Supramolecular Porphyrin–DABCO Array in Single‐ and Double‐Stranded Polynorbornenes

Abstract

Zinc-porphyrin-appended norbornene derivative 6, the corresponding dimer 7, coherently aligned single-stranded polynorbornene 5, and zinc-porphyrin-linked double-stranded polymeric ladderphane 3 have been used for complexation with 1,4-diazabicyclo[2.2.2]octane (DABCO) to generate an array of porphyrin-DABCO supramolecular scaffolds. The stoichiometries of the complex formation are analyzed in detail by (1)H NMR spectroscopy as well as absorption and emission spectroscopic methods. Bidentate ligand DABCO is found to form with 7, 5, and 3 to give 2-to-1 porphyrin-DABCO sandwich structures. Monomer 6, on the other hand, forms a 2-to-1 porphyrin-DABCO sandwich structure at high concentration (20 mM), but a 1-to-1 porphyrin-DABCO complex at low concentration (10(-6) M). Time-resolved fluorescence decays revealed a similar behavior for the 2-to-1 porphyrin-DABCO sandwich structures that are formed from 3, 5, and 7.

End Group Modification of Polynorbornenes

“…We have previously established that, upon treatment with the first‐generation Grubbs catalyst 3 , norbornenes fused with N ‐arylpyrrolidine 4 afford the corresponding polynorbornenes 5a (Figure ) with isotactic stereochemistry and all double bonds in trans ‐configuration . Thus, when the ROMP was quenched with 2 , 5b with an allyl acetate end group was obtained in 85% yield.…”

“…Upon treatment with the first generation of Grubbs catalyst, norbornenes fused with N ‐arylpyrrolidene moiety undergo ROMP stereoselectively giving the corresponding 2D comb‐like polynorbornenes with isotactic stereochemistry and all double bonds in trans ‐configuration . These protocols have recently been used for the construction of a series of polynorbornene‐based double‐stranded ladderphanes 1 9 having a range of aromatic, antiaromatic, and 3D organic and organometallic linkers, L, with diverse structural variety. Significant interactions between aromatic linkers in these ladderphanes may take place as evidenced by fluorescence quenching, excimer formation, as well as Soret band splitting (in prophyrin‐containing ladderphanes).…”

“…Significant interactions between aromatic linkers in these ladderphanes may take place as evidenced by fluorescence quenching, excimer formation, as well as Soret band splitting (in prophyrin‐containing ladderphanes). [8c‐d],, These interesting photophysical properties might find potential applications, if the polymer could be assembled onto a suitable substrate. One of the approaches would involve a modification of the end group, so that the polymer may anchor onto a solid surface for device fabrications.…”

Double‐stranded ladderphanes with C2‐symmetric planar chiral ferrocene linkers

“…Site specific control by a chiral auxilliary at the terminal position is known to induce helical chirality . We recently reported a series of covalently linked, DNA‐like double‐stranded symmetrical ladderphanes 1 by ring opening metathesis polymerization of the corresponding bisnorbornene derivatives 2 . In addition to three dimensional organic or organometallic linkers, a range of different oligoaryls has been used to connect two strands into ladder‐like polymers.…”

“…We recently reported a series of covalently linked, DNA‐like double‐stranded symmetrical ladderphanes 1 by ring opening metathesis polymerization of the corresponding bisnorbornene derivatives 2 . In addition to three dimensional organic or organometallic linkers, a range of different oligoaryls has been used to connect two strands into ladder‐like polymers. Significant electronic interactions between aromatic linkers have been observed, as evidenced by fluorescence quenching, excimer formation, (a), and Soret band splitting, when porphyrin moieties are used as connectors .…”