No abstract

Chiral tris(phenylisoxazolyl)benzenes possessing a perylenebisimide moiety assembled to form helical stacks. The self-assembling behavior of the helical stacks responded to changes in solvent properties, temperature, and concentration. Strong circular dichroism (CD) and circularly polarized luminescence (CPL) of their assemblies were displayed, and were controlled by external stimuli.

Self-assembled supramolecular polymers consist of molecular components that are held together through noncovalent interactions. The reversible noncovalent interactions can be used to produce healable, stimuli-responsive, and switchable supramolecular polymers. This new class of intelligent polymer materials, with macroscopic properties that might be turned on and off by external stimuli, has helped supramolecular polymer chemistry to gain momentum within the field of polymer science.[1] The design of wellorganized polymer architectures requires the integration of certain supramolecular components that must be capable of creating the strong noncovalent interactions necessary for producing an appreciable degree of polymerization. Multiple hydrogen-bonding, [2] hydrophobic, [3] cation-dipole, [4] CH/p, [5] and aromatic electron donor-acceptor [6] interactions are often employed in the synthesis of functional supramolecular polymers.Supramolecular porphyrin polymers have recently attracted attention because of their creative applications in photoactive devices. Coordination-driven self-assembly is one of the most useful approaches for building large and elaborate porphyrin architectures. [7] However, self-assembly of porphyrins in organic media, driven by weak noncovalent forces, such as van der Waals and CH/p interactions, is very limited, [8] even though the porphyrin moiety possesses a flat and electron-rich surface that creates the possibility of attractive van der Waals, stacking, and charge-transfer interactions. Recently, we have developed a bisporphyrin cleft connected by a pyridine dicarboxamide linker that assembles to form a unique complementary dimer in organic media.[9] The competitive complexation of a flat, electron-deficient aromatic guest into the bisporphyrin cleft leads to a p donor-acceptortype host-guest complex.[10] These supramolecular motifs should be useful for the synthesis of supramolecular porphyrin polymers.[11] To investigate this strategy, a p donoracceptor-type host-guest motif was incorporated into the heteroditopic monomer 1. The electron-deficient guest moiety, 4,5,7-trinitrofluorenone-2-carboxylate (TNF), can bind within the bisporphyrin cleft through a charge-transfer interaction, and iterative head-to-tail host-guest complexation should produce a new supramolecular polymer (Figure 1). Herein, we report the novel molecular recognition-directed supramolecular polymerization of monomer 1 in solution and solid state.The self-assembly of 1 was studied in solution using fluorescence and UV/Vis absorption spectroscopies (see Figure S1 in the Supporting Information). The fluorescence spectrum of 1 in toluene was temperature dependent; strong emission bands (l ex = 501 nm) at 363 K were observed at 657 and 719 nm, which are characteristic of a porphyrin core, but the emission bands gradually diminished upon cooling the solution. When the temperature reached 263 K, 80 % of the emission was quenched. The TNF moiety is a good energy acceptor. Therefore, this quenching can be rationalized ...

A biscalix[5]arene-C60 supramolecular structure was utilized for the development of supramolecular fullerene polymers. Di- and tritopic hosts were developed to generate the linear and network supramolecular polymers through the complexation of a dumbbell-shaped fullerene. The molecular association between the hosts and the fullerene were carefully studied by using (1) H NMR, UV/Vis absorption, and fluorescence spectroscopy. The formation of the supramolecular fullerene polymers and networks was confirmed by diffusion-ordered (1) H NMR spectroscopy (DOSY) and solution viscometry. Upon concentrating the mixtures of di- or tritopic hosts and dumbbell-shaped fullerene in the range of 1.0-10 mmol L(-1) , the diffusion coefficients of the complexes decreased, and the solution viscosities increased, suggesting that large polymeric assemblies were formed in solution. Scanning electron microscopy (SEM) was used to image the supramolecular fullerene polymers and networks. Atomic force microscopy (AFM) provided insight into the morphology of the supramolecular polymers. A mixture of the homoditopic host and the fullerene resulted in fibers with a height of (1.4±0.1) nm and a width of (5.0±0.8) nm. Interdigitation of the alkyl side chains provided secondary interchain interactions that facilitated supramolecular organization. The homotritopic host generated the supramolecular networks with the dumbbell-shaped fullerene. Honeycomb sheet-like structures with many voids were found. The growth of the supramolecular polymers is evidently governed by the shape, dimension, and directionality of the monomers.

Nature precisely manipulates primary monomer sequences in biopolymers. In synthetic polymer sequences, this precision has been limited because of the lack of polymerization techniques for conventional polymer synthesis. Engineering the primary monomer sequence of a polymer main chain represents a considerable challenge in polymer science. Here, we report the development of sequence-controlled supramolecular terpolymerization via a self-sorting behavior among three sets of monomers possessing mismatched host–guest pairs. Complementary biscalix[5]arene-C60, bisporphyrin-trinitrofluorenone (TNF), and Hamilton’s bis(acetamidopyridinyl)isophthalamide-barbiturate hydrogen-bonding host–guest complexes are separately incorporated into heteroditopic monomers that then generate an ABC sequence-controlled supramolecular terpolymer. The polymeric nature of the supramolecular terpolymer is confirmed in both solution and solid states. Our synthetic methodology may pave an avenue for constructing polymers with tailored sequences that are associated with advanced functions.