Supramolecular Assemblies by Charge-Transfer Interactions between Donor and Acceptor Chromophores

J-aggregation, its impact on excited state dynamics and unique solvent effects on macroscopic assembly of a core-substituted naphthalenediimide

Herein we reveal a straightforward supramolecular design for the H-bonding driven J-aggregation of an amine-substituted cNDI in aliphatic hydrocarbons. Transient absorption spectroscopy reveals sub-ps intramolecular electron transfer in isolated NDI molecules in a THF solution followed by a fast recombination process, while a remarkable extension of the excited state lifetime by more than one order of magnitude occurred in methylcyclohexane likely owing to an increased charge-separation as a result of better delocalization of the charge-separated states in J-aggregates. We also describe unique solvent-effects on the macroscopic structure and morphology. While J-aggregation with similar photophysical characteristics was noticed in all the tested aliphatic hydrocarbons, the morphology strongly depends on the "structure" of the solvents. In linear hydrocarbons (n-hexane, n-octane, n-decane or n-dodecane), formation of an entangled fibrillar network leads to macroscopic gelation while in cyclic hydrocarbons (methylcyclohexane or cyclohexane) although having a similar polarity, the cNDI exhibits nanoscale spherical particles. These unprecedented solvent effects were rationalized by establishing structure-dependent specific interactions of the solvent molecules with the cNDI which may serve as a general guideline for solvent-induced morphology-control of structurally related self-assembled materials.

Seeded on-surface supramolecular growth for large area conductive donor–acceptor assembly

A seeded, on-surface, supramolecular growth leads to large area conductive donor–acceptor assembly via evaporation-assisted growth from active termini of solution-formed sheaf-like seeds.

Intramolecular charge transfer interactions and molecular order of rod like mesogens

Photophysical studies, VT-XRD and¹³C solid state NMR investigation of three ring based dimethylamino mesogens reveal intramolecular charge transfer, smectic A_dmesophase and molecular order.

Face-to-face stacking in sulfonamide based bis-ethylene bridged heteroaromatic dimers

Four sulfonamide based bis-ethylene bridged heteroaromatic dimers were crystallized in offset face-to-face stacked geometry. Further, density functional theory revealed that crystallized structures were the most stable conformers.

Nanofibrous hydrogels self-assembled from naphthalene diimide (NDI)/amino acid conjugates

A new approach is proposed for the design of NDI-capped supramolecular hydrogels.

Solvent-induced reversible solid-state colour change of an intramolecular charge-transfer complex

A dynamic intramolecular charge-transfer complex reversibly changes colours due to solvent-inclusion induced geometric changes in the donor and acceptor interaction.

The marriage of endo-cavity and exo-wall complexation provides a facile strategy for supramolecular polymerization

The marriage of exo-wall interactions and endo-cavity inclusion provides a new strategy for the construction of supramolecular polymers from unfunctionalized neutral receptors.

Donor–acceptor interaction-driven folding of linear naphthalene–glycol oligomers templated by a rigid bipyridinium rod

The construction of folded and helical supramolecular structures through the self-assembly of a series of flexible linear oligomers induced by a rigid rod-like template has been demonstrated.

Protein–polymer therapeutics: a macromolecular perspective

The development of protein–polymer hybrids emerged several decades ago with the vision that their synergistic combination will offer macromolecular hybrids with manifold features to succeed as the next generation therapeutics.

Synthesis of monolateral and bilateral sulfur-heterocycle fused naphthalene diimides (NDIs) from monobromo and dibromo NDIs

Monolateral and bilateral sulfur-heterocycle fused naphthalene diimides (NDIs) are successfully synthesized from monobromo and dibromo NDIs via nucleophilic aromatic substitution reactions and the subsequent oxidative aromatization processes.

Extended supramolecular organization of π-systems using yet unexplored simultaneous intra- and inter-molecular H-bonding motifs of 1,3-dihydroxy derivatives

Simultaneous intra- and inter-molecular H-bonding among 1,3-dihydroxyl derivatives with acceptor chromophores leads to fibrillar gelation facilitating π-stacking and specific donor intercalation.

Pseudopeptide Foldamers designed for photoinduced intramolecular electron transfer

Hybrid foldamers equipped with a donor and an acceptor unit exhibit unexpected conformations affecting the photoinduced electron transfer ability. The donor quenching efficiency depends both on the nature and on the secondary structure of the linker.

Conducting nanofibers and organogels derived from the self-assembly of tetrathiafulvalene-appended dipeptides

We demonstrate the nonaqueous self-assembly of a low-molecular-mass organic gelator based on an electroactive p-type tetrathiafulvalene (TTF)-dipeptide bioconjugate. We show that a TTF moiety appended with diphenylalanine amide derivative (TTF-FF-NH2) self-assembles into one-dimensional nanofibers that further lead to the formation of self-supporting organogels in chloroform and ethyl acetate. Upon doping of the gels with electron acceptors (TCNQ/iodine vapor), stable two-component charge transfer gels are produced in chloroform and ethyl acetate. These gels are characterized by various spectroscopy (UV-vis-NIR, FTIR, and CD), microscopy (AFM and TEM), rheology, and cyclic voltammetry techniques. Furthermore, conductivity measurements performed on TTF-FF-NH2 xerogel nanofiber networks formed between gold electrodes on a glass surface indicate that these nanofibers show a remarkable enhancement in the conductivity after doping with TCNQ.

Multiple CH···O interactions involving glycol chains as driving force for the self-assembly of amphiphilic Pd(II) complexes

We demonstrate that the self-assembly in polar media and gelation of an amphiphilic Pd(II) complex with pendant chlorine ligands are governed by cooperative intra- and interstrand CH···O interactions between peripheral triethylene glycol chains leading to slipped π-stacks.

Engineering orthogonality in supramolecular polymers: from simple scaffolds to complex materials

Owing to the mastery exhibited by Nature in integrating both covalent and noncovalent interactions in a highly efficient manner, the quest to construct polymeric systems that rival not only the precision and fidelity but also the structure of natural systems has remained a daunting challenge. Supramolecular chemists have long endeavored to control the interplay between covalent and noncovalent bond formation, so as to examine and fully comprehend how function is predicated on self-assembly. The ability to reliably control polymer self-assembly is essential to generate "smart" materials and has the potential to tailor polymer properties (i.e., viscosity, electronic properties) through fine-tuning the noncovalent interactions that comprise the polymer architecture. In this context, supramolecular polymers have a distinct advantage over fully covalent systems in that they are dynamically modular, since noncovalent recognition motifs can be engineered to either impart a desired functionality within the overall architecture or provide a designed bias for the self-assembly process. In this Account, we describe engineering principles being developed and pursued by our group that exploit the orthogonal nature of noncovalent interactions, such as hydrogen bonding, metal coordination, and Coulombic interactions, to direct the self-assembly of functionalized macromolecules, resulting in the formation of supramolecular polymers. To begin, we describe our efforts to fabricate a modular poly(norbornene)-based scaffold via ring-opening metathesis polymerization (ROMP), wherein pendant molecular recognition elements based upon nucleobase-mimicking elements (e.g., thymine, diaminotriazine) or SCS-Pd(II) pincer were integrated within covalent monofunctional or symmetrically functionalized polymers. The simple polymer backbones exhibited reliable self-assembly with complementary polymers or small molecules. Within these systems, we applied successful protecting group strategies and template polymerizations to enhance the control afforded by ROMP. Main-chain-functionalized alternating block polymers based upon SCS-Pd(II) pincer-pyridine motifs were achieved through the combined exploitation of bimetallic initiators and supramolecularly functionalized terminators. Our initial design principles led to the successful fabrication of both main-chain- and side-chain-functionalized poly(norbornenes) via ROMP. Utilizing all of these techniques in concert led to engineering orthogonality while achieving complexity through the installation of multiple supramolecular motifs within the side chain, main chain, or both in our polymer systems. The exploitation and modification of design principles based upon functional ROMP initiators and terminators has resulted in the first synthesis of main-chain heterotelechelic polymers that self-assemble into A/B/C supramolecular triblock polymers composed of orthogonal cyanuric acid-Hamilton wedge and SCS-Pd(II) pincer-pyridine motifs. Furthermore, supramolecular A/B/A triblock copolymers were realized through the amalgamation of functionalized monomers, ROMP initiators, and terminators. To date, this ROMP-fabricated system represents the only known method to afford polymer main chains and side chains studded with orthogonal motifs. We end by discussing the impetus to attain functional materials via orthogonal self-assembly. Collectively, our studies suggest that combining covalent and noncovalent bonds in a well-defined and precise manner is an essential design element to achieve complex architectures. The results discussed in this Account illustrate the finesse associated with engineering orthogonal interactions within supramolecular systems and are considered essential steps toward developing complex biomimetic materials with high precision and fidelity.

Supramolecular electron donor–acceptor complexes formed by perylene diimide derivative and conjugated phenazines

The nanostructure and binding mode of the perylene diimide–phenazine complex can be modulated by the phenazine derivative substituents.

Mechanically strong, fluorescent hydrogels from zwitterionic, fully π-conjugated polymers

Mechanically strong supramolecular hydrogels can be obtained by combining a rigid, fully π-conjugated polymer backbone and zwitterionic side chains.

Charge-transfer interactions for the fabrication of multifunctional viral nanoparticles

In this paper, a facile strategy to fabricate multifunctional viral nanoparticles was described by introducing charge-transfer interactions between a pyrenyl motif with dinitrophenyl and pyridinium-contained guest molecules.