Phthalocyanine, Porphyrin, Cyclodextrin, and Polymer Systems Suitable for Studying by Circular Dichroism, Magnetic Circular Dichroism, and/or Electrochemistry

Abstract

We introduce some representative studies from our laboratory, mostly from the 21st Century. We are interested in the synthesis, optical spectroscopy, such as magnetic circular dichroism (MCD), circular dichroism (CD), and electrochemistry of large aromatic molecules such as porphyrins and phthalocyanines, as well as cyclodextrin and polymer systems showing CD activity.In this paper, we mainly summarize our representative studies in the 21st Century, and some work from the period 19752000 which was not included in our previous account. 1 We have been engaged in research on phthalocyanine (Pc), porphyrin (Por), and cyclodextrin (CDx) systems which show physicochemically intriguing properties, mainly from the standpoints of optical spectroscopy, such as magnetic circular dichroism (MCD), circular dichroism (CD), and electrochemistry. In particular, we have always endeavored to present model systems for the above spectroscopies so that readers can learn how to properly analyze their systems using these powerful and beautiful spectroscopic techniques.In order to reduce the possibility of wrongly interpreting spectroscopic and electrochemical properties, we have often prepared a series of compounds differing in size and symmetry, and if possible, have always tried to interpret the data conceptually first and then by using molecular orbital (MO) calculations. In exemplary cases, we explained the method of analysis in detail, with a view to instructing organic chemists and biochemists how to analyze their data using our methods. New Subporphyrins and SubphthalocyaninesPhthalocyanines (Pcs) are well-known because of their easy synthesis and robust properties. About 20 years ago, we became interested in finding robust, practical red dyes or pigments, since those known up to that time were weak and faded away with time. Pcs consist of four isoindole units and exhibit blue or green colors, and we felt that if we could create Pc-like compounds consisting of three isoindole units, these might be colored red. On the basis of these thoughts, we checked the Chemical Abstracts, and found that compounds consisting of three isoindole units, presently called subphthalocyanine (subPc) 1 (Scheme 1), were first reported in 1972, 2 and structures were elucidated by X-ray spectroscopy in 1974. 3From then however, these compounds did not attract the attention of researchers until we published a ring-expansion reaction leading to mono-substituted Pcs in 1990. 4 The following year, we reported the synthesis and properties of a planar subPc dimer containing t-butyl groups, but this was a mixture of several isomers.5 In order to confirm its ³ structure, we prepared the corresponding totally fluorinated congeners, 2.6 This contained two, so-called, cis and trans isomers, and these were separated, crystallized, and analyzed by X-ray spectroscopy. As a result of a cone-shaped C 3v structure of the subPc unit, these isomers have either a boat-or chair structure (Figure 1), while spectroscopically, little difference was observed. As shown in Figur...

Optically Active Porphyrin and Phthalocyanine Systems

“…Osuka and co-workers pioneered research on meso – meso , meso –β, and β–β linked Bis-Ps, and successfully isolated chiral meso – meso and β–β doubly linked Bis-P 68 (Figure ), whose enantiomers have CD spectra with the anticipated mirror-image symmetry. − The X-ray structural analysis demonstrates that the two P rings adopt a near-coplanar confirmation with a helical twisted, probably due to steric hindrance between the hydrogen atoms at neighboring pyrrole β protons. An exciton chirality analysis of the CD spectra was attempted.…”

Synthesis and electrochemistry of phthalocyanines bearing [(3,4-dimethoxybenzyl)oxy] groups

“…30,31 Their electrochemical properties are easily arranged by changing the metal center, number, and position of substituents.…”

“…25−29 Metallophthalocyanines are studied owing to their interesting electrochemical properties. 30,31 Their electrochemical properties are easily arranged by changing the metal center, number, and position of substituents. Metallophthalocyanines have proven to be functional species for electrocatalysts, sensors, and electrochromic devices because of their rich redox behavior owing to central metals having different oxidation states.…”

Construction of high‐throughput magnetic circular dichroism measurement system and its application to research on magnetic and optical properties of phthalocyanine complexes

“…Magnetic circular dichroism (MCD) spectroscopy is an analytical technique that measures the difference in absorption of left‐handed circularly polarized (lcp) and right‐handed circularly polarized (rcp) light induced by a magnetic field. MCD spectroscopy, when combined with absorption spectroscopy, is commonly used to investigate the electronic structure and magnetic and optical characteristics of highly symmetric molecules with photophysical properties, such as phthalocyanines and porphyrins 1–24 . In these reported studies, MCD and absorption spectral measurements have been performed for a wide range of metal complexes with various central metal ions, axial ligands, and substituents.…”