Noncovalent synthesis of homo and hetero-architectures of supramolecular polymers via secondary nucleation.

The synthesis of supramolecular polymers with controlled architecture is a grand challenge in supramolecular chemistry. Although living supramolecular polymerization via primary nucleation has been extensively studied for controlling the supramolecular polymerization of small molecules, the resulting supramolecular polymers have typically exhibited one-dimensional morphology. In this report, we present the synthesis of intriguing supramolecular polymer architectures through a secondary nucleation event, a mechanism well-established in protein aggregation and the crystallization of small molecules. To achieve this, we choose perylene diimide with 2-ethylhexyl chains at the imide position as they are capable of forming dormant monomers in solution. Activating these dormant monomers via mechanical stimuli and hetero-seeding using propoxyethyl perylene diimide seeds, secondary nucleation event takes over, leading to the formation of three-dimensional spherical spherulites and scarf-like supramolecular polymer heterostructures, respectively. Therefore, the results presented in this study propose a simple molecular design for synthesizing well-defined supramolecular polymer architectures via secondary nucleation.

Pathway Selection in Temporal Evolution of Supramolecular Polymers of Ionic π-systems: Amphiphilic Organic Solvent Dictates the Fate of Water.

Understanding solvent-solute interactions is essential to designing and synthesising soft materials with tailor-made functions. Although the interaction of the solute with the solvent mixture is more complex than the single solvent medium, solvent mixtures are exciting to unfold several unforeseen phenomena in supramolecular chemistry. Here we report two unforeseen pathways observed during the hierarchical assembly of cationic perylene diimides (cPDIs) in a water and amphiphilic organic solvent (AOS) mixtures. When the aqueous supramolecular polymers (SPs) of cPDIs are injected into AOS, initially kinetically trapped short SPs are formed, which gradually transform into thermodynamically stable high aspect ratio SP networks. Using various experimental and theoretical investigations, we found that this temporal evolution follows two distinct pathways depending on the nature of the water-AOS interactions. If the AOS is isopropanol (IPA), water is released from cPDIs into bulk IPA due to strong hydrogen bonding interactions, which further decreases the monomer concentration of cPDIs (Pathway-1). In the case of dioxane AOS, cPDIs monomer concentration further increases as water is retained among cPDIs (Pathway-2) due to relatively weak interactions between dioxane and water. Interestingly, these two pathways are accelerated by external stimuli such as heat and mechanical agitation.

Supramolecular Engineering of Ti3 C2 Tx MXene -Perylene Diimide Hybrid Electrodes for the Pseudocapacitive Electrochemical Storage of Calcium Ions.

The rare combination of metallic conductivity and surface redox activity enables 2D MXenes as versatile charge storage hosts for the design of high-rate electrochemical energy storage devices. However, high charge density metal ions including but not limited to Ca+2 and Mg+2 pose challenges such as sluggish solid-state diffusion and also inhibiting the charge transfer across electrode-electrolyte interfaces. In this work, free-standing hybrid electrode architectures based on 2D titanium carbide-cationic perylene diimide (Ti3 C2 Tx @cPDI) via supramolecular self-assembly are developed. Secondary bonding interactions such as dipole-dipole and hydrogen bonding between Ti3 C2 Tx and cPDI are investigated by zeta potential and Fourier-transformed infrared (FTIR) spectroscopy . Ti3 C2 Tx @cPDI free-standing electrodes show typical volumetric capacitance up to 260 F cm-3 in Mg2+ and Ca2+ aqueous electrolytes at charging times scales from 3 minutes to a few seconds. Three-dimensional (3D) Bode maps are constructed to understand the charge storage dynamics of Ti3 C2 Tx @cPDI hybrid electrode in an aqueous Ca-ion electrolyte. ,Pseudocapacitance is solely contributed by the nanoscale distribution of redox-active cPDI supramolecular polymers across 2D Ti3 C2 Tx . This study opens avenues for the design of a wide variety of MXene@redox active organic charge hosts for high-rate pseudocapacitive energy storage devices.

Post-synthetic π-extension of perylene conjugated porous polymer via APEX reactions: tunable optical and gas storage properties.

Double post-synthetic modification is used for the π-extension of perylene based conjugated porous polymers (CPPs) using sequential annulative π-extension (APEX) reactions. This approach enabled us to synthesize new CPPs rendered with donor-acceptor rigid π-systems such as benzoperylene anhydride (BPA-CPP) and benzoperylene benzimidazole (BPBI-CPP) with distinct optical properties. Despite its low surface area, BPBI-CPP shows good CO2 uptake and pH responsive behaviour owing to the presence of benzimidazole rings.

Synthesis and Self-assembly of Benzoperylene Benzimidazoles: Tunable Morphology with Aggregation-Induced Enhanced Emission.

Benzoperylene benzimidazoles (BPBIs) based π-systems were synthesized and their self-assembly in both non-polar and polar solvents investigated. Due to the presence of donor and acceptor functional groups, BPBIs absorb light up to 600 nm and display red fluorescence (575-800 nm). Depending on the solvent and side chain, BPBIs self-assemble into various nanostructures such as nanoribbons, nanorods, nanofibers and nanoparticles. Notably, these ordered nanostructures are formed by BPBIs in both polar and non-polar solvents without the aid of hydrogen bonding and amphiphilic interactions due to the presence of a large rigid π-system. Interestingly, BPBIs follow a weakly cooperative mechanism during the self-assembly. Moreover, BPBIs show aggregation-induced enhanced emission (AIEE) in all the self-assembled nanostructures which is not common for rigid π-systems.

Solvent-free autocatalytic supramolecular polymerization.

Solvent-free chemical manufacturing is one of the awaited technologies for addressing an emergent issue of environmental pollution. Here, we report solvent-free autocatalytic supramolecular polymerization (SF-ASP), which provides an inhibition-free template-assisted catalytic organic transformation that takes great advantage of the fact that the product (template) undergoes a termination-free nucleation-elongation assembly (living supramolecular polymerization) under solvent-free conditions. SF-ASP allows for reductive cyclotetramerization of hydrogen-bonding phthalonitriles into the corresponding phthalocyanines in exceptionally high yields (>80%). SF-ASP requires the growing polymer to form hexagonally packed crystalline fibres, which possibly preorganize the phthalonitriles at their cross-sectional edges for their efficient transformation. With metal oleates, SF-ASP produces single-crystalline fibres of metallophthalocyanines again in exceptionally high yields, which grow in both directions without terminal coupling until the phthalonitrile precursors are completely consumed. By taking advantage of this living nature of polymerization, multistep SF-ASP without/with metal oleates allows for the precision synthesis of multi-block supramolecular copolymers.

Giant spin pumping at the ferromagnet (permalloy) - organic semiconductor (perylene diimide) interface.

Pure spin current based devices have attracted great interest in recent days. Spin current injection into non-magnetic materials is essential for the design and development of such pure spin current based devices. In this context, organic semiconductors (OSCs) can be potential non-magnetic materials over widely explored heavy metals. This is due to the relatively low spin-orbit coupling of OSCs, which is essential to host the spin current with a large spin diffusion length and long spin-relaxation time. This research work demonstrates the harvesting of spin currents at the perylene diimide (PDI)/permalloy (Py) based OSC interface. The observed high linewidth broadening of 2.18 mT from the ferromagnetic resonance spectra indicates the presence of giant spin pumping from Py to PDI. The resultant spin-mixing conductance, 1.54 × 1018 m-2 quantifies the amount of spin current injected from Py to PDI, which is in a similar range to ferromagnet/heavy metals.

Supramolecular Depolymerization in the Mixture of Two Poor Solvents: Mechanistic Insights and Modulation of Supramolecular Polymerization of Ionic π-Systems.

Solvents are fundamentally essential for the synthesis and processing of soft materials. Supramolecular polymers (SPs), an emerging class of soft materials, are usually stable in single and mixtures of poor solvents. In contrast to these preconceived notions, here we report the depolymerization of SPs in the mixture of two poor solvents. This surprising behavior was observed for well-known cationic perylene diimides (cPDIs) in the mixtures of water and amphiphilic organic solvents such as isopropanol (IPA). cPDIs form stable SPs in water and IPA but readily depolymerize into monomers in 50-70 vol% IPA containing water. This is due to the selective solvation of the π-surface of cPDIs by alkyl chains of IPA and ionic side chains by water, as evidenced by molecular dynamic simulations. Moreover, by systematically changing the ratio between water and amphiphilic organic solvent, we could achieve an unprecedented supramolecular polymerization both by increasing and decreasing the solvent polarity.

Distinct Pathways in "Thermally Bisignate Supramolecular Polymerization": Spectroscopic and Computational Studies.

In general, supramolecular polymers are thermally labile in solution and easily depolymerized upon heating. This dynamic nature is beneficial in many aspects but limits certain applications. Recently, we developed "thermally bisignate supramolecular polymerization", through which a polymer is formed upon heating as well as cooling in a hydrocarbon solvent containing a small amount of alcohol. Here, we present a detailed mechanistic picture for this polymerization based on both spectroscopic and computational studies. For this particular type of polymerization, we mainly employed a copper porphyrin derivative ((S)PORCu) as a monomer with eight hydrogen-bonding (H-bonding) amide units in its chiral side chains. Because of a strong multivalent interaction, the resulting supramolecular polymer displayed an extraordinarily high thermal stability in a hydrocarbon medium such as methylcyclohexane (MCH)/chloroform (CHCl3) (98/2 v/v; denoted as MCH*). However, when a small volume (<2.0 vol %) of ethanol (EtOH) was added to this solution at ambient temperatures as a H-bond scavenger, the supramolecular polymer dissociated into its monomers. Here, it should be noted that, both upon cooling (clustering of EtOH) and heating (lower-critical-solution-temperature behavior, LCST), the monomer was liberated from the H-bond scavenger and underwent supramolecular polymerization. In this Article, we conducted detailed spectroscopic studies, analyzed the results using theoretical models, and eventually succeeded in supporting the pathways explaining why the monomer deactivated by the H-bond scavenger turns active upon both heating and cooling. We also investigated the thermally bisignate nature of the supramolecular polymerization of other monomers such as triphenylamine ((S)TPA) and pyrene ((S)Py) derivatives together with free-base ((R)POR2H) and zinc porphyrin ((S)PORZn) derivatives and rationalized the large potential for this multicomponent supramolecular polymerization.