Biologically inspired 3Fe4S cluster as structural mimics of FeMoco M-cluster

A 3Fe4S cluster related to M-cluster of Mo-nitrogenase is reported. [K(THF)₅][Fe₃(μ-bdt)₂(μ-PPh₂)(CO)₅] ( 1 ) is synthesized from photo-assisted structural rearrangement of [K(THF)₂][(μ,κ²-bdt)Fe₂(μ-PPh₂)(CO)₅] under visible light irradiation. The molecular structure of 1 consists of a Fe₃ core bearing one dithiolate bridge and the second dithiolate group capping onto the metallic plane. The structural motif of 1 is analogous to that of Mo-participated 3Fe4S unit in M-cluster of Mo-nitrogenase, with the similar Fe-Fe and Fe-S bond distances. Upon protonation in 193 K, a Fe-hydride species ( 1H ) is generated and characterized to possess the bridging hydride group (δ = −12.57 ppm) by ¹H-NMR spectroscopy and DFT calculation. In CH₃CN solution, complex 1 exhibits a reversible reduction and oxidation process at $E_{1/2}^{\mathrm{red}}$ = −1.94 V and $E_{1/2}^{\mathrm{ox}}$ = −0.18 V, respectively, at 273 K. The reduction behavior of 1 in CH₂Cl₂ solution at 243 K displays a slight modification in the presence of trifluoroacetic acid, revealing a moderate anodic potential shift (~50 mV). The current amplitude of the reduction wave is linearly increased with the increasement of acid added, indicative of the catalytic event.     

UF4 and the High-Pressure Polymorph HP-UF4

A laboratory-scale synthesis of UF₄ is presented that utilizes the reduction of UF₆ with sulfur in anhydrous hydrogen fluoride. An excess of sulfur can be removed by vacuum sublimation, yielding pure UF₄, as shown by powder X-ray diffraction, micro X-ray fluorescence analysis, infrared and Raman spectroscopy, as well as magnetic measurements. Furthermore, a single-crystalline, high-pressure modification of UF₄ was obtained in a multi-anvil press at elevated temperatures. The high-pressure polymorph HP-UF₄ was characterized by means of single-crystal and powder X-ray diffraction, as well as by magnetic measurements, and presents a novel crystal structure type. Quantum-chemical calculations show the HP-modification to be 10 kJ mol⁻¹ per formula unit higher in energy compared to UF₄.     

Hydrogen-bonded 1D and 2D Assemblies of Tetraiso-butyl-resorcin[4]arene in the Crystalline State

1 INTRODUCTION There is continuing interest in the assembly of molecular capsules based on concomitant formation of multiple hydrogen bonds between smaller mole- cular components[1]. A particularly attractive buil- ding block is calix[4]resorcinarenes with eight pen- dant hydroxyl functional groups[2]. In a crystal engi- neering design strategy for molecular self-assembly, cocrystallization of C-methylcalix[4]resorcinarenes with nitrogen-donor molecules such as pyridines in the presence …     

Noble-Gas Difluoride Complexes of MOF4 (M=Mo,W); Syntheses,Structures and Bonding of NgF2 ⋅ MOF4 and XeF2 ⋅ 2MOF4 (Ng=Kr,Xe)

The NgF₂ ⋅ MOF₄ (Ng=Kr, Xe; M=Mo, W) and XeF₂ ⋅ 2MOF₄ complexes were synthesized in anhydrous HF (aHF) solvent and melts, respectively. Their single-crystal X-ray diffraction (SCXRD) structures show NgF₂ ⋅ MOF₄ and XeF₂ ⋅ 2MOF₄ have F_t−Ng−F_b- - -M arrangements, in which the NgF₂ ligands coordinate to MOF₄ through Ng−F_b- - -M bridges. The XeF₂ ligands of XeF₂ ⋅ 2MOF₄ also coordinate to F₃OM−F_b’- - -M'OF₄ moieties through Xe−F_b- - -M bridges to form F_t−Xe−F_b- - -M(OF₃)−F_b’- - -M'OF₄, where XeF₂ coordinates trans to the M=O bond and F_b’ coordinates trans to the M’=O bond. The Ng−F_t, Ng−F_b, and M- - -F_b bond lengths of NgF₂ ⋅ nMOF₄ are consistent with MOF₄ and F₃OM−F_b’- - -M'OF₄ fluoride-ion affinity trends: CrOF₄<MoOF₄<WOF₄≈F₃OMo−F_b’- - -Mo'OF₄<F₃OW−F_b’- - -W'OF₄. The [- -(F₄OMo)(μ₃-F)H- - -(μ-F)H- -]_∞ solvate was also synthesized in aHF and characterized by SCXRD. Quantum-chemical calculations show the M- - -F_b bonds of NgF₂ ⋅ MOF₄ and XeF₂ ⋅ 2MOF₄ are predominantly electrostatic, σ-hole type bonds.     

Spectral and thermal studies on copper(II) complexes of acenaphthaquinonemono(4-methylquinolinyl) hydrazone

Cu(II) complexes of acenaphthaquinonemono(4-methylquinolinyl)hydrazone (AMH) of general composition [CuLX₂] (whereL=AMH;X=Cl, Br, I, OAc or NO₃) with the exception of sulphato complex, where the composition is found to be [CuLSO₄]₂ have been synthesized and characterized by elemental analyses, magnetic moment measurements, conductivity measurements, IR, electronic and EPR spectral techniques and by thermal analysis. A planar geometry is indicated for all the complexes. TG curves show one step decomposition of complexes and formation of CU₂O at the end of the step.One of the author (P.K.S.) is thankful to UGC, New Delhi (India), for providing financial assistance and is also indebted to the Department of Chemistry, University of Delhi, Delhi (India) for providing the necessary laboratory facilities.     

One-dimensional Hydrogen-bonded Polymer Based on Tetra-iso-butyl-resorcin[4]arene and 2,6-Diacetylpyridine

1INTRODUCTIONResorcin[4]arenesarecavity-shapedmacro-cycleswhichcanbeeasilysynthesizedfromresor-cinolandaldehydesinthepresenceofacidiccataly-sis[1].Theyareattachedmuchinterestinthefieldofsupramolecularchemistryasartificialreceptorsandstartingmaterialsforthepreparationofmoresophis-ticatedmolecules[2].Duetotheirstructuralfeaturestheyplayanimportantroleashostmoleculesforavarietyofneutralandchargedguestcompounds[3].Theresorcin[4]arenesusuallyadoptfourdifferentcon-formers,crown(rccc,C4),boat(rc…     

4-氨基邻苯二甲酰亚胺衍生物作为荧光探针的应用

介绍了近年来4-氨基邻苯二甲酰亚胺(AP)类荧光探针在主-客体化学、金属离子测定、溶剂化动力学及各种有序分子聚集体(如胶束、反胶束)性质研究方面的进展。     

Ni[B2(SO4)4] and Co[B2(SO4)4]: Unveiling Systematic Trends in Phyllosilicate Analogue Borosulfates

Borosulfates are compounds analogous to silicates, with heteropolyanionic subunits of vertex-linked (SO₄)- and (BO₄)-tetrahedra. In contrast to the immense structural diversity of silicates, the number of borosulfates is yet very limited and the extent of their properties is still unknown. This is particularly true for representatives with phyllosilicate and tectosilicate analogue anionic substructures. Herein, we present Ni[B₂(SO₄)₄] and Co[B₂(SO₄)₄], two new borosulfates with phyllosilicate analogue topology. While the anionic subunits of both structures are homeotypic, the positions of the charge compensating cations differ significantly: Ni^II is located between the borosulfate layers, while Co^II—in contrast—is embedded within the layer. Detailed analysis of these two structures based on single-crystal X-ray diffraction, magnetochemical investigations, X-ray photoelectron spectroscopy, and quantum chemical calculations, unveiled the reasons for this finding. By in silico comparison with other divalent borosulfates, we uncovered systematic trends for phyllosilicate analogues leading to the prediction of new species.     

Stabilizing the LaCoAl4 Structure through Indium‐Magnesium Substitution in CeRhIn4−xMgx (x = 0.79 and 0.84) – An Indide with Magnesium Centered Indium Cubes

The intermetallic compounds CeRhIn_4?xMg_x (x = 0.79 and 0.84) were prepared from the elements in sealed tantalum ampoules in a high‐frequency furnace. The samples were investigated by X‐ray powder and single crystal diffraction: LaCoAl₄ type, Pmma, a = 829.5(2), b = 433.56(9), c = 740.2(2) pm, wR2 = 0.0458, 651 F² values, 25 variables for CeRhIn_3.21Mg_0.79 and a = 831.44(10), b = 433.49(10), c = 741.04(10) pm, wR2 = 0.0543, 915 F² values, 25 variables for CeRhIn_3.16Mg_0.84. The indium atoms build up two‐dimensional networks perpendicular to the b axis in an AA stacking sequence leaving slightly distorted trigonal, square and pentagonal prismatic voids for the rhodium, magnesium, and cerium atoms. Both square prismatic voids show small magnesium/indium mixing. The shortest interatomic distances occur for the Rh–Mg contacts (257 pm). Together, the rhodium, indium, and magnesium atoms build up three‐dimensional [RhIn_4?xMg_x] networks in which the cerium atoms fill distorted pentagonal channels.     

Pocket and antipocket conformations for the CH4@C84 endohedral fullerene

The endohedral fullerene CH₄@C₈₄ has been studied using density functional theory (DFT) and second‐order Møller–Plesset perturbation theory (MP2). In addition to the structure with a C? H bond of CH₄ in a tetrahedral pocket conformation, we find an alternative minimum, very close in energy (6.3–9.5 kJ/mol higher according to the level of theory), with the methane inverted, which we call the antipocket conformation. Computed IR spectra are reported for CH₄@C₈₄ and also for the reference system CH₄@C₆₀. The calculated vibrational levels, in a harmonic approximation, reveal close‐lying translational, librational, and shell‐vibrational modes. The results are also presented for the isoelectronic species NH@C₆₀. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

A Systematic Survey of the Reactivity of Chlorinated N2P2, NP3 and P4 Ring Systems

The reactivity of the four-membered NP₃ ring system [RN(μ-PCl)₂PR] (R=Mes*=2,4,6-tri-tert-butylphenyl) towards Lewis acids, Lewis bases, and reducing agents was investigated. Comparisons with the literature-known, analogous cyclic compounds [ClP(μ-NR)]₂ (R=Ter=2,6-dimesitylphenyl) and [ClP(μ-PR)]₂ (R=Mes*) are drawn, to obtain a better systematic understanding of the reactivity of cyclic NP species. Apart from experimental results, DFT computations are discussed to further the insight into bonding and electronic structure of these compounds.     

Plasma-chemical reactions in weakly decomposed CCl4

For the case of weak feed gas decomposition, where the concentration of CCl₄ exceeds those of decomposition and built-up products, the emission of CCl* is shown to originate from dissociative excitation of CCl₄. With electron concentration measured independently, the kinetics of CCl₄ decomposition has been extracted from the time dependence of the CCl* intensity. Supported by EPR determinations of radical concentrations in rapidly flowing CCl₄ and CCl₄/O₂ afterglows, the primary decomposition reaction is shown to be the electron impact dissociation into CCl₃ and Cl. Its rate constant (k ₁=4×10^–8 cm³s^–1) indicates strongly that dissociative electron attachment is the main reaction channel at least at r.f. power densities just above the threshold of a self-maintaining discharge. At extremely low mean electron energies the emission of a continuum is observed, which is tentatively ascribed to the radiative CCl₃-Cl recombination.