Removal Of Ligands Research Articles

Surface Engineering of Room Temperature-Grown Inorganic Perovskite Quantum Dots for Highly Efficient Inverted Light-Emitting Diodes.

Inorganic cesium lead bromide quantum dots (CsPbBr3 QDs) are usually synthesized via a high-temperature process (hot injection, HI). This process is similar to that used for the synthesis of other semiconductor QDs (i.e., CdSe@ZnS), which limits their potential cost advantage. CsPbBr3 QDs can also be synthesized at room temperature (RT) in a low cost and easily scalable process, which, thus, is one of the greatest advantages of the CsPbBr3 QDs. However, light-emitting diodes (LEDs) fabricated using RT-QDs exhibit poor performance compared to those of HI-QDs. In fact, QDs are surrounded by insulating ligands to maintain their colloidal stability but these ligands need to be removed to obtain high-performance LEDs. Here, we show that ligand removal techniques used for HI-QDs are not sufficient in the case of RT-QDs. Additional ligand engineering and annealing steps are necessary to remove the excess of ligands from RT-QD films while preventing the coalescence of the QDs. The eventual surface defects induced by annealing can be healed by a subsequent photoactivation step. Moreover, the use of solution processable inorganic charge transport layers can reduce the fabrication costs of LEDs. We fabricated an inverted LED based on a metal oxide electron transport layer and a RT-QD emitting layer which exhibited a maximum current efficiency of 17.61 cd A-1 and a maximum luminance of 22 825 cd m-2.

Probing ligand removal and ordering at quantum dot surfaces using vibrational sum frequency generation spectroscopy

HypothesisControlling nanomaterial interfaces for emerging technologies has driven the need to understand the molecular species located there; however, challenges arise using traditional analytical techniques to directly characterize the molecular structure and local environments of these interfacial species due to their low relative populations. We hypothesized that vibrational sum frequency generation (vSFG) spectroscopy would be uniquely sensitive to the chemical modification of nanoparticle surfaces that is obscured using traditional bulk sensitive methods. ExperimentsOctadecylamine ligands were removed from model CdSe quantum dot surfaces using a common precipitation-resuspension procedure with polar protic and aprotic nonsolvents. Vibrational spectra of the ligands at the surface were collected with vSFG to directly probe the ligand ordering and coverage. Photoluminescence (PL), optical absorption, NMR, and mass spectrometry measurements were conducted for comparison. FindingsvSFG was found to be sensitive to subtle changes in ligand disorder over multiple precipitation-resuspension washes, and a limit to the number of ligand molecules removed from the surface and subsequent amount of disorder introduced to their packing was clearly observed. We also find that nonsolvents do not remain associated with the surface after washing.

Electrophilic substitution reaction as a facile and general approach for reactive removal of native ligands from nanocrystals surface

Surface property that strongly affects physical and chemical performances of inorganic nanocrystals (NCs) is a key enabler for NCs applications. Here, we report a facile, versatile and general strategy for reactive removal of NCs surface ligands based on electrophilic substitution reaction, in which an electrophile directly reacts with the electron-rich coordinating headgroup of surface-tethered ligands to form a non-coordinating product. This process leads to the break of NC-ligand bond, thereby achieving reactive removal of surface ligands. Based on this strategy, various hydrophobic NCs with different compositions and morphologies can be transferred into polar and hydrophilic media while preserving their size and shape. More importantly, the treated NCs present a great improvement in catalytic and biological performances in comparison with the untreated counterparts. This work not only provides a versatile ligand removal strategy for NCs surface modification but also opens up more opportunities for applications in the fields of electronics, catalysis and biotechnology.

Closed-Locked and Apo-Resting State Structures of the Human α7 Nicotinic Receptor: A Computational Study.

Nicotinic acetylcholine receptors, belonging to the Cys-loop superfamily of ligand-gated ion channels (LGICs), are membrane proteins present in neurons and at neuromuscular junctions. They are responsible for signal transmission, and their function is regulated by neurotransmitters, agonists, and antagonists drugs. A detailed knowledge of their conformational transition in response to ligand binding is critical to understanding the basis of ligand-receptor interaction, in view of new pharmacological approaches to control receptor activity. However, the scarcity of experimentally derived structures of human channels makes this perspective extremely challenging. To contribute overcoming this issue, we have recently reported structural models for the open and the desensitized states of the human α7 nicotinic receptor. Here, we provide all-atom structural models of the same receptor in two different nonconductive states. The first structure, built via homology modeling and relaxed with extensive Molecular Dynamics simulations, represents the receptor bound to the natural antagonist α-conotoxin ImI. After comparison with available experimental data and computational models of other eukaryotic LGICs, we deem it consistent with the "closed-locked" state. The second model, obtained with simulations from the spontaneous relaxation of the open, agonist-bound α7 structure after ligand removal, recapitulates the characteristics of the apo-resting state of the receptor. These results add to our previous work on the active and desensitized state conformations, contributing to the structural characterization of the conformational landscape of the human α7 receptor and suggesting benchmarks to discriminate among conformations found in experiments or in simulations of LGICs. In particular key interactions at the interface between the extracellular domain and the transmembrane domain are identified, that could be critical to the α7 receptor function.

Cobalt catalyzed synthesis of α, β-unsaturated esters from esters and alcohols via mild O2-interrupted hydrogen borrowing

The implementation of direct and mild catalytic synthesis of products from benign materials using inexpensive catalysts is a major goal of chemists. Herein, a mild O2-interrupted hydrogen borrowing strategy using easily accessible and high efficient cobalt complex was reported for direct synthesis of α, β-unsaturated esters from unactivated esters and alcohols. This new route had good tolerance on broad substrate scope (alcohols, acetates, propionates and dios) and functional group with the highest yield of 89.1%. Systematic mechanism investigation revealed the cobalt complex was activated by t-BuOK via double deprotonation of PN5P ligand and removal of dichloro ligands, followed by two-fold alcohols activation and dehydrogenation. Also, the oxygen atmosphere was demonstrated very crucial for such interrupted hydrogen borrowing pathway.

Nanoscale Generation of Robust Solid Films from Liquid-Dispersed Nanoparticles via in Situ Atomic Force Microscopy: Growth Kinetics and Nanomechanical Properties

Inorganic metal-oxide nanoparticles have been identified as candidate materials for replacing zinc dialkyldithiophosphate (ZDDP) antiwear additives in automotive lubricants due to their ability to form protective antiwear tribofilms. However, the nanoscale mechanisms that control the growth and properties of these tribofilms remain unknown. Here, we present the results of an in situ study of the kinetics of nanoparticle tribofilm growth using colloidal-probe atomic force microscopy (AFM). We report on the nucleation and growth of antiwear tribofilms formed with a dispersion of a novel zirconia (ZrO2) nanoparticle additive in low-viscosity oil. Tribofilms in this study are generated in situ at the lubricated nanoscale contact of the colloidal-probe AFM, which helps elucidate the effects of localized contact parameters on tribofilm nucleation and growth. The results strongly support that ZrO2 nanoparticle tribofilms grow through a process of stress-activated tribosintering, after removal of organic ligands that attached to the nanoparticles. In contrast to ZDDP-derived tribofilms, ZrO2 tribofilm growth occurs across temperatures from -25 to 100 °C. Nanomechanical properties of the resulting tribofilms are found to approach values for single-crystal and conventionally sintered macroscale structures, suggesting the potential for robust wear protection across a broader range of conditions than those where ZDDP is effective.

Switching the nature of catalytic centers in Pd/NHC systems by solvent effect driven non-classical R-NHC Coupling.

A well-established oxidative addition of organic halides (R-X) to N-heterocyclic carbene (NHC) complexes of palladium(0) leads to formation of (NHC)(R)PdII (X)L species, the key intermediates in a large variety of synthetically useful cross-coupling reactions. Typical consideration of the cross-coupling catalytic cycle is based on the assumption of intrinsic stability of these species, where the subsequent steps involve coordination of the second reacting partner. Thus, high stability of the intermediate (NHC)(R)PdII (X)L species is usually taken for granted. In the present study it is discussed that such intermediates are prone to non-classical R-NHC intramolecular coupling process (R = Me, Ph, Vinyl, Ethynyl) that results in removal of NHC ligand and generation of another type of Pd catalytic system. DFT calculations (BP86, TPSS, PBE1PBE, B3LYP, M06, wB97X-D) clearly show that outcome of R-NHC coupling process is not only determined by chemical nature of the organic substituent R, but also strongly depends on the type of solvent. The reaction is most favorable in polar solvents, whereas the non-polar solvents render the products less stable. © 2019 Wiley Periodicals, Inc.

Chloride Supports O2 Activation in the D201G Facial Triad Variant of Factor-Inhibiting Hypoxia Inducible Factor, an α-Ketoglutarate Dependent Oxygenase.

α-Ketoglutarate (αKG) dependent oxygenases comprise a large superfamily of enzymes that activate O2 for varied reactions. While most of these enzymes contain a nonheme Fe bound by a His2(Asp/Glu) facial triad, a small number of αKG-dependent halogenases require only the two His ligands to bind Fe and activate O2. The enzyme "factor inhibiting HIF" (FIH) contains a His2Asp facial triad and selectively hydroxylates polypeptides; however, removal of the Asp ligand in the Asp201→Gly variant leads to a highly active enzyme, seemingly without a complete facial triad. Herein, we report on the formation of an Fe-Cl cofactor structure for the Asp201→Gly FIH variant using X-ray absorption spectroscopy (XAS), which provides insight into the structure of the His2Cl facial triad found in halogenases. The Asp201→Gly variant supports anion dependent peptide hydroxylation, demonstrating the requirement for a complete His2X facial triad to support O2 reactivity. Our results indicated that exogenous ligand binding to form a complete His2X facial triad was essential for O2 activation and provides a structural model for the His2Cl-bound nonheme Fe found in halogenases.

Characterization of CTLA4 Trafficking and Implications for Its Function

CTLA4 is an essential negative regulator of T-cell immune responses and a key checkpoint regulating autoimmunity and antitumor responses. Genetic mutations resulting in quantitative defects in the CTLA4 pathway are also associated with the development of immune dysregulation syndromes in humans. It has been proposed that CTLA4 functions to remove its ligands CD80 and CD86 from opposing cells by a process known as transendocytosis. A quantitative characterization of CTLA4 synthesis, endocytosis, degradation, and recycling and how these affect its function is currently lacking. In a combined in vitro and in silico study, we developed a mathematical model and identified these trafficking parameters. Our model predicts optimal ligand removal in an intermediate affinity range. The intracellular CTLA4 pool as well as fast internalization, recovery of free CTLA4 from internalized complexes, and recycling is critical for sustained functionality. CD80-CTLA4 interactions are predicted to dominate over CD86-CTLA4. Implications of these findings in the context of control of antigen-presenting cells by regulatory T cells and of pathologic genetic deficiencies are discussed. The presented mathematical model can be reused in the community beyond these questions to better understand other trafficking receptors and study the impact of CTLA4 targeting drugs.

Selective Removal of Ligands from Colloidal Nanocrystal Assemblies with Non-Oxidizing He Plasmas

Helium plasmas are attractive reagents for the removal of organics from hybrid materials because of their minimal ablative power and relative inertness, compared to oxidizing feed gases such as O2 and highly ablative inert gases such as Ar. This work describes the use of dilute helium plasmas to selectively remove the organic ligands from films of colloidal nanoparticles (i.e., colloidal nanoparticle assemblies). We determine the relative contribution to etching of different plasma species in a model system consisting of films of ZrO2 nanoparticles capped with trioctylphosphine oxide. Unexpectedly, we find that the strong ultraviolet radiation of He plasma is only a minor contributor to etching (25% of the etched carbon). Excited He species are responsible for most of the etching (75% of the etched carbon). Carbon concentrations as low as 3.5 atom % can be achieved under non-optimized plasma processing conditions.

Low-temperature direct synthesis of high quality WS2 thin films by plasma-enhanced atomic layer deposition for energy related applications

Tungsten disulfide (WS2) thin films are grown on several types of substrates by plasma-enhanced atomic layer deposition (PEALD) technique using tungsten hexacarbonyl [W(CO)6] and H2S plasma at a relatively low temperature of 350 °C. The method delivers polycrystalline WS2 film with (0 0 2) preferential growth and the high quality films could be successfully grown with as low as 30 ALD cycles (corresponding to ∼3 nm of thickness). Density functional theory (DFT) calculation results reveal that both adsorption of W(CO)6 and removal of CO ligand would be facilitated by usage of H2S plasma by generating the different defect sites on the basal plane. The typical self-limiting film growth (growth rate of ∼0.1 nm/cycle), characteristic of ideal ALD, is clearly observed with both the precursor and reactant pulsing time. X-ray diffractometry (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS) are performed in details to study the as-grown WS2 film on Si/SiO2 substrate. The analysis results confirm the formation of polycrystalline film, with high purity and well-defined stoichiometry. The as-deposited WS2 films are then explored as an electrode in the field of energy generation as well as energy storage. The films are uniformly and conformally grown on high surface-area 3 dimensional Ni-foam that show excellent activity towards hydrogen evolution reaction (HER). Significantly low overpotential of ∼280 mV is observed at a high operational current density of 100 mA cm−2 during HER in acid electrolyte. In addition, the as-grown films on stainless steel substrate also reveal the stable electrochemical performances in Na-ion battery as an anode with reasonably high areal capacity of ∼44.5 μAh cm−2 at the end of 50 charge-discharge cycles.

Toward Solution Syntheses of the Tetrahedral Au20 Pyramid and Atomically Precise Gold Nanoclusters with Uncoordinated Sites.

A long-standing objective of cluster science is to discover highly stable clusters and to use them as models for catalysts and building blocks for cluster-assembled materials. The discovery of catalytic properties of gold nanoparticles (AuNPs) has stimulated wide interests in gaseous size-selected gold clusters. Ligand-protected AuNPs have also been extensively investigated to probe their size-dependent catalytic and optical properties. However, the need to remove ligands can introduce uncertainties in both the structures and sizes of ligand-protected AuNPs for catalytic applications. Ideal model catalysts should be atomically precise AuNPs with well-defined structures and uncoordinated surface sites as in situ active centers. The tetrahedral ( Td) Au20 pyramidal cluster, discovered to be highly stable in the gas phase, provided a unique opportunity for such an ideal model system. The Td-Au20 consists of four Au(111) faces with all its atoms on the surface. Bulk synthesis of Td-Au20 with appropriate ligands would allow its catalytic and optical properties to be investigated and harnessed. The different types of its surface atoms would allow site-specific chemistry to be exploited. It was hypothesized that if the four corner atoms of Td-Au20 were coordinated by ligands the cluster would still contain 16 uncoordinated surface sites as potential in situ catalytically active centers. Phosphine ligands were deemed to be suitable for the synthesis of Td-Au20 to maintain the integrity of its pyramidal structure. Triphenyl-phosphine-protected Td-Au20 was first observed in solution, and its stability was confirmed both experimentally and theoretically. To enhance the synthetic yield, bidentate diphosphine ligands [(Ph)2P(CH2) nP(Ph)2 or L n] with different chain lengths were explored. It was hypothesized that diphosphine ligands with the right chain length might preferentially coordinate to the Td-Au20. Promising evidence was initially obtained by the formation of the undecagold by the L3 ligand. When the L8 diphosphine ligand was used, a remarkable Au22 nanocluster with eight uncoordinated Au sites, Au22(L8)6, was synthesized. With a tetraphosphine-ligand (PP3), a new Au20 nanocluster, [Au20(PP3)4]Cl4, was isolated with high yield. The crystal structure of the new Au20 core did not reveal the expected pyramid but rather an intrinsically chiral gold core. The surface of the new chiral-Au20 was fully coordinated, and it was found to be highly stable chemically. The Au22(L8)6 nanocluster represents the first and only gold core with uncoordinated gold atoms, providing potentially eight in situ catalytically active sites. The Au22 nanoclusters dispersed on oxide supports were found to catalyze CO oxidation and activate H2 without ligand removal. With further understanding about the formation mechanisms of gold nanoclusters in solution, it is conceivable that Td-Au20 can be eventually synthesized, allowing its novel catalytic and optical properties to be explored. More excitingly, it is possible that a whole family of new atomically precise gold nanoclusters can be created with different phosphine ligands.

Robust Removal of Ligands from Noble Metal Nanoparticles by Electrochemical Strategies

Ligand-stabilized metal nanoparticles (MNPs) have attracted much attention due to their promising catalytic applications. Fully/partially removing these ligands is critical to realize their proper functions. The traditional ligand-removing approaches (e.g., thermal annealing) focus on the ligand side. Herein, we demonstrate an electrochemical method that pays attention to the MNPs side. By rationally regulating the potential (oxidizing Pt and hydrogen evolution) to construct robust Pt–O or Pt–H covalent bond to displace Pt–ligand coordination bond, the approach could effectively remove almost all kinds of ligands from Pt NPs. For the oxidizing Pt method, up potential > 1.3 V and cycling number (n) > 20 are preferred to completely remove the ligands. The water-soluble ligands (such as poly(vinylpyrrolidone), cetyltrimethylammonium bromide, sodium acetate) can be removed by just one cycle after thoroughly being washed by water to remove the unattached ligands. However, the oil-soluble ligands (such as oleyl...

A Protein-Based Encapsulation System with Calcium-Controlled Cargo Loading and Detachment.

Protein-based encapsulation systems have a wide spectrum of applications in targeted delivery of cargo molecules and for chemical transformations in confined spaces. By engineering affinity between cargo and container proteins it has been possible to enable the efficient and specific encapsulation of target molecules. Missing in current approaches is the ability to turn off the interaction after encapsulation to enable the cargo to freely diffuse in the lumen of the container. Separation between cargo and container is desirable in drug delivery applications and in the use of capsids as catalytic nanoparticles. We describe an encapsulation system based on the hepatitis B virus capsid in which an engineered high-affinity interaction between cargo and capsid proteins can be modulated by Ca2+ . Cargo proteins are loaded into capsids in the presence of Ca2+ , while ligand removal triggers unbinding inside the container. We observe that confinement leads to hindered rotation of cargo inside the capsid. Application of the designed container for catalysis was also demonstrated by encapsulation of an enzyme with β-glucosidase activity.

A Protein‐Based Encapsulation System with Calcium‐Controlled Cargo Loading and Detachment

AbstractProtein‐based encapsulation systems have a wide spectrum of applications in targeted delivery of cargo molecules and for chemical transformations in confined spaces. By engineering affinity between cargo and container proteins it has been possible to enable the efficient and specific encapsulation of target molecules. Missing in current approaches is the ability to turn off the interaction after encapsulation to enable the cargo to freely diffuse in the lumen of the container. Separation between cargo and container is desirable in drug delivery applications and in the use of capsids as catalytic nanoparticles. We describe an encapsulation system based on the hepatitis B virus capsid in which an engineered high‐affinity interaction between cargo and capsid proteins can be modulated by Ca2+. Cargo proteins are loaded into capsids in the presence of Ca2+, while ligand removal triggers unbinding inside the container. We observe that confinement leads to hindered rotation of cargo inside the capsid. Application of the designed container for catalysis was also demonstrated by encapsulation of an enzyme with β‐glucosidase activity.

Atomic layer deposition of Pt@CsH2PO4 for the cathodes of solid acid fuel cells

Atomic layer deposition (ALD) has been used to apply continuous Pt films on powders of the solid acid CsH2PO4 (CDP), in turn, used in the preparation of cathodes in solid acid fuel cells (SAFCs). The film deposition was carried out at 150 °C using trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe3) as the Pt source and ozone as the reactant for ligand removal. Chemical analysis showed a Pt growth rate of 0.09 ± 0.01 wt%/cycle subsequent to an initial nucleation delay of 84 ± 20 cycles. Electron microscopy revealed the contiguous nature of the films prepared using 200 or more cycles. The cathode overpotential (0.48 ± 0.02 V at a current density of 200 mA/cm2) was independent of Pt deposition amount beyond the minimum required to achieve these continuous films. The cell electrochemical characteristics were moreover extremely stable with time, with the cathode overpotentials increasing by no more than 10 mV over a 100 h period of measurement. Thus, ALD holds promise as an effective tool in the preparation of SAFC cathodes with high activity and excellent stability.

Synthesis of CuInS2 Quantum Dots/In2S3/ZnO Nanowire Arrays with High Photoelectrochemical Activity

Decoration of CuInS2 (CIS) quantum dots (QDs) on ZnO nanowires (NWs) with an interlayer of In2S3 as photoelectrode has been successfully fabricated on FTO via the simple solution routes for photoelectrochemical (PEC) application. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction are utilized to systematically analyze the morphology and structure of the CIS QD/In2S3/ZnO NWs heterostructure. The composition of this multilayer heterostructure and the removal of QD ligands by a thermal process are confirmed by X-ray photoelectron spectra. In comparison with CIS QDs/ZnO NWs, the CIS QD/In2S3/ZnO heterostructural photoelectrode displays an efficient charge separation and carrier transport path for photocurrent up to 2.4 mA·cm–2 that is competitive with other Cd- and Pb-free QD-based materials. In addition, Mott–Schottky analysis demonstrates the negative shift of the flat band in the CIS QD/In2S3/ZnO, which benefits the early onset potential. Significantly, this hierarchical ...

Acid-Assisted Ligand Exchange Enhances Coupling in Colloidal Quantum Dot Solids.

Colloidal quantum dots (CQDs) are promising solution-processed infrared-absorbing materials for optoelectronics. In these applications, it is crucial to replace the electrically insulating ligands used in synthesis to form strongly coupled quantum dot solids. Recently, solution-phase ligand-exchange strategies have been reported that minimize the density of defects and the polydispersity of CQDs; however, we find herein that the new ligands exhibit insufficient chemical reactivity to remove original oleic acid ligands completely. This leads to low CQD packing and correspondingly low electronic performance. Here we report an acid-assisted solution-phase ligand-exchange strategy that, by enabling efficient removal of the original ligands, enables the synthesis of densified CQD arrays. Our use of hydroiodic acid simultaneously facilitates high CQD packing via proton donation and CQD passivation through iodine. We demonstrate highly packed CQD films with a 2.5 times increased carrier mobility compared with prior exchanges. The resulting devices achieve the highest infrared photon-to-electron conversion efficiencies (>50%) reported in the spectral range of 0.8 to 1.1 eV.

Thermal behavior study of palladium(II) complexes containing the iminic ligand N,N′-bis(3,4-dimethoxybenzaldehyde) ethane-1,2-diamine

This study describes the synthesis, characterization and thermal behavior study of the Schiff base N,N′-bis(3,4-dimethoxybenzaldehyde)ethane-1,2-diamine (C.1) and four new compounds of palladium(II) N,N-chelate coordination, with the general formula [Pd(X1)(X2)(3,4dm-1,2am)] where 3,4dm-1,2am=N,N′-bis(3,4-dimethoxybenzaldehyde)ethane-1,2-diamine, X1 = X2 = Cl− (C.2), X1 = X2 = Cl− and Br− (C.3), X1 = X2 = N3− (C.4) and X1 = X2 = NCO− (C.5). The compounds were characterized by elemental analysis, infrared vibrational spectroscopy (IR) and nuclear magnetic resonance (NMR) 1H and 13C. The TG/DTA curves showed that the thermal decomposition of the C2–C.5 complexes occurred in steps that involve the removal of both inorganic and organic ligand, and palladium oxidation steps forming palladium(II) oxide followed by the reduction of PdO into Pd(0), this being the constituent of the residual mass observed at the end of the TG curves, which have values consistent with the expected ones. The formed compounds can be ordered according to thermal stability considering the initial decomposition temperature (C.5 > C.2 > C.3 > C.4).

Enantiopure versus Racemic Mixture in Reversible, Two-Step, Single-Crystal-to-Single-Crystal Transformations of Copper(II) Complexes.

The reaction of chiral sodium complexes, 1∞ [Na(S-valmetH)]⋅H2 O (1-S) and 1∞ [Na(R-valmetH)]⋅H2 O (1-R), with copper(II) acetate affords chiral one-dimensional coordination polymers with the formulas 1∞ [Cu(S-valmet)(H2 O)]⋅H2 O (2-S) and 1∞ [Cu(R-valmet)(H2 O)]⋅H2 O (2-R) (R/S-valmetH2 are Schiff base proligands resulting from the condensation reactions between o-vanillin and R/S-methionine). The copper ions are connected by the carboxylato groups belonging to the amino-acid moieties, resulting in infinite chains showing syn-anti out-of-plane bridging mode. The circular dichroism spectra of 1-S, 1-R, 2-S, and 2-R confirm their enantiomeric nature. Compounds 2-S and 2-R undergo a two-step single-crystal-to-single-crystal transformation, with the elimination of the lattice and coordinated water molecules: 1∞ [Cu(S-valmet)(H2 O)]⋅H2 O (2-S)→1∞ [Cu(S-valmet)]⋅H2 O (3-S⋅H2 O)→1∞ [Cu(S-valmet)] (3-S) and 1∞ [Cu(R-valmet)(H2 O)]⋅H2 O (2-R)→1∞ [Cu(R-valmet)]⋅H2 O (3-R⋅H2 O)→1∞ [Cu(R-valmet)] (3-R), respectively. During these transformations, every pair of face-to-face chains present in 2-S (or 2-R) has been "zipped up" into a chiral double chain through the removal of the aqua ligands and their replacement by the carboxylato oxygen atoms from the neighboring chain. Consequently, each carboxylato group now bridges three copper ions. The conversion of the single chains, 2-S and 2-R, into the double chains, 3-S and 3-R, is accompanied by a change of the strength of the exchange interactions between the copper ions: weak antiferromagnetic couplings are observed in compound 2-S (J/kB =-1.23(5) K, H=-2J ΣSi Si+1 ) and relatively strong in compound 3-S (J/kB =-76.0(8) K). When the racemic mixture of the ligands, R,S-valmetH2 , is employed, in the same experimental conditions, a racemic mixture of mononuclear compounds, [Cu(R,S-valmet)(H2 O)2 ]⋅H2 O (4-RS), is obtained. Compound 4-RS also undergoes a SCSC transformation with the elimination of the lattice and one of the coordinated water molecules, resulting in a racemic mixture of chiral chains, 1∞ [Cu(R-valmet)(H2 O)]⋅1∞ [Cu(S-valmet)(H2 O)] (5-RS). In this compound, the coupling of the copper(II) ions within the chains is weak and ferromagnetic (J/kB =+0.10(2) K). These results prove that the chirality of the valmetH2 ligands (optically pure or racemic mixture) plays a key role in the self-assembly process of the copper(II) complexes.