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Molecular Building Blocks (molecular + building_block)
Selected AbstractsNovel Molecular Building Blocks Based on the Boradiazaindacene Chromophore: Applications in Fluorescent Metallosupramolecular Coordination PolymersCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2009Ö. Altan Bozdemir Dr. Abstract Bright polymers: Fluorescent coordination polymers made up of versatile functionalized bodipy (boron-dipyrrin) chromophore building blocks, such as that depicted, are described. Polymerization is signaled by changes in fluorescence emission intensity and shifts in peak emission wavelengths. We designed and synthesized novel boradiazaindacene (Bodipy) derivatives that are appropriately functionalized for metal-ion-mediated supramolecular polymerization. Thus, ligands for 2-terpyridyl-, 2,6-terpyridyl-, and bipyridyl-functionalized Bodipy dyes were synthesized through Sonogashira couplings. These fluorescent building blocks are responsive to metal ions in a stoichiometry-dependent manner. Octahedral coordinating metal ions such as ZnII result in polymerization at a stoichiometry corresponding to two terpyridyl ligands to one ZnII ion. However, at increased metal ion concentrations, the dynamic equilibria are re-established in such a way that the monomeric metal complex dominates. The position of equilibria can easily be monitored by 1H,NMR and fluorescence spectroscopies. As expected, although open-shell FeII ions form similar complex structures, these cations quench the fluorescence emission of all four functionalized Bodipy ligands. Bu çal,,mada, metal iyonlar, arac,l,,,yla supramoleküler polimerizasyon için uygun ,ekilde fonksiyonland,r,lm,, yeni boradiazaindasen (Bodipy) türevleri tasarlanm,, ve sentezlenmi,tir. Bu amaçla, ligand olarak Sonogashira reaksiyonu ile 2- ve 2,6-terpiridil ve bipiridil gruplar,n, içeren Bodipy boyarmaddeleri sentezlenmi,tir. Bu floresan yap, bloklar, stokiyometriye ba,l, bir biçimde metal iyonlar,na duyarl,l,k gösterirler. ZnIIgibi oktahedral koordinasyon e,ilimi olan metal iyonlar,, iki terpiridil ligand,na bir ZnIIiyonu tekabül edecek bir stokiyometride polimerizasyona yol açmaktad,rlar. Bununla beraber, yüksek metal iyonu deri,imlerinde monomerik metal kompleksinin bask,n olaca,, bir biçimde, dinamik dengeler yeniden kurulmaktad,r. Bu dengelerin pozisyonu1H,NMR ve fluoresans spektroskopileriyle kolayl,kla izlenebilmektedir. Beklenildi,i gibi, benzer kompleks yap,lar olu,turmas,na ra,men FeIIiyonu, sentezlenen tüm fonksiyonalize Bodipy ligandlar,n,n emisyonlar,n, sönümlendirmektedir. [source] Self-Assembled Monolayers into the 21st Century: Recent Advances and ApplicationsELECTROANALYSIS, Issue 2 2003Justin Gooding Abstract The modification of an interface on a molecular level with more than one molecular ,building block' is essentially an example of the ,bottom,up' fabrication principle of nanotechnology. The fabrication of such integrated molecular systems in electrochemistry has seen rapid progress in recent years via the development of sensing interfaces fabricated using self-assembled monolayers (SAMs). This review outlines recent advances and applications of self-assembled monolayers for modifying electrodes with an emphasis on the development of integrated molecular systems. First, some basic issues regarding fabricating integrated molecular systems, such as the role of the surface topography of the electrode and patterning surfaces, are discussed. Subsequently an overview of recent developments in pH, inorganic and bio sensing involving the use of SAMs is given. Finally emerging trends in using molecular building blocks in the fabrication of integrated molecular systems, such as nanotubes, dendrimers and nanoparticles, are reviewed. [source] Supramolecular Crystal Engineering at the Solid,Liquid Interface from First Principles: Toward Unraveling the Thermodynamics of 2D Self-AssemblyADVANCED MATERIALS, Issue 13 2009Carlos-Andres Palma Abstract The formation of highly ordered 2D supramolecular architectures self-assembled at the solid,solution interfaces is subject to complex interactions between the analytes, the solvent, and the substrate. These forces have to be mastered in order to regard self-assembly as an effective bottom-up approach for functional-device engineering. At such interfaces, prediction of the thermodynamics governing the formation of spatially ordered 2D arrangements is far from being fully understood, even for the physisorption of a single molecular component on the basal plane of a flat surface. Two recent contributions on controlled polymorphism and nanopattern formation render it possible to gain semi-quantitative insight into the thermodynamics of physisorption at interfaces, paving the way towards 2D supramolecular crystal engineering. Although in these two works different systems have been chosen to tackle such a complex task, authors showed that the chemical design of molecular building blocks is not the only requirement to fulfill when trying to preprogram self-assembled patterns at the solid,liquid interface. [source] Atomic-Level Studies of Molecular Self-Assembly on Metallic SurfacesADVANCED MATERIALS, Issue 10-11 2009Giulia Tomba Abstract Shrinking devices to the nanoscale, while still maintaining accurate control on their structure and functionality is one of the major technological challenges of our era. The use of purposely directed self-assembly processes provides a smart alternative to the troublesome manipulation and positioning of nanometer-sized objects piece by piece. Here, we report on a series of recent works where the in-depth study of appropriately chosen model systems addresses the two key-points in self-assembly: building blocks selection and control of bonding. We focus in particular on hydrogen bonding because of the stability, precision and yet flexibility of nanostructures based on this interaction. Complementing experimental information with advanced atomistic modeling techniques based on quantum formalisms is a key feature of most investigations. We thus highlight the role of theoretical modeling while we follow the progression in the use of more and more complex molecular building blocks, or "tectons". In particular, we will see that the use of three-dimensional, flexible tectons promises to be a powerful way to achieve highly sophisticated functional nanostructures. However, the increasing complexity of the assembly units used makes it generally more difficult to control the supramolecular organization and predict the assembling mechanisms. This creates a case for developing novel analysis methods and ever more advanced modeling techniques. [source] Assembling DNA into Advanced Materials: From Nanostructured Films to Biosensing and Delivery Systems,ADVANCED MATERIALS, Issue 21 2007Abstract The past decade has witnessed a rapid expansion in the design and assembly of engineered materials for biological applications. However, such applications place limitations on the molecular building blocks that can be used. Requirements for polymer-based building blocks include biocompatibility, biodegradability, and stimuli-responsive behavior. Many traditional polymers used in materials science are limited in at least one of these areas, so new polymers need to be explored. As we outline here, DNA is one such polymer that shows promise in developing the next generation of ,smart' materials for biomedical and diagnostic applications. [source] Self-assembled organic nanotubes: Toward attoliter chemistryJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2008Toshimi Shimizu Abstract Diverse chemical functionalization of the inner and outer surfaces of the nanotubes enables us to sense and visualize the encapsulation and transport behavior of biomacromolecular guests. The event occurs specifically in attoliter volume nanospace inside the hollow cylinder of the nanotubes. Comparison of the organic nanotube history with that of well-known carbon nanotubes and a variety of molecular building blocks as tube-forming compounds were first introduced. Asymmetric organic nanotubes with different inner and outer surfaces were discussed in terms of molecular design, immobilization of functional moieties, and molecular packing. Finally, the practical examples of the organic nanotubes as a nanocontainer, nanochannel, and nanopipette were also described to feature the concept of "attoliter chemistry." © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2601,2611, 2008 [source] Spatial arrangement of molecules in homomolecular Z' = 2 structuresACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2006Elna Pidcock The Box Model of crystal packing describes unit cells in terms of a limited number of arrangements of molecular building blocks. An analysis of Z,, 1 structures has shown that cell dimensions are related to molecular dimensions in a systematic way and that the spatial arrangement of molecules in crystal structures is very similar, irrespective of Z or space group. In this paper it is shown that the spatial arrangement of molecules in Z, = 2 structures are, within the context of the Box Model, very similar to that found for Z,, 1 structures. The absence of crystallographic symmetry does not appear to affect correlations between molecular dimensions and cell dimensions, or between the packing patterns and the positions of molecules in the unit cell, established from the analysis of Z,, 1 structures. The preference shown by Z, = 2 structures for low surface-area packing patterns and the observation that strong energetic interactions are most often found between the large faces of the independent molecules reaffirms the importance of molecular shape in crystal packing. [source] Halogeno(triazolyl)zinc complexes as molecular building blocks for metal,organic frameworksACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Jörg Lincke The isomorphous title complexes, dichlorido[4-(3,5-dimethyl-4H -1,2,4-triazol-4-yl)benzoic acid-,N1]zinc(II) dihydrate, [ZnCl2(C11H11N3O2)2]·2H2O, and dibromido[4-(3,5-dimethyl-4H -1,2,4-triazol-4-yl)benzoic acid-,N1]zinc(II) dihydrate, [ZnBr2(C11H11N3O2)2]·2H2O, were synthesized and crystallized by slow evaporation of the solvent from a solution of the ligand and either zinc chloride or zinc bromide, respectively, in water/ethanol. The ZnII ions occupy twofold axes in the noncentrosymmetric orthorhombic space group Fdd2. The metal ion is approximately tetrahedrally coordinated by two monodentate triazole groups of the ligands and additionally by two halide ions. The water molecules incorporate the complexes into a three-dimensional framework made up by hydrogen bonds. Furthermore, each complex possesses two hydrogen-bond-donor sites represented by the carboxy groups and two acceptor sites at the noncoordinating N atoms of the triazoles. [source] Self-Organisation in the Assembly of Gels from Mixtures of Different Dendritic Peptide Building BlocksCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2007Andrew Abstract This paper investigates dendritic peptides capable of assembling into nanostructured gels, and explores the effect on self-assembly of mixing different molecular building blocks. Thermal measurements, small angle X-ray scattering (SAXS) and circular dichroism (CD) spectroscopy are used to probe these materials on macroscopic, nanoscopic and molecular length scales. The results from these investigations demonstrate that in this case, systems with different "size" and "chirality" factors can self-organise, whilst systems with different "shape" factors cannot. The "size" and "chirality" factors are directly connected with the molecular information programmed into the dendritic peptides, whilst the shape factor depends on the group linking these peptides together,this is consistent with molecular recognition hydrogen bond pathways between the peptidic building blocks controlling the ability of these systems to self-recognise. These results demonstrate that mixtures of relatively complex peptides, with only subtle differences on the molecular scale, can self-organise into nanoscale structures, an important step in the spontaneous assembly of ordered systems from complex mixtures. [source] Precursors of Biological Cofactors from Ultraviolet Irradiation of Circumstellar/Interstellar Ice AnaloguesCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2005Uwe J. Meierhenrich Priv.-Doz. Abstract Biological cofactors include functionalized derivatives of cyclic tetrapyrrole structures that incorporate different metal ions. They build up structural partnerships with proteins, which play a crucial role in biochemical reactions. Porphyrin, chlorin, bacteriochlorin, and corrin are the basic structures of cofactors (heme, chlorophyll, bacteriochlorophyll, siroheme, F 430, and vitamin B12). Laboratory and theoretical work suggest that the molecular building blocks of proteins (,-amino acids) and nucleic acids (carbohydrates, purines, and pyrimidines) were generated under prebiotic conditions. On the other hand, experimental data on the prebiotic chemistry of cofactors are rare. We propose to search directly for the pathways of the formation of cofactors in the laboratory. Herein we report on the detection of N-heterocycles and amines in the room-temperature residue obtained after photo- and thermal processing of an interstellar ice analogue under high vacuum at 12 K. Among them, hexahydro-1,3,5-triazine and its derivatives, together with monopyrrolic molecules, are precursors of porphinoid cofactors. Hexahydropyrimidine was also detected. This is the first detection of these compounds in experiments simulating circumstellar/interstellar conditions. Except for 2-aminopyrrole and 2,4-diaminofuran, which were only found in 13C-labeled experiments, all the reported species were detected in both 12C- and 13C-labeled experiments, excluding contamination. The molecules reported here might be present in circumstellar/interstellar grains and cometary dust and could be detected by the Stardust and Rosetta missions. [source] | |||||||||||||