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H‐bonding driven J‐type aggregation and cooperative supramolecular polymerization of a sulfur‐substituted chiral naphthalene‐diimide (NDI)‐derivative (S,S)‐NDI‐2 in decane leads to remarkable enhancement of fluorescence quantum yield (43.3 % from 0.5 % in the monomeric state) and intense CPL signal in the aggregated state with a high luminescence dissymmetry factor (glum) of 4.6×10−2. A mixture of NDI‐2 with a structurally similar NDI‐derivative NDI‐1 (mixture of racemic (S,S)‐ and (R,R)‐ isomers and the achiral derivative) in 1:9 (NDI‐2/NDI‐1) ratio, when heated and slowly cooled to room temperature, showed no enhanced CD band, indicating lack of any preferential helicity. However, when a monomeric solution of the NDI‐1 in tetrahydrofuran (THF) was injected to preformed seed of NDI‐2 in decane, a prominent CD signal appeared, indicating chiral amplification resulting in induced CPL with high glum value of 2.0×10−2 from mostly (>98.5 %) diastereomeric mixture. [ABSTRACT FROM AUTHOR]

Oligothiophene derivatives have been extensively studied as p‐type semiconducting materials in organic electronics applications. This work reports the synthesis, self‐assembly and photophysical properties of acceptor–donor–acceptor (A–D–A)‐type oligothiophene derivatives by end‐group engineering of quaterthiophene (QT) with naphthalene monoimide (NMI) chromophores that are further connected to a trialkoxy benzamide wedge. Conjugation to the NMI units reduces the HOMO–LUMO gap significantly, and consequently the absorption spectrum exhibits a bathochromic shift of about 50 nm compared with QT. Furthermore, extended H‐bonding interactions among the amido groups of the peripheral wedges produce entangled fibrillar nanostructures and gelation in hydrocarbon solvents such as methylcyclohexane, wherein the A–D–A chromophore exhibits typical H‐aggregation. On the contrary, the fact that the same chromophore, lacking only the amido units, does not produce gels or H‐aggregates indicates strong impact of H‐bonding on the self‐assembly. Computational studies revealed the electronic properties of the chromophore and predicted the geometry of a dimer in the H‐aggregate that reasonably matches with the experimental results. Bulk electrical conductivity measurements determined an excellent conductivity of 2.3×10−2 S cm−1 for the H‐aggregated system (OT‐1), which is two orders of magnitude higher than that of the same chromophore lacking the amido groups (OT‐2). [ABSTRACT FROM AUTHOR]

Programmable assembly of biomolecules is a fast growing research area that aims to emulate nature's elegance in creating numerous hierarchical self‐assembled structures, which are responsible for unimaginably difficult biological functions. Protein assembly is a particularly challenging task, owing to their structural diversity, conformational heterogeneity, and high molecular weight. This article reveals the ability of a supramolecular structure‐directing unit (SSDU) to regulate the entropically favourable supramolecular assembly of a covalently conjugated protein (bovine serum albumin (BSA)) to produce well‐defined protein‐decorated micelles with remarkably high thermal stability, suppression of the thermal denaturation of the protein, and retention of enzymatic activity. Furthermore, a SSDU‐appended thermo‐responsive poly(N‐isopropylacrylamide) (PNIPAM) co‐assembles with the SSDU–BSA conjugate because, in both cases, assembly was primarily driven by specific molecular recognition between the SSDUs. However, the resulting supramolecular protein–polymer conjugate exhibits distinctly different polymersome structure to that of the micellar particle produced by the protein‐SSDU conjugate. In this case, the enzymatic activity can be significantly suppressed above the lower critical solution temperature of supramolecularly conjugated PNIPAM, possibly due to collapse of the de‐solvated polymer chains on the protein surface. [ABSTRACT FROM AUTHOR]

Herein we describe the H‐bonding‐regulated nanostructure, thermodynamics, and multivalent binding of two bolaamphiphiles NDI‐1 and NDI‐2 consisting of a hydrophobic naphthalene diimide connected to a hydrophilic wedge by a H‐bonding group and a glucose moiety on its two arms. NDI‐1 and NDI‐2 differ by the single H‐bonding group, namely, hydrazide or amide, which triggers the formation of vesicles and cylindrical micelles, respectively. Although the extended H‐bonding ensures stacking with head‐to‐head orientation and the formation of an array of the appended glucose moieties in both systems, the adaptive cylindrical structure exhibited superior multivalent binding with concanavalin A (ConA) to that of the vesicle. A control amphiphile lacking a H‐bonding group assembled with a random lateral orientation to produce spherical micelles without any notable multivalent binding. Bonded with a purpose: Two bolaamphiphiles consisting of a hydrophobic naphthalene diimide unit connected at one end to a hydrophilic wedge by a H‐bonding group (hydrazide or amide) and at the other to a glucose moiety showed distinct H‐bonding‐regulated behavior with the formation of vesicles or cylindrical micelles (see picture). The adaptive cylindrical micelles formed by amide H‐bonding exhibited superior multivalent binding with concanavalin A. [ABSTRACT FROM AUTHOR]

An adaptable and efficient molecular recognition pair has been established by taking advantage of the complementary nature of donor-acceptor interactions together with the strength of hydrogen bonds. Such distinct molecular recognition propagates in orthogonal directions to effect extended alternating co-assembly of two different appended molecular entities. The dimensions of the assembled structures can be tuned by stoichiometric imbalance between the donor and acceptor building blocks. The morphology of the self-assembled material can be correlated with the ratio of the two building blocks. [ABSTRACT FROM AUTHOR]

Self-assembly of a series of carboxylic acid-functionalized naphthalene diimide (NDI) chromophores with a varying number ( n=1-4) of methylene spacers between the NDI ring and the carboxylic acid group has been studied. The derivatives show pronounced aggregation due to the synergistic effects of H-bonding between the carboxylic acid groups in a syn- syn catemer motif and π stacking between the NDI chromophores. Solvent-dependent UV/Vis studies reveal the existence of monomeric dye molecules in a 'good' solvent such as chloroform and self-assembly in 'bad' solvents such as methylcyclohexane. The propensity of self-assembly is comparable for all samples. Temperature-dependent spectroscopic studies show high thermal stability of the H-bonding-mediated self-assembled structures. In the presence of a protic solvent such as MeOH, self-assembly can be suppressed, suggesting a decisive role of H-bonding, whereas π stacking is more a consequence of than a cause for self-assembly. Syn- syn catemer-type H-bonding is supported by powder XRD studies and the results corroborate well with DFT calculations. The morphology as determined by AFM is found to be dependent on the value of n; with increasing n, the morphology gradually shifts from 2D nanosheets to 1D nanofibers. Emission spectra show sharp emission bands with relatively small Stokes shifts. In addition, a rather broad emission band is observed at longer wavelengths because of the in situ formation of excimer-type species. Due to such a heterogeneous nature, the emission spectrum spans almost the entire red-green-blue region. Depending on the value of n, the ratio of intensities of the two emission bands is changed, which results in a tunable luminescent color. Furthermore, in the case of n=1 and 3, almost pure white light emission is observed. Time-resolved photoluminescence spectra show a very short lifetime (a few picoseconds) of monomeric dye molecules and biexponential decays with longer lifetimes (on the order of nanoseconds) for aggregated species. Current-voltage measurements show electrical conductivity in the range of 10−4 S cm−1 for the aggregated chromophores, which is four orders of magnitude higher than the value for a structurally similar NDI control molecule lacking the H-bonding functionality. [ABSTRACT FROM AUTHOR]

This paper describes the spontaneous vesicular assembly of a naphthalene-diimide (NDI)-based non-ionic bolaamphiphile in aqueous medium by using the synergistic effects of π-stacking and hydrogen bonding. Site isolation of the hydrogen-bonding functionality (hydrazide), a strategy that has been adopted so elegantly in nature, has been executed in this system to protect these moieties from the bulk water so that the distinct role of hydrogen bonding in the self-assembly of hydrazide-functionalized NDI building blocks could be realized, even in aqueous solution. Furthermore, the electron-deficient NDI-based bolaamphiphile could engage in donor-acceptor (D-A) charge-transfer (CT) interactions with a water-insoluble electron-rich pyrene donor by virtue of intercalation of the latter chromophore in between two NDI building blocks. Remarkably, even when pyrene was located between two NDI blocks, intermolecular hydrogen-bonding networks between the NDI-linked hydrazide groups could be retained. However, time-dependent AFM studies revealed that the radius of curvature of the alternately stacked D-A assembly increased significantly, thereby leading to intervesicular fusion, which eventually resulted in rupturing of the membrane to form 1D fibers. Such 2D-to-1D morphological transition produced CT-mediated hydrogels at relatively higher concentrations. Instead of pyrene, when a water-soluble carboxylate-functionalized pyrene derivative was used as the intercalator, non-covalent tunable in-situ surface-functionalization could be achieved, as evidenced by the zeta-potential measurements. [ABSTRACT FROM AUTHOR]

This paper reports comprehensive studies on the mixed assembly of bis-(trialkoxybenzamide)-functionalized dialkoxynaphthalene (DAN) donors and naphthalene-diimide (NDI) acceptors due the cooperative effects of hydrogen bonding, charge-transfer (CT) interactions, and solvophobic effects. A series of DAN as well as NDI building blocks have been examined (wherein the relative distance between the two amide groups in a particular chromophore is the variable structural parameter) to understand the structure-dependent variation in mode of supramolecular assembly and morphology (organogel, reverse vesicle, etc.) of the self-assembled material. Interestingly, it was observed that when the amide functionalities are introduced to enhance the self-assembly propensity, the mode of co-assembly among the DAN and NDI chromophores no longer remained trivial and was dictated by a relatively stronger hydrogen-bonding interaction instead of a weak CT interaction. Consequently, in a highly non-polar solvent like methylcyclohexane (MCH), although kinetically controlled CT-gelation was initially noticed, within a few hours the system sacrificed the CT-interaction and switched over to the more stable self-sorted gel to maximize the gain in enthalpy from the hydrogen-bonding interaction. In contrast, in a relatively less non-polar solvent such as tetrachloroethylene (TCE), in which the strength of hydrogen bonding is inherently weak, the contribution of the CT interaction also had to be accounted for along with hydrogen bonding leading to a stable CT-state in the gel or solution phase. The stability and morphology of the CT complex and rate of supramolecular switching (from CT to segregated state) were found to be greatly influenced by subtle structural variation of the building blocks, solvent polarity, and the DAN/NDI ratio. For example, in a given D-A pair, by introducing just one methylene unit in the spacer segment of either of the building blocks a complete change in the mode of co-assembly (CT state or segregated state) and the morphology (1D fiber to 2D reverse vesicle) was observed. The role of solvent polarity, structural variation, and D/A ratio on the nature of co-assembly, morphology, and the unprecedented supramolecular-switching phenomenon have been studied by detail spectroscopic and microscopic experiments in a gel as well as in the solution state and are well supported by DFT calculations. [ABSTRACT FROM AUTHOR]

Supramolecular Assembly In their Communication on page 1606 ff., S. Ghosh et al. describe the generation of two bolaamphiphiles with different H‐bonding motifs (hydrazide or amide) and their distinct behavior in the multivalent binding of concanavalin A. [ABSTRACT FROM AUTHOR]

Supramolecular Chemistry Complementary donor (D)–acceptor (A) chromophores assemble with long‐range order by hydrogen bonding and produce charge‐transfer organogels. In the presence of excess donor, extended fibrils get truncated and the gel is destroyed. For more details see the Communication by S. Ghosh, A. Paul et al. on page 1908 ff. The authors thank Mr. Gopal Krishna Manna for his help in the preparation of the frontispiece. [ABSTRACT FROM AUTHOR]