A comparative study of conjugated polymers derived from the two 10 pi electron circuits of naphthalene and methano[10]annulene is presented. The annulene pi topology allows for a greater degree of intrapolymer charge delocalization, a key structural parameter for enhancing the performance of organic semiconductors. Molecular design and synthesis based upon unusual aromatic cores will enable facile transport properties that would not ordinarily be realized under the 6 pi electron aromatic paradigm.

Conjugated polymers and small molecules containing the nonplanar aromatic 1,6-methano [10]annulene were synthesized in an effort to understand how torsional differences between planar and nonplanar πelectron components influence the electronic properties of π-conjugated materials. The polymers and small molecule model systems contain commonly employed aromatic subunits such as thiophene, diketopyrrolopyrrole, and 2,1,3benzothiadiazole, leading to electron donor and donor−acceptor polymers. The curved geometry of 1,6-methano[10]annulene can lead to reduced local torsional strain in semiconducting polymers relative to large planar aromatics, potentially increasing intrapolymer conjugation. The relative amount of effective conjugation length increase granted by the annulene in each system of regioisomers was interrogated through the use of UV−vis and photoluminescence spectroscopy and electrochemistry, and it was found that 1,6methano[10]annulene relieves some torsional strain associated with solubilizing alkyl chains clashing with aromatic rings along the polymer backbone. The polymers were also found to be highly disordered in thin films yet still provided reasonable hole mobilities (ca. 10 −4 cm 2 /(V s)) in OFET devices. These results suggest that methano [10]annulene or other curved aromatics may prove useful in the future development of organic electronics.

The synthesis of a new bisfuranyl monomer, 2,7-bis(2-furanyl)-1,6-methano[10]annulene, is presented. Its properties and those of its polymer, synthesized via electropolymerization, are compared to those of the known furan-arene-furan monomers and their respective polymers. Investigation using UV-vis spectroscopy, cyclic voltammetry, and spectroelectrochemistry indicated that the 1,6-methano[10] annulene copolymer has properties rivaling those of the copolymers containing traditional aromatic cores. These results are rationalized in conjunction with DFT calculations, and they further the premise that 1,6-methano[10]annulene can be viewed as a viable building block for advanced π-conjugated electronic materials.

Unusual aromatics outside of the 6π-electron motif offer promise for functional electronic materials, and we frame this claim in the context of 10π-electron aromatics. The evolution of our understanding of 10π-electron aromatics is discussed briefly, from azulene to the [10]

The synthesis of precursors to pi-conjugated cyclopropenium polymers is described. Monomers for chemical and electrochemical manipulation are easily prepared through electrophilic substitution of in situ generated cyclopropenium cations that are then hydrolyzed to the respective cyclopropenones. The unusually strong dipole moment associated with the cyclopropenone renders this core formally aromatic, an electronic structure that becomes more important within individual monomers upon protonation of the carbonyl function with trifluoroacetic acid or alkylation with triethyloxonium salts. The electronic properties of cyclopropenone polymers in their pristine states and after acidification are discussed along with conjugated carbonyl-containing polymers that are also acid sensitive but without the added element of aromaticity. We find that the increased contributions of cyclopropenium cation aromaticity restrict the quinoidal charge carriers due to the energetically less favorable proposition of disrupting the local aromatic stabilization.