The redox potential of a supramolecular porphyrin–phthalocyanine heterodimer was perturbed by the stacking of an extra metalloporphyrin to the phthalocyanine. This stacking gave rise to π–π and electrostatic interactions between the tetracationic dimer and the tetraanionic metalloporphyrin, with a Au(III) metalloporphyrin exhibiting a larger effect than Cu(II) and Pd(II) complexes among square planar complexes.

AbstractA multiply interlocked catenane with a novel molecular topology was synthesized; a phthalocyanine bearing four peripheral crown ethers was quadruply interlocked with a cofacial porphyrin dimer bridged with four alkylammonium chains. The supramolecular conjugate has two nanospaces surrounded by a porphyrin, a phthalocyanine, and four alkyl chains to accommodate guest molecules. Because the phthalocyanine can move along the alkyl chains, it acts as an adjustable wall, thus permitting the invasion of large molecules into the nanospaces without spoiling the affinity of the association. The dynamic molecular invasion allowed the intercalation of dianionic porphyrins into both nanospaces with high affinity. A photometric titration experiment revealed the two-step inclusion phenomenon. The multiply interlocked catenane complexed with three Cu2+ ions, and the spin–spin interaction was switched off by the intercalation of dianionic porphyrins.

Self-assembly based on reversible metal–ligand bond formation is useful for the synthesis of discrete supramolecular nanoarchitectures. However, the architectures constructed by this technique sometimes suffer from kinetic instability due to the dissociation of metal–ligand bonds, especially under highly diluted conditions or in the presence of competitive ligands or metal ions. In this study, a kinetically stabilized metallomacrocycle was synthesized in one pot via the combination of metal-mediated self-assembly and subsequent oxidative “locking” of the coordination bonds. The macrocycle consists of four Co ions and four bis-bidentate ligands L2−. The complexation of labile Co(II) ions with the ligands afforded the macrocycle with four-fold rotational symmetry, exhibiting the right-angled geometries of the β-diketonate ligands on the carbazole. The subsequent oxidation of the Co(II) ions inside the macrocycle into Co(III) ions made the metal–ligand bonds almost inert, thus affording a kinetically locked 4:4 metallomacrocycle. This macrocycle showed high stability even in the presence of an excess amount of competitive ligands. X-ray crystallography of the macrocycle indicated that it assembled in a columnar manner, forming one-dimensional nanochannels in the middle of the column.

We report synthesis of novel macrocyclic molecules and their metal complexes as well as their thermotropic columnar liquid-crystalline behavior. The macrocyclic ligands were prepared size-selectively based on dynamic covalent chemistry. X-ray study of a model macrocycle with short alkyl chains revealed that they were discrete and highly symmetric, with an inner vacant cavity of 9 Å diameter enclosed by a 56π planar ring composed of four bis(salicylidene)-o-phenylenediamine (salphen) moieties alternating with four carbazoles. Ni2+ and Cu2+ ions were incorporated into the four salphen ligands and formed square-planar metal complexes inside the macrocycles. From the structural and thermal analyses via X-ray diffraction measurements, differential scanning calorimetry, and polarized optical-microscopic observations, it was revealed that the macrocyclic ligand and its metal complexes self-assembled into columnar liquid-crystalline phases depending on the temperature and displayed a highly fluid character over a wide range of temperatures. The peripheral alkyl chains were influential in controlling the temperature range and flowability of the liquid-crystalline phases, and the range of the liquid-crystalline temperature of the metallo-macrocycles was significantly higher than those of the metal-free macrocycles. To the best of our knowledge, these are the first examples of thermotropic columnar liquid crystals of macrocyclic metal complexes with a large hollow area.

To generate integrated organized molecular properties, multiple molecular components are required to be assembled into the molecular system with sequential and spatial accuracy in accordance with the design of the molecular assembly. Herein, we present a novel programmable synthesis of a cofacially stacked porphyrin array via repetitive construction of a peptide duplex. We designed and synthesized a novel porphyrin having two artificial amino acid moieties at the trans meso-positions. The amino acid moieties can be connected with another porphyrin unit by repetitive doubly coupling reactions to afford the peptide duplex bridged by the porphyrins. In the duplex, the porphyrin units are stacked cofacially, and the efficient electronic communication among the arrayed porphyrin units was characterized by split redox waves in the cyclic voltammograms. We also demonstrated the three different square-planar metal ions, namely Cu2+, Ni2+, and Pd2+, were arranged inside the ladder-type porphyrin array in a programmable fashion.

We report the preparation and crystal structure of a triply stacked metal complex array in which a Cu–phthalocyanine is sandwiched between different Cu–porphyrins. The discrete heterogeneous assembly was prepared through formation of a fourfold rotaxane from a tetradactyl porphyrin with alkylammonium moieties and a phthalocyanine bearing four crown ethers and the subsequent formation of an ionic complex between the fourfold rotaxane and a tetraanionic porphyrin. The tetraanionic porphyrin, Cu–TPPS4–, is selectively bound to the fourfold rotaxane through cooperative π–π and ionic interactions. The crystal structure revealed the columnar stacked array of the three planar building components in a precise order and spatial arrangement that promote intermolecular electronic communication.

We present a novel strategy to synthesize multi-molecular arrays in a programmable way by stepwise elongation based on repetition of two-fold rotaxane formation and construction of threads. A cofacially triply stacked porphyrin array was obtained via the repetitive two-fold rotaxane formation.

We report synthesis of a hetero-dinuclear metal complex in a four-fold rotaxane, in which a Cu2+–porphyrin and a Zn2+–phthalocyanine are cofacially stacked. Interaction between the two metal complexes in the rotaxane was investigated by a UV-Vis absorption spectral study.

We report the synthesis of a novel quinone-sandwiched porphyrin in which two benzoquinones are connected oppositely at the meso positions of a porphyrin through rigid 3-amido 2,2′-bipyridine linkers. 1H-NMR and single crystal X-ray analyses revealed that the quinone-sandwiched porphyrin has a folded structure in which the porphyrin unit was inserted into the two quinone moieties via π-stacking. Insertion of a Zn(II) ion into the porphyrin center induced a drastic conformational change which is resulted in coordination of the oxygen atoms of both benzoquinone moieties to the Zn-porphyrin to afford a 6-coordinated structure.

Besides the biological importance of DNA as genetic information storage and expression, DNA has great potential to act as a smart molecule for programmable self-assembly of functional units since it is possible to encode molecular assembled systems using sequences of nucleobases in a designable fashion. Recently, we have reported a novel base-pairing motif in DNA duplex that is based on the replacement of hydrogen-bonded base pairs by metal-mediated base pairs. This review covers our recent approaches to precise programming of metal arrays by means of artificial DNA templates.

We report synthesis of a hetero-dinuclear metal complex in a four-fold rotaxane, in which a Cu2+–porphyrin and a Zn2+–phthalocyanine are cofacially stacked. Interaction between the two metal complexes in the rotaxane was investigated by a UV-Vis absorption spectral study.

The redox potential of a supramolecular porphyrin–phthalocyanine heterodimer was perturbed by the stacking of an extra metalloporphyrin to the phthalocyanine. This stacking gave rise to π–π and electrostatic interactions between the tetracationic dimer and the tetraanionic metalloporphyrin, with a Au(III) metalloporphyrin exhibiting a larger effect than Cu(II) and Pd(II) complexes among square planar complexes.

We present a novel strategy to synthesize multi-molecular arrays in a programmable way by stepwise elongation based on repetition of two-fold rotaxane formation and construction of threads. A cofacially triply stacked porphyrin array was obtained via the repetitive two-fold rotaxane formation.

Self-assembly based on reversible metal–ligand bond formation is useful for the synthesis of discrete supramolecular nanoarchitectures. However, the architectures constructed by this technique sometimes suffer from kinetic instability due to the dissociation of metal–ligand bonds, especially under highly diluted conditions or in the presence of competitive ligands or metal ions. In this study, a kinetically stabilized metallomacrocycle was synthesized in one pot via the combination of metal-mediated self-assembly and subsequent oxidative “locking” of the coordination bonds. The macrocycle consists of four Co ions and four bis-bidentate ligands L2−. The complexation of labile Co(II) ions with the ligands afforded the macrocycle with four-fold rotational symmetry, exhibiting the right-angled geometries of the β-diketonate ligands on the carbazole. The subsequent oxidation of the Co(II) ions inside the macrocycle into Co(III) ions made the metal–ligand bonds almost inert, thus affording a kinetically locked 4:4 metallomacrocycle. This macrocycle showed high stability even in the presence of an excess amount of competitive ligands. X-ray crystallography of the macrocycle indicated that it assembled in a columnar manner, forming one-dimensional nanochannels in the middle of the column.