21/n space group. The asymmetric units of 1 and 2 contain two M(II) ions [M=Zn(II) and Ni(II) in 1 and Cu(II) and Pd(II) in 2], four cyanide ligands, one 4aepy ligand and one coordinated ligand (ammine in 1 and aqua in 2) in a distorted tetragonal coordination geometry. The crystal structures of the complexes revealed that three cyanide groups are terminal whereas one different cyanide group behaves as bridging ligand. The most important features of the complexes are the presence of obvious M⋯π [M(II)=Ni(II) or Pd(II)] interactions. The spectral and thermal analysis results also support the crystal structures of the complexes.

Rie Makiura

Rie Makiura

Synthesis and characterization of three new 1-D polymeric [M2(4-azidopyridine)4(μ1,1-N3)2(μ1,3-N3)2]n (M = Ni, Co, Cd) complexes

Three one-dimensional azido-bridged metal(II) complexes, [Ni2(4-azpy)4(μ1,1-N3)2(μ1,3-N3)2]n (1), [Co2(4-azpy)4(μ1,1-N3)2(μ1,3-N3)2]n (2), and [Cd2(4-azpy)4(μ1,1-N3)2(μ1,3-N3)2]n (3), (4-azpy=4-azidopyridine) were synthesized and characterized by UV–Vis, IR spectroscopy and by single crystal diffraction. The three iso-structural complexes exhibit distorted octahedral geometry around the metal(II) centers, terminal 4-azidopyridine ligands in trans-dispositions and alternating doubly bridged EO- and doubly bridged EE-azido ligands giving rise to polymeric 1-D systems. The asymmetric nature of the azide groups is increasing from EE- via EO- to covalent bonded N3-group in the 4-azidopyridine ligand. The magnetic properties of complexes 1 and 2 are reported.

One-dimensional 8-hydroxyquinoline metal complex nanomaterials: synthesis, optoelectronic properties, and applications

One-dimensional (1D) 8-hydroxyquinoline metal complex nanomaterials exhibit distinctive characteristics that differ from those of their bulk counterparts. Owing to their small size, shape anisotropy, unique structures, and novel properties, these organometallic 1D nanostructures are promising candidates for various devices. This review highlights current progress in the synthesis of 1D 8-hydroxyquinoline metal complex nanomaterials and summarizes their optoelectronic properties and applications. The mainly synthetic strategies are divided into three categories, which include vapor phase growth, solution phase growth, and self-assembly. Special attention is paid to the formation mechanisms and the control measures for 1D nanostructured 8-hydroxyquinoline metal complexes. Other new methods such as template-based synthesis and electrospinning are briefly described. Merits and shortcomings of each synthetic strategy are simply discussed. Then, a variety of optoelectronic properties including luminescence, field emission, charge transport, photoconductivity, and photo-switching properties are reviewed, and their applications in optoelectronic devices, field emission, and templates are also surveyed. In the end, concise conclusions are provided, and personal perspectives on future investigations of 1D 8-hydroxyquinoline metal complex nanomaterials are proposed.

Calorimetric Study of MMX Chain Complexes Having Alkyl Groups, Ni2(EtCS2)4I and Ni2(n-PrCS2)4I

Heat capacities of halogen-bridged one-dimensional binuclear metal complexes (so-called MMX chain) having alkyl groups, Ni 2 (RCS 2 ) 4 I (R = Et and n -Pr), were measured by adiabatic and relaxation calorimetry. For each complex, a small broad thermal anomaly due to a spin-Peierls transition was observed around 40 K. For Ni 2 ( n -PrCS 2 ) 4 I, a first-order phase transition was observed at 205.6 K. The enthalpy and entropy of transition were estimated to be about 4.05 kJ mol -1 and 19.7 J K -1 mol -1 , respectively. The magnitude of thermal anomaly shows that the effect of molecular dynamics of ligand on the electronic state in one-dimensional chain is small for Ni complexes having localized electrons in comparison with Pt complexes.

Structural and magnetic characterization of one-dimensional oxalato-bridged metal(II) complexes with 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole ligand: A supramolecular open-framework

A new family of one-dimensional oxalato-bridged metal(II) complexes with formula {[M(ox)(abpt)]·4H 2O} n [M II = Mn ( 1), Fe ( 2), Co ( 3), Zn ( 4); ox = oxalate dianion; abpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole] has been synthesized and chemically, structurally and magnetically characterized. The crystal structures of compounds 2– 4 have been solved by single crystal X-ray diffraction, whereas complex 1 has been studied by means of X-ray powder diffraction methods. All of them are isomorphous and crystallize in the triclinic space group P 1 ¯ . The metal atoms are bridged by bis-bidentate oxalate anions forming zig-zag chains in which bidentate chelating abpt ligands complete the octahedral O 4N 2 donor set. The crystal structures show an open-framework that contains rectangular channels in which easily removable hydrogen bonded ribbons of water molecules are located. The occurrence of antiferromagnetic intrachain interactions for compounds 1–3 was determined by cryomagnetic susceptibility measurements.

Direct Determination of Low-Dimensional Structures: Synchrotron X-ray Scattering on One-Dimensional Charge-Ordered MMX-Chain Complexes

A powerful method to determine the hidden structural parameters in functional molecules has been developed. Local valence arrangements that dominate the material properties are sometimes not three-dimensionally ordered. This method that comprises diffuse X-ray scattering and resonant X-ray scattering is suitable in such cases. Using this method, we present clear evidence of the low-dimensional valence arrangement in two halogen-bridged one-dimensional metal complexes, so-called MMX chains. This family allows us to control many physical and structural parameters by chemical substitution of bridging halogen, counterions, or metal ions, and one of our samples carries an unusual metallic phase. It is demonstrated with this complex that the present method makes it possible to have microscopic insight to low-dimensionally ordered systems.

Structure and magnetic properties of one-dimensional metal complexes constructed from alternating dicyanamide linked through binuclear metal tetra-2-pyridylpyrazine subunits

The syntheses, structures and magnetic properties of three 1-D complexes with the formulae [Co 2(tppz)(dca) 4] ( 1), [Ni 2(tppz)(dca) 4]C 2H 5OH ( 2) and [Cu 2(tppz)(dca)(Cl) 2](dca) · H 2O ( 3), where tppz = tetra-2-pyridylpyrazine and dca = dicyanamide, are described. Complexes 1– 3 are one-dimensional metal-complexes. In 1 the dinuclear tppz-chelated Co(II) centers are linked by two double μ 1,5-dca ligands. Compound 2 forms a ladder-like structure in which the rungs are formed by bis-chelating tppz bridged dinuclear Ni(II) ions and the uprights by μ 1,5-dca units. Compound 3 forms a helical chain structure which consists of alternately single μ 1,5-dca linked dinuclear tppz-chelated Cu-centers. The temperature dependence of magnetic measurements show antiferromagnetic couplings between two metal ions with a pathway through tppz and μ 1,5-dca in all cases, with J = −1.10 cm −1, J′ = −0.05 cm −1 for 1, J = −1.28 cm −1, J′ = −0.11 cm −1 and D = 9.50 cm −1 for 2, and J = −10.26 cm −1, J′ = −0.06 cm −1 for 3.

Alkyl Group as Entropy Reservoir in an MMX Chain Complex, Pt2(n-PenCS2)4I

Heat capacity of halogen-bridged one-dimensional binuclear metal complex (so-called MMX chain) having four n-pentyl groups, Pt2(n-PenCS2)4I, was measured by adiabatic calorimetry. A first-order phase transition was observed at 207.4 K when measurement was made after cooling from room temperature. The enthalpy and entropy of transition were determined to be 10.19 kJ mol(-1) and 49.1 J K(-1) mol(-1), respectively. A monotropic phase transition was observed at 324 K on heating, and the entropy of transition was essentially null. The sample once heated above 324 K never returned to the initial phase at room temperature and underwent a higher-order phase transition at 173 K and a first-order phase transition at 220.5 K. The enthalpy and entropy of the first-order phase transition were estimated to be 11.6 kJ mol(-1) and 52.4 J K(-1) mol(-1), respectively. The magnitude of the entropy gain at the phase transition from the initial room-temperature phase to the high-temperature phase at 324 K shows that in Pt2(n-PenCS2)4I a large amount of entropy reserved in alkyl chain is transferred to dithiocarboxylato groups upon the phase transition, as in the cases of Pt2(n-PrCS2)4I and Pt2(n-BuCS2)4I.

Shear stress effects on electronic spectra on the one-dimensional bis(diphenylglyoximato)metal (II) complexes, M(dpg)2 [M=Ni and Pt] under high pressure

We have developed a new sapphire-anvil cell to generate shear stress at high pressures. The new cell is similar to a diamond-anvil cell. Bis(diphenylglyoximato)metal(II), M(dpg)2(M = Ni and Pt) are pressure-sensitive one-dimensional metal complexes. By use of this cell we have observed in situ the shear stress effect on a thin film of M(dpg)2 under the microscope. Furthermore, electronic absorption spectra of both complexes have been simultaneously measured under applied shear deformation and non-hydrostatic conditions. When the pressure is increased, the color of a thin film of Pt(dpg)2 turns from red-brown at ambient pressure to green at 0.4 GPa. One sapphire anvil is rotated by applied force in order to generate the shear stress at 0.4 GPa. The color of the thin film changes remarkably from green to yellow at the outer part on the anvil, but the color at the center is green, insensitive to the shear stress. The region changed by the shear stress can be observed with the naked eye. Absorption spectra of the yellow region at the outer part change markedly; the intensity of the d-p band decreases sharply and this peak abruptly shifts to the near-infrared region. On the other hand, electronic spectra at the center part are insensitive to the shear deformation. The similar shear stress effect on the optical spectrum of Ni(dpg)2 is also observed. We have found that electronic states of M(dpg)2 essentially change by applying shear deformation.(Contributed by Hiroo INOKUCHI, M. J. A., Nov. 12, 2003)

Synthesis, characterisation, crystal structures, and magnetic properties of one-dimensional oxalato-bridged metal(II) complexes with 3-hydroxypyridine and isoquinoline

One-dimensional oxalato-bridged metal(II) compounds of formula [M(μ-ox)(L) 2] n [L=3-hydroxypyridine (pyOH) or isoquinoline (isq)] have been synthesised and characterised by FT-IR spectroscopy, TG-DTA techniques, variable-temperature magnetic measurements and X-ray diffraction methods. The complexes [M(μ-ox)(pyOH) 2] n [M=Co ( 1), Ni ( 2)] are isomorphous and crystallise in the orthorhombic space group Pnab. The compounds [M(μ-ox)(isq) 2] n [M=Co ( 3), Ni ( 4), Cu ( 5)] are also isomorphous and belong to the monoclinic space group C2/ c. Crystal structures consist of zig-zag chains in which cis-[M(L) 2] 2+ units are sequentially bridged by bis-bidentate oxalato ligands with intrachain M⋯M distances in the range 5.38–5.49 Å. The divalent metal centres have a distorted octahedral coordination with four oxygen atoms from two symmetry-related bridging oxalato ligands and the pyridinic nitrogen atoms from two cis-oriented aromatic ligands. Magnetic susceptibility measurements in the temperature range 2.0–300 K show the occurrence of antiferromagnetic intrachain interactions for the compounds 1– 4 and a weak ferromagnetic coupling for 5.

Syntheses, crystal structures, and magnetic properties of one-dimensional oxalato-bridged Co(II), Ni(II), and Cu(II) complexes with n-aminopyridine (n = 2-4) as terminal ligand.

The reaction of M(ox) x 2H(2)O (M = Co(II), Ni(II)) or K(2)(Cu(ox)(2)) x 2H(2)O (ox = oxalate dianion) with n-ampy (n = 2, 3, 4; n-ampy = n-aminopyridine) and potassium oxalate monohydrate yields one-dimensional oxalato-bridged metal(II) complexes which have been characterized by FT-IR spectroscopy, variable-temperature magnetic measurements, and X-ray diffraction methods. The complexes M(mu-ox)(2-ampy)(2) (M = Co (1), Ni (2), Cu (3)) are isomorphous and crystallize in the monoclinic space group C2/c (No. 15), Z = 4, with unit cell parameters for 1 of a = 13.885(2) A, b = 11.010(2) A, c = 8.755(1) A, and beta = 94.21(2) degrees. The compounds M(mu-ox)(3-ampy)(2).1.5H(2)O (M = Co (4), Ni (5), Cu (6)) are also isomorphous and crystallize in the orthorhombic space group Pcnn (No. 52), Z = 8, with unit cell parameters for 6 of a = 12.387(1), b = 12.935(3), and c = 18.632(2) A. Compound Co(mu-ox)(4-ampy)(2) (7) crystallizes in the space group C2/c (No. 15), Z = 4, with unit cell parameters of a = 16.478(3) A, b = 5.484(1) A, c = 16.592(2) A, and beta = 117.76(1) degrees. Complexes M(mu-ox)(4-ampy)(2) (M = Ni (8), Cu (9)) crystallize in the orthorhombic space group Fddd (No. 70), Z = 8, with unit cell parameters for 8 of a = 5.342(1), b = 17.078(3), and c = 29.469(4) A. All compounds are comprised of one-dimensional chains in which M(n-ampy)(2)(2+) units are sequentially bridged by bis-bidentate oxalato ligands with M.M intrachain distances in the range of 5.34-5.66 A. In all cases, the metal atoms are six-coordinated to four oxygen atoms, belonging to two bridging oxalato ligands, and the endo-cyclic nitrogen atoms, from two n-ampy ligands, building distorted octahedral surroundings. The aromatic bases are bound to the metal atom in cis (1-6) or trans (7-9) positions. Magnetic susceptibility measurements in the temperature range of 2-300 K show the occurrence of antiferromagnetic intrachain interactions except for the compound 3 in which a weak ferromagnetic coupling is observed. Compound 7 shows spontaneous magnetization below 8 K, which corresponds to the presence of spin canted antiferromagnetism.

Franz–Keldysh oscillation in the interband absorption spectrum of one-dimensional bis(dimethylglyoximato)platinum(II) complex

The electronic structure of a one-dimensional metal complex, bis(dimethylglyoximato)platinum(II), was investigated by measurements of photoconductivity and electroabsorption (EA). The EA spectrum exhibited a large oscillatory signal just above the excitonic absorption band. The position of the oscillatory EA signal was located near the onset of the photoconductivity, and the oscillation profile showed field-dependent broadening. These features can be explained as the characteristics of the Franz–Keldysh (FK) effect. The oscillatory EA signal is reproducible by a numerical calculation of the FK effect, in which the effect of the one-dimensionality of this electronic system is taken into account.

Mix-Crystallization of Two Dioxime Platinum Complexes by Coevaporation for Synthesizing One-Dimensional Superstructure

Mixed crystals of the one-dimensional metal complexes, bis(dimethylglyoximato)platinum(II) and bis(diethylglyoximato)platinum(II), were synthesized by a coevaporation technique. The continuous energy shift of the d−p transition was observed in the UV−vis absorption spectra of the coevaporated films. This energy shift shows that despite the difference in the crystal lattices between the two precursor complexes, both the metal complexes had mixed into the same column forming one-dimensional superstructures. Conventional X-ray diffraction and total reflection X-ray diffraction measurements showed that the anisotropic variation of the lattice constants depends on the mixing ratio. While the lattice constant parallel to the columns was approximately proportional to the mixing ratio, the variation of the constants perpendicular to the columns deviated substantially from a linear relation. This indicates that the one-dimensional framework of the mixed columns was maintained even though there is significant lattice mismatch between the precursor metal complexes.

Ultrafast relaxation processes of excitons in one-dimensional platinum complexes

Optical response due to the photo-excited carrier or exciton dynamics in the excited state of a one-dimensional metal complex (Pt(dmg) 2) has been investigated by femtosecond pump-probe spectroscopy. Measurements were made under various excitation photon energies within the absorption band which originates from the delocalized electronic states along the 1-D chain. Around the lowest-energy absorption peak, absorption bleaching was found to be larger and its decay faster compared to those in higher-energy region. Furthermore, an induced absorption which is considered to be due to a bi-exciton or relaxed excited state was observed.

Nonlinear Refractive Indices of One-Dimensional Metal Complexes by z-Scan Method

Z-scan measurements using a tunable picosecond laser were performed on one-dimensional metal complexes to investigate the nonlinear refraction and nonlinear absorption. Nonlinear refractive indices were measured to be positive/negative at wavelengths shorter/longer than the excitonic peak. Strong saturable absorption was noticeable on resonance, although small induced absorption was observed at the absorption tail. Optical nonlinearities were enhanced due to the resonance effect to give the maximum values of -8. 1× 10−7 esu and -6.7 × 10−7 esu for Re χ(3) and Im χ(3), respectively.

Femtosecond Spectroscopy of One-Dimensional Metal Complexes

We have investigated the temperature dependence of the absorption spectrum of the one-dimensional metal complex (Pt(dmg)2) and the relaxation dynamics of its photo-excited states using a femtosecond pump-probe method. At lower temperature than 150K, four peaks(P1-P4) appear in the region of the absorption band due to the metal chain, where P1 and P2 are dominant components in the absorption at 90K although they are very small at 300K. In the pump and probe spectroscopy at 90K, the bleaching first rises up very rapidly(<200fs) and decays within 1ps in the energy region of P1. This is followed by slower rise-up with the time constant of 60ps. The slow component of the bleaching is due to the increase of the lattice temperature. The relaxation processes in Pt(dmg)2 are discussed.

Third-order nonlinear optical properties of one-dimensional metal complexes by the pump-probe method

Various metal complexes have received attention for their large third order nonlinear susceptibilities. Thin films of d 8 transition metal complexes with dionedioxime have been shown to form stacks perpendicular to the molecular plane, with the central metal ions forming a quasi-one dimensional chain of delocalized electrons. Results of wavelength dependent pump-probe measurements on these materials are presented, along with interpretation in terms of saturation of the lowest excitonic transition.

Alloying of Linear Metal Chains in the One-Dimensional Metal Complexes and Their THG Property

Abstract Alloying of metals forming linear chains in the one-dimensional metal complexes was performed by use of vacuum evaporation technique. Mixture of two different metal complexes with dimethylglyoxime could be fabricated into a thin film with optical quality. They showed a strong d-p transition band in the visible region, and their peak wavelengths subsequently varied in proportion to the mixing ratio of metal complexes. Their third-order nonlinear optical property was also investigated by third-harmonic generation measurements.

Reversible control of the nonlinear optical activity of one-dimensional metal complexes

Reversible controllability of the third-order nonlinear optical activity has been demonstrated on a one-dimensional metal complex. Iodine penetration to a film sample causes disappearance of the d-p transition absorption band of the metal complex and remarkable decline of two-odd orders in the third-order nonlinear susceptibility. The deactivated optical nonlinearity was completely restored by removing iodine from the film with heating. The observed alterations in optical nonlinearities are mainly caused by the fluctuation of metal-metal interaction in the linear metal chain.