The catalytic enhancements of enzymes loaded on DNA nanostructures have been attributed to the characteristics provided by highly negative charges on the surface of scaffold, such as modulation of the...

Sumanene is a typical buckybowl molecule with C3v symmetry. We observed a fluorescence excitation spectrum and a dispersed fluorescence spectrum of sumanene in a supersonic jet. Bowl effects were clarified by comparing the spectra with those of triphenylene (D3h symmetry), which is a planar prototype of nonplanar sumanene. The S1 (1)A1 ← S0 (1)A1 transition is symmetry allowed. We found the 0(0)(0) band in the fluorescence excitation spectrum at 357.78 nm; this band was missing in the forbidden S1 (1)A1(') ← S0 (1)A1(') transition of triphenylene. The transition moment was shown to be along the oblate symmetric top axis (out of plane) by the observed rotational contour. A large number of vibronic bands were observed, unlike in triphenylene. Some were considered to be out-of-plane vibrational modes, which lead to a bowl-to-bowl inversion reaction assisted by in-plane vibrations. We found that the vibronic bands were markedly weak in the high energy region of triphenylene-d12. This indicates that the fluorescence quantum yield is very low at the high vibrational levels in the S1 state due to the rapid radiationless transition. The main process is considered to be internal conversion to the S0 state. The nonplanar structural distortion may also enhance radiationless transitions. We could not, however, observe weakening of the vibronic bands in the fluorescence excitation spectrum of sumanene.

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Single crystals of sumanenetrione and the iodinated derivative were found to possess a columnar packing structure with characteristic eclipsed stacks in a convex-to-concave fashion. In each column, the molecules are perfectly stacked without twisting and slipping in contrast to pristine sumanene. The neighboring columns are arranged in the opposite directions.One of the characteristic features of buckybowls, 1 bowlshaped aromatic hydrocarbons, is their columnar packing structure in the crystal state. Many buckybowls, including sumanene (1) (Figure 1), exhibit columnar packing in which the bowl-shaped molecules are stacked in a convex-to-concave fashion because this particular pattern results in highly favored intermolecular ππ interactions (Figure 2). 13 Typically, the columnar packing structures are classified into two types, (A) unidirectional and (B) opposite structures, with regard to the direction of the columns. Because of this columnar structure, buckybowls show characteristic solid-state properties such as high electron conductivity. 3a,4,5 Sumanenetrione (2) 2a,4a,6 (Figure 1), a fully oxygenated compound at all the benzylic positions of 1, is a very unique bowlshaped aromatic ketone that is expected to possess many properties such as an electron-accepting bowl and a key intermediate for the synthesis of benzyl-substituted compounds. Synthesis of 2 and the substituted chiral trimethylsumanenetrione 2c,7 has been reported, and their properties have been investigated, namely their dynamic behavior regarding bowl inversion and bowl chirality, 2c,7 the deep bowl structure by theoretical calculations, 2c,7 their photophysical properties, 4a and the chemical reactivity. 2a,6 In addition, a unique photophysical property of 1 and 2 in the solid state has also been reported. 4a The coreshell assembly consisting of the aggregates of nanocrystals of 1 (shell) and 2 (core) was fabricated by a stepwise reprecipitation method, and exhibited amplification of emission from the nanocrystals of 2 through energy transfer from the nanocrystals of 1. In this phenomenon, the interaction of the bowl structures at the interface of the nanocrystals of 1 and 2 might be the key issue. Unfortunately, however, the nanocrystal of 2 was only characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystal structure was not solved because the poor crystallinity of 2 was not suitable for single-crystal X-ray crystallographic analysis. Therefore, the single-crystal structure of 2, especially the packing pattern, is highly desired. In addition, 2 does not possess benzylic CH groups, which might play an important role in defining the packing structure (vide infra) such that the packing pattern of 2 might be different from that of other sumanene derivatives. Recently, we succeeded in obtaining the single crystals of 2 and iodinated derivative 3 for X-ray analysis, and elucidated their unique eclipsed columnar packing. Here, we report the details of these crystal structures.The single crystal of 2...