Supramolecular Polymerization Triggered by Molecular Recognition between Bisporphyrin and Trinitrofluorenone

Abstract

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 Tightly Stretched Ultralong Supramolecular Multiporphyrin Array Propagated by Double‐Strand Formation

“…[13] Furthermore, the cyclizationo ft wo terminals of the telechelics upramolecular polymer fatally competes with the propagations tep of supramolecular polymerization.T herefore, the supramolecular polymer has as trong propensityt oa dopt ac yclic topology insteado falinear topology such increasing the excluded-volume effect of polymer chains ( Figure 1). [19] Otherwise, the elaborate design of extraordinarily long telechelic chain unit that disfavors cyclizationp rovides an ultralong supramolecularp olymer. [18] This dilemma is circumvented as long as the conditions exceed the EM concentration, as typically employed for supramolecular polymerization.…”

Supramolecular Polymerization Engineered with Molecular Recognition

“…The goal of our design of a molecular monomer toward the supramolecular porphyrin polymer was to introduce guest G1 at the molecular tail of bisporphyrin cleft 10 via a certain linkage. Heteroditopic monomer 11 possesses the electron‐deficient guest moiety 4,5,7‐trinitro‐fluorenone‐2‐carboxylate (TNF) . The electron‐deficient TNF moiety can dock within the bisporphyrin cleft via a charge‐transfer interaction (Scheme ).…”

“…Heteroditopic monomer 11 possesses the electron-deficient guest moiety 4,5,7-trinitrofluorenone-2-carboxylate (TNF). [47] The electron-deficient TNF moiety can dock within the bisporphyrin cleft via a charge-transfer interaction (Scheme 4). The head-to-tail complexation results in the supramolecular polymerization.…”

Supramolecular Chemistry: From Host-guest Complexes to Supramolecular Polymers

“…Based on our previous fi ndings with bisporphyrin complexes, a π donor acceptor type host guest interaction was incorporated into a heteroditopic monomer 9 (Scheme 6). 35 The electron defi cient guest moiety, 4,5,7 trinitro fl uorenone 2 carboxylate (TNF), can dock within the bisporphyrin cleft via a charge transfer interaction. The iterative head to tail supramolecular polymerization is demonstrated.…”