Molecular Cluster Complexes Research Articles

Синтез, строение и физико-химические свойства молекулярных кластерных комплексов рения с терминальными лигандами — молекулами 4-фенилпиридина

Четыре новых кластерных комплекса рения с общей формулой транс-[Re6Q8(ppy)4X2]n(ppy) (Q = S, Se; X = Cl, Br; ppy = 4-фенилпиридин) получены взаимодействием солей Csn[Re6Q8X6]·2H2O (Q = S, n = 4; Q = Se, n = 3; X = Cl или Br) с расплавом 4-фенилпири­дина. Исследование монокристаллов соединений методом РСА показало, что их структуры содержат молекулярные фрагменты транс-[Re6Q8(ppy)4X2], упакованные вместе с сольватными молекулами 4-фенилпиридина и связанные с этими молекулами слабыми взаимодействиями, которые включают водородные связи и p-стекинг ароматических колец. Обнаружено, что тип упаковки различается для разных галогенидных и халькогенидных лигандов кластерного комплекса. Полученные соединения нерастворимы в воде и органических растворителях. Изучение люминесценции кристаллических образцов показало, что вещества проявляют эмиссию в красной области спектра с максимумами на 708—718 нм, квантовыми выходами эмиссии 0.01—0.03 и временами жизни эмиссии порядка 4 мкс. В электронной структуре соединений присутствуют лигандцентрированные уровни LUMO—LUMO+3, локализованные между металлцентрированными HOMO и LUMO+4.

Dynamics of three-particle fragmentation of (CO2)23+ ions produced by intense femtosecond laser fields

In a momentum coincidence measurement experiment, we studied the three-body fragmentation dynamics of carbon dioxide dimers in intense femtosecond laser fields. The three-dimensional momentum vectors and kinetic energies of the fragments were recorded in a cold-target recoil-ion momentum spectrometer. An analysis shows that ${({\mathrm{CO}}_{2})}_{2}{}^{3+}$ breaks up into ${\mathrm{CO}}_{2}{}^{+}+{\mathrm{CO}}^{+}+{\mathrm{O}}^{+}$ ions through both concerted and sequential fragmentation channels. These two fragmentation channels are consistent with the instantaneous and metastable dissociation channels in the dissociation dynamics of ${\mathrm{CO}}_{2}{}^{2+}$ ion breakup into ${\mathrm{CO}}^{+}$ and ${\mathrm{O}}^{+}$ ions. From Coulomb explosion imaging, our results show that, for the parallel sliding structure of the carbon dioxide dimer molecules, the angle between the C=O bond and the van der Waals bond is $48{}^{\ensuremath{\circ}}$, and the intermolecular nuclear distance $R({\mathrm{CO}}_{2}\text{\ensuremath{-}}{\mathrm{CO}}_{2})$ is 4.0 \AA{}. By tracing the direction of the fragmentation ions, the ${\mathrm{O}}^{+}$ was found to be produced from the C=O bond that is closer to the center of the C-C bond during direct dissociation. These results indicate that the dynamic characteristics of the monomer is retained and gives rise to new dynamics in the molecular cluster complexes. Finally, we have measured angular distributions of ion fragments produced by different dissociation channels of ${({\mathrm{CO}}_{2})}_{2}$, and the results reveal that the structure of the dimer and its relative orientation in the laser field govern the ionization dynamics.

Ultrafast Dissociation of Metastable CO^{2+} in a Dimer.

We triply ionize the van der Waals bound carbon monoxide dimer with intense ultrashort pulses and study the breakup channel (CO)_{2}^{3+}→C^{+}+O^{+}+CO^{+}. The fragments are recorded in a cold target recoil ion momentum spectrometer. We observe a fast CO^{2+} dissociation channel in the dimer, which does not exist for the monomer. We found that a nearby charge breaks the symmetry of a X^{3}Π state of CO^{2+} and induces an avoided crossing that allows a fast dissociation. Calculation on the full dimer complex shows the coupling of different charge states, as predicted from excimer theory, gives rise to electronic state components not present in the monomer, thereby enabling fast dissociation with higher kinetic energy release. These results demonstrate that the electronic structure of molecular cluster complexes can give rise to dynamics that is qualitatively different from that observed in the component monomers.

Metal- and Ligand-Supported Reduction of the {Fe2S2} Cluster as a Path to Formation of Molecular Group 13 Element Complexes {Fe2S2M} (M = Al, Ga)

The first examples of molecular cluster complexes with the Fe2S2(CO)6 moiety covalently bound to the group 13 elements Al and Ga have been synthesized and characterized. The complexes [(Cp*M)Fe2(μ3-S)2(CO)6] with M = Al (1), Ga (2) have been synthesized by the reduction of [Fe2S2(CO)6] by the corresponding M(I) complexes [AlCp*]4 and [GaCp]. Analogously, upon reduction of [Fe2S2(CO)6] by a Ga(II) complex, [(dpp-Bian)Ga]2 (dpp-Bian = 1,2-bis{(2,6-diisopropylphenyl)imino}acenaphthene), the compound [((dpp-Bian)Ga)Fe2(μ3-S)2(CO)6] (3) is formed. The M atoms in 1 and 2 are coordinated by the two S atoms; thus, the fragment Fe2S2(CO)6 is considered to be dianionic. The Cp* moiety is bound differently to the Al (η5) and Ga (η2) atoms, which can be rationalized on the basis of DFT calculations showing different orbital structures for the analogous compounds. In compound 3 the Ga atom is coordinated by the two S atoms as well; therefore, the fragment Fe2S2(CO)6 is considered to be dianionic, while the Bian ligand is radical anionic, as confirmed by the structure, EPR spectra, and DFT. The redox-active Bian ligand thus takes part in the reduction of the Fe2S2 cluster and changes its formal charge (−2 → −1), along with the Ga center (+2 → +3). Analogously to 3, the Al complex [((dpp-Bian)Al)Fe2(μ3-S)2(CO)6] (4) is formed in solution and detected by EPR, but it is not stable enough to be crystallized. In contrast to the case for 1 and 2, the calculated molecular and electronic structures of 3 and 4 are similar.

New Hexanuclear Niobium Cluster Compounds with Pyridine and N‐Methylpyrrolidone Ligands: [Nb6Cl12(Pyr)6][AlCl4]2 and [Nb6Cl12(NMP)6][GaCl4]2

AbstractThe study is focused on the preparation, characterization, and structure elucidation of two new molecular cluster complexes of niobium, one with an aromatic N donor ligand, the other one with an O‐carboxamide ligand: [Nb6Cl12(Pyr)6][AlCl4]2 (1) (Pyr = pyridine) and [Nb6Cl12(NMP)6][GaCl4]2 (2) (NMP = N‐methyl‐pyrrolidone). The synthesis of such substituted niobium cluster compounds, starting from easily accessible A4I[Nb6Cl18] (AI = alkali metal cation) materials is best done using a two‐step protocol. First the solid state precursor is heated together with acetonitrile and in the second step the ligand exchange is performed. The molecular structures of 1 and 2 in the solid state were determined by single‐crystal X‐ray diffraction. The infrared spectrum of 1 was recorded as well.

Crystal structures of trans-[Re6S8(CN)2L4] complexes, L = pyridine or 4-methylpyridine

The structures of three novel octahedral rhenium cluster compounds [Re6S8(CN)2(py)4]·H2O (1), [Re6S8(CN)2(4-Mepy)4] (2), [Re6S8(CN)2(4-Mepy)4]·4-Mepy (3) (py = pyridine, 4-Mepy = 4-methylpyridine) are determined by X-ray crystallography. Crystal data are: C2/m space group, a = 14.813(1) A, b = 14.772(1) A, c = 9.2122(6) A, β = 119.085(2)°, V = 1761.7(2) A3, dx = 3.318 g/cm3, R = 0.0585 (1); I41/amd space group, a = 16.0018(3) A, c = 14.7186(5) A, V = 3768.81(16) A3, dx = 3.169 g/cm3, R = 0.0489 (2); P21/c space group, a = 9.0452(4) A, b = 15.8065(7) A, c = 15.2951(6) A, β = 103.700(2)°, V = 2124.57(16) A3, dx = 2.957 g/cm3, R = 0.0245 (3). Molecular cluster complexes interact via π-π stacking affording 3D frameworks in 1 and 2 and chains in 3.

Neutron Diffraction Studies on a 4-Coordinate Hydrogen Atom in an Yttrium Cluster

A four-coordinate hydrogen atom has been unambiguously located, by single-crystal neutron diffraction for the first time, in the center of the tetrahedral metal complex Y4H8(Cp')4(THF) [Cp'=C5Me4(SiMe3)]. The core of the molecule consists of a tetranuclear cluster with one interstitial, one face-bridging, and six edge-bridging hydride ligands. The compound was prepared via the reaction of YCp'(CH2SiMe3)2(THF) with gaseous H2. Neutron data were collected on a 4 mm3 crystal at the Quasi-Laue diffractometer VIVALDI at ILL (Grenoble)1a and on an 8 mm3 crystal at the SXD diffractometer at ISIS (Didcot). The final agreement factor is R = 8.9% for 4171 reflections. The existence of 4-coordinate hydrogen now completes the series of high-connectivity hydride ligands located in the interstitial cavities of molecular cluster complexes. We had previously reported the existence of 6-coordinate hydrogen in the octahedral cavity of [HCo6(CO)15]- in 1979, and 5-coordinate hydrogen in the square pyramidal cavities of [H2Rh13(CO)24]3- in 1997, also via single-crystal neutron analyses.

W6S8 Inorganic Clusters with Organic TTF Derivative Ligands: in Pursuit of Multidimensional Conductive Networks

A series of new molecular cluster complexes with TTF derivative ligands attached to an inorganic W6S8 core were prepared, namely W6S8(PEt3-nTTFn)6 (n = 1, 2). By incorporating two useful structural motifs (the well-known π−π stacking geometry of TTF molecules and the high symmetry of octahedral clusters) into one network structure, we constructed multidimensional networks. Single-crystal X-ray diffraction studies revealed intercluster TTF π-contacts in one and two dimensions, for W6S8(PEt2TTF)6 and W6S8(PEtTTF2)6, respectively. The redox properties of W6S8(PEt2TTF)6 were studied by cyclic voltammetry. Mid- and far-IR and XPS (X-ray photoelectron spectroscopy) characterizations were performed on both the W6S8(PEt2TTF)6 cluster and its oxidized product, which helped to elucidate the identity of the poorly crystalline oxidized product. Four-point contact electrical conductivity measurements were performed on a pressed pellet of the oxidized powder product W6S8(PEt2TTF)6·xPF6 (x ≈ 5) with σRT ≈ 1 × 10-4 S cm-1, whereas the neutral cluster complex is insulating at room temperature.

Molecular Cluster Complexes with Facial Arene Ligands

AbstractFor Abstract see ChemInform Abstract in Full Text.

A strong metal-support interaction between mononuclear and polynuclear transition metal complexes and oxide supports which dramatically affects catalytic activity

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA strong metal-support interaction between mononuclear and polynuclear transition metal complexes and oxide supports which dramatically affects catalytic activityDennis A. Hucul and Alan BrennerCite this: J. Phys. Chem. 1981, 85, 5, 496–498Publication Date (Print):March 1, 1981Publication History Published online1 May 2002Published inissue 1 March 1981https://doi.org/10.1021/j150605a009RIGHTS & PERMISSIONSArticle Views178Altmetric-Citations58LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (454 KB) Get e-Alerts