3D framework containing Cu4Br4 cubane as connecting node with strong ferroelectricity

The methanolothermal reaction of (S)-1,4-diallyl-2-methylpiperazine (DAMP) with an excess CuBr affords a novel homochiral 3D framework (DAMP)3(Cu4Br4)2(H2O)3 (1) in which Cu4Br4 cubane acts as a connecting node to mimic the pure inorganic role in the ferroelectricity to enhance the remnant polarization value which is comparable to that of BaTiO3 synthesized by peptide-assisted synthesis.     

Electronic transitions involved in the absorption spectrum and dual luminescence of tetranuclear cubane [Cu4I4(pyridine)4] cluster: a density functional theory/time-dependent density functional theory investigation

We present a combined density functional theory (DFT)/time-dependent density functional theory (TDDFT) study of the geometry, electronic structure, and absorption and emission properties of the tetranuclear "cubane" Cu4I4py4 (py = pyridine) system. The geometry of the singlet ground state and of the two lowest triplet states of the title complex were optimized, followed by TDDFT excited-state calculations. This procedure allowed us to characterize the nature of the excited states involved in the absorption spectrum and those responsible for the dual emission bands observed for this complex. In agreement with earlier experimental proposals, we find that while in absorption the halide-to-pyridine charge-transfer excited state (XLCT*) has a lower energy than the cluster-centered excited state (CC*), a strong geometrical relaxation on the triplet cluster-centered state surface leads to a reverse order of the excited states in emission.     

Cu6S4 cluster based twelve-connected face-centered cubic and Cu19I4S12 cluster based fourteen-connected body-centered cubic topological coordination polymers

Hydrothermal reaction of Cu(MeCO2)2, (4-pyridylthio)acetic acid and NH4SCN resulted in a twelve-connected face-centered cubic topological metal-organic framework [Cu3(pdt)2(CN)] (pdt = pyridinethiolate) in which Cu6S4 clusters act as twelve-connected nodes and pyridine rings and cyanides act as connectors. As an extension, an unprecedented fourteen-connected body-centered cubic coordination polymer [Cu19I4(pdt)12(SH)3] has been synthesized by three methods, in which nanosized chiral Cu19I4S12 clusters act as fourteen-connected nodes and triple pyridine rings and hydrosulfides act as connectors. The in situ S-C(sp(3)), S-C(sp(2)), and S-C(sp) cleavage reactions have been observed in the work.     

Probing the intrinsic electronic structure of the cubane [4Fe-4S] cluster: nature's favorite cluster for electron transfer and storage

The cubane [4Fe-4S] is the most common multinuclear metal center in nature for electron transfer and storage. Using electrospray, we produced a series of gaseous doubly charged cubane-type complexes, [Fe4S4L4]2- (L = -SC2H5, -SH, -Cl, -Br, -I) and the Se-analogues [Fe4Se4L4]2- (L = -SC2H5, -Cl), and probed their electronic structures with photoelectron spectroscopy and density functional calculations. The photoelectron spectral features are similar among all the seven species investigated, revealing a weak threshold feature due to the minority spins on the Fe centers and confirming the low-spin two-layer model for the [4Fe-4S](2+) core and its "inverted level scheme". The measured adiabatic detachment energies, which are sensitive to the terminal ligand substitution, provide the intrinsic oxidation potentials of the [Fe4S4L4]2- complexes. The calculations revealed a simple correlation between the electron donor property of the terminal thiolate as well as the bridging sulfide with the variation of the intrinsic redox potentials. Our data provide intrinsic electronic structure information of the [4Fe-4S] cluster and the molecular basis for understanding the protein and solvent effects on the redox properties of the [4Fe-4S] active sites.     

An unprecedented 8-fold interpenetrating diamondoid-like coordination polymer containing a Cu+(4)(RCO2)(4) cluster as connecting node

The reaction of Cu(I)(CH(3)CN)(4)BF(4) with 4-pyridylacrylic acid (4-HPYA) affords an unprecedented 8-fold interpenetrating diamondoid-like coordination polymer network [Cu(I)(3)(4-PYA)(2)(H(2)O)(BF(4)) ] (1) with a Cu(+)(4)(CO(2))(4) cluster as connecting node. The interpenetration in metal coordination polymers is the highest degree ever found within diamondoid nets containing a cluster as connecting note. Its fluorescent property was also reported.     

Rational design of the first closed coordination capsule with octahedral outer shape

The rational synthesis of an octahedral coordination capsule in which the triangular faces are covered by single ligands is described herein. Starting with tris(2-hydroxybenzylidene)triaminoguanidinium chloride [H(6)L]Cl, we observed an oxidative cyclization of this ligand in the presence of PPh(4) (+) ions resulting in the complex [Pd(H(2)L')(PPh(3))] (1). The use of 5,5-diethylbarbiturate (bar(2-)) as a bridging ligand in the presence of [Co(en)(3)](3+) (en=ethylenediamine) leads to the formation of a rectangular box with the formula (Et(4)N)(6)[[Co[(PdCl)(Pd)L](2)(mu-bar)](2)] (2). The analysis of the architecture of compounds 1 and 2 enables the development of a self-assembly strategy for the synthesis of an octahedral coordination cage 3 with the formula Na(4)(Et(3)NH)(12)[(Pd(3)L)(8)[mu-(bar)](12)].x H(2)O. Compound 3 was characterized by (13)C-MAS-NMR spectroscopy and single-crystal structure analysis.     

Two three-dimensional 2p-3d-4f heterometallic frameworks featuring a Ln6Cu24Na12 cluster as a node

Two three-dimensional 2p-3d-4f heterometallic frameworks featuring a nanosized Ln(6)Cu(24)Na(12) (Ln = Gd, Dy) cluster as a node have been obtained under microwave irradiation conditions through the reaction of H(2)ANMA (H(2)ANMA = L-alanine-N-monoacetic acid), Cu(NO(3))(2), and Ln(NO(3))(3) (Ln = Gd for 1, Dy for 2) with NaOH in deionized water. Investigations on the magnetic properties show that 1 exhibits ferrimagnetic behavior. The electrical conductivity measurements reveal that 1 behaves as a proton conductor.     

Cleavage of C-S bonds with the formation of a tetranuclear Cu(I) cluster

The treatment of a ligand, 2,6-bis((4-(pyridin-2-yl)pyrimidin-2-ylthio)methyl)-4-chlorophenol (ClPPT2), with cuprous chloride under a weak base condition led to the formation of a neutral CuI4-centered cluster [Cu4(PPT2)4], whose X-ray diffraction analysis indicated that C-S bonds of the ligand were cleaved in the course of the reaction. To explain the C-S bond cleavage, a reasonable mechanism has been proposed. In support of it, four additional ligands, 2,6-bis((4-(pyridin-2-yl)pyrimidin-2-ylthio)methyl)-4-methylphenol (MePPT2), 2,6-bis((4-(pyridin-3-yl)pyrimidin-2-ylthio)methyl)-4-methylphenol (MePPT3), 2,6-bis((4-(pyridin-3-yl)pyrimidin-2-ylthio)methyl)-4-chlorophenol (ClPPT3), and 5-((4-(pyridin-3-yl)pyrimidin-2-ylthio)methyl)-2-hydroxybenzaldehyde (HBPPT2) were further tested to undertake the analogous reaction, and the cleaved products in these experiments were detected by electrospray ionization mass spectrometry techniques to clarify the process.     

Computational design of tetrahedral silsesquioxane-based porous frameworks with diamond-like structure as hydrogen storage materials

A novel type of three-dimensional (3D) tetrahedral silsesquioxane-based porous frameworks (TSFs) with diamond-like structure was computationally designed using the density functional theory (DFT) and classical molecular mechanics (MM) calculations. The hydrogen adsorption and diffusion properties of these TSFs were evaluated by the methods of grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The results reveal that all designed materials possess extremely high porosity (87–93 %) and large H₂ accessible surface areas (5,268–6,544 m² g^?1). Impressively, the GCMC simulation results demonstrate that at 77 K and 100 bar, TSF-2 has the highest gravimetric H₂ capacity of 29.80 wt%, while TSF-1 has the highest volumetric H₂ uptake of 65.32 g L^?1. At the same time, the gravimetric H₂ uptake of TSF-2 can reach up to 4.28 wt% at the room temperature. The extraordinary performances of these TSF materials in hydrogen storage made them enter the rank of the top hydrogen storage materials so far.     

A heterometallic, heterovalent Cu(I)/Sn(II/IV)/S cluster with an unprecedented Cu4Sn core and stannacyclopentane units

[(Ph3PCu(I))6{(CH2)4Sn(IV)S2}6Cu(I)4Sn(II)], a walnut-type, heterometallic, heterovalent cluster, as confirmed by density functional theory calculations, was obtained under reductive solvothermal conditions and features an unprecedented metalloid core within a metal sulfide shell and an organic surface.     

Cu4I4-cubane cluster based on tris(p-anisyl)arsine: Synthesis,crystal structure and photophysical properties

A new cubane cluster [Cu₄I₄(AsAn₃)₄] was synthesized in 82% yield by the reaction of tris(p-anisyl)arsine (AsAn₃) with CuI. At ambient temperature, this cluster exhibits bright yellow-green phosphorescence (λ_max = 546 nm) with the quantum yield of 35% and 4.1 μs decay time.     

X-ray emission and X-ray photoelectron studies of the electronic structure of the polymeric cubane cluster compounds Mo4S4Cl4, GaMo4S8, and GaMo4S4Te4

X-ray emission and X-ray photoelectron spectroscopy was used to study the electronic structures of the polymeric cubane cluster compounds Mo₄S₄Cl₄, GaMo₄S₈, and GaMo₄S₄Te₄. It is revealed that the ligand orbitals make significant contributions to the highest occupied molecular orbitals (M−M bonds). Substitution in the series Cl−S−Te increases the covalence of the metal—bridging ligand bonds. The experimental spectra allowed the construction of a qualitative scheme of the electronic structure of Mo₄S₄Cl₄. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 1038–1045, November–December, 1995. Translated by I. Izvekova     

Rational design and molecular diversity for the construction of anti-alpha-bungarotoxin antidotes with high affinity and in vivo efficiency

The structure of peptide p6.7, a mimotope of the nicotinic receptor ligand site that binds alpha-bungarotoxin and neutralizes its toxicity, was compared to that of the acetylcholine binding protein. The central loop of p6.7, when complexed with alpha-bungarotoxin, fits the structure of the acetylcholine binding protein (AChBP) ligand site, whereas peptide terminal residues seem to be less involved in toxin binding. The minimal binding sequence of p6.7 was confirmed experimentally by synthesis of progressively deleted peptides. Affinity maturation was then achieved by random addition of residues flanking the minimal binding sequence and by selection of new alpha-bungarotoxin binding peptides on the basis of their dissociation kinetic rate. The tetra-branched forms of the resulting high-affinity peptides were effective as antidotes in vivo at a significantly lower dose than the tetra-branched lead peptide.     

Mixed-valence Cu(II)Cu(I)15I17 cluster builds up a 3D metal-organic framework with paramagnetic and thermochromic characteristics

Four cubane-like Cu4I4 units are assembled around an iodine atom to form the giant, mixed-valent Cu(II)Cu(I)15I17 cluster. The Cu(II)Cu(I)15I17 cluster and a bipyrazole linker form a 3D open framework with paramagnetic and thermochromic properties. This paper also touches on the resemblance of this cluster to the self-similar object of a Sierpinski tetrahedron.     

Modulation of metal-metal separations in a series of Ag(I) and intensely blue photoluminescent Cu(I) NHC-bridged triangular clusters

A series of picolyl-substituted NHC-bridged triangular complexes of Ag(I) and Cu(I) were synthesized upon reaction of the corresponding ligand precursors, [Him(CH(2)py)(2)]BF(4) (1a), [Him(CH(2)py-3,4-(OMe)(2))(2)]BF(4) (1b), [Him(CH(2)py-3,5-Me(2)-4-OMe)(2)]BF(4) (1c), [Him(CH(2)py-6-COOMe)(2)]BF(4) (1d), and [H(S)im(CH(2)py)(2)]BF(4) (1e), with Ag(2)O and Cu(2)O, respectively. Complexes [Cu(3)(im(CH(2)py)(2))(3)](BF(4))(3) (2a), [Cu(3)(im(CH(2)py-3,4-(OMe)(2))(2))(3)](BF(4))(3) (2b), [Cu(3)(im(CH(2)py-3,5-Me(2)-4-OMe)(2))(3)](BF(4))(3), (2c), [Ag(3)(im(CH(2)py-3,4-(OMe)(2))(2))(3)](BF(4))(3), (3b), [Ag(3)(im(CH(2)py-3,5-Me(2)-4-OMe)(2))(3)](BF(4))(3) (3c), [Ag(3)(im(CH(2)py-6-COOMe)(2))(3)](BF(4))(3) (3d), and [Ag(3)((S)im(CH(2)py)(2))(3)](BF(4))(3) (3e) were easily prepared by this method. Complex 2e, [Cu(3)((S)im(CH(2)py)(2))(3)](BF(4))(3), was synthesized by a carbene-transfer reaction of 3e, [Ag(3)((S)im(CH(2)py)(2))(3)](BF(4))(3), with CuCl in acetonitrile. The ligand precursor 1d did not react with Cu(2)O. All complexes were fully characterized by NMR, UV-vis, and luminescence spectroscopies and high-resolution mass spectrometry. Complexes 2a-2c, 2e, and 3b-3e were additionally characterized by single-crystal X-ray diffraction. Each metal complex contains a nearly equilateral triangular M(3) core wrapped by three bridging NHC ligands. In 2a-2c and 2e, the Cu-Cu separations are short and range from 2.4907 to 2.5150 ?. In the corresponding Ag(I) system, the metal-metal separations range from 2.7226 to 2.8624 ?. The Cu(I)-containing species are intensely blue photoluminescent at room temperature both in solution and in the solid state. Upon UV excitation in CH(3)CN, complexes 2a-2c and 2e emit at 459, 427, 429, and 441 nm, whereas in the solid state, these bands move to 433, 429, 432, and 440 nm, respectively. As demonstrated by (1)H NMR spectroscopy, complexes 3b-3e are dynamic in solution and undergo a ligand dissociation process. Complexes 3b-3e are weakly photoemissive in the solid state.     

Click-triazole: coordination of 2-(1,2,3-triazol-4-yl)-pyridine to cations of traditional tetrahedral geometry (Cu(I), Ag(I))

Coordination studies of the pyridine-triazole diad to copper(i) and silver(i) reveal the potential and conditions for the solution- and solid-state self-assembly of supramolecular architectures based on this motif.