Multiethynyl Corannulenes: Synthesis, Structure, and Properties

Abstract

Syntheses, crystal structures, ab initio density functional theory computations, and photophysical properties of 1,6-di-, 1,2,5,6-tetra-, and 1,3,5,7,9-pentaethynyl-substituted corannulenes (classes 3, 4, and 5, respectively) are reported. Classes 3 and 4 were prepared from the corresponding corannulenyl bromides and terminal alkynes in excellent yields (nine examples, with yields of 57-92%) using the Sonogarshira reaction. Class 5 was prepared from 1,3,5,7,9-pentacholorocorannulene and trimethylalkynylstannanes using a modification of Nolan's procedure (8 examples, with yields of 45-93%). The molecular packing in crystals of 1,6-diphenylethynyl-2,5-dimethylcorannulene (3-Ph2) displays a polar columnar structure with all of the molecule bowls oriented in the same direction. Similarly, 1,2,5,6-tetrakis(3,5-dimethylphenylethynyl)corannulene [4-Ar(c)5] and 1,3,5,7,9-pentakis(3,5-dimethylphenylethynyl)corannulene [5-Ar(c)5] form columnar structures, but the bowls are oriented in opposing directions. Additionally, the number of attached alkynyl arms is correlated with an increase in bowl depth of the corrannulene nucleus. Most of the aryl derivatives displayed high-quantum-efficiency solution luminescence and variable emission wavelengths that were dependent on the nature of the substitution.

Tunable Photochemical/Redox Properties of (Phenylthio)ncorannulenes: Application to a Photovoltaic Device

“…1868 depths (hub-to-rim) in the two molecules of 6b are 0.866 and 0.908 Å, respectively, which is close to the bowl depth of 1 (0.87 Å). 25 In 7b, with ten substituents, five above and five below the rim, the steric demands flatten the bowl considerably (0.486 Å). 10 …”

Synthesis, Structures, and Physical Properties of Aromatic Molecular-Bowl Hydrocarbons

“…Preparations of tetraethynylcorannulenes 41 [37][38][39] and tetraarylcorannulenes 42 [37,38] were accessed by Pd-catalyzed Sonogashira and Suzuki reactions, respectively, in good to excellent yields (Scheme 10). Similarly, 1,2,5,6-tetramethylcorannulene (43) was obtained in good yield from 18 by the Ni-catalyzed protocol [37,38].…”

“…Similarly, 1,2,5,6-tetramethylcorannulene (43) was obtained in good yield from 18 by the Ni-catalyzed protocol [37,38]. Tetrasubstituted corannulene 44 with two kinds of functional groups was prepared from 21 by the Sonogashira reaction [39].…”

“…Extension of the alkyl substituents (for example to ethyl) at the 1,6,7,10 positions also limits the degree of bromination. Nonetheless, ring closure of hexabromides 20 regioselectively to dibromocorannulenes 21 can be achieved by the base promoted procedure (Method C, Scheme 5) [25,39,40 Although methods A-C are efficient in generating corannulene derivatives, they would be problematic for sensitive functionality like the ester moiety. For example, cyclization of precursors 22 (R 1 ¼CO 2 Me) is doomed to failure under the reduction conditions of Methods A and B or in the presence of aqueous base as in Method C. A protocol developed by Sygula et al formed the corannulene core by a nickelmediated intramolecular coupling of benzyl and benzylidene bromides (Method D, Scheme 6) [26,27].…”

“…The representative examples include 28-F (0.87 Å) [40], 28-Cl (0.86 Å) [40], 21c (0.80 Å) [40], and 23c (0.82 Å) [41]. 1,2,5,6-Tetrabromocorannulene 18 is an exception; its bowl depth was determined to be 0.91 Å [39].…”