Papers by Antonella Badia
Elucidating the influence of the monolayer interface versus bulk on the macroscopic properties (e... more Elucidating the influence of the monolayer interface versus bulk on the macroscopic properties (e.g., surface hydrophobicity, charge transport, and electron transfer) of organic self-assembled monolayers (SAMs) chemically anchored to metal surfaces is a challenge. This article reports the characterization of prototypical SAMs of n-alkanethiolates on gold (CH3(CH2)nSAu, n = 6-19) at the macroscopic scale by electrochemical impedance spectroscopy and contact angle goniometry, and at the molecular level, by infrared reflection absorption spectroscopy. The SAM capacitance, dielectric constant, and surface hydrophobicity exhibit dependencies on both the length (n) and parity (nodd or neven) of the polymethylene chain. The peak positions of the CH2 stretching modes indicate a progressive increase in the chain conformational order with increasing n between n = 6 and 16. SAMs of nodd have a greater degree of structural gauche defects than SAMs of neven. The peak intensities and positions of the CH3 stretching modes are chain length independent but show an odd-even alternation of the spatial orientation of the terminal CH3. The correlations between the different data trends establish that the chain length dependencies of the dielectric constant and surface hydrophobicity originate from changes in the polymethylene chain conformation (bulk), while the odd-even variation arises primarily from a difference in the chemical composition of the interface related to the terminal group orientation. These findings provide new physical insights into the structure-property relation of SAMs for the design of ultrathin film dielectrics as well as the understanding of stereostructural effects on the electrical characteristics of tunnel junctions.
Canadian Journal of Chemistry, 2020
The ability of organic self-assembled monolayers (SAMs) to act as insulating barriers to electron... more The ability of organic self-assembled monolayers (SAMs) to act as insulating barriers to electron transfer, ion transport, or molecular diffusion is critical to their application in a variety of technologies. The use of appropriate analytical tools to characterize the dielectric properties of these molecular thin films is important for the control of structural defects and establishing structure–property relations. In this context, we analyze the ionic permeability and dielectric response of SAMs formed from a homologous series of n-alkanethiolates (CH3(CH2)nS, where n = 9, 11, 13, 15, 17, and 19) on gold using the immittance quantities of the complex impedance, capacitance, and permittivity available from the same electrochemical impedance spectroscopy (EIS) measurement. The most sensitive parameters and frequency range for characterizing the capacitive behavior and assessing the ion-blocking quality of the SAMs under non-Faradaic conditions are identified. We also investigate the ...
Journal of the American Chemical Society, 2018
Microcantilever transducers can be valuable tools for the investigation of physicochemical proces... more Microcantilever transducers can be valuable tools for the investigation of physicochemical processes in organized molecular films. Gold-coated cantilevers are used here to investigate the electrochemomechanical behavior of redox-active self-assembled monolayers (SAMs) of ferrocenylalkanethiolates (Fc(CH2)nS) of different alkyl chain lengths. A significant odd-even effect is observed in the surface stress and cantilever movement generated by the oxidation of the SAM-confined ferrocenes as the number of methylene units n in the SAM backbone is varied. We demonstrate that stronger alkyl chain-chain interactions are at the origin of the larger surface stresses generated by SAMs with an even versus odd n. The findings highlight the impact of subtle structural effects and weak van der Waals interactions on the mechanical actuation produced by redox reactions in selfassembled systems.
ECS Transactions, 2011
The electrochemically-activated deflection of free-standing microcantilevers has received conside... more The electrochemically-activated deflection of free-standing microcantilevers has received considerable interest for chemical sensing and nanoactuation. The development and optimization of this type of microcantilever transduction still requires a molecular-level understanding of the surface stress changes that cause the cantilever to bend. We present here the results of an on-going investigation of the electroactuation dynamics of gold-coated microcantilevers modified with model, redox-active ferrocenylalkanethiolate self-assembled monolayers. The microcantilever transducer enables the observation of the electrochemical transformation of the surface-confined ferrocenes to ferroceniums. We find that the ferrocenylalkanethiolate monolayer induces charge-normalized surface stress changes that are at least 10-fold greater than those generated by multilayers of the conducting polymers commonly used for electroactuation. The effects of the electrolyte anion and ferrocene coverage on the m...
Nano Letters, 2002
A new methodology has been used to create an extensive array of nanometer-sized features. The Ar ... more A new methodology has been used to create an extensive array of nanometer-sized features. The Ar + milling of Si/SiO x and gold surfaces covered with a diblock copolymer mask with an intrinsic topological nanopattern yields transfer of the nanopattern. Mask removal was tracked using XPS, and the final arrays were characterized by AFM and LFM. Friction contrast observed throughout the transferred pattern is associated with a surface water layer.
Langmuir, 1996
ABSTRACT The structure and dynamical behavior of short and long chain alkanethiols, CH3(CH2)7SH a... more ABSTRACT The structure and dynamical behavior of short and long chain alkanethiols, CH3(CH2)7SH and CH3(CH)17SH, and of a hydroxyalkanethiol, HO(CH2)16SH, adsorbed onto gold nanoparticles were studied by variable temperature solid-state 13C NMR spectroscopy. In both the solution and solid state, the resonances of the first three carbons next to the sulfur headgroup disappear upon binding to the gold, indicating a strong interaction with the surface. A 13C-enriched sample, CH3(CH2)12*CH2SH/gold, displays a broad resonance centered at 42 ppm for the carbon next to the sulfur headgroup. Whereas the solid-state 13C shifts of CH3(CH2)7SH/gold are essentially the same as in solution, the methylene carbons of CH3(CH2)17SH and HO(CH2)16SH/gold shift downfield by 4.5 ppm in the solid state, indicating that the chains crystallize into an extended all-trans conformation. The high conformational order, along with reduced methylene proton line widths in the CH3(CH)17SH/gold sample, indicates that the chains are undergoing large-amplitude motions about their long axes. Molecular mobility increases toward the unbound ends which have a higher population of gauche conformers. Relaxation measurements show the coexistence of motionally restricted all-trans chains and a smaller population of liquid-like conformationally disordered chains in CH3(CH2)17SH/gold at room temperature. The two types of chains are proposed to arise from close packing of the gold colloidal spheres, resulting in interstitial spaces and regions where chains of neighboring colloids can interdigitate to produce ordered domains. Phase transitions of the thiol-capped gold nanocrystals, which are detected by differential scanning calorimetry, are shown to involve a reversible disordering of the alkyl chains.
Langmuir, 2003
A new methodology has been developed to create an extensive pattern of parallel stripes, ∼150-250... more A new methodology has been developed to create an extensive pattern of parallel stripes, ∼150-250 nm wide, in phospholipid bilayers supported on mica. These striped bilayers are prepared by the Langmuir-Blodgett (LB) film technique. A striped monolayer consisting of two phospholipids in different states (condensed and liquid-expanded) is used to direct the deposition of the solid-and liquidlike phases of a second mixed monolayer during LB transfer. We also demonstrate that bilayer stripes can be generated by the condensation of phospholipids over the solidlike stripe domains of the underlying monolayer for a one-component film deposited just below the liquid-expanded-to-liquid-condensed phase transition pressure. Nonionic detergent extraction of the liquidlike phase from these LB films resulted in bilayerthick phospholipid stripes separated by a mica surface. A periodic array of grooves was produced by the selective adsorption of protein onto the mica regions of the detergent-treated bilayer. The LB film deposition of binary mixtures of solid-phase-and fluid-phase-forming phospholipids constitutes a novel strategy to create linear surface patterns that can be used to direct the deposition of molecules.
Langmuir, 2010
Metal-reactive organosulfur groups were patterned onto mica and silicon surfaces by dewetting ins... more Metal-reactive organosulfur groups were patterned onto mica and silicon surfaces by dewetting instabilities during the Langmuir-Blodgett (LB) deposition of phase-separated mixed phospholipid monolayers. Monolayers were formed from binary mixtures of dipalmitoylphosphatidylcholine (DPPC), dilauroylphosphatidylcholine (DLPC), and their ω-methyldisulfide-dialkylphosphatidylcholine analogues, DSDPPC and DSDLPC. Patterns of highly parallel stripes of condensed DPPC or DSDPPC, protruding by 0.7-0.9 nm from a fluid matrix of DLPC or DSDLPC, were observed over areas extending at least 30 Â 30 μm 2 in the LB films. The average stripe width varied from ca. 150 to 500 nm, depending on the lipid composition and deposition pressure. X-ray photoelectron spectroscopy confirmed that the phospholipid-monolayer-bound methydisulfides react with Au vapor to form a gold-thiolate species. The adsorption of thermally evaporated Au, Ag, and Cu onto DSDPPC/DLPC and DPPC/DSDLPC patterns was investigated by field emission gun scanning electron microscopy (FEGSEM) and atomic force microscopy (AFM). A change in phase contrast is observed in FEGSEM and AFM over the methyldisulfide-functionalized areas following metal deposition due to metal-thiolate bond formation. An increase in step height between the DSDPPC stripes and nonfunctionalized DLPC background following metal deposition, as well as the resistance of the metal-coated DSDPPC or DSDLPC regions to detergent extraction from the surface, attest to a selective metallization of the pattern. Our results indicate that the preferential adsorption of vapor-deposited metal onto the ω-methyldisulfide-terminated phase occurs at submonolayer coverages. The chemical reactivity exhibited by the organosulfur-modified phospholipid LB films make these templates potentially interesting for the fabrication of solid-supported patterns of metal nanostructures.
Langmuir, 2013
This contribution offers a comprehensive understanding of the factors that govern the morphologie... more This contribution offers a comprehensive understanding of the factors that govern the morphologies of Langmuir−Blodgett (LB) monolayers of amphiphilic diblock copolymers (BCs). This is achieved by a detailed investigation of a wide range of polystyrenepoly(4-vinyl pyridine) (PS-P4VP) block copolymers, in contrast to much more limited ranges in previous studies. Parameters that are varied include the block ratios (mainly for similar total molecular weights, occasionally other total molecular weights), the presence or not of 3-npentadecylphenol (PDP, usually equimolar with VP, with which it hydrogen bonds), the spreading solution concentration ("low" and "high"), and the LB technique (standard vs "solvent-assisted"). Our observations are compared with previously published results on other amphiphilic diblock copolymers, which had given rise to contradictory interpretations of morphology formation. Based on the accumulated results, we re-establish early literature conclusions that three main categories of LB block copolymer morphologies are obtained depending on the block ratio, termed planar, strand, and dot regimes. The block composition boundaries in terms of mol % block content are shown to be similar for all BCs having alkyl chain substituents on the hydrophilic block (such as PS-P4VP/PDP) and are shifted to higher values for BCs with no alkyl chain substituents (such as PS-P4VP). This is attributed to the higher surface area per repeat unit of the hydrophilic block monolayer on the water surface for the former, as supported by the onset and limiting areas of the Langmuir isotherms for the BCs in the dot regime. 2D phase diagrams are discussed in terms of relative effective surface areas of the two blocks. We identify and discuss how kinetic effects on morphology formation, which have been highlighted in more recent literature, are superposed on the compositional effects. The kinetic effects are shown to depend on the morphology regime, most strongly influencing the strand and, especially, planar regimes, where they give rise to a diversity of specific structures. Besides film dewetting mechanisms, which are different when occurring in structured versus unstructured films (the latter previously discussed in the literature), kinetic influences are discussed in terms of chain association dynamics leading to depletion effects that impact on growing aggregates. These depletion effects particularly manifest themselves in more dilute spreading solutions, with higher molecular weight polymers, and in composition regimes characterized by equilibrium degrees of aggregation that are effectively infinite. It is by understanding these various kinetic influences that the diversity of structures can be classified by the three main composition-dependent regimes.
Journal of the American Chemical Society, 2005
The layer-by-layer growth of multilayer assemblies of two polysaccharides, the polyanion hyaluron... more The layer-by-layer growth of multilayer assemblies of two polysaccharides, the polyanion hyaluronan (HA) and the polycation chitosan (CH), was investigated using atomic force microscopy (AFM) and surface plasmon resonance (SPR) spectroscopy, with primary emphasis on the effect of the polysaccharide molecular weights on the film thickness and surface morphology. The HA/CH multilayers exhibit an exponential increase of the optical film thickness with the number of deposited bilayers. We show that the multilayer thickness at a given stage depends on the size of both CH, the diffusing polyelectrolyte, and HA, the nondiffusing species. Assemblies (12 bilayers) of high molecular weight polysaccharides (HA, 360 000; CH, 160 000) were twice as thick (∼900 nm vs ∼450 nm) as those obtained with low molecular weight polymers (HA, 30 000; CH, 31 000), as assessed by AFM scratch tests. The exponential growth rate is the same for the high and low molecular weight pairs; the larger film thicknesses observed by SPR and by AFM arising from an earlier onset of the steep exponential growth phase in the case of the high molecular weight pair. In all cases, isolated islets form during the deposition of the first CH layer onto the underlying HA. Upon further film growth, individual islets coalesce into larger vermiculate features. The transition from distinct islands to vermiculate structures depends on the molecular weights of the polysaccharides and the lower molecular weight construct presents larger wormlike surface domains than the high molecular weight pair.
Journal of the American Chemical Society, 2009
Supporting Information S2 Experimental Section Materials and Methods. The following compounds wer... more Supporting Information S2 Experimental Section Materials and Methods. The following compounds were purchased and used without further purification: 1-undecanethiol (C 11 SH, 98%, Sigma-Aldrich), 11-bromoundecanoic acid (≥98%, Fluka), perchloric acid (70%, Fluka), ferrocene (≥98%, Fluka), and sodium perchlorate (98%, Sigma-Aldrich). 11-Ferrocenyl-1-undecanethiol (FcC 11 SH) was prepared starting from ferrocene and 11bromoundecanoic acid according to the procedure of Creager and Rowe. 1 The purity and identity of the product was verified by thin layer chromatography (silica gel, hexanes/ethyl acetate 99:1 v/v) and 1 H NMR (400 MHz, CDCl 3), and are consistent with those previously reported. The perchlorate electrolyte solution consisted of 0.01 M HClO 4 /0.1M NaClO 4 (pH 3.1, 20 C 589nm n° = 1.33) and was prepared with deionized-distilled water obtained by purification of distilled water with a Milli-Q Gradient system (Millipore, Bedford, MA). The resistivity of the purified water was 18.2 MΩ•cm, and its surface tension, measured at 24 °C, was 72 mN m-1. The perchlorate electrolyte solution was purged with nitrogen for at least 20 min prior to running electrochemical measurements. Preparation and Characterization of the SAM-Gold Substrates. V-and rectangular-shaped silicon nitride microcantilevers were purchased from Veeco (MLCT-NOHW, Santa Barbara, CA). Six microcantilevers of different geometric dimensions and spring constants are mounted on a single chip substrate. The experiments described in the present study predominantly used the V-shaped microcantilevers with spring constants (k) of 0.01 and 0.13 N m-1 , as well as the rectangular-shaped microcantilever of k = 0.02 N m-1. We also used rectangular silicon/silicon oxide microcantilevers obtained from MikroMasch USA (CSC12/tipless/without Al, Wilsonville, OR). The V-and rectangular-shaped microcantilevers had dimensions in the range of 85-350 µm length, 18-35 µm width, and 0.6-1.0 µm thickness. The typical dimensions provided by the manufacturer and the experimentally determined spring constants for the microcantilevers used in our experiments are listed in Table S1.
Journal of the American Chemical Society, 2013
Oxidoreduction of self-assembled monolayers (SAMs) of ferrocenyldodecanethiolate on gold in aqueo... more Oxidoreduction of self-assembled monolayers (SAMs) of ferrocenyldodecanethiolate on gold in aqueous solutions of surfaceactive sodium n-alkyl sulfates (NaC n SO 4) of 6, 8, 10, and 12 carbons is investigated by cyclic voltammetry and surface plasmon resonance. The effects of surfactant micellization and alkyl chain length on the redox response of the surface-tethered ferrocenes are examined. The SAM redox electrochemistry is sensitive to the surfactant aggregation state in solution. The nonideal behavior of the sodium alkyl sulfates at concentrations above the critical micelle concentration leads to a non-Nernstian variation of the SAM redox potential with concentration. The presence of micelles in solution results in decreased anodic-tocathodic peak separations and anodic peak full widths at half-maximum. A longer alkyl chain length results in an increased ability of the alkyl sulfate anion to ion pair with the SAM-bound ferrocenium, resulting in oxidation of the ferrocene at lower potential. A comparison of the SAM redox potential at a fixed surfactant concentration of ideal behavior suggests a 4.5 × 10 4 difference in the ion-pairing abilities of the shorter-chain C 6 SO 4 − and longerchain C 12 SO 4 −. One-half of the available SAM-bound ferrocenes are oxidized in the NaC n SO 4 electrolyte. Surfactant anions adsorb and assemble onto the SAM surface by specific ion-pairing interactions between the sulfate headgroups and oxidized ferrocenium species, forming an interdigitated monolayer in which the surfactant anions alternate between a heads-down and heads-up orientation with respect to the SAM. The work presented points to applications of ferrocenylalkanethiolate SAMs as anion-selective membranes, probes of micelle formation, and surfaces for the electrochemically switchable assembly of organosulfates.
Journal of the American Chemical Society, 2005
Enzymes are appealing nanolithography tools due to their high specificity and efficiency at catal... more Enzymes are appealing nanolithography tools due to their high specificity and efficiency at catalyzing chemical reactions under mild conditions in aqueous medium. Recent studies have demonstrated the feasibility of using enzymes to create specific nanoscale motifs in organic thin film surfaces. 1 Directing and confining the enzyme reaction to defined regions of a surface remains, however, the fundamental challenge in enzyme-promoted lithography. The main strategy adopted to date is to use the direct-writing capability of scanning probe microscopy and enzyme-modified or-coated probes to direct the enzyme toward a desired location of a homogeneous film surface. 1b-d Alternative approaches that do not require proximal probes 1 to localize the enzymatic action must be explored to evaluate the scope and versatility of enzyme lithography. We have investigated the possibility of spatially directing a stereospecific lipolytic enzyme reaction using surface patterns of the biologically active and inactive enantiomers of the lipid substrate. We used phospholipase A 2 (PLA 2), an interfacially active, calcium-dependent enzyme which catalyzes cleavage of the sn-2 ester linkage of glycerophospholipids, yielding fatty acid and lysophospholipid. 2 The natural L lipid form is hydrolyzed; PLA 2 binds but does not cleave the physicochemically identical D form. 3 Atomic force microscopy (AFM) studies of the degradation of onecomponent, supported planar bilayers of solid-condensed L-Rdiacylphosphatidylcholines (di-C n PCs) have shown that enzymatic hydrolysis starts at hole defects (i.e., exposed lipid cleavage sites), and that PLA 2 degrades both top and bottom layers. 4 We report herein the stereoselectiVe PLA 2 hydrolysis of nanoscale stripe patterns in bilayer films consisting of the L and D isomers of di-C 12 PC (DLPC) and di-C 16 PC (DPPC). Bilayers, consisting of condensed or solid-like DPPC stripes in a fluid DLPC matrix, were prepared by successive Langmuir-Blodgett transfer of two phase-separated DPPC/DLPC (1:3) monolayers from the air/water interface to mica at a surface pressure of 25 mN/m, as previously described. 5 The resulting pattern results from the superposition of the condensed DPPC stripe domains and fluid DLPC phases present in both layers (Figure 1), as revealed by detergent extraction of the fluid phase from these films 5 and visualized by near-field scanning optical microscopy 6. Structural characterization of the striped bilayer and its formation mechanism have been reported elsewhere. 5 By using combinations of the L, D, and DL (racemic) forms of DPPC and DLPC, we have generated novel membrane templates with built-in stereochemical control over the PLA 2 activity. Each of the enantiomer combinations exhibited the same bilayer pattern structure as the one shown in Figure 2A for D-DPPC/DL-DLPC. Parallel stripes of a thicker DPPC phase are observed; these are ∼1.1 nm higher than the surrounding matrix 5,6 and occupy 18 (5% of the total surface area. Regions of narrower broken stripes (width ≈ 130-190 nm) are dispersed among areas of wider continuous lines (width ≈ 200-300 nm). 5,7 Bilayer-deep holes,
Journal of Nanoscience and Nanotechnology, 2006
The stability of polyelectrolyte multilayer assemblies was investigated with emphasis on the effe... more The stability of polyelectrolyte multilayer assemblies was investigated with emphasis on the effects of solution ionic strength, pH, and polymer molecular weight on the film thickness and surface topography. The multilayers consisting of two polysaccharides, the polyanion sodium hyaluronate (HA) and the polycation chitosan (CH) were studied using surface plasmon resonance (SPR) spectroscopy, impedance quartz crystal microbalance (QCM), and atomic force microscopy (AFM). SPR/QCM experiments show that coatings consisting of four HA/CH bilayers assembled at pH 4.5 in the presence of 0.15 M NaCl are stable in NaCl solutions of concentration less than 0.8 M. These multilayers are stable when placed in contact with aqueous solutions ranging in pH from 3.5 to 9. The molecular weight of the polysaccharides has only a marginal effect on the stability of the films in the range explored here (HA: Mn = 360,000 or 31,000 g/mol; CH: Mn = 160,000 or 30,000 g/mol). AFM imaging reveals that different mechanisms may account for the multilayers stability versus salt and pH treatments. While increasing the ionic strength induces reorganization of the surface topography from isolated spherical islets to elongated worm-like features, changes in pH have no appreciable effects on the coating topography prior to complete disintegration.
The Journal of Chemical Physics, 2004
The microscopic structure of Langmuir films of derivatized gold nanoparticles has been studied as... more The microscopic structure of Langmuir films of derivatized gold nanoparticles has been studied as a function of area/particle on the water surface. The molecules (AuSHDA) consist of gold particles of mean core diameter Dϳ22 Å that have been stabilized by attachment of carboxylic acid terminated alkylthiols, HS-(CH 2) 15-COOH. Compression of the film results in a broad plateau of finite pressure in the surface pressure versus area/particle isotherm that is consistent with a first-order monolayer/bilayer transition. X-ray specular reflectivity ͑XR͒ and grazing incidence diffraction show that when first spread at large area/particle, AuSHDA particles aggregate two dimensionally to form hexagonally packed monolayer domains at a nearest-neighbor distance of aϭ34 Å. The lateral positional correlations associated with the two-dimensional ͑2D͒ hexagonal order are of short range and extend over only a few interparticle distances; this appears to be a result of the polydispersity in particle size. Subsequent compression of the film increases the surface coverage by the monolayer but has little effect on the interparticle distance in the close-packed domains. The XR and off-specular diffuse scattering ͑XOSDS͒ results near the onset of the monolayer/bilayer coexistence plateau are consistent with complete surface coverage by a laterally homogeneous monolayer of AuSHDA particles. On the high-density side of the plateau, the electron-density profile extracted from XR clearly shows the formation of a bilayer in which the newly formed second layer on top is slightly less dense than the first layer. In contrast to the case of the homogeneous monolayer, the XOSDS intensities observed from the bilayer are higher than the prediction based on the capillary wave model and the assumption of homogeneity, indicating the presence of lateral density inhomogeneities in the bilayer. According to the results of Bragg rod measurements, the 2D hexagonal order in the two layers of the bilayer are only partially correlated.
Inorganic Chemistry, 2005
The synthesis and characterization of nine coordination networks based on 1,3-bis(phenylthio)prop... more The synthesis and characterization of nine coordination networks based on 1,3-bis(phenylthio)propane, L(3), and silver(I) salts of PF(6)(-) (1), CF(3)COO(-) (2), CF(3)CF(2)COO(-) (3), CF(3)CF(2)CF(2)COO(-) (4), p-TsO(-) (5, 6), and CF(3)SO(3)(-) (7-9) are reported. Only 1 and other "isostructural" complexes with weakly coordinating anions such as ClO(4)(-) and SbF(6)(-) are of the host-guest type. In all the other complexes, the anions and the acetone molecules, when present, are coordinated to the metal. Most of the complexes studied here form a 2D-coordination network. Only 4 and 5 adopt a polymer-like chain structure. The packing of the chains of 4 is pseudohexagonal compact, while that of 5 is of the centered type. In complex 1, the silver atom is tetrahedrally coordinated to the sulfur atoms of four different ligands. The PF(6)(-) anions and acetone molecules, sandwiched between silver-ligand cationic sheets, are held through van der Waals interactions. In each of the three perfluorocarboxylates (2-4), two silver atoms are joined by the anions in a diatomic bridging mode. The Ag...Ag distances are sufficiently short to indicate weak metal...metal interactions. The dimeric units in 2 and 3 are interconnected through the ligands, thereby generating a 2D-network of neutral sheets, while, in 4, the dimeric units are bound to four ligands and a 1D-coordination polymer is generated. In the case of the sulfonate anions (p-TsO(-) and CF(3)SO(3)(-)), the crystallization solvent influences the structure adopted. Thus, in 5, 7, and 9 obtained from petroleum ether, or other nonpolar solvents, two silver atoms are bound in a double-bridge fashion, while a monobridge mode is noted for 6 and 8, both recrystallized from diethyl ether. In 8, both bridging types are observed. The thermogravimetric investigation, in the room temperature-450 degrees C interval, of complexes 1, 3, and 7, which incorporate acetone molecules in their crystal structures, reveals a two-step weight loss for 1 (the acetone molecules are lost first followed by the ligands, leaving behind the silver salt), while complexes 3 and 7 decompose in a single step to metallic silver.
Inorganic Chemistry, 2006
This report describes the synthesis and X-ray characterization of a series of L n AgX complexes w... more This report describes the synthesis and X-ray characterization of a series of L n AgX complexes wherein L n) PhS(CH 2) n SPh (n) 2, 4, 6, 10) and X) CF 3 SO 3-, CF 3 COO-, CF 3 CF 2 COO-, CF 3 CF 2 CF 2 COO-, NO 3-, and ClO 4-. This study was undertaken in order to rationalize the structure of the coordination networks formed as a function of the anion coordinating strength and the ligand structure. The following complexes were examined: with L 2 , CF 3 SO 3-(1), CF 3 COO-(2), ClO 4-(3); L 4 , CF 3 SO 3-(4), CF 3 COO-(5), CF 3 CF 2 COO-(6), CF 3 CF 2 CF 2 COO-(7); L 6 , CF 3 COO-‚H 2 O (8), CF 3 CF 2 COO-(9), CF 3 CF 2 CF 2 COO-(10); and L 10 , NO 3-(11). The anions selected are classified in three groups of increasing coordinating strength: perchlorates, fluorosulfonates, and perfluorocarboxylates. Except in two cases, all complexes form 2D-coordination networks. The 2D-network in 1 (L 2 , CF 3 SO 3-) is made up of Ag(I) and L 2 , while the anion is only a terminal co-ligand that completes the trigonal coordination around Ag(I). In 4 (L 4 , CF 3 SO 3-), a 1D-coordination polymer, [Ag−L 4 −] ∞ , is observed where the anions are coordinated to Ag(I) in a trigonal fashion. The perfluorocarboxylates form tetrameric units in a zigzag shape, but only with the L 4 ligand. In these (6 and 7), the silver−silver distances are very short, especially those of the central bond, indicating the presence of weak Ag−Ag interactions. Dimers, with short silver−silver distances, are observed with ligands L 2 and L 6 and perfluorocarboxylates. In 8 (L 6 , CF 3 COO-‚H 2 O), a 3D channel-like structure is built through water molecules that connect adjacent layers. An unusual stoichiometry is noted in 3 (L 2 , ClO 4-, acetone); Ag:L is 4:2.5. In 11 (L 10 and NO 3-), the nitrate acts as a bidentate ligand and an [Ag−NO 3 −] ∞ chain is formed. Adjacent chains are linked by the L 10 ligands into a 2D-coordination network.
Inorganic Chemistry, 2008
Crystal Growth & Design, 2006
The complexes obtained with small anions, perflurocarboxylates, and trifluoromethane sulfonate co... more The complexes obtained with small anions, perflurocarboxylates, and trifluoromethane sulfonate consist of 2D coordination networks with topologically comparable [Ag-L]∞ layer structures. The anions, located between the layers, complete the tetrahedral coordination ...
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Papers by Antonella Badia