| Research Abstract |
Studies on the syntheses of the macrocyclic conjugated diaza compounds (diazaannulenes) as well as the octaethylporphyrin (OEP) derivatives connected with the vinylene-linkage were carried out and also on their diamagnetic ring current effects as a measure of aromaticity of diaza[n]annulenes were examined by means of ^1H NMR and electronic absorption spectra. Firstly, a variety of diaza[n]annulene derivatives was synthesized and examined their aromatic properties, proving that incorporation of nitrogen atom into the pi-electronic conjugation system reduces their ring currents as compared with those of the corresponding hydrocarbons. In relation with diaza[n]annulenes, an [11][13] fulvalene derivative has been successfully synthesized and verified its aromaticity also based on X-ray crystallography. Then, partial hydrogenations of bisdehydro[13]- and [15]annulenones were carried out in the presence of catalyses. Structures and tropicities of their hydrogenation products were examined al
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so based on the optimized geometries by means of molecular mechanics (MM3) calucalations. Furthermore, annuleneones as the constituent starting meterials for diaza[n]annulenes were transformed to the corresponding fulvenes bearing various substituents. Their tropicities were examined and compared with those of the known compounds.
Secondly, aromaticity of octaethylporphyrin (OEP) was studied from various structural viewpoints. Complexes of vinylene-bridged bis(OEP)-M and tris(OEP)-M with d^8 transition-metal ions (M=Ni(II), Pd(II), and Pt(II)) were synthesized. ^1H NMR spectra varied more drastically for (Z)-bis(OEP)-M, with respect to those of OEP-M, while electronic absorption spectra for (E)-isomers. Electronic properties at the ground state were examined, proving that the interaction between the constituent QEP rings through the vinylene-linkages is more intensive for tris(OEP)-M than for bis(OEP)-M and yet for the Ni complex than for the Pd and Pt ones. Various mixed complexes of vinylene-bridged bis- and tris(octaethylporphyrin)s (bis(OEP)-(M I-M2) and tris(OEP)-(M1-M2-M3)) with d^8 transition-metal ions M ((M1, M2, M3) : (Ni(II), Pd(lI), Pt(II)) were also synthesized by selective metalations of the corresponding free-bases with M(TI)X salts. Electronic structures of tris(OEP)-(M1-M2-M3) proved to be affected by the heavier metals more intensively, resulting in the largest splitting of Soret band for the Ni-Pd-Pt complex. Oxidation potential E_t values of tris(OEP)-(M1-M2-M3) suggested that the Ni-Pd-Pt complex possesses the electron-releasing ability almost the same as the Pd-Pd-Pd one. In the case of bis(OEP)-(M1-M2), the (E)-isomers exhibited the reduction of electron-releasing ability regularly in order of the heavier metal complexes, while the (Z)-isomers exhibited little dependency of the electron-releasing ability upon the incorporated metals. Less
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