Akihiko Tsuda

Doubly meso‐β‐Linked Diporphyrins from Oxidation of 5,10,15‐Triaryl‐Substituted NiII– and PdII – Porphyrins

Lower oxidation potentials than for the monomeric starting materials are displayed by the diporphyrins obtained by one-electron oxidation with tris(4-bromophenyl)ammonium hexachloroantimonate [see, for example, Eq. (1)]. This and the strong red shift observed for the Soret bands of the product are indicative of extensively delocalized π-electron systems in the fused diporphyrin. Ar=3,5-di-tert-butylphenyl.

Discrete Conjugated Porphyrin Tapes with an Exceptionally Small Bandgap

An Ag I -promoted meso-meso coupling reaction has been extended to prepare discrete 100 nm long linear arrays of porphyrins. Oxidation of the resulting phenyl end-capped meso-meso linked porphyrins using a combination of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and Sc I I I (OTf) 3 directly produces fully π-conjugated fused porphysin arrays (porphyrin tapes) of 10 nm molecular size. This research news article presents their synthesis. X-ray crystal structures, and optical and electronic properties. Among these, the extremely small highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) optical gaps that reach into the infrared region suggest many applications of these compounds in materials science.

Synthesis of meso-β doubly linked porphyrin tapesElectronic supplementary information (ESI) available: 1H NMR spectra. See http://www.rsc.org/suppdata/cc/b3/b302032k/

The oxidation of 5,15-bis(3,5-di-tert-butylphenyl) Ni(II)-porphyrin 1b with Sc(OTf)3 and DDQ led to production of meso-beta doubly linked Ni(II)-porphyrin tapes that have large pi-electronic communications over the arrays.

Spectroscopic visualization of sound-induced liquid vibrations using a supramolecular nanofibre

The question of whether sound vibration of a medium can bring about any kind of molecular or macromolecular events is a long-standing scientific controversy. Although it is known that ultrasonic vibrations with frequencies of more than 1 MHz are able to align certain macromolecules in solution, no effect has yet been reported with audible sound, the frequency of which is much lower (20-20,000 Hz). Here, we report on the design of a supramolecular nanofibre that in solution becomes preferentially aligned parallel to the propagation direction of audible sound. This phenomenon can be used to spectroscopically visualize sound-induced vibrations in liquids and may find application in a wide range of vibration sensing technologies.

Ground and excited states of linked and fused zinc porphyrin dimers: Symmetry adapted cluster (SAC)-configuration interaction (CI) study

The symmetry adapted cluster (SAC)/SAC-configuration interaction method was applied to calculate the ground and excited states of zinc porphyrin monomers (without and with phenyl groups, ZnP and ZnPPh, respectively) and meso–meso linked (Zn2PMM) and doubly fused (Zn2PDF) zinc porphyrin dimers. Various features of the absorption spectra are studied, clarified, and assigned theoretically. The calculated electronic spectrum of ZnPPh, in comparison with that of ZnP, showed that the phenyl groups affect the spectrum in both the peak positions and intensities. In the dimers, Zn2PMM and Zn2PDF, the interactions of the monomer’s four-orbitals result in an eight-orbital model of the dimers, which plays an important role in the interpretation of the excited states observed in the spectra. In Zn2PMM, the interaction is smaller and each peak in the split Soret (BI and BII) bands consists of two peaks, in contrast to the prediction based on Kasha’s exciton rule. In Zn2PDF, the interaction between the two monomer units...

Excitation energy migration processes in self-assembled porphyrin boxes constructed by conjugated porphyrin dimers.

meso-Pyridine-appended alkynylene-bridged zinc(II) porphyrin dimers D2 and D4 assemble spontaneously, in noncoordinating solvents such as toluene, into tetrameric porphyrin boxes B2 and B4, respectively. Interestingly, the formation of Bn from Dn leads to the two kinds of self-assembled porphyrin boxes constructed by planar and orthogonal conformers, respectively. Excitation energy migration processes within these assemblies have been investigated in detail by using both steady-state and time-resolved spectroscopic methods. The pump-power dependence on the femtosecond transient absorption decay profiles is directly associated with the excitation energy migration process within the Bn boxes, where the exciton-exciton annihilation time is well-described in terms of the Foster-type incoherent energy hopping model. Consequently, the excitation energy hopping rates in porphyrin boxes constructed by planar and orthogonal conformers have been estimated to be (approximately 1.2 ps)(-1) and (approximately 1 ps)(-1), respectively. Furthermore, the porphyrin boxes constructed by orthogonal conformers show additional slow excitation energy hopping rates of (approximately 12 ps)(-1). Overall, the dihedral angle in the constituent dimers is a key factor to control the energy transfer efficiency for the fabrication of artificial light-harvesting complexes using conjugated porphyrin dimer systems.

π-Conjugated multiporphyrin box via self-assembly of an ethynylene-bridged zinc porphyrin dimer

An ethynylene-bridged zinc porphyrin dimer bearing metal-coordinating groups, such as bis[{5-(4-pyridyl)-15-(3,5-didodecyloxyphenyl)porphyrinato}zinc] Z2, self-assembles in CHCl3 to form a rectangular-shaped supramolecular nano box, in which all the Z2 units preferentially adopt a planar conformation with a syn-parallel geometry as for the pyridyl groups.

STM images of individual porphyrin hexamers; meso–meso singly linked orthogonal hexamer and meso–meso, β–β, β–β triply-linked planar hexamer on Cu(100) surface

Geometrical structures of chain porphyrin arrays adsorbed on Cu(100) are observed by STM: a bridge-like bent structure for meso–meso singly linked orthogonal hexamer, whereas a rigid planar and one-dimensionally stacked structure for meso–meso, β–β, β–β triply-linked hexamer.

Photochemical Molecular Storage of Cl2, HCl, and COCl2: Synthesis of Organochlorine Compounds, Salts, Ureas, and Polycarbonate with Photodecomposed Chloroform

Chloroform is available as not only an organic solvent but also photochemical molecular storage for synthetically important chemicals such as Cl(2), HCl, and COCl(2). We have succeeded in synthesizing organochlorine compounds, hydrochloric salt of amines, ureas, organic carbonates, and polycarbonate in practical high yields with photodecomposed chloroform.

Oxidative direct coupling of metalloporphyrins

A variety of directly-linked diporphyrins can be prepared by an oxidative coupling reaction of 5,15-diaryl metalloporphyrins. Regioselectivity of the coupling reaction depends on the metal in the porphyrin core; ZnII-porphyrins favor meso-meso coupling and PdII-porphyrins favor meso-β coupling. β-β Linked diporphyrins were isolated for the first time from the oxidation of 5,15-diaryl PdII-porphyrin with DDQ and Sc(OTf)3.