Masaaki Suzuki

Calix[4]pyrroles with unsubstituted meso-positions were synthesized by precipitating the products from reaction mixtures. The introduction of meso-spiroadamantyl subunits resulted in the scrambling of oligopyrrole intermediates during [2 + 2] condensation reactions. This process afforded a combination of cis- and trans-arranged isomers, as well as significant spectroscopic modifications arising from close contacts between the adjacent π-planes by the bulky adamantyl groups attached to the meso-positions in a spiro configuration.

Calix[4]pyrroles, also known as porphyrinogens, are precursors of porphyrins and normally undergo further oxidation when the cyclic intermediates have hydrogen atoms at their meso-positions, resulting in the formations of fully oxidized macrocycles. Therefore, the isolation of calix[4]pyrroles with meso-hydrogen atoms is still problematic and such species appear almost only in discussions of the formation mechanisms of naturally occurring tetrapyrroles. Since isolated such species show unstable natures for air-oxidation, there is a possibility that meso-unsubstituted cyclic tetrapyrroles have been less reported (Buchler and Scheidt et al. Liebigs Ann. Chem. 1987 , 305.; Sessler et al. Angew. Chem. Int. Ed. 2000, 39, 1055–1058.).

We synthesized a 5,10-bis(trifluoromethyl)tetrabenzoporphyrin copper complex (cis-2CF₃-TBPCu) by first treating 5,10-bis(trifluoromethyl)tetrabutanoporphyrin (cis-2CF₃-TbP) with copper(II) acetate. The subsequent oxidation of the resulting 5,10-bis(trifluoromethyl)tetrabutanoporphyrin copper complex (cis-2CF₃-TbPCu) was achieved using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The crystal structure of cis-2CF₃-TBPCu exhibited remarkably short N–Cu distances and was extremely nonplanar. Although the exact reason for the occurrence of these features remains unclear, it can possibly be attributed to the coordination of copper ions of +3 valency in the radical anionic ligand.

Various halogen atoms can be installed at the termini of tripyrrin, which is an acyclic conjugated pyrrolic triad. In addition to our previous report on brominated derivatives, chloro- and iodo-terminated derivatives were afforded by treatment with sodium hypochlorite and iodine, respectively, along with their zinc complexes by subsequent metalation. Solution and solid-state studies of these products revealed that significant absorption shifts and structural modification were caused by the termini.

We have developed a new reverse dispersion retardation film with a thickness of 4 for IPS panels, which achieves excellent viewing angle performance, notably for oblique contrast ratio and color. HDR‐IPS panels applied this reverse retardation film could achieve a significant improvement of the halo viewing from oblique angle.

Nucleophilic substitution reactions of cyanuric chloride with a series of β-dicarbonyls give triply β-dicarbonyl-embedded 1,3,5-triazines. Their subsequent but spontaneous tautomeric transformation leads to circularly linked, intramolecular, multi-hydrogen bonding networks. Their structural elucidation by X-ray crystallography showed elongated double bonds and shortened single bonds. This is likely due to a resonance hybrid formed via tautomerisation and simultaneous proton transfer.

Bromine‐terminated tripyrrin, a partial porphyrin structure, is synthesized by saponification of tripyrrane dimethyl ester and subsequent treatment with an aqueous bromine solution. In this reaction, bromine serves as a decarboxylating, oxidizing, and brominating agent. The resulting ligand can be coordinated with a metal ion such as Re ⁺ , which is not easily encapsulated in porphyrin cores. Nucleophilic substitution reactions at the brominated positions were also investigated, particularly the substitution with diethylamino and/or ethoxy groups. Structural elucidation was carried out by X‐ray crystallography, which revealed the flatter frameworks of the free bases and distorted geometries of the metal complexes. Such chemical modifications dramatically influence the photophysical properties, such as UV‐visible absorption, and are promising for bio‐related applications such as SPECT imaging probes.

We report a deprotection-induced aromaticity switching from nonaromatic to a 22π aromatic macrocycle of 3-oxypyripentaphyrin(0.1.1.1.0) with strong NIR absorption.