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Highly Curved Bowl‐Shaped Fragments of Fullerenes: Synthesis, Structural Analysis, and Physical Properties
Author(s) -
Chen MinKuan,
Hsin HsinJu,
Wu TsunCheng,
Kang BoYan,
Lee YenWei,
Kuo MingYu,
Wu YaoTing
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201303357
Subject(s) - crystallography , chemistry , planar , polar , curvature , wavelength , geometry , optics , physics , computer graphics (images) , mathematics , astronomy , computer science
Highly curved buckybowls 3 , 4 , and 5 were synthesized from planar precursors, fluoranthenes 8 , benzo[ k ]fluoranthenes 10 and naphtho[1,2‐ k ]‐cyclopenta[ cd ]fluoranthenes 12 , respectively, using straightforward palladium‐catalyzed cyclization reactions. These fluoranthene‐based starting materials were easily prepared from 1,8‐bis(arylethynyl)naphthalenes 6 . Both buckybowls 3 and 4 are fragments of C 60 , whereas 5 is a unique subunit of C 70 . The curved structures were identified by X‐ray crystallography, and they are deep bowls. The maximum π‐orbital axis vector (POAV) pyramidalization angle in both 3 and 4 is 12.8°. Such a high curvature is very rarely obtained. Buckybowls 5 are less curved than the others because they have a lower density of five‐membered rings, analogous to the tube portion of C 70 . Cyclopentaannulation increases the bowl depths of 3 and 4 , but not the maximum POAV pyramidalization angle. Among the eight buckybowls studied herein, five form polar crystals. The bowl‐to‐bowl inversion dynamics of these buckybowls can be classified into two types; one has a planar transition structure, whereas the other has an S‐shaped transition structure. A larger longitudinal length of these buckybowls corresponds to a stronger preference for the latter. The photophysical properties of these buckybowls were examined and compared with those of C 60 and C 70 . Buckybowls 5 have absorption bands at wavelengths greater than 450 nm, which are similar to those of C 70 . The chiral resolution of the mono‐substituted buckybowl 4 ac was also studied by using HPLC with a chiral column.