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The exploration of the structure-directing effects of small amines that are selective for the crystallization of MMT-type zeolite phases by employing molecular modeling is reported.

The importance of the electrocrystallization approach in constructing and precisely controlling the morphology and stoichiometry of Co[[TCNQ].sub.2] (TCNQ = tetracyanoquinodimethane) based materials is presented. The findings show that the electrocrystallization process occurs through two distinctly different, potential-dependent nucleation-growth mechanisms.

A study conducted shows that the [.sup.17.O]-enriched water vapor involves during the crystallization of molecular sieves by the dry-gel conversion methods. [.sup.17.O] NMR is a sensitive technique for monitoring the role of water in the formation of molecular sieves by dry-gel conversion methods.

Models of MnO2 nanoparticles, with full atomistic detail, are generated using a simulated amorphization and recrystallization strategy. Molecular graphical snapshots of the crystallization process are presented.

The related parameters of cation size and valence that control the crystallization of Sr3CaRu2O9 into a 1:2 B-site-ordered perovksite structure were explored by cationic substitution at the strontium and calcium sites and application of high pressure. The size of calcium relative to ruthenium is a critical structure-determining factor in Sr3CaRu2O9.

The study focuses on the potential influence that insoluble calcite seeds might play in the crystallization of cholesterol monohydrate. The theoretical and experimental approach brings us closer to a molecular scale by which one can understand that the energetic barriers to cholesterol nucleation can be reduced by some physiological conditions.

Research is presented describing the preparation, crystallization, and solid-state characterization, of a spiro-biphenalenyl radical which is monomeric in the solid state. Curie behaviour (1 spin per molecule) occurs throughout a 10-400 Kelvin temperature range.

A molecular dynamics simulation study of the (001) and (011) interfaces of crystalline alpha-resorcinol with water was conducted to determine the mechanism by which solvent exerts its influence during the process of crystallization. Results indicate that the adsorption of water molecules is stronger at the slower growing (011) face. Findings infer that the stronger binding of the water molecules at the (011) surface acts to retard crystal growth rather than enhance it as predicted by the surface roughening theory.

The synthesis, crystal structure, physical characterization and band structure of the compound Ti2Nb6O12 were examined. The compound crystallizes in an original structure type based on Nb6O18 clusters and exhibits intercluster connectivity similar to that found in the 'Chevrel phases.' The effect of the basic cluster type and cluster connectivity on the band structure of the materials is described.

A synthesis of the high-silica zeolite UTD-1 was undertaken using a fluoride medium and an innovative texture method for structure determination and a high-resolution synchrotron powder diffraction data. The procedure resulted in UTD-1F, a structure with 69 non-H atoms in the asymmetric unit which is considered the largest structure derived from powder diffraction data. Succeeding Rietveld improvement of the structure in Pc were discovered to be stable and with no indication of disorder in its framework.

Research was conducted to examine the helical coordination polymers arising from achiral components. Chirality is caused by a pyrimidine-Cd2+ helical array and is preserved in all the crystals in the same chirality resulting from single-colony homochiral crystal growth. A new ligand-induced homochiral solid-state helix winding is presented where chirality can be regulated by seeding.

Simultaneous static and dynamic light scattering was used to examine the formation of clusters in nucleating hen egg white lysozyme-NaCl solutions. Angular dependent measurements of the average cluster diffusion coefficient and the total scattered intensity indicated pronounced structure peaks at the initial nucleation stages. These peaks suggest an ordering similar to that observed in highly concentrated colloidal suspensions.

The chiral chemistry breaking process of the 1,1'-binaphthyl has been investigated. The results showed that the compound racemizes rapidly as a supercooled melt at 150 degrees C. The melt solidified as a conglomerate of crystals, some being R-(-) and the others S-(+)-enantiomers. A large enantiomeric excess in almost every crystallization was observed when crystallization was performed on a 2.00 gram sample with constant stirring. The results showed that chiral symmetry breaking can be realized in crystallization from a melt by mere stirring.

A study was conducted to demonstrate that crystallization from solution can be simulated using the method of molecular dynamics for a model solute/solvent system consisting of atomic species characterized by the Lennard-Jones potential function. Crystallization in highly supersaturated systems involved liquid-liquid phase separation followed by nucleation in the solute phase. The nucleation event in such systems did not appear to be influenced by the solvent.

A study was conducted to investigate the crystal structures of N-methylated diphenylguanidines to clarify their bonding and electronic properties and the conformation of its derivatives to establish water-soluble oligomers with multilayered aromatic structures. X-ray analyses, IR and Raman spectroscopies were performed to examine the electron delocalization of the unsabstantiated guanidium ion, C+(NH2)3. The ions exhibited chiral propeller structures and revealed a helical arrangement of aromatic compounds which allow their usage in materials science and medicinal chemistry.

The synthesis and structure of crystalline clathrates formed from guanidium ions, the 4,4'-biphenyldisulfonate pillar and suitable guest benzene compounds are reported. Molecular guest and host-guest interactions influenced the formation of the brick architecture resulting from the reactions. The framework accommodates the steric demands and occupancies of various aromatic guests by puckering of the flexible hydrogen-bonded network and the rotation of the pillars about their long axes.

A study was conducted on bond shift rearrangement of chloro-, bromo-, and iodobullvalene in the solid state and in solution. The findings indicate that these bullvalenes exist as isomers 2 and 3 and undergo thermally activated bond shift rearrangement. Moreover, bromo- and iodobullvalene crystallize in the form of isomer 2 in the solid state while their lattices are well ordered but the molecules are disordered orientationally.

A study was conducted on aggregation and nucleation events induced by simple electrolytes such as NaCl. The results indicate the existence of a delicate balance between the conditions that optimize charge screening and those promoting gel formation. Moreover, a nonmonotonic behavior of dimensionalities and exponents is seen when the latter are plotted as a function of lysozyme or electrolyte concentration.

A study was conducted on hydrothermal crystallization of zeolite Li-A(BW) followed in situ by time resolved synchrotron X-ray powder diffraction. The findings indicate that intermediate amorphous or solute phases were significantly absent. Moreover, the results suggest that the hydrothermal conversion of zeolite LTA into zeolite Li-A(BW) is a solution-mediated process.

The synthesis and characterization of a metal-chelating lipid which targets proteins to surfaces has been described to promote two-dimensional protein crystallization via histidine coordination. The lipid has unsaturated oleyl tails to provide the necessary monolayer fluidity and uses the metal chelator iminodiacetate-copper (IDA) as the hydrophilic headgroup. The utility of this lipid for 2D protein crystallization is revealed using the protein streptavidin. Fluorescence microscopy demonstrates the streptavidin crystallization process.

The synthesis of the crystalline InP was found to proceed through the solution-liquid-solid (SLS) mechanism of crystal growth. This mechanism was found to work well for the organometallic synthesis of crystalline covalent nonmolecular solids when the chemical manipulations are done at low temperatures and in solution-based systems. These preliminary findings can be used as basis for further studies on conventional, solution-phase organometallic chemistry relevant to the synthesis of nonmolecular inorganic materials.

Synchrootron grazing incidence x-ray diffraction experiments were performed to compare the crystalline packing arrangements between enantiomerically pure and racemic alpha-amino acid amphiphiles. Specifically, zwitterionic RHC(NH3+)CO2- monolayers on water surface and on glycine aqueous solutions were observed. The results, which proved the feasibility of synthesizing alpha-amino acids of heterochiral or homochiral crystallinity, showed that the addition of glycine improves two-dimensional crystalline formation.

The viability of making polymers liquid crystalline is investigated. The molecular clip produced has 12 long aliphatic chains and can induce liquid-crystalline properties in various molecules via molecular recognition. Molecular recognition is thus proven to be effective as a tool for providing molecules with unique materials properties. The concept of introducing liquid crystalline properties by host-quest interactions is shown to be very general and can be applied to both low molecular weight and polymeric quest molecules.

The synthesis and structures of two major members, ((18C6)K)(Cd(SCN)3) (1) and ((18C6)2Na2(H2O)2)1/2(Cd(SCN)3) (2), of a new organic polymers with organic spacers (IPOS) series with the general formula (H-G)(M-L), where the organic cation (H-G)q+ is a host (H)-guest (G) complex and the inorganic anion (M-L)q- is a metal (M)-ligand (L) coordination polymer, are presented. A detailed study of the structures of 1 and 2 showed parallel and antiparallel arrangements, respectively, of the infinite anionic (Cd(SCN)(sub 3)(super -))(sub infinity) polymeric zig-zag chains.

An examination of the initial crystallization phase of native and dimethylated beta-cyclodextrins using small-angle static light scattering found that a single-step mechanism is responsible for the crystal formation of native beta-cyclodextrin. A more complex mechanism for the crystal formation of the heptakis(2,6)-di-O-methyl-beta-CD was noted. It was also found to involve a fast and a slow process. Crystallization exponents suggest that crystallization proceeds with the formation of spherical clusters which unite further to form rod-shaped macrocrystals.

The nucleation energy of InSe during its crystallization from bulk amorphous indium-selenium alloys was characterized as a function of the composition of the amorphous intermediate via a Kissinger analysis of differential scanning calorimetry. Specifically, a minimum in the activation energy for the nucleation and growth of InSe around a one-to-one stoichiometry. This may be explained as the maximum driving force per unit volume for nucleation at the stoichiometric composition.

A series of molecular dynamics (MD) simulations were performed on the TIP4P and SPC/E low-temperature models for water subject to applied electric field to examine the mechanism of electrofreezing of supercooled liquid water. Observations were made at constant densities ranging from 0.9 to 1.00 g/cm3 and at a temperature of 250 Kelvin for a field of 0.5 volts per angstrom. Intermediate structures resembling low-density amorphous ices were formed. Meanwhile, polar ice crystals were formed when electrofield was applied at constant density conditions rather than constant pressure conditions.

A study of the kinetics of stirred crystallization that generates large symmetry revealed the variation of concentration with time, as the crystallization proceeds. Secondary nucleation in the stirred system is responsible for the major difference in the two concentration vs time curves. The secondary nuclei, generated in the stirred system only when the parent crystal attains greater size, ensure that the proposed kinetics can precisely reproduce experimental data.

The effect of stereochemical factors on monolayer-actuated inorganic crystallization processes is investigated via the nucleation of BaSO4 under n-eicosyl sulfate monolayers. Nucleation results in oriented crystals, which may be attributed to partial matching of cation-cation distances with the interheadgroup spacings and the stereochemical compatibility between the anionic motif and sulfate headgroups. Nucleation is influenced greatly by the ability of the organic surface to imitate the lattice geometry of cations and stereochemistry of oxyanions in particular crystal faces.

The ESR measurements and the preliminary results of the crystal structure analysis on single crystals of C60 anion radical salts are reported. The occurence of concurrent crystal lattice degradation is proposed because the ESR spectral change cannot be accounted for solely by the decomposition of PPN+C60. X-ray diffraction studies show that structure demostrated a zigzag arrangement. The single crystals also showed no conductivity in room temperature.

Microscale wells have provided a flexible platform for controlling the crystallization of protein crystals with sizes as small as 600 nm industry-standard crystallization conditions. The surface-patterned method to generate protein crystals has provided an alternative approach to produce drug crystals with well-defined sizes and shapes that are useful in delivery applications.

A simple reaction-diffusion system is described in which spatiotemporal changes in the flux of precipitant have controlled the growth of protein microcrystals over an array of microscopic wells. This system has realized multiple crystal-growth conditions in a single experiment and has related the qualities/dimensions of the forming microcrystals to the schedule of precipitant delivery and to the underlying nucleation/growth parameters.

The article explains the synthesis of several manganese and magnesium homochiral materials that exhibit excellent homochiral connectivity. The honeycomb channels of such materials are found to be decorated with homochiral chains.

The two-dimensional (2D) and 3D molecular crystallization of tectons is attained by an integrated approach using X-ray diffraction and molecular synthesis. The results have provided new guidelines for designing 2D and 3D molecular glasses and also models for their structures and phenomenon of polyamorphism.

The organocatalytic stereoselective ring-opening polymerization of rac-lactide (rac-LA) is described by using the dimeric phosphazene base as catalyst to produce highly isotactic polylactide (PLA) stereocomplex. Highly isotactic polymers with high melting point and high crystallinity are obtained due to the effective cocrystallization between isotactic poly(L-LA) (PLLA) blocks and poly-(D-LA) (PDLA) blocks.

As-made and calcined ITQ-12 zeolites are structurally characterized by analyzing their vibrational modes. The vibrational analysis has highlighted several aspects of the host-guest interaction, structure-direction issues, which have included the role of fluoride anions in allowing the crystallization of silica structures with strained double-four rings and the role played by the framework flexibility.

The study of the interaction of Mycobacterium tuberculosis enoyl-ACP reductase with 1,2,isonicotinoyl-NAD(P) [INH-NADP] adducts is being discussed. The analysis has been extremely helpful, as it gives a complete analysis of the mechanism of the action and resistance to isoniazid.

Sonochemistry as a method to prepare nanostructured organic cocrystals is described. The method takes into account inherent differences in solubilities encountered in cocrystals and is shown to succeed where reprecipitation alone fails.

A comprehensive molecular-scale view of calcium oxalate monohydrate (COM) shape modification by citrate, obtained through a combination of in situ atomic force microscopy and molecular modeling is presented. The result shows that while the most important factors determining binding strength are coordination between COO- groups on citrate and Ca ions in the lattice, and others may provide favorable environment due to the ability of the steps-edge to accommodate all Ca-COO(super -)coordination with minimal strain.

A methodology to control the phenomenon of crystal polymorphism through the use of diverse libraries of polymer heteronuclei, including both commercially available polymers and combinatorially synthesized cross-linked polymers. This new approach for exploring polymorph space offers the advantage of high throughput crystallization to discover multiple polymorphs combined with the ability to selectively produce a given form from a single solvent and temperature condition by simple varying the nature of the polymer substrate.

An enatioselective synthesis of avrainvillamide is described. It was observed that (-)-avrainvillamide undergoes spontaneous dimerization to form (+)-stephacidin B in the presence of triethylamine.

The results of classical trajectory (CT) calculations on the sticking of protons to the basal plane (0001) face of crystalline ice, for normal incidence at a surface temperature of 80 K are presented. The calculation is performed for moderately low incidence energies (E(sub i)) ranging from 0.05 to 4.0 eV.

A simple system of calcite paired with polystyrene sulfonate (PSS) that undergoes mesocrystal formation is presented. The results show that the porous mesocrystals are composed of nanocrystals with exposed, highly positive (001) faces, ideal for the adsorption of PSS.

A potentially new synthetic strategy for preparing discrete inorganic clusters, and the use of the strategy to prepare the first crystalline example of an inorganic tridecameric Ga cluster is discussed. Robust crystals of the nitrate-deficient gallium cluster [Ga(sub 13)(mu(sub 3)-OH)6(mu(sub 2)-OH)18(H2O)24](NO3)15 are formed using Ga(NO3)3(H2O)6 as a nitrate source for the conversion of nitrosobenzene to nitrobenzene, which is known to proceed using nitric acid.

The single-walled carbon nanotube (SWNT)/H(sub 2)SO(sub 4) interaction that induces short-range orientational order which templates the crystallization of free acid with specific orientations is presented. It is found that graphite is less chemically active than nanotubes and thus cannot be protonated by superacid, only with the aid of electric potential can H(sub 2)SO(sub 4) intercalate and dope graphite to form graphite intercalation compounds.

The optimal control theory applied to the development of solid state NMR dipolar recouping experiments where the challenge is to minimize the loss of signal due to crystallite-orientation dependencies is reported. It is felt that the approach could have an impact on future solid-state NMR experiments.

The experiments performed with evaporation-driven colloidal crystallization in a cylindrical configuration are presented. For deposition inside the cylindrical capillaries, capillary radius itself sets the radius of curvature.

A general hydrothermal reaction-crystallization route, using bulky powders as precursors to synthesize uniform multicomponent Na2V6O16. 3H2O single-crystalline nanobelts on a large scale is reported. The strategy could be extended to prepare other multicomponent 1D nanomaterials including ammonium, alkali-metal or alkali-earth metal vanadium oxide bronze hydrated compounds and other transition metal oxyfluoride products.

The crystallographic analysis of labile molecules is performed through in situ preparation in the fluid state of voids of a crystalline porous coordination network. The results have helped in understanding the new aspects and applications of single-crystal-to-single-crystal transformations.

A unique method of directed crystallization of dilute colloidal silica in coexistence with pyridine (Py) under a temperature gradient is presented. The well-oriented, large single-domain crystals in short time with sharp and deep transmission dips and a good spatial uniformity in the Bragg wavelength were fabricated using the method.