Cluster Self-assembly Research Articles

Combinatorial and topological modeling of cluster self-assembly of the crystal structure of zeolites

Combinatorial and topological modeling of packings of symmetrically connected polyhedral T12 clusters (hexagonal prisms), which are most widespread in crystal structures of zeolites, has been performed. Packings of T12 clusters are periodic 1D chains (11 types) and 2D microlayers (15 types). 2D microlayers that can be involved in the self-assembly of 3D zeolite structures described by tetracoordinated T nets are selected. Computer methods (the ToposPro program package) have been used to establish a correspondence with zeolites CHA (Chabazite, Ca6(H2O)40Al12Si24O72), AEI (AlPO-18, Al24P24O96), SAV ((C18H42N6)2(H2O)7Mg5Al19P24O96), KFI (Na30(H2O)98Al30Si66O192), GME (Gmelinite, (Ca,Na)4(H2O)24Al8Si16O48), AFX (SAPO-56, H3Al23Si5P20O96), and AFT (AlPO-52, Al36P36O144) for 7 out of 11 obtained models of 3D frameworks. Modeling of 3D polytypes of the GME (1L type)–AFX (2L type)–AFT (3L type) family has resulted in a new 3L polytype with the following crystallographic parameters: a =13.75 A, c = 30.00 A, V = 4912.0 A3, sp. gr. P\(\bar 6\)m2 (no. 187). It is established that the 2D self-assembly of known zeolite structures is accompanied by pairwise binding of all (T12 + T12) clusters with the formation of 4Т rings, and the number of bonds between complementary chains during the formation of microlayers is maximum. Three types of obtained frameworks, which have no analogs among zeolites, exhibit low chain connectivity during microlayer formation in all cases.

Symmetry and topology code (program) of crystal structure cluster self-assembly for molecular and framework compounds

This is a review over the state of art in self-organization in crystal-forming systems where a long-range order appears spontaneously in the arrangement of nanoscale structural units of any nature (atomic clusters, molecules, metal clusters), which initially existed in a dynamic state as a chaotic mixture. Combinatorial topological analysis algorithms are provided to restore, from structure data, the convergent matrix crystal structure self-assembly code in the form of the sequence of significant elementary events. The model is universal and has first been used to model the cluster self-assembly of crystal structures for all elemental compounds that are formed at the solution-solid interface and from a gas phase, namely: Cu-cF4 (FCC), Fe-cI2 (BCC), Mg-hP2 (HCP), Hg-hR1, B12-hR12, Ga-oC8,C6-hP4 (graphite, GRA),C6-cF8 (Diamond, DIA), Sn-tI4, N2-cP8, P4-mC16, As6-hR2, O3-oP24 (Ozone), S3-hP9, Se3-hP6, Po-cP1, F2-mC8, and Cl2-oC8. Cluster modeling and crystal-chemical analysis are carried out for a large crystal-chemical family NaCl-cF8. The dimorphs of TeO2-oP24 (tellurite, TEL) and TeO2-tP12 (paratellurite, PAR) and the icosahedral structures of WAl12-cI26 and sillenite Bi12SiO20-cI66 are considered. Frequency analysis of topological and symmetry pathways in the formation and evolution of clusters (from primary chain S31 through microlayer S32 to microframework S33) elucidates new crystal-formation trends in diverse chemical systems at the microscopic level.

Elucidating self-assembly mechanisms of uranyl-peroxide capsules from monomers.

Self-assembly of uranyl peroxide polyoxometalates (POMs) in alkaline peroxide solutions has been known for almost a decade, but in these dynamic solutions that contain high concentrations of base and peroxide the reaction pathway could never be discerned, mixed species are obtained, and reproducibility is sometimes a challenge. Here we elucidate the reaction mechanisms utilizing self-assembly of the U24 cluster, [UO2(O2)(OH)]24(24-), from monomers as a model system. Using Raman as our main spectroscopic probe, we learned that the monomeric species is persistent in water at room temperature indefinitely. However, if a redox-active transition metal catalyst (copper (Cu(2+)) or cobalt (Co(2+))) is added, self-assembly is accelerated in a significant manner, forming U24 peroxide clusters in several hours, which is a good time scale for studying reaction mechanisms. From semiquantitative treatment of the spectroscopic data, we elucidate reaction mechanisms that are consistent with prior structural and computational studies that suggest uranyl peroxide rings templated by alkalis are the building units of clusters. By understanding aqueous speciation and processes, we are moving toward assuming control over cluster self-assembly that has been mastered for decades now in the analogous transition-metal POM systems.

Cluster self-assembly of centered cubes of copper(I) with dialkyldithiophosphate ligands. X-ray structures of [Cu8(DDP)6(μ8-X)]PF6 (DDP = S2P(OiPr)2; X = Cl or Br) and their relationship to oxide and sulfide centered zinc(II) dialkyldithiophosphates, [Zn4(DDP)6(μ4-S or O)

A high purity synthesis of chloride-{Cu8[S2P(OiPr)2]6(μ8-Cl)}[PF6] (1) and bromide-{Cu8[S2P(OiPr)2]6(μ8-Br)}[PF6] (2) centered Cu8 cubic clusters has been achieved through the reaction of [Cu(CH3CN)4]PF6 and NH4[S2P(OiPr)2] in the presence of [BzEt3N]X (X=Cl or Br) in THF upon addition of an appropriate oxidant. The nearly perfect Cu8 cube encapsulates the closed shell ions Cl− or Br−. The six diisopropyl dithiophosphate ligands bridge across each face of the Cu8 cube to form a nearly regular icosahedron of S atoms about the centered Cu8 cube. The eight Cu(I) atoms are located at the cube corners with an average Cu–Cu distance of 3.113(2) and 3.167(1) Å (1 and 2, respectively). The average Cu–S distance is 2.282(2) Å in 1 and 2.295(3) Å in 2. There appears to be a direct structural relationship between these centered cubal structures and the tetranuclear zinc(II) oxide and sulfide centered dialkyldithiophosphates, [Zn4(DDP)6(μ4-S or O)] which have the classic “basic” beryllium acetate geometry. The structural relationship to the hexanuclear clusters Cu6[S2P(OR)2]6, R=ethyl or n-butyl, also are described.

Cluster self-assembly of di[gold(I)]halonium cations.

Treatment of gold(I) halide complexes of the type L-Au-X [where L = PPh(3), PEt(3) with X = Cl, Br, I, or L = 2,6-(MeO)(2)C(6)H(3)PPh(2) with X = Cl] with AgSbF(6) in the molar ratio 2:1 in dichloromethane/tetrahydrofuran at -78 degrees C affords high yields of di[gold(I)]halonium salts of the formula [X[Au(PR(3))](2)](+) SbF(6)(-) (2-8). A determination of the crystal structures of the four triarylphosphine complexes (2-4, 8) revealed the presence of novel tetranuclear dications with a highly symmetrical structure (point group S(4)) that arises from self-assembly of the dinuclear monocations through a set of four equivalent aurophilic Au-Au interactions. A comparison with two reference structures of corresponding chloronium perchlorate and bromonium tetrafluoroborate salts with monomeric, dinuclear cations shows that the geometry of the latter is greatly altered on dimerization to optimize the interactions between the closed-shell metal centers (Au: 5d(10)). Weak metallophilic bonding clearly becomes significant only in crystal lattices where anions with a larger ionic radius (SbF(6)(-) vs. BF(4)(-), ClO(4)(-)) reduce the otherwise dominant role of strong interionic Coulomb forces. The results indicate that aurophilic bonding is indeed an ubiquitous, quite dependable mode of intermetallic interactions provided that the right environment is chosen to allow the weak forces to become operative.