We succeeded in the first isolation of a single pure regioisomer of a C70–acene monoadduct. 1,9-Diels–Alder monoadducts of C70 with pentacene derivatives were obtained by not only the Diels–Alder reaction but also a one-pot reaction using stable dihydropentacene derivatives, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and C70. The X-ray crystallographic study of a single pure regioisomer 2b confirmed positions of the linkage between C70 and acenes for the first time, and revealed unique columnar stacks.

The highly soluble [60]fullerene-pentacene monoadducts 2 a and 2 b were synthesized by a Diels-Alder reaction between [60]fullerene and pentacene derivatives. The single-crystal X-ray diffraction analysis of 2 a revealed an attractive intermolecular interaction between [60]fullerene moiety of one molecule and the pentacene arms of an adjacent molecule, resulting in the formation of head-to-tail dimers in solution. This self-association behavior of 2 a and 2 b was also observed by 1 H NMR and fluorescence spectroscopy in chloroform. Both the excitation and emission wavelengths can be modulated via the concentration of 2 a and 2 b.Fluorescent materials that respond to external stimuli [1][2][3][4] are of great interest, both from a fundamental materials science perspective and with respect to practical applications in sensors, [5,6] security papers, [7,8] optoelectronic switches, [9,10] and information-storage devices. [11,12] Especially methods to control the self-assembly structures of such materials in the solid state or in solution have attracted much attention, due to the potential utility in switchable dual-emission materials. [13][14][15][16][17][18][19][20][21][22][23][24][25][26] However, examples for molecules that are capable of switching the wavelength of not only the emission but also the excitation by changing their self-assembled structures remain scarce. [27,28] Fullerene-pentacene monoadducts represent in this context highly promising prospectives, as they exhibit switchable dual emission and dual excitation on account of the presence of two fluorophores (fullerene and naphthalene moieties) and their nested crystal packing, i. e., each fullerene moiety nests within the pentacene arms of an adjacent monoadduct via p-p interactions. [29][30][31][32] However, studies on the self-association and fluorescence behavior of fullerene-pentacene monoadducts in solution have not yet been reported, most likely due to a lack of soluble derivatives. We were therefore interested in preparing highly soluble fullerene-pentacene monoadducts. Herein, we describe the self-assembly and fluorescence properties of [60]fullerene-pentacene monoadducts in solution.Highly soluble [60]fullerene-pentacene monoadducts 2 a and 2 b were synthesized by Diels-Alder reactions between [60] fullerene and the previously reported pentacene derivatives 1 a and 1 b, [33] respectively (Scheme 1). A solution of 1 a and [60] fullerene in o-dichlorobenzene was stirred for 20 h at 45 8C under an atmosphere of argon in the dark. After purification by column chromatography on silica gel (eluent: CHCl 3 ) and GPLC (CHCl 3 ), brown crystals of 2 a were obtained in 89 % yield. A similar reaction using 1 b instead of 1 a afforded 2 b in 75 % yield. As expected, 2 a and 2 b are highly soluble in various organic solvents including toluene, benzene, benzonitrile, THF, chloroform, and dichloromethane. Moreover, 2 a and 2 b are stable in the dark and can be kept for several months at room temperature, i. e., retro-Diels-Alder reactions of 2 a and 2 b ...

The thermally and photolytically induced disproportionation of 6,13-dihydropentacene derivatives into tetrahydropentacenes and pentacenes results in unique solid-state fluorescence.

The first isolation of a single pure regioisomer of a C70—acene monoadduct is reported.

This study demonstrated that naftopidil was clinically efficacious in the treatment of BPH patients with OAB.