Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C₃₆H₁₂ open geodesic polyarene

Abstract

SummaryCircumtrindene (6, C36H12), one of the largest open geodesic polyarenes ever reported, exhibits fullerene-like reactivity at its interior carbon atoms, whereas its edge carbons react like those of planar polycyclic aromatic hydrocarbons (PAHs). The Bingel–Hirsch and Prato reactions – two traditional methods for fullerene functionalization – afford derivatives of circumtrindene with one of the interior 6:6 C=C bonds modified. On the other hand, functionalization on the rim of circumtrindene can be achieved by normal electrophilic aromatic substitution, the most common reaction of planar PAHs. This peripheral functionalization has been used to extend the π-system of the polyarene by subsequent coupling reactions and to probe the magnetic environment of the concave/convex space around the hydrocarbon bowl. For both classes of functionalization, computational results are reported to complement the experimental observations.

Chemistry at the interior atoms of polycyclic aromatic hydrocarbons

“…14). 44 The reaction is site-selective for the 6:6 bonds at the point of greatest curvature (largest POAV angles), where the LUMO coefficients are also the largest. With C 60 , the formation of 2 : 1, 3 : 1, and higher multiple adducts complicates the Bingel reaction, but with circumtrindene the reaction stops at the 1 : 1 adduct.…”

Understanding the reactivity of polycyclic aromatic hydrocarbons and related compounds

“…In general, it is found that, similar to planar PAHs, larger systems are systematically more reactive than their smaller counterparts. 5,29 The reactivity of these curved systems has been traditionally rationalized by applying Fukui's Frontier Molecular Orbital (FMO) theory 30 and the degree of pyramidalization of the trigonal carbon atoms, which can be quantitatively expressed in terms of the angle between the p p -orbital axis vectors, also known as the POAV index. 31 However, these approaches are not always reliable reactivity descriptors for these species, as recently highlighted by Scott.…”

“…31 However, these approaches are not always reliable reactivity descriptors for these species, as recently highlighted by Scott. 5,29 For this reason, we decided to apply our ASM-EDA approach to gain further insight into the factors controlling the reactivity of these species. 32 To this end, we investigated the Diels-Alder reactions between cyclopentadiene and the interior atoms of the bowlshaped PAHs depicted in Fig.…”

Of Twists and Curves: Electronics, Photophysics, and Upcoming Applications of Non‐Planar Conjugated Organic Molecules

“…Contrastingly, in Rotatable NPCOMs which include non‐fused twisted molecular architectures such as U‐shaped, square‐shaped, X‐shaped, hash mark‐shaped NPCOMs, the π‐conjugation is disrupted or diminished rather abruptly at a particular location due to the twisting of certain fragments out of the molecular plane . NPCOMs with such twisted architectures are quite prevalent due to ease of synthesis and facile tunability of the functional groups, which allows access to diverse architectures and unique properties.…”