Solid-state Organization Research Articles

Interactions of zinc(II), magnesium(II) and calcium(II) with aminomethane-1,1-diphosphonic acids in aqueous solutions

Complex formation equilibria of the aminomethane-1,1-diphosphonic acids with Zn II, Mg II and Ca II have been studied by potentiometric pH titrations and by means of NMR spectroscopy. The ligands exhibit a strong tendency to form protonated species over a wide range of pH. The most efficient binding mode in all the studied systems is the formation of the six-membered chelate ring involving oxygens of both phosphonate groups. An evident preference for the formation of multinuclear complexes is noted in the case of zinc(II). Magnesium demonstrates preference for mononuclear complexes, whereas calcium(II) tends to form insoluble species with most of the studied ligands. The structures of the main complex species are discussed with respect to the priorities in the hydrogen-bond network organization in solid state.

Solid-state organization of poly(methylmethacrylate)–poly(methylphenylsiloxane) based interpenetrating networks

Three interpenetrating networks based on polymethylphenylsiloxane (PMPS) and polymethylmethacrylate (PMMA) with different compositions were prepared. They were investigated using differential scanning calorimetry (DSC) and high-resolution solid-state 13C NMR techniques, in order to study the heterogeneous character of the domains involved in these materials at the nanoscopic scale. DSC observed broad glass transitions of the PMPS chains. 13C cross-polarization (CP) experiments clearly showed that the aromatic PMPS carbons have a rate of CP which is composition dependent, indicating that PMPS and PMMA chains are interpenetrating at a very low spatial scale. These results were supported by T 1 ρ ( 1H) and 13C line width measurements as a function of temperature. Moreover, T 1 ρ ( 1H) measurements indicated that PMMA chains are rather homogeneously distributed whereas PMPS chains belong either to interpenetrating domains or to PMPS-rich domains.

Molecular organization and solution properties of N-substituted aminomethane-1,1-diphosphonic acids

The crystal structures of N-n-pentylaminomethane-1,1-diphosphonic (1), N-pyrrolidinomethane-1,1-diphosphonic (2), N-(3-carboxy-2-pyridyl)aminomethane-1,1-diphosphonic (3a) and N-(5-methyl-2-pyridyl)aminomethane-1,1-diphosphonic (3c) acids are determined and discussed with respect to their packing patterns and solid state organization. The molecular association and the possible aggregate forms in solution, resulting from the supramolecular features of these materials, are considered. The solution UV and NMR studies are focused on the N-2-pyridylaminomethane-1,1-diphosphonic acids 3a–e in order to establish the influence of the structural changes in passing from 3- to 5- or 6-pyridyl substituted aminomethane-1,1-diphosphonic acids on their general complexation properties.

Soluble polydiacetylenes: molecular properties and solid state organization

The solution properties of a novel soluble polydiacetylene, poly[1,6-bis(3,6-dihexadecyl- N-carbazolyl)-2,4-hexadiyne] (polyDCHD-HS), have been investigated by use of spectroscopic (UV–VIS absorption, fluorescence and FT-Raman) and light scattering techniques in benzene and toluene. The unique spectroscopic and molecular properties of these solutions are reported and discussed in relation to the particular interactions of the polymer substituents with aromatic solvents. The introduction of the long alkyl-substituents on the carbazolyl side groups not only improves the processability relative to the parent unsubstituted polymer but also suppresses the chromic effects observed in other soluble polydiacetylenes. The side groups are also responsible for the peculiar supramolecular organization observed in the powder phase of the red form.

Molecular Crystal Architecture and Optical Properties of a Thiohelicenes Series Containing 5, 7, 9, and 11 Rings Prepared via Photochemical Synthesis

Helicenes are intrinsically chiral helical molecules structurally characterized by ortho-fusion of aromatic rings. A series of racemic heterohelicenes composed of thiophene and benzene rings alternated in the helical chain were prepared via photochemical irradiation. The availability of large systems containing 9 and 11 condensed rings allows a better understanding of both optical properties and solid-state organization of thiohelicene molecules. The conformation and the crystal architecture of thiohelicenes, containing up to 11 rings show ring distortions smaller than in carbohelicenes. All the crystals obtained are racemates, and heterochiral assembling is dominant also for the larger systems.

Self-Assembling Cyclic Peptide Cylinders as Nuclei for Crystal Engineering

A supramolecular recognition interface is formed through the self-assembly of cyclic D,L-peptides. Phenyl–phenyl interactions direct the solid-state organization of dimeric peptide cyclo[(-L-Phe-D-MeN-Ala-L-hPhe-D-MeN-Ala)2] (1) by forming clusters of edge-to-face contacts between dimers (shown left), which suggests that these peptide scaffolds may be useful subunits for crystal engineering. Supporting information for this article is available on the WWW under http://www.angewandte.com or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Self-Assembling Cyclic Peptide Cylinders as Nuclei for Crystal Engineering.

A supramolecular recognition interface is formed through the self-assembly of cyclic D,L-peptides. Phenyl-phenyl interactions direct the solid-state organization of dimeric peptide cyclo[(-L-Phe-D-Me N-Ala-L-hPhe-D-Me N-Ala)2 ] (1) by forming clusters of edge-to-face contacts between dimers (shown left), which suggests that these peptide scaffolds may be useful subunits for crystal engineering.

Synthesis and characterization of PEE-PEO diblock copolymers with complementary end-groups for hydrogen-bond heteroassociation

Poly(ethylethylene-b-ethylene oxide) (PEE-PEO) diblock copolymers with pyridine-benzoic acid end-groups for heterodimeric hydrogen bonding were designed as a possible means to noncentrosymmetric organizations by spontaneous self-assembly. These end-functionalized polymers were synthesized by anionic living polymerization with protected initiator and terminating reagents. A series of polymeric intermediates with different end-groups was characterized by proton nuclear magnetic resonance, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and gel permeation chromatography. Preliminary studies of solid-state organization by differential scanning calorimetry and small-angle X-ray scattering provided evidence for a long-range order that was sensitive to chain length, copolymer composition, and end-group structure. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 207–219, 2000

ChemInform Abstract: Fluorinated Distyrylbenzene Chromophores: Effect of Fluorine Regiochemistry on Molecular Properties and Solid‐State Organization.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Fluorinated Distyrylbenzene Chromophores: Effect of Fluorine Regiochemistry on Molecular Properties and Solid-State Organization

A series of fluorinated distyrylbenzene (DSB) derivatives were synthesized and studied in order to probe the effect of fluorine substitution on molecular properties and on the arrangement of molecules in the solid state. Reaction of 1,4-diiodobenzene with 4-fluorostyrene or pentafluorostyrene in the presence of Pd(OAc)2 gives trans-trans-bis(4-fluorostyryl)benzene (2Ft) and trans-trans-1,4-bis(pentafluorostyryl)benzene (10Ft), respectively. Bis(2,5-difluorostyryl)benzene (4Ft) was prepared by the reaction of 2,5-difluorobenzaldehyde with p-xylylenebis-(triphenylphosphonium bromide) in the presence of LiOEt in EtOH. Coupling of 1,4-dibromo-2,5-difluorobenzene with styrene, 4-fluorostyrene, or pentafluorostyrene using Pd(OAc)2 gives 1,4-bis(styryl)-2,5-difluorobenzene (2Fc), 1,4-bis(4-fluorostyryl)-2,5-difluorobenzene (2Fc2Ft), and 1,4-bis(pentafluorostyryl)-2,5-difluorobenzene (2Fc10Ft), respectively. Absorption spectroscopy shows that DSB, 2Ft, 2Fc, 2Fc2Ft, 4Ft, 10Ft, and 2Fc10Ft have a λmax at approximat...

Solid state organisation of C60 by inclusion crystallisation with triptycenes†

Triptycene and azatriptycene act as concave receptor molecules for C60, resulting in the solid state organisation of C60 in a layered and a hexagonal pattern, respectively.

Improved synthesis of functionalized sexithiophenes

Yields of functioualized sexithiophenes through the Stille reactien are greatly ameliorated using in situ generated Pd(AsPh3) 4 as the catalyst. The regic6pecific synthesis of a new head-to-head/taii-to-tail hexa(methylsulfanyl)sexithiophene is reported. All sexithiophmes were distilled under high vacuum to reach the degree of purity required for use in elec~ordc appficatio~as. © 1997 Elsevier Science Ltd. The finding that oligothiophenes are good electroactive materials for applications in organic field effect transistors and electrooptical devices has prompted an increasing need for amelioration of the synthetic procedures for the preparation of these compounds and for more efficient purification and characterization methods.1-4 We have recently started a research aimed at achieving the control of both the degree of purity and the solid state organization of oligothiophenes - which are key features in the optimization of electric conductivity and luminescence properties of these compounds - through appropriate funetionalization of the aromatic skeleton, which renders the compounds soluble and processable. We report here our results on the effect of the change of palladium(0) catalyst ligands in the preparation of polysubstituted sexithiophenes through the StiUe reaction. 6 To our knowledge, only commercially available Pd(PPh3) 4 has been used so far to prepare oligothiophenes through the StiUe coupling and no studies on catalyst tailoring for the synthesis of these compounds have been carried out. An improvement over the typical Stifle conditions would be a useful development in the synthesis of oligothiophenes, since the Stille reaction is compatible with a great number of functional groups 6 and funetionalizing oligothiophenes in the c~ or 13 positions is a way to tailor their properties. 1-4 The reaction chosen for the study of the Stille coupling in the presence of different catalysts generated in situ is shown in Scheme 1. Reaction conditions and yields are reported in Table 1. The palladium catalyzed coupling of the dibromoquaterthiophene 1 with the 2-trialkyltin derivatives 2, 3 was studied in the presence of triphenylphosphine, triphenylarsine and tri-(2-furyl)phosphine as the palladium(0) ligands and with tetrahydrofuran or toluene as solvents at the refinxing temperatures of 65 and 110 °C, respectively. Although iodine is a better leaving group than bromine and consequently should be better suited for the rate determining transmetallation step of the Stilie reaction, 6 we preferred to use the dibromo derivative 1 to avoid the risk of polymerization of the substrate. Indeed we found that in the Stille reaction conditions the diiodo derivative of substituted quaterthiophenes - which are easily prepared by reported methodsT, 5d- may give rise to polymerization.

Self-Assembly and Disassembly of Regioregular, Water Soluble Polythiophenes: Chemoselective Ionchromatic Sensing in Water

The development of polythiophene (PT) derivatives with essentially 100% head-to-tail (HT) couplings1,2 has led to the discovery of materials that self-assemble both in solution and in the solid state. Light-scattering studies on regioregular, HTpoly(3-dodecylthiophene) (HT-PDDT) show that a supramolecular organization occurs via intermolecular aggregation.3 This solution aggregation is precursive to a microcrystalline, self-assembled structure which has been characterized by X-ray studies.1,2,4 Polythiophenes possessing this metastable organization evidence high electrical conductivities1,2,5-8 and very small bandgaps. Previous work in our lab has shown that both conformational order and solid state organization in regioregular PT derivatives are remarkably sensitive to the placement and nature of the substituent chains.1,6,7,9 This sensitivity provides the opportunity to design new conducting polymers in which self-assembly is controlled by environmental factors. One remarkable example is HT-2,5-poly(thiophene-3-propionic acid) (3, PTPA). This polymer was designed such that upon deprotonation, water soluble polythiophene salts are formed.10 Both 3 and its partially deprotonated derivative 5 undergo protein-like hydrophobic assembly, with subsequent H-bond stabilization, to generate a self-assembled conducting polymer aggregate. Varying the size of the counterion in the carboxylate polymer changes the effective steric bulk of the substituent. Small cations favor a self-assembled (purple) state and large cations can completely disrupt the aggregated phase. In fact, a remarkable chemoselective counterion size-dependent chromaticity (Figure 1) is observed for polymer 5. The UV-vis λmax can be varied over a 130 nm range (from purple to yellow) simply by changing the countercation. Initially, we prepared the carboxylate precursor polymer 2 using the Ni(dppp)Cl2 cross-coupling method for the synthesis of HT polythiophenes.5,6,9 This method leads to low molecular weights (Mn ) 1.5-3.0 K), low yields (<5%), and polymers that show variable ionic chromaticity. However, the regioregular oxazoline polythiophene (2) (Mn ) 8 K, PDI ) 1.2) is prepared (Scheme 1) from monomer11 1 in high yields (84%)

Do molecular dipole interactions influence solid state organization?

A statistical analysis of molecular dipole moments within three space groups (P1, P1, and P21) was carried out. The magnitude of the molecular dipole moment does not vary significantly between centrosymmetric (P1) and noncentrosymmetric (P1 and P21) space groups and does not correlate with relative molecular orientations within the P21 space group. Thus, the high preference for organic molecules to crystallize in one of the centrosymmetric arrangements cannot be attributed to dipole-dipole interactions.

Influence of molecular dipole interactions on solid-state organization

Influence of molecular dipole interactions on solid-state organization