Author Correction: Self-assembled poly-catenanes from supramolecular toroidal building blocks.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Self-assembled poly-catenanes from supramolecular toroidal building blocks.

Mechanical interlocking of molecules (catenation) is a nontrivial challenge in modern synthetic chemistry and materials science1,2. One strategy to achieve catenation is the design of pre-annular molecules that are capable of both efficient cyclization and of pre-organizing another precursor to engage in subsequent interlocking3-9. This task is particularly difficult when the annular target is composed of a large ensemble of molecules, that is, when it is a supramolecular assembly. However, the construction of such unprecedented assemblies would enable the visualization of nontrivial nanotopologies through microscopy techniques, which would not only satisfy academic curiosity but also pave the way to the development of materials with nanotopology-derived properties. Here we report the synthesis of such a nanotopology using fibrous supramolecular assemblies with intrinsic curvature. Using a solvent-mixing strategy, we kinetically organized a molecule that can elongate into toroids with a radius of about 13 nanometres. Atomic force microscopy on the resulting nanoscale toroids revealed a high percentage of catenation, which is sufficient to yield 'nanolympiadane'10, a nanoscale catenane composed of five interlocked toroids. Spectroscopic and theoretical studies suggested that this unusually high degree of catenation stems from the secondary nucleation of the precursor molecules around the toroids. By modifying the self-assembly protocol to promote ring closure and secondary nucleation, a maximum catenation number of 22 was confirmed by atomic force microscopy.

Orthogonal self-assembly of an organoplatinum(II) metallacycle and cucurbit[8]uril that delivers curcumin to cancer cells.

Curcumin (Cur) is a naturally occurring anticancer drug isolated from the Curcuma longa plant. It is known to exhibit anticancer properties via inhibiting the STAT3 phosphorylation process. However, its poor water solubility and low bioavailability impede its clinical application. Herein, we used organoplatinum(II) ← pyridyl coordination-driven self-assembly and a cucurbit[8]uril (CB[8])-mediated heteroternary host-guest complex formation in concert to produce an effective delivery system that transports Cur into the cancer cells. Specifically, a hexagon 1, containing hydrophilic methyl viologen (MV) units and 3,4,5-Tris[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]benzoyl groups alternatively at the vertices, has been synthesized and characterized by several spectroscopic techniques. The MV units of 1 underwent noncovalent complexation with CB[8] to yield a host-guest complex 4. Cur can be encapsulated in 4, via a 1:1:1 heteroternary complex formation, resulting in a water-soluble host-guest complex 5. The host-guest complex 5 exhibited ca 100-fold improved IC50 values relative to free Cur against human melanoma (C32), melanoma of rodents (B16F10), and hormone-responsive (MCF-7) and triple-negative (MDA-MB231) breast cancer cells. Moreover, strong synergisms of Cur with 1 and 4 with combinatorial indexes of <1 across all of the cell lines were observed. An induced apoptosis with fragmented DNA pattern and inhibited expression of phosphor-STAT3 supported the improved therapeutic potential of Cur in heteroternary complex 5.

Supramolecular Polymers Capable of Controlling Their Topology.

One important class of supramolecular materials is one-dimensionally elongated supramolecular polymers, in which monomers are associated by reversible intermolecular interactions, yielding a fibrous morphology. Unlike frequently reported conventional supramolecular polymers based on, for instance, host-guest interactions, those composed of one-dimensionally stacked π-conjugated molecules can be encoded with high degrees of internal order by cooperative association of the rigid aromatic monomers, endowing such supramolecular polymers with extraordinary properties and functionality. However, their internal order has not yet been exploited to manipulate the complex landscape of well-defined states of the supramolecular polymer backbone, which may induce new functionalities beyond the intrinsic properties of the backbones. This Account will focus on the inceptive phase of our research on supramolecular polymers with high degrees of internal order able to impart intrinsic curvature to their backbones. Initially, we developed a naphthalene molecule functionalized with barbituric acid, which forms uniform toroidal short fibers with diameters of approximately 16 nm via the formation of hydrogen-bonded cyclic hexamers (rosettes). As we thought the uniformity of the toroid size to arise from the intrinsic curvature generated upon stacking of the rosettes, we exploited this intrinsic curvature to design continuously curved extended supramolecular polymers by extension of such molecular π-systems. The intrinsic curvature produced by the monomers with more expanded π-systems indeed gave us access to higher-order structures (topologies) ranging from randomly folded to helically folded coils in extended supramolecular polymers. We will discuss the kinetic aspects of the generation of intrinsic curvature for topology control, including the formation of toroidal structures resulting from ring-closing processes. For extended supramolecular polymers with well-defined topologies, we will discuss manipulation of a complex landscape of well-defined states by external stimuli. The incorporation of a photoresponsive azobenzene chromophore in the original naphthalene molecular scaffold allowed us to reversibly destroy or recover the curvature of the main chain through trans- cis photoisomerization. By means of this photocontrollable curvature, we have demonstrated light-induced unfolding of helically folded structures into entirely stretched structures. Furthermore, a direct extension of the π-conjugated core provided us with access to unprecedented supramolecular polymers with emergent time-dependent topology transitions. Molecules with a naphthalene core conjugated with two phenylene units kinetically afforded supramolecular polymers that consist of helically folded and misfolded domains. Upon aging the supramolecular polymer solution, we observed spontaneous folding of the misfolded domains in a time scale of days, eventually obtaining a supramolecular polymer topology analogous to the tertiary structure of proteins. These supramolecular polymers with unrivaled and active topologies provide new prospects for supramolecular polymers as one-dimensional nanomaterials.

Effect of an Aromatic Solvent on Hydrogen-Bond-Directed Supramolecular Polymerization Leading to Distinct Topologies.

Beyond phenomenon, self-assembly of synthetic molecules, is now becoming an essential tool to design supramolecular materials not only in the thermodynamically stable state but also in kinetically trapped states. However, an approach to design complex self-assembly processes comprising different types of self-assembled states remains elusive. Herein, an example of such systems is demonstrated based on a unique supramolecular polymer mediated by supermacrocyclization of hydrogen-bonding π-conjugated molecules. By adding an aromatic solvent into nonpolar solutions of the monomer, spontaneous nucleation triggered by supermacrocyclization was suppressed so that isothermal supramolecular polymerization could be achieved from kinetically formed topological variants and amorphous agglomerates to afford helicoidal structures hitherto obtainable only with very slow cooling of a hot solution. By increasing the proportion of aromatic solvent further, another self-assembly path was found, based on competing extended hydrogen-bonded motifs affording crystalline nanowires.

Topological Impact on the Kinetic Stability of Supramolecular Polymers.

Kinetically formed metastable molecular assemblies have attracted increasing interest especially in the field of supramolecular polymers. In most cases, metastable assemblies are ensemblies of aggregates based on the same supramolecular motif but with different lengths or sizes, and therefore their kinetic stabilities are experimentally indistinguishable. Herein, we demonstrate a topological effect on kinetic stabilities in a complex mixture of metastable supramolecular polymers. Our azobenzene-incorporated monomer upon heating in nonpolar solvent at ambient temperature kinetically forms complex mixtures of supramolecular polymers with cyclized and open-ended randomly coiled topologies. Upon further heating, we obtained thermodynamically stable twisted fibrils organizing into crystalline fibers. Through the direct visualization of the complex supramolecular polymer mixtures by atomic force microscopy, we demonstrate that the cyclized supramolecular polymer has superior kinetic stability compared to the open-ended species toward the thermal transformation into twisted fibrils. Since the superior kinetic stability of the cyclized species can be attributed to the absence of aggregate termini, we could convert them fully into the thermodynamic species through photoinduced opening of the cyclized structures.

Hierarchical Assemblies of Supramolecular Coordination Complexes.

Hierarchical self-assembly (HAS) is a multilevel organization process that first assembles elementary molecular units into ordered secondary structures via noncovalent interactions, which further act as the building blocks to form more complex multifunctional superstructures at the next level(s). The HAS strategy has been used as a versatile method for the preparation of soft-matter nanoarchitectures of defined size and morphologies, tunable luminescence, and biological importance. However, such preparation can be greatly simplified if well-defined dynamic structures are employed as the cores that upon linking form the desired nanoarchitectures. Discrete supramolecular coordination complexes (SCCs) with well-defined shapes, sizes, and internal cavities have been widely employed to construct hierarchical systems with functional diversity. This Account summarizes the prevailing strategies used in recent years in the preparation of SCC-based HASs and illustrates how the combination of dynamic metal-ligand coordination with other interactions was used to obtain hierarchical systems with interesting properties. HASs with dual orthogonal interactions involving coordination-driven self-assembly and hydrogen bonding/host-guest interaction generally result in robust and flexible supramolecular gels. Likewise, hybridization of SCCs with a suitable dynamic covalent network via a hierarchical strategy is useful to prepare materials with self-healing properties. The intrinsic positive charges of the SCCs also make them suitable precursors for the construction of HASs via electrostatic interactions with negatively charged biological/abiological molecules. Furthermore, the interplay between the hydrophilic and lipophilic characters of HASs by varying the number and spacial orientation of alkyl/oxyethylene chains of the SCC is a simple yet controllable approach to prepare ordered and tunable nanostructures. Certain SCC-cored hierarchical systems exhibit reversible polymorphism, typically between micellar, nanofiber, and vesicular phases, in response to various external perturbations: heat, photoirradiation, pH-variance, redox-active agents, etc. At the same time, multiple noncovalent interaction mediated HASs are growing in numbers and are promising candidates for obtaining functionally diverse materials. The photophysical properties of SCC-based HASs have been used in many analytical applications. For example, embedding tetraphenylethene (TPE)-based pyridyl ligands within metallo-supramolecular structures partially restricts the molecular rotations of its phenyl rings, endowing the resultant SCCs with weak emissions. Further aggregation of such HASs in suitable solvents results in a marked enhancement in emission intensity along with quantum yields. They act as sensitive sensors for different analytes, including pathogens, drugs, etc. HASs are also useful to develop multidrug systems with cooperative chemotherapeutic effects. Hence, the use of HASs with theranostic SCCs combining cell-imaging agents and chemotherapeutic scaffolds is a promising drug delivery strategy for cancer theranostics. At the same time, their responsiveness to stimuli, oftentimes due to the dynamic nature of the metal-ligand interactions, play an important role in drug release via a disassembly mechanism.

Self-Assembly of Metallacages into Multidimensional Suprastructures with Tunable Emissions.

Cubic metallacages were arranged into multidimensional (one-, two-, and three-dimensional) suprastructures via multistep assembly. Four new shape-controllable, hybrid metallacages with modified substituents and tunable electronic properties were prepared using dicarboxylate ligands with various substituents (sodium sulfonate, nitro, methoxyl, and amine), tetra-(4-pyridylphenyl) ethylene, and cis-(PEt3)2Pt(OTf)2. The as-prepared metallacages were used as building blocks for further assembly. Diverse suprastructures with tunable emissions (λmax from 451 to 519 nm) and various substituents (-SO3Na, -NO2, -OCH3, and -NH2) were prepared depending on the substituents and solvents used.

Alanine-Based Chiral Metallogels via Supramolecular Coordination Complex Platforms: Metallogelation Induced Chirality Transfer.

Chiral self-assemblies constantly attract great interest because of their potential to provide insight into biological systems and materials science. Herein we report on the efficient preparation of alanine-based chiral metallacycles, rhomboids 1D and 1L and hexagons 2D and 2L using a Pt(II) ← pyridyl directional bonding approach. The metallacycles are subsequently assembled into nanospheres at low concentration, that generate chiral metallogels at high concentration driven by hydrogen bonding, hydrophobic and π-π interactions. The gels consist of microscopic chiral nanofibers with well-defined helicity, as confirmed by circular dichroism (CD) and scanning (SEM) and transmission electron (TEM) microscopies. Given these results, we expect this technique will not only unlock interesting new approaches to understand homochirality in nature but also allow the design of versatile soft materials containing chiral supramolecular cores.

Carbon-Nanotube-Mediated Electrochemical Transition in a Redox-Active Supramolecular Hydrogel Derived from Viologen and an l-Alanine-Based Amphiphile.

A two-component hydrogelator (16-A)2 -V(2+) , comprising an l-alanine-based amphiphile (16-A) and a redox-active viologen based partner (V(2+) ), is reported. The formation the hydrogel depended, not only on the acid-to-amine stoichiometric ratio, but on the choice of the l-amino acid group and also on the hydrocarbon chain length of the amphiphilic component. The redox responsive property and the electrochemical behavior of this two-component system were further examined by step-wise chemical and electrochemical reduction of the viologen nucleus (V(2+) /V(+) and V(+) /V(0) ). The half-wave reduction potentials (E1/2 ) associated with the viologen ring shifted to more negative values with increasing amine component. This indicates that higher extent of salt formation hinders reduction of the viologen moiety. Interestingly, the incorporation of single-walled carbon nanotubes in the electrochemically irreversible hydrogel (16-A)2 -V(2+) transformed it into a quasi-reversible electrochemical system.

Multifarious facets of sugar-derived molecular gels: molecular features, mechanisms of self-assembly and emerging applications.

The remarkable capability of nature to design and create excellent self-assembled nano-structures, especially in the biological world, has motivated chemists to mimic such systems with synthetic molecular and supramolecular systems. The hierarchically organized self-assembly of low molecular weight gelators (LMWGs) based on non-covalent interactions has been proven to be a useful tool in the development of well-defined nanostructures. Among these, the self-assembly of sugar-derived LMWGs has received immense attention because of their propensity to furnish biocompatible, hierarchical, supramolecular architectures that are macroscopically expressed in gel formation. This review sheds light on various aspects of sugar-derived LMWGs, uncovering their mechanisms of gelation, structural analysis, and tailorable properties, and their diverse applications such as stimuli-responsiveness, sensing, self-healing, environmental problems, and nano and biomaterials synthesis.

Differential response of cholesterol based pyrimidine systems with oxyethylene type spacers to gelation and mesogen formation in the presence of alkali metal ions.

A new series of lipophilic cholesteryl derivatives of 2,4,6-trichloro-pyrimidine-5-carbaldehyde has been synthesized. Oxyethylene spacers of variable lengths were inserted between the hydrogen bonding promoting pyrimidine core and the cholesteryl tail in order to understand their effect on the self-assembly of these compounds. Only compound 1a with the shortest spacer formed a gel in organic solvents such as n-butanol and n-dodecane. While other members (1b and c) having longer spacers led to sol formation and precipitation in n-butanol and n-dodecane respectively. The self-assembly phenomena associated with the gelation process were investigated using temperature-dependent UV-Vis and CD-spectroscopy. The morphological features of the freeze-dried gels obtained from different organic solvents were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The solid phase behaviours of these molecules and their associated alkali metal ion complexes were explored using polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The molecular arrangements in the xerogel and in the solid state were further probed using a wide-angle X-ray diffraction (WAXD) technique. Analysis of the wide-angle X-ray diffraction data reveals that this class of molecules adopts a hexagonal columnar organization in the gel and in the solid state. Each slice of these hexagonal columnar structures is composed of a dimeric molecular-assembly as a building block. Significant changes in the conformation of the oxyethylene chains could be triggered via the coordination of selected alkali metal ions. This led to the production of interesting metal ion promoted mesogenic behaviour.

Remarkable regioisomer control in the hydrogel formation from a two-component mixture of pyridine-end oligo(p-phenylenevinylene)s and N-decanoyl-L-alanine.

N-Decanoyl-L-alanine (DA) was mixed with either colorless 4,4'-bipyridine (BP) or various derivatives such as chromogenic oligo(p-phenylenevinylene) (OPV) functionalized with isomeric pyridine termini in specific molar ratios. This mixtures form salt-type gels in a water/ethanol (2:1, v/v) mixture. The gelation properties of these two-component mixtures could be modulated by variation of the position of the ''N'' atom of the end pyridyl groups in OPVs. The presence of acid-base interactions in the self-assembly of these two-component systems leading to gelation was probed in detail by using stoichiometry-dependent UV/Vis and FTIR spectroscopy. Furthermore, temperature-dependent UV/Vis and fluorescence spectroscopy clearly demonstrated a J-type aggregation mode of these gelator molecules during the sol-to-gel transition process. Morphological features and the arrangement of the molecules in the gels were examined by using scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) techniques. Calculation of the length of each molecular system by energy minimization in its extended conformation and comparison with the XRD patterns revealed that this class of gelator molecules adopts lamellar organizations. Rheological properties of these two-component systems provided clear evidence that the flow behavior could be modulated by varying the acid/amine ratio. Polarized optical microscopy (POM), differential scanning calorimetry (DSC), and XRD results revealed that the solid-phase behavior of such two-component mixtures (acid/base=2:1) varied significantly upon changing the proton-acceptor part from BP to OPV. Interestingly, the XRD pattern of these acid/base mixtures after annealing at their associated isotropic temperature was significantly different from that of their xerogels.

Induction of supramolecular chirality in the self-assemblies of lipophilic pyrimidine derivatives by choice of the amino acid-based chiral spacer.

A new family of supramolecular organogelators, based on chiral amino acid derivatives of 2,4,6-trichloro-pyrimidine-5-carbaldehyde, has been synthesized. L-alanine was incorporated as a spacer between the pyrimidine core and long hydrocarbon tails to compare the effect of chirality and hydrogen bonding to that of the achiral analogue. The role of aromatic moiety on the chiral spacer was also investigated by introducing L-phenyl alanine moieties. The presence of intermolecular hydrogen-bonding leading to the chiral self-assembly was probed by concentration-dependent FTIR and UV/Vis spectroscopies, in addition to circular dichroism (CD) studies. Temperature and concentration-dependent CD spectroscopy ascribed to the formation of ß-sheet-type H-bonded networks. The morphology and the arrangements of the molecules in the freeze-dried gels were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) techniques. Calculation of the length of each molecular system by energy minimization in its extended conformation and comparison with the small-angle XRD pattern reveals that this class of gelator molecules adopts a lamellar organization. Polarized optical microscopy (POM) and differential scanning calorimetry (DSC) indicate that the solid state phase behavior of these molecules is totally dependent on the choice of their amino acid spacers. Structure-induced aggregation properties based on the H-bonding motifs and the packing of the molecule in three dimensions leading to gelation was elucidated by rheological studies. However, viscoelasticity was shown to depend only marginally on the H-bonding interactions; rather it depends on the packing of the gelators to a greater extent.

Effects of a delocalizable cation on the headgroup of gemini lipids on the lipoplex-type nanoaggregates directly formed from plasmid DNA.

Lipoplex-type nanoaggregates prepared from pEGFP-C3 plasmid DNA (pDNA) and mixed liposomes, with a gemini cationic lipid (CL) [1,2-bis(hexadecyl imidazolium) alkanes], referred as (C16Im)2Cn (where Cn is the alkane spacer length, n = 2, 3, 5, or 12, between the imidazolium heads) and DOPE zwitterionic lipid, have been analyzed by zeta potential, gel electrophoresis, SAXS, cryo-TEM, fluorescence anisotropy, transfection efficiency, fluorescence confocal microscopy, and cell viability/cytotoxicity experiments to establish a structure-biological activity relationship. The study, carried out at several mixed liposome compositions, α, and effective charge ratios, ρeff, of the lipoplex, demonstrates that the transfection of pDNA using CLs initially requires the determination of the effective charge of both. The electrochemical study confirms that CLs with a delocalizable positive charge in their headgroups yield an effective positive charge that is 90% of their expected nominal one, while pDNA is compacted yielding an effective negative charge which is only 10-25% than that of the linear DNA. SAXS diffractograms show that lipoplexes formed by CLs with shorter spacer (n = 2, 3, or 5) present three lamellar structures, two of them in coexistence, while those formed by CL with longest spacer (n = 12) present two additional inverted hexagonal structures. Cryo-TEM micrographs show nanoaggregates with two multilamellar structures, a cluster-type (at low α value) and a fingerprint-type, that coexist with the cluster-type at moderate α composition. The optimized transfection efficiency (TE) of pDNA, in HEK293T, HeLa, and H1299 cells was higher using lipoplexes containing gemini CLs with shorter spacers at low α value. Each lipid formulation did not show any significant levels of toxicity, the reported lipoplexes being adequate DNA vectors for gene therapy and considerably better than both Lipofectamine 2000 and CLs of the 1,2-bis(hexadecyl ammnoniun) alkane series, recently reported.

Distinct seed topologies enable comparison of elongation and secondary nucleation pathways in seeded supramolecular polymerization.

The influence of seed topologies on seeded supramolecular polymerization was examined using helicoidal and toroidal supramolecular polymer seeds. The addition of these seeds to a supersaturated solution of monomers led to distinct nucleation-growth kinetics, which were attributed to the significant difference between the elongation from helicoid termini and secondary nucleation catalyzed by the toroid surface.

Fine-tuning of the size of supramolecular nanotoroids suppresses the subsequent catenation of nano-[2]catenane.

A judicious combination of ring-closing supramolecular polymerization and secondary nucleation can hierarchically organize a diphenylnaphthalene barbiturate monomer bearing a 3,4,5-tri(dodecyloxy)benzyloxy unit into self-assembled nano-polycatenanes composed of nanotoroids. In our previous study, nano-polycatenanes of variable length have been formed uncontrollably from the monomer that provides nanotoroids with sufficiently wide inner void space wherein secondary nucleation is driven by non-specific solvophobic interaction. In this study, we found that the elongation of the alkyl chain length of the barbiturate monomer decreases the inner void space of nanotoroids while increasing the frequency of secondary nucleation. These two effects resulted in an increase in the yield of nano-[2]catenane. This unique property observed in our self-assembled nanocatenanes might be extended to a controlled synthesis of covalent polycatenanes using non-specific interactions.

How does the spacer length of cationic gemini lipids influence the lipoplex formation with plasmid DNA? Physicochemical and biochemical characterizations and their relevance in gene therapy.

Lipoplexes formed by the pEGFP-C3 plasmid DNA (pDNA) and lipid mixtures containing cationic gemini surfactant of the 1,2-bis(hexadecyl dimethyl ammonium) alkanes family referred to as C16CnC16, where n=2, 3, 5, or 12, and the zwitterionic helper lipid, 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE) have been studied from a wide variety of physical, chemical, and biological standpoints. The study has been carried out using several experimental methods, such as zeta potential, gel electrophoresis, small-angle X-ray scattering (SAXS), cryo-TEM, gene transfection, cell viability/cytotoxicity, and confocal fluorescence microscopy. As reported recently in a communication (J. Am. Chem. Soc. 2011, 133, 18014), the detailed physicochemical and biological studies confirm that, in the presence of the studied series lipid mixtures, plasmid DNA is compacted with a large number of its associated Na+ counterions. This in turn yields a much lower effective negative charge, qpDNA−, a value that has been experimentally obtained for each mixed lipid mixture. Consequently, the cationic lipid (CL) complexes prepared with pDNA and CL/DOPE mixtures to be used in gene transfection require significantly less amount of CL than the one estimated assuming a value of qDNA−=−2. This drives to a considerably lower cytotoxicity of the gene vector. Depending on the CL molar composition, α, of the lipid mixture, and the effective charge ratio of the lipoplex, ρeff, the reported SAXS data indicate the presence of two or three structures in the same lipoplex, one in the DOPE-rich region, other in the CL-rich region, and another one present at any CL composition. Cryo-TEMand SAXS studies with C16CnC16/DOPE-pDNA lipoplexes indicate that pDNA is localized between the mixed lipid bilayers of lamellar structures within a monolayer of ∼2 nm. This is consistent with a highly compacted supercoiled pDNA conformation compared with that of linear DNA. Transfection studies were carried out with HEK293T, HeLa, CHO, U343, and H460 cells. The α and ρeff values for each lipid mixture were optimized on HEK293T cells for transfection, and using these values, the remaining cells were also transfected in absence (-FBS-FBS) and presence (-FBS+FBS) of serum. The transfection efficiency was higher with the CLs of shorter gemini spacers (n=2 or 3). Each formulation expressed GFP on pDNA transfection and confocal fluorescence microscopy corroborated the results. C16C2C16/DOPE mixtures were the most efficient toward transfection among all the lipid mixtures and, in presence of serum, even better than the Lipofectamine2000, a commercial transfecting agent. Each lipid combination was safe and did not show any significant levels of toxicity. Probably, the presence of two coexisting lamellar structures in lipoplexes synergizes the transfection efficiency of the lipid mixtures which are plentiful in the lipoplexes formed by CLs with short spacer (n=2, 3) than those with the long spacer (n=5, 12).

Hydrogen bond-directed supramolecular polymorphism leading to soft and hard molecular ordering.

Transformation of metastable supramolecular stacks of hydrogen-bonded rosettes composed of an ester-containing barbiturated naphthalene into crystalline nanosheets occurs through the rearrangement of hydrogen-bonding patterns. The involvement of the ester group in the crystalline hydrogen-bonded pattern is demonstrated, guiding us to a new molecular design that can afford supramolecular polymorphs with soft and hard molecular packing.