Synthesis and metalation of polycatechol nanohoops derived from fluorocycloparaphenylenes

Due to their unique topology and distinct physical properties, cycloparaphenylenes (CPPs) are attractive building blocks for new materials synthesis. While both noncovalent interactions and irreversible covalent bonds have been used to link CPP monomers into extended materials, a coordination chemistry approach remains less explored. Here we show that nucleophilic aromatic substitution reactions can be leveraged to rapidly introduce donor groups (-OR, -SR) onto polyfluorinated CPP rings. Demethylation of methoxide-substituted CPPs produces polycatechol nanohoop ligands that are readily metalated to produce well-defined, multimetallic CPP complexes. As catechols are recurring motifs throughout coordination chemistry and dynamic covalent chemistry, the polycatechol nanohoops reported here open the door to new strategies for the bottom-up synthesis of atomically precise CPP-based materials.

[n]Cyclodibenzopentalenes as Antiaromatic Curved Nanocarbons with High Strain and Strong Fullerene Binding

Conjugated nanohoops provide a platform to study structure-property relationships; they are attractive hosts for supramolecular chemistry as well as promising candidates as new organic materials. We herein present [n]cyclodibenzopentalenes ([n]CDBPs) as antiaromatic analogues of [n]cycloparaphenylenes. Platinum-mediated macrocyclization of dibenzopentalene boronic esters provided the trimer and tetramer with strain energies of up to 80 kcal mol^-1. In the solid state, the cylindrical [4]CDBP molecules align to form columnar structures. The larger hoop [4]CDBP binds both fullerenes C₆₀ and C₇₀ with temperature-dependent exchange behavior, providing higher activation energies for the exchange compared to [10]CPP. The antiaromatic character of the [n]CDBPs paired with the cyclic conjugation leads to high HOMO energies and lowered LUMO energies with band gaps below 2 eV. This work presents a new class of the antiaromatic and nonalternant curved nanocarbons with intriguing supramolecular and ambipolar optoelectronic properties.

Synthesis and Properties of Conjugated Nanohoops Incorporating Dibenzo[a,e]pentalenes: [2]DBP[12]CPPs

Conjugated nanohoops allow studying the effect of cyclic conjugation and bending on the incorporated π-systems. To date, no such system containing antiaromatic units has been reported. We herein present [12]cycloparaphenylenes incorporating two dibenzo[a,e]pentalene units: [2]DBP[12]CPP nanohoops. Dibenzo[a,e]pentalene is a nonalternant hydrocarbon with antiaromatic character. The syntheses and optoelectronic properties of two different [2]DBP[12]CPP nanohoops with electronically modifying substituents are reported, accompanied by TDDFT calculations.

Optical properties and magnetic flux-induced electronic band tuning of a T-graphene sheet and nanoribbon

Tetragonal graphene (T-graphene) is a theoretically proposed dynamically stable, metallic allotrope of graphene.