Increasing interest in innovative supramolecular materials has spurred efforts to develop head-to-tail monomers possessing a host moiety as a head and a guest moiety as a tail, making them capable of forming supramolecular polymers through intermolecular associations while avoiding intramolecular cyclization. This competition between the intramolecular cyclization and the intermolecular association is influenced by conformational entropy, relying on the flexibility of the linker chain that connects the host moiety to the guest moiety in a head-to-tail monomer. However, there are limited reports presenting a quantitative thermodynamic picture describing the conformational entropy in ring−chain equilibrium processes. Here, we report the quantitative evaluation of the role of conformational entropy in the ring−chain equilibrium mechanism of the supramolecular polymerization of a headto-tail monomer possessing a bisporphyrin host and a trinitrofluorenone guest connected with various alkyl chains as linkers. The supramolecular polymerization of the head-to-tail monomers was studied using UV/vis, NMR, and diffusion-ordered spectroscopy spectroscopic techniques and viscometry. The thermodynamic parameters of the ring−chain equilibrium were determined in the initial stage of the supramolecular polymerization. The conformational entropy, which relies on the flexibility of the linker, had a significant influence on the critical polymerization concentration. This quantitative discussion of ring−chain competition is expected to provide a foundation for the proper design of artificial head-to-tail monomers that form supramolecular polymers.

The host–guest complexation of a bisporphyrin cleft with various electron-deficient guest molecules was studied in solution and in the solid-state. X-ray crystal structures of a bisporphyrin cleft with naphthalene dianhydride and 2,4,7-trinitrofluorenone reveal that these guest molecules were located within the bisporphyrin cleft and formed ideal π–π stacking interactions in a host–guest ratio of 1:1. Isothermal titration calorimetry determined the binding constants and thermodynamic parameters for the 1:1 host–guest complexations in 1,2-dichloroethane and toluene. Two types of enthalpy–entropy compensation effects were found: (1) The tightly stacked host–guest structures restrict guest movement within the cleft, which results in significant desolvation with large intrinsic entropies. (2) The loosely bound guests maintain their molecular freedom within the bisporphyrin cleft, which leads to less desolvation with small intrinsic entropies. Chiral guest encapsulation directed the clockwise and anticlockwise twisted conformations of the bisporphyrin units, which induced bisignate CDs.

The dynamic helix interconversion of the C60-appended polyacetylene was directed by the molecular recognition of a chiral biscalix[5]arene.

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Tetrakis(porphyrin) molecular cleft was prepared by Suzuki-Miyaura cross coupling between a bis(porphyrin) boronate ester and 1,4-bis(4-iodophenyl)-1,3-butadiyne. The overall yield of the Tetrakis(porphyrin) was found to be more than doubled compared to that reported previously. The successful preparation of tetrakis(porphyrin) was characterized by a combination of nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HRMS). Furthermore, HRMS evidenced the formation of supramolecular polymeric species driven by bis(porphyrin)-bis(porphyrin) dimerization in the gas phase.