Photoinduced Processes of Supramolecular Nanoarrays Composed of Porphyrin and Benzo[ghi ]perylenetriimide Units through Triple Hydrogen Bonds with One-Dimensional Columnar Phases

Synthesis and self-assembly of a penta[60]fullerene bearing benzo[ghi]perylenetriimide units

New penta(organo)fullerene bearing five benzo[ghi]perylenetriimide units has been synthesized to form self-assemblies through π–π interactions.

Highly Stable Supramolecular Donor-Acceptor Complexes Involving a Bis(18-Crown-6)azobenzene as Weak Donor: Structure-Property Relationships

The physicochemical properties of highly stable supramolecular donor-acceptor (D-A) complexes of a bis(18-crown-6)azobenzene (weak π-donor) with a series of bis(ammonioalkyl) derivatives of viologen-like molecules (π-acceptors) in acetonitrile were studied using cyclic voltammetry, UV-vis absorption spectroscopy, ¹H NMR spectroscopy, and density functional theory (DFT) calculations. The crystalline structures of the bis(crown)azobenzene and its complex with a bis(ammoniopropyl) derivative of 2,7-diazapyrene were determined by X-ray diffraction analysis. In solution, all of the supramolecular D-A complexes studied have a pseudocyclic structure owing to ditopic coordination of the ammonium groups of the acceptor to the crown ether moieties of the donor. These complexes show somewhat lower stability as compared with the previously studied complexes of the related derivative of stilbene (strong π-donor), which is explained by the relatively weak intermolecular charge-transfer (CT) interactions. Time-dependent DFT calculations predict that the low-energy CT transition in the D-A complex of the bis(crown)azobenzene with a bis(ammoniopropyl) derivative of 4,4'-bipyridine lies between the local ππ* and nπ* transitions of the azobenzene. The absorption band associated with the CT transition is indiscernible in the spectrum since it is overlapped with broad and more intense ππ* and nπ* bands. It was found that the E → Z photoisomerization quantum yield of the bis(crown)azobenzene decreases by almost an order of magnitude upon the complexation with the 4,4'-bipyridine derivative. This effect was tentatively attributed to the intermolecular electron transfer that occurs in the ¹ππ* excited state of the azobenzene and competes with the ¹ππ* → ¹ nπ* internal conversion.

Synthesis and Electrochemical and Photophysical Properties of Azaterrylene Derivatives

A series of terrylene derivatives, such as monoazaterrylene (MATerry), 1,6-diazaterrylene (DiATerry) and pristine terrylene (Terry), were synthesized by changing the number of nitrogen atoms at the bay region (1 and 6 positions of the Terry core). The electrochemical measurements suggested that the first one-electron reduction and oxidation potentials became positively shifted with increasing numbers of nitrogen atoms. This agreed with the energies of the corresponding highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) states estimated by DFT methods. In contrast, the HOMO-LUMO gaps approximately remained constant. This trend is quite similar to the spectroscopic behaviors observed by absorption and fluorescence spectra. The solvent polarity-dependent spectroscopic trends of DiATerry suggested the intramolecular charge-transfer (ICT) characters. The evaluation of the excited-state dynamics in various solvents indicated the electronic configurational changes of the excited states relative to the ground state via the ICT. This was supported by the Lippert-Mataga plots. Finally, the reversible protonation and deprotonation processes were also observed.