One hundred years of helicene chemistry. Part 3: applications and properties of carbohelicenes

Abstract

Carbohelicenes are a class of fascinating chiral helical molecules which have a rich history in chemistry. Over a period of almost 100 years, chemists have developed many methods to prepare them in a racemic or in a non-racemic form. They also possess a series of interesting chiral, physical, electronic and optical properties. However, their utilization in chemistry or chemistry-related fields has rarely appeared in a detailed and comprehensive review. It is the purpose of this review to collect fundamental applications and functions involving carbohelicenes in various disciplines such as in materials science, in nanoscience, in biological chemistry and in supramolecular chemistry. From the numerous synthetic methodologies reported up to now, carbohelicenes and their derivatives can be tailor-made for a better involvement in several subfields. Among those domains are: nanosciences, chemosensing, liquid crystals, molecular switches, polymers, foldamers, supramolecular materials, molecular recognition, conductive and opto-electronic materials, nonlinear optics, chirality studies and asymmetric synthesis. Helicene chemistry is now at a developmental stage, where sufficient application data are now collected and are extremely useful. They provide many more ideas for setting up the basis for future innovative applications.

Complexation and Electronic Communication between Corannulene‐Based Buckybowls and a Curved Truxene‐TTF Donor

“…The convex surface often shows reactivity patterns similar to those seen for fullerenes. For example, upon treatment of C 26 H 12 , the smallest fullerene fragment featuring a [6,6] double bond, under the conditions for 1,3-dipolar cycloaddition, carbine addition, or nucleophilic addition of MeLi, it exhibits reactions as found for [60]fullerene, that is, addition reactions at the central [6,6] ring junction. If it is subjected to Friedel-Crafts alkylation conditions, C 26 H 12 behaves like an ordinary PAH, that is, it reacts at the double bonds located at the edges.…”

“…If it is subjected to Friedel-Crafts alkylation conditions, C 26 H 12 behaves like an ordinary PAH, that is, it reacts at the double bonds located at the edges. [14] A more complex scenario occurs if more than one type of [6,6] double bond is present in the buckybowl. For example, for the larger circumtrindene (C 36 H 12 ) [15] under 1,3-dipolar cycloaddition conditions, the process is site-selective for [6,6] bonds located at the point of greatest curvature.…”

“…[14] A more complex scenario occurs if more than one type of [6,6] double bond is present in the buckybowl. For example, for the larger circumtrindene (C 36 H 12 ) [15] under 1,3-dipolar cycloaddition conditions, the process is site-selective for [6,6] bonds located at the point of greatest curvature. [14] This chemical reactivity resembles that observed for C 70 .…”

“…[1][2][3] If PAHs are formed solely by fused benzene rings, their structure remains planar, except in helicenes [4][5][6] or highly strained cyclic derivatives, [7][8][9][10][11] whereas PAHs featuring five-membered rings as part of their structure adopt nonplanar equilibrium geometries. In an extreme scenario, spherical fullerenes evolve upon embedding twelve five-membered rings into a PAH structure.…”

Dynamic Helicity Control of Oligo(salamo)-Based Metal Helicates

“…These helical structures could have a dynamic feature because they are spontaneously formed from flexible molecules via reversible processes and maintained by non-covalent interactions. While the advantage of static helical structures, such as helicenes [6][7][8][9][10], is to provide a stable chiral field that would remain intact irrespective of the environment, it would sometimes be advantageous to construct dynamic helical structures that can change their chirality depending on the situations (Figure 1). In this context, dynamic helical structures that are spontaneously constructed by non-covalent interactions would be useful to achieve responsive functions.…”