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Monodisperse dendrimer-coated gold nanoparticles with a spherical shape have been obtained by direct reduction of HAuCl4 with sodium borohydride in the presence of dodecanethiol as a stabilizer and subsequent functionalization by ligand exchange reaction with polybenzylic thiolated dendrons. The substitution pattern of the dendrimeric units plays a fundamental role in the rate of the functionalization exchange process and consequently conditions the size and the polydispersity of the NPs obtained. An ulterior growth process occurs by thermal stimuli (150 °C) in a solvent-free environment. This method, carried out in mild conditions, allows the formation of highly monodisperse gold NPs with different sizes for different time reactions, and we discuss the mechanisms involved in this process. Finally, we demonstrate the chemical composition and stability of our compounds by structural, thermal, and chemical characterization of the samples before and after thermal treatment., This work was supported by the MINECO-FEDER funds (project PGC2018-097583-B-I00) and Gobierno de Aragón-FSE (Research Group E47_20R). The authors acknowledge the use of SAI (UZ), CEQMA (UZ-CSIC), and LMA (UZ-CSIC) services. J. A. Ulloa thanks the Becas-Chile program of the National Commission for Scientific and Technological Research (CONICYT, Chile) for his PhD grant.

We report here on a series of redox active benzothiadiazole-based luminophores ffinctionalized on one edge with a phenyl-nonyl substituent, which confers these molecules a rodlike shape and a tendency to self-assemble into layered superstructures. On the other edge, the molecules are endowed with different p-substituted phenyl rings, which allows the modulation of their redox and optical properties on the basis of the electronic nature of the terminal substituents. We have found that just one lateral alkyl chain is sufficient to induce mesomorphism in these molecules, which present nematic or smectic mesophases upon therinal treatment. Single-crystal analysis allows us to get an insight into the nature of the forces responsible for different supramolecular assemblies in these derivatives, and point to a strong contribution of the terminal groups in the different arrangements observed. The interesting redox and optical properties together with their self-assembling tendencies render these new materials interesting candidates for optoelectromcs.

We have prepared nanoporous polymers from columnar hexagonal hydrogen-bonded complexes, whose order is fixed by coumarin photoinduced [2 + 2] cycloaddition (photodimerization). Two different hydrogen-bonded complexes were used and consisted of a melamine (M) or tris(triazolyl)triazine (T) derivative acting as central templates and three peripheral carboxylic acids containing coumarin units. These coumarin units were employed for the cross-linking process by photodimerization in order to fix the LC arrangement. Template removal leads to the formation of self-standing nanoporous polymers keeping the columnar hexagonal order. Two nanoporous polymers with different pore diameters were obtained depending on size of the utilized template. These polymers with carboxylic acids at the pore surface demonstrate the ability to selectively adsorb certain molecules depending on their size. Moreover, after base treatment of the nanoporous polymers, they are able to adsorb cationic dyes over anionic and larger cations, demonstrating size- and charge-selective adsorption., This work was supported by the MINECO-FEDER funds (project CTQ2015-70174), Gobierno de Aragon-FSE (Research Group E04). The authors acknowledge the use of the SAI (UZ) and CEQMA (UZ-CSIC) Services. A. Concellon thanks MINECO (Spain) for his PhD grant.

The development of the site-selective Suzuki–Miyaura cross-coupling of dibromoanthracene as an efficient strategy toward organic light emitting diodes (OLEDs) is disclosed in this article. An unprecedented step-economic palladacycle-promoted triple Suzuki coupling protocol allowed the synthesis of three new OLED emitters and could prove to be a useful general strategy for researchers working in this field. Characterization of the synthesized molecules by UV–vis spectroscopy and thermogravimetric analysis–differential scanning calorimetry followed by density functional theory studies of the different properties strongly confirms the derivatives possess more significant hole mobility character than electron transfer capability.

Highly conductive coaxial supramolecular wires are prepared by using a new family of Janus dendrimers that combines two rigid aromatic parts and two flexible aliphatic parts. The two external regions consist of a promesogenic block based on a third generation Percec-type dendron with four terminal dodecyloxy alkyl chains, whereas the two internal regions are formed by one, two, or three carbazole units bearing flexible spacers. These functional Janus dendrimers self-organize in columnar liquid crystal phases with a strong coaxial segregation within each column. Interestingly, the charge mobility studies revealed that these Janus dendrimers display semiconductor properties with hole mobility values up to 0.5 cm2 V–1 s–1, depending on the packing within the columns which can be tuned by the number of carbazole functional units. The high hole mobility values measured in these materials are among the highest values reported for columnar liquid crystals., This work was supported by the MINECO-FEDER funds (project CTQ2015-70174), Gobierno de Aragón-FSE (Research Group E04). Authors would like to acknowledge the use of the SAI (UZ) and CEQMA (UZ-CSIC) Services. A. Golemme is grateful for support from the ELIOTROPO project (PON03PE_00092_2). R. Termine was supported by the MERAVIGLIE project (CUP J28C17000080006).

Electrical conductance across a molecular junction is strongly determined by the anchoring group of the molecule. Here we highlight the unusual behavior of 1,4-bis(1H-pyrazol-4-ylethynyl)benzene that exhibits unconventional junction current versus junction-stretching distance curves, which are peak-shaped and feature two conducting states of 2.3 × 10-4 G0 and 3.4 × 10-4 G0. A combination of theory and experiments is used to understand the conductance of single-molecule junctions featuring this new anchoring group, i.e., pyrazolyl. These results demonstrate that the pyrazolyl moiety changes its protonation state and contact binding during junction evolution and that it also binds in either end-on or facial geometries with gold contacts. The pyrazolyl moiety holds general interest as a contacting group, because this linkage leads to a strong double anchoring of the molecule to the gold electrode, resulting in enhanced conductance values., P.C. and J.L.S. are grateful for financial assistance from Ministerio de Economía y Competitividad from Spain and fondos FEDER in the framework of projects MAT2016-78257-R and CTQ2015-70174-P, respectively. J.L.S. also acknowledges the funded project Hierarchical Self Assembly of Polymeric Soft Systems, “SASSYPOL”, from the seventh Framework Programme (CEE, ref-607602). L.I.H., S.M., J.L.S, and P.C. acknowledge support from DGA/Fondos FEDER (construyendo Europa desde Aragón) for funding PLATON (E31_17R) and CLIP (E47_17R) research groups. This work was additionally supported by the EPSRC “QuEEN” programme Grant EP/N017188/1. Further support from the UK EPSRC is acknowledged, through Grant Nos. EP/M014452/1, EP/P027156/1, and EP/N03337X/1. Support from the European Commission is provided by the FET Open project 767187 – QuIET and the Iraqi Ministry of Higher Education (SL-20). A.K.I. acknowledges financial support from Tikrit University (Iraq). D.C.M., A.V. and R.J.N. gratefully acknowledge funding by EPSRC through grants EP/M005046/1, EP/M014169/1, and EP/M029522/1.

Three cyclic trinuclear pyrazolate complexes with Au(I), Ag(I), or Cu(I) have been studied. These complexes have interesting and distinct optical and thermal properties depending on the metal, namely, liquid crystalline behavior, red or deep-red phosphorescence at room temperature, thermoluminochromism, and response to silver ions. The selected ligand, 4-hexyl-3,5-dimethylpyrazolate, maximizes the effect that the nature of the metals has on the properties of the complexes, thus allowing the intermolecular metallophilic interactions to be responsible for the optical properties. Moreover, the gold and silver complexes show columnar liquid crystal phases at high temperature. All of the complexes have good solubility properties for processing as poly(methyl methacrylate) (PMMA) doped films. Films of the gold, silver, and copper complexes show interesting optical behavior such as wide-range color switching or phosphorescence turn-on upon cooling. In addition, films of the gold complex show a bright color switching (red to blue) in the presence of silver ions. The gold and copper complexes are bright phosphors with phosphorescent quantum yields of 90% in PMMA films, the highest values reported for this class of compounds at room temperature., This work was supported by MINECO-FEDER, UE (projects MAT2015-66208-C3-1-P, CTQ2015-70174-P, CTQ2014-53033-P, CTQ2016-75816C2-1-P), Gobierno de Aragón FSE, UE, and Catedra IQE (Industrias Quimicas del Ebro) for a postgraduate grant (J.C.).

A synthetic strategy has been developed to prepare liquid crystalline cyclotriphosphazenes that have two different types of mesogenic units linked to the same phosphorus atom. Hexachlorocyclotriphosphazene, N3P3Cl6, was reacted with 3 mol of the calamitic unit 4-cyano-4'-hydroxybiphenyl to give a mixture of compounds in which the nongem-trans-trisubstituted derivative N3P3Cl3(OC6H4C6H4{CN}-p)3 was the major product. The substitution of all three chlorine atoms in this nongeminal compound gave rise to the hydroxyl-functional phosphazenes, nongem-trans-N3P3(OC6H4C6H4{CN}-p)3(OC6H4{OH}-p)3 or nongem-trans-N3P3(OC6H4C6H4{CH3}-p)3(OC6H4{OH}-p)3, from which the second mesogenic unit, a polycatenar one, was introduced. The chemical structure of the resulting materials, deduced from spectroscopic and MALDI-TOF techniques, was in accordance with monodisperse, fully functionalized cyclotriphosphazenes. Mesomorphism is highly dependent on the terminal group of the calamitic units, and liquid crystal phases were only detected on the cyano-derivatives. The calamitic or columnar nature of the mesophase depends on the number of alkyl chains of the polycatenar moieties., This work was supported by the MICINN, Spain, under the projects CTQ2015-70174-P, MAT2014-55205-P, and CTQ2011-22589, FEDER, Gobierno de Aragon-Fondo Social Europeo (Spain, Dpto. de Innovación, Investigación y Universidad, groups E-97 and E-09).

The electronic distribution of some haloethynylbenzene derivatives may favor the formation of two-dimensional organizations by combining halogen and hydrogen bonds. In order to highlight this strategy, we have prepared seven cocrystals and analyzed their structures. 1,4-Bis(iodoethynyl)benzene, 1,4-bis(bromoethynyl)benzene, and 1,3-bis(iodoethynyl)benzene were used as halogen bond donors and 1,2-bis(4-pyridyl)ethylene, pyridazine, propanone, hexamethylenetetramine, and 2,8-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (Tröger’s base) were employed as halogen bond acceptors. The crystal structures of seven halogen-bonded complexes show C–X···Y (X = I, Br; Y = N, O) distances shorter than the sum of the van der Waals radii, and six of them contain the edge-to-edge C–H···X (X = I, Br) supramolecular hydrogen bond synthon. The stabilization energies with basis set superposition error correction of hydrogen bond synthons have been determined by DFT calculations, and they are in the range 2.9 to 5.7 kcalmol–1. To gain a deeper understanding of these interactions, noncovalent interaction methodology was also applied., Thanks are given to Crystallography Service from the University of Zaragoza (Spain), University of Pais Vasco (Spain), and National University of Singapore. This work was supported by the Ministerio de Economia y Competitividad, under the projects MAT2012-38538-C03-01, MAT2014- 55205-P, Fondo Europeo de Desarrollo Regional (FEDER), and Gobierno de Aragon. L.G. thanks the Ministerio Economia y Competitividad and J.M. thanks Ministerio de Educacion Cultura y Deporte for a grant (FPU14/06003).

In the search for effective vehicles to carry genetic material into cells, we present here new pseudodendrimers that consist of a hyperbranched polyester core surrounded by amino-terminated 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) dendrons. The pseudodendrimers are readily synthesized from commercial hyperbranched bis-MPA polyesters of the second, third, and fourth generations and third-generation bis-MPA dendrons, bearing eight peripheral glycine moieties, coupled by the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). This approach provides globular macromolecular structures bearing 128, 256, and 512 terminal amino groups, and these can complex pDNA. The toxicity of the three pseudodendrimers was studied on two cell lines, mesenchymal stem cells, and HeLa, and it was demonstrated that these compounds do not affect negatively cell viability up to 72 h. The complexation with DNA was investigated in terms of N-to-P ratio and dendriplex stability. The three generations were found to promote internalizing of pDNA into mesenchymal stem cells (MSCs), and their transfection capacity was compared with two nonviral commercial transfection agents, Lipofectamine and TransIT-X2. The highest generations were able to transfect these cells at levels comparable to both commercial reagents., This work was financially supported by the MINECO-FEDER funds (under the projects CTQ2015-70174-P and MAT2015-66208-C3-1-P) and the Gobierno de Aragón-FSE (E04 research groups). A.L. thanks the MECD for his FPU grants (FPU12/05210) R.G. thanks DGA for his PhD grant.

A novel approach to ambipolar semiconductors based on hydrogen-bonded complexes between a star-shaped tris(triazolyl)triazine and triphenylene-containing benzoic acids is described. The formation of 1:3 supramolecular complexes was evidenced by different techniques. Mesogenic driving forces played a decisive role in the formation of the hydrogen-bonded complexes in the bulk. All of the complexes formed by nonmesogenic components gave rise to hexagonal columnar (Col) liquid crystal phases, which are stable at room temperature. In all cases, X-ray diffraction experiments supported by electron density distribution maps confirmed triphenylene/tris(triazolyl)triazine segregation into hexagonal sublattices and lattices, respectively, as well as remarkable intracolumnar order. These highly ordered nanostructures, obtained by the combined supramolecular H-bond/columnar liquid crystal approach, yielded donor/acceptor coaxial organization that is promising for the formation of ambipolar organic semiconductors with high mobilities, as indicated by charge transport measurements., This work was financially supported by the MINECO-FEDER funds (projects MAT2015-66208-C3-1-P, CTQ2015-70174-P, MAT2012-38538-CO3-02), the Gobierno de Aragon-FSE (E04 research group and EPIF grant to B.F.), and the Gobierno Vasco (Project IT 1130-16). A.G. acknowledges support from the ELIOTROPO project (PON03PE_00092_2). R.T. was supported by MIUR under the PRIN 2012 JHFYMC project.

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence., Two novel series of dendrimers synthesised by the ionic grafting of poly(propylene imine) PPI-(NH2)n (n = 4, 8, 16, 32, 64 primary amines on the surface) with bifunctional dendrons of two generations (G1COOH, G2COOH) derived from 2,2-bis(hydroxymethyl)propanoic acid (bis-MPA) were prepared. The dendrons contain a carboxyl group at their apex and electroactive carbazole groups and mesogenic units on their periphery. The occurrence of proton transfer from the carboxylic acid to the amine groups was confirmed by IR and NMR measurements. The liquid crystalline behavior has been investigated by means of differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffractometry (XRD). All ionic dendrimers were liquid crystalline (nematic, smectic or columnar mesophases). The type of mesophase depends on the dendrimer generation as well as on the dendron generation. The electrochemical behavior of the ionic dendrimers was investigated by cyclic voltammetry (CV). Scanning electron microscopy (SEM) studies revealed that electrochemical deposition of the material on the conducting substrate takes place. The UV-vis absorption and emission properties of the ionic hybrid dendrimers have been investigated. All the compounds are luminescent at room temperature and the intensity is related to the number of carbazole units present in the molecule., This work was supported by MINECO Spain, under Project CTQ2012-35692 and FEDER funding, EU, and by the Gobierno de Aragón (Research Group E04). S.C. thanks the MICINN (Spain) for an FPI grant. The authors also acknowledge the Microscopy Service of the Universidad de Zaragoza, and Nuclear Magnetic Resonance, Mass Spectrometry, Elemental Analysis and Thermal Analysis Services of CEQMA, Universidad de Zaragoza-CSIC (Spain).

et al., We report the synthesis, mesomorphic behavior, and mobility values of a series of highly ordered N-substituted triindole-based columnar liquid crystals. Shortening the length of N-alkylic substituents from N-dodecyl to N-methyl chains results in a drastic approach of the disks within the columns and in an impressive increase in charge carrier mobility. An study of aggregation in solution provide insights into the intermolecular forces responsible of the reduction of the intrastack distance as the size of the N-alkyl chains is decreased and offer evidence of stabilization of the columns by the contribution of cooperative CH−π interactions. The materials presented here exhibit mobility values, even in totally misaligned columnar phases, that may compete with those of the best polycrystalline organic semiconductors, without the need of costly vacuum evaporation processes., Support by Comunidad Autónoma de Madrid under project S2009/MAT-1756 and by Ministerio de Ciencia e Innovación (Spain) under projects CTQ2010-18813, CTQ2009-09030/BQU, MAT2011-27978-C02-01 are gratefully acknowledged.

Supramolecular hydrogelators based on amphiphilic glycolipids have been prepared by clicking different sugar polar heads to a hydrophobic linear chain by copper(I)-catalyzed azide-alkyne [3 + 2] cycloaddition. The influence of the sugar polar head on the gelation properties in water has been studied, and the liquid crystalline properties of the amphiphilic materials have also been characterized. Stable hydrogels at room temperature have been obtained and the fibrillar supramolecular structures formed by the self-assembly have been studied by different microscopic techniques on the dried gel (xerogel) and hydrated conditions in order to characterize the micro- and nanostructures. Self-assembly gives rise to supramolecular ribbons with a torsion that is related to a chiral supramolecular arrangement of amphiphiles. The formation of an opposite helical arrangement of the ribbons has been found to depend on the sugar polar head. This fact was confirmed by circular dichroism (CD). © 2012 American Chemical Society., Financial support from the Spanish MINECO project MAT2011-27978-C02-01, Fondo Europeo de Desarrollo Regional (FEDER), and Gobierno de Aragón, and Fondo Social Europeo is gratefully acknowledged.

We have successfully grown ultrasmall cobalt nanostructures (lateral size below 30 nm) by optimization of the growth conditions using focused electron-beam-induced deposition techniques. This direct-write nanolithography technique is thus shown to produce unprecedented resolution in the growth of magnetic nanostructures. The challenging magnetic characterization of such small structures is here carried out by means of electron holography techniques. Apart from growing ultranarrow nanowires, very small Hall sensors have been created and their large response has been unveiled.

A wide variety of ionic dendritic macromolecules based on bent-shaped structures have been synthesized and fully characterized. Regular polypropyleneimine dendrimers (PPI) of different generations and a random hyperbranched polymer (PEI) were selected as dendritic cores. Different bent-core structures derived from the 3,4′-biphenyl angular core with 5 or 6 aromatic rings as well as short and long terminal chains and spacers have been used for this study. The bent-core structure acts as strong driving force for the supramolecular arrangement of this type of macromolecules. All of the ionic dendritic polymers prepared show mesogenic behavior over broad temperature ranges, even if the carboxylic acid precursors were not mesomorphous. An extensive chemical structure-supramolecular organization relationship has been proposed for first time for this kind of bent-core dendrimer. Two types of supramolecular packing with lamellar and columnar order have been proposed on the basis of polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction. Additionally, fibers that present anisotropic optical behavior can be drawn from the materials. These results open new and stimulating possibilities for both bent-core based and dendritic supramolecular systems, with interest in basic and applied supramolecular chemistry and materials science scenarios. © 2011 American Chemical Society., Financial support from the Spanish Government (MICINNFEDER project MAT2009-14636-C03-01, CTQ2009-09030, DGA project E04), and Juan de la Cierva and JAE-DOC (N.G.) programs, and DGA (M.C. and J.V.) fellowship program are gratefully acknowledged.

Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens substituted with different chiral alkoxy chains, starting from commercially available 4-(4′-bromophenyl)phenol. Depending on the position of the chiral center and the polar nature of the target molecules as determined by the electron withdrawing end-groups, different types of smectic liquid crystals are formed. The liquid crystal phases are fully characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. In two cases, the molecular chirality is transferred to the supramolecular assembly, which is proved by circular dichroism measurements in the chiral mesophase. © 2010 American Chemical Society., We thank the CCC of the UAM and the following institution for financial support: MEC (Spain), grants CTQ2007-65683, CTQ2006-15611-CO2-01, and MAT2008- 06522-C02.

The achiral 4-methoxy-4-(p-methoxyphenyl)-cyclohexanone ethylene ketal (1) resolves spontaneously. The crystal structure is solved in chiral spatial group P2(1). Because compound 1 is composed of only light atoms (C, H, O) it is not possible to determine its absolute structure configuration. An efficient procedure for the absolute structure configuration determination of flexible molecules containing only light atoms is proposed, based on the combination of X-ray diffraction, solid-state VCD, and DFT calculations. © 2010 American Chemical Society., The authors are grateful to the CICYTFEDER Spainish project (MAT96-1073-C02, CTQ2009-13129- C02-02, and MAT2008-06522-C02) and the Government of Aragón and Madrid (Project MADRISOLAR, ref S-0505/PPQ/0225).

The synthesis and characterization of ionic liquid crystal dendrimers and hyperbranched polymers based on the ammonium salts of commercially available dendrimers poly propylene imine) [PPI-(NH2)n](with n ) 16), and poly(amidoamine) [PAMAM-(NH2)n] (with n ) 16), and random hyperbranched poly(ethyleneimine) (PEI) and the prepared fully methylated PEI (namely PEIMe) with 5-(4-cyanophenylazophenyloxy)pentanoic acid (CAzPA) are reported. The occurrence of proton transfer from the carboxylic acid to the amine groups was confirmed by IR and NMR measurements. 5-(4-nophenylazophenyloxy)pentanoic acid does not show mesogenic properties. However, all synthesized ionic complexes displayed a nematic mesophase. The liquid crystalline behavior was investigated by means of differential scanning calorimetry, polarizing light optical microscopy, and X-ray diffractometry. Themogravimetry analysis was carried out in order to determine the stability of the complexes, all of which have their mesophase-isotropic liquid transition under the temperature of 5% weight loss. Birefringence has been induced using 488 nm linearly polarized light in thin films of the ionic dendritic polymers containing azobenzene moieties. High and stable values of the in-plane order parameter up to 0.67 have been reached., This work has been supported by CICYT FEDER Spanish Projects MAT2005-06373-CO2-01 and CTQ2006-15611-CO2-01 and by the Gobierno de Aragón. Carlos Sánchez is grateful to MCYT and European Social Fund for support under the Ramón y Cajal program.

12 pages, 10 figures, 2 tables., A series of liquid crystalline azobenzene codendrimers with light-driven properties has been prepared by chemical modification of the third generation of an amine-terminated poly(propylene imine) (PPI) dendrimer. These photoactive dendrimers were obtained by grafting the photochromic 4-cyanoazobenzene and/or liquid crystalline 4-cyanobiphenyl units onto the periphery of PPI. The synthesized dendrimers include different percentages of each functional unit randomly distributed in the dendritic shell. The chemical structures of the dendrimers were characterized by several techniques to determine their composition. In particular, MALDI-TOF analysis provided detailed information about the chemical composition of the dendrimers. The photo-induced orientation of azobenzene groups in thin films of these dendrimers was studied. Illumination with either blue (488 nm) or UV (350 nm) linearly polarized light at room temperature gave rise to a stable dichroism and moderate birefringence values when 80% (molar ratio) of the units are azobenzene. In addition, pre-irradiation of the films with unpolarized UV light gave rise to higher birefringence values., This work was supported by the CICYTFEDER Spanish projects MAT2003-07806-C02-01, MAT2005- 06373-C02, the “Ramón y Cajal” program (MCYTMEC), and funding from the Government of Aragón.

8 pages, 10 figures, 3 tables., Several new cis-[RhCl(CO)2(Ln)] complexes have been prepared using different polycatenar pyrazole ligands (Ln) in order to obtain columnar liquid crystalline arrangements. The topology of the ligand plays an essential role, and a mesophase is induced at room temperature from a nonmesogenic pyrazole only when it is symmetrically substituted with six decyloxy chains. The single-crystal structure of a methoxy-substituted analogue, 3,5-bis(3,4,5-trimethoxyphenyl)pyrazole, is formed by globular tetrameric structures held together by H-bonding. However, parallel dimers are present in the corresponding cis-chlorodicarbonylrhodium(I) complex, a situation that explains the induction of a columnar mesophase in the decyloxy-substituted complex. The XRD pattern of the mesophase is consistent with a hexagonal symmetry in which the columns are formed by molecules assembled in an antiparallel mode. The crystal-to-mesophase transition was also detected by spectroscopic techniques as a shift in the IR carbonyl stretching bands and the appearance of a charge-transfer band in the absorption spectrum with thermochromic behavior., We thank the CICYT-FEDER MAT2003-07806-C02-01, BQU2000/1170, and the Programa Ramón y Cajal from the Ministerio de Educación y Ciencia (MEC), Spain, and the Gobierno de Aragón for financial support.

6 pages, 7 figures, 2 tables., The results of the study presented here show a new example of the use of liquid crystals and the interactions involved in the mesomorphic state to build up complex molecular organizations. We have pursued a design strategy in which hydrogen bonding allows the combination of the ð-stacking tendency of melamine and the lateral interaction capability of V-shaped molecules, which has been extensively demonstrated through nematic, smectic, or columnar mesophases. This combination addresses the formation of columnar arrangements with inherent helical organization. In this work, nonmesomorphic as well as mesomorphic V-shaped acids, with a structure similar to banana liquid crystals, have been complexed to a 2,4,6-triamino-1,3,5-triazine derivative in a proportion 3 to 1, respectively. Hydrogen-bonded supramolecules whose formation and stability in solution have been proven by infrared and NMR techniques have been thus obtained. DOSY experiments have allowed us to assess in solution the presence of the complexes and their tetrameric composition. All the complexes display mesogenic ability, and their mesomorphic organization has been studied by X-ray diffraction and CD spectroscopy. Results allow us to propose a helical columnar model for the mesophase originated from a propeller-like conformation of the supramolecular complexes., This work was supported by the CICYT project MAT2003-07806-CO2-01, FEDER funding (EU), and the DGA. We warmly thank Blanca Serrano for her effort in the drawings of the models presented in Figure 5.

7 pages, 7 figures, 3 tables., The synthesis and characterization of a new family of ionic liquid crystal dendrimers consisting of the ammonium salts of the commercially available poly(propylene imine) (G = 1−5) dendrimers and 4-decyloxy-, 3,4-didecyloxy-, and 3,4,5-tridecyloxybenzoic acids are reported. The liquid crystalline behavior was investigated by means of differential scanning calorimetry, polarizing-light optical microscopy, and X-ray diffractometry. Dendrimers with mono- and didecyloxybenzoate moieties show lamellar mesomorphism, namely, smectic A, whereas those with tridecyloxybenzoate units show columnar mesomorphism: rectangular for G = 1 and hexagonal for G = 2−5. On the basis of the experimental results, we propose models both at the molecular level and in the mesophase for all the materials., This work has been supported by the CICYT of Spain and the FEDER funds (EU) under Project Nos. MAT2002-04118-C02-01 and MAT2003-07806-C01, by the European Union under the RTN Project “Supermolecular Liquid Crystal Dendrimers (LCDD)” (No. HPRN-CT2000-00016), and by the Diputación General de Arago´n. R.M.-R. acknowledges a fellowship from the Ministerio de Educación y Ciencia (Spain).

6 pages, 3 figures, 4 tables, 1 appendix.-- Supporting Information Available: http://pubs.acs.org., Two families of liquid crystal dendrimers consisting of a dendrimeric core [fourth and fifth generations of poly(amidoamine) (PAMAM) and poly(propyleneimine) (DAB)] and several large-sized mesogenic units (incorporating three, six, and nine terminal alkoxy chains) have been prepared. The study of these materials reveals the existence of a hexagonal columnar mesomorphism in all cases. We propose a model to explain this behavior based on theoretical calculations made from experimental X-ray diffraction data. The plasticity of the dendrimeric cores, related to their conformational freedom, allows the macromolecules to adopt a cylindrical shape in which the mesogenic units are accommodated around the central core. As a result of this cylindrical symmetry of the molecules, a supramolecular columnar arrangement is present in the mesophase. A complete degree of functionalization of some of the dendrimers would prevent the appearance of a columnar mesophase according to our model. However, we have found that, in all cases, the number of promesogenic units attached to the dendrimer cores is lower than that possible, which permits the cylindrical arrangement of the macromolecules and the existence of columnar mesomorphism., This work has been supported by the CICYT of Spain and the FEDER funds (E. U.) under the Projects MAT2002- 04118-C02-01 and MAT2003-07806-C01, by the European Union under the RTN Project “Supermolecular Liquid Crystal Dendrimers (LCDD)” (HPRN-CT2000-00016), and by the Diputación General de Aragón. R.M.R. acknowledges a fellowship from the Ministerio de Educación y Ciencia (Spain).

Rh(OCOCR3)(cod)Ln (1-6) and cis-Rh(OCOCR3)(CO)2Ln (7-12) (R = H, F; cod = 1,5-cycloctadiene; Ln = NC5H4CH=NC6H4OCnH 2n+1 with n = 2, 8, 14) complexes have been prepared by the reaction of the Ln ligands with the corresponding dimers [Rh(OOCCR3)(cod)]2 or [Rh(OOCCR3)(CO)2]2 (R = H, F). The cis-dicarbonyl compounds 7-12 decompose in dichloromethane solution to form square-planar clusters of 64 electrons, Rh4(OOCCH3)4(CO)4 Ln 4 (13-18). The molecular structure of Rh4(OOCCH3)4(CO)4L14 4 (15) has been determined by X-ray investigation. The complex is centrosymmetric, and the four rhodium atoms define a rectangle. Two alternant metal-metal bonds of the rectangle are bridged by two carbonyl groups; the other two remaining Rh-Rh bonds are bridged by two acetate groups. Each metal completes its coordination sphere with the pyridinic ligand NC5H4CH=NC6H4OC14H 29. Crystal data for 15: space group P1, a = 10.300 (1) Å, b = 11.166 (1) Å, c = 26.216 (3) Å; α = 89.29 (1)°, β = 88.68 (1)°, γ = 72.17 (1)°; 4491 reflections, R = 0.041, Rw = 0.041. The complexes [Rh4(OOCCH3)4(CO)4(py)4] (19, 20; R = H, F; py = pyridine) are also reported. © 1991 American Chemical Society.

The liquid-crystal behavior of four series of ionic complexes of silver(I) with structure [AgL2]+X- have been investigated by using differential scanning calorimetry (DSC), optical microscopy, and X-ray diffraction techniques. Two different nonmesogenic pyridine derivatives, NC5H4CH=NC6H4OCnH 2n+1 and NC5H4COOC6H4OCnH 2n+1, were used as ligands (L) and four anions, BF4 -, CF3SO3 -, NO3 -, and PF6 -, as counterions (X-). The influence of both the organic ligand and counterion on the liquid-crystal properties of these complexes was studied. These complexes displayed mesogenic behavior identical with that exhibited by typical calamitic liquid crystals. Some of the complexes exhibited additional stable phases between the low-temperature solid phase and the liquid-crystalline phase. A comparative study has shown that pyridinecarboxylate derivatives show higher transition temperatures and wider mesophase ranges than similar imine derivatives. With regard to counterions, the less voluminous the anion, the broader the mesophase range and the lower the melting point. © 1990 American Chemical Society., This work was supported by the EEC (Project ST2J-0387-C).

We acknowledge support from the EC Twinning (Grant No. ST2J-0387-c), the Royal Society, the SERC, and the Spanish Ministry of Education.