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We examine the effects of fusing two benzofurans to s‐indacene (indacenodibenzofurans, IDBFs) and dicyclopenta[b,g]naphthalene (indenoindenodibenzofurans, IIDBFs) to control the strong antiaromaticity and diradical character of these core units. Synthesis via 3‐functionalized benzofuran yields syn‐IDBF and syn‐IIDBF. syn‐IDBF possesses a high degree of paratropicity, exceeding that of the parent hydrocarbon, which in turn results in strong diradical character for syn‐IIDBF. In the case of the anti‐isomers, synthesized via 2‐substituted benzofurans, these effects are decreased; however, both derivatives undergo an unexpected ring‐opening reaction during the final dearomatization step. All the results are compared to the benzothiophene‐fused analogues and show that the increased electronegativity of oxygen in the syn‐fused derivatives leads to enhancement of the antiaromatic core causing greater paratropicity. For syn‐IIDBF increased diradical character results from rearomati‐zation of the core naphthalene unit in order to relieve this paratropicity. [ABSTRACT FROM AUTHOR]

A freely soluble dianthracenoindacene derivative has been synthesized using an 'inside-out' Friedel-Crafts alkylation method and is the first fluorescent diacenoindacene reported. Linear fusion of the anthracenes is confirmed by X-ray diffraction studies on the neutral molecule as well as its dianion. Based on predictions from our previous studies, this is also the least antiaromatic diacenoindacene derivative yet to be prepared, which is reflected in its highly negative and irreversible reduction. With its paratropicity essentially eliminated, we posit that the molecule is no longer deactivated by a conical intersection, typical of antiaromatic molecules, and therefore fluorescence is restored. This follows the trend shown in the related dianthracenopentalenes, with the reappearance of fluorescence when the outer acene groups are extended to linearly-fused anthracene moieties. [ABSTRACT FROM AUTHOR]

Herein we report the synthesis and characterization of four donor/acceptor‐fused s‐indacenes via the late‐stage oxidation of a family of unsymmetrical benzofuran/benzothiophene‐s‐indacene regioisomers. A thorough study of their properties through experimental and computational analysis has revealed the effect of asymmetry on the molecular properties associated with antiaromaticity, as well as a strong correlation between antiaromaticity and intramolecular charge transfer (ICT). The strength of the charge transfer depends on the fusion orientation of the donor and acceptor motifs relative to the s‐indacene core. The two most antiaromatic oxidized isomers exhibit strong evidence of ICT with 30 and 40 nm solvatochromic shifts. [ABSTRACT FROM AUTHOR]