Synthesis, Spectroscopic, and Electrochemical Studies of 1,2‐Naphthalene‐Ring‐Fused Tetraazachlorins, ‐bacteriochlorins, and ‐isobacteriochlorins: The Separation and Characterization of Structural Isomers

Abstract

1,2-Naphthalene-ring-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized. Procedures for the synthesis of the starting materials, that is, derivatives of 1,2-naphthalenedicarboxylic acid, have been reinvestigated and improved. Nine possible derivatives, including four, two, and three structural isomers of TACs, TABCs, and TAiBCs, respectively, were separated by using thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC), and the structure of each isomer was determined by (1)H NMR spectroscopy combined with the NOE technique. The formation ratio of each isomer was rationalized in terms of the intramolecular steric repulsion effect, which was predicted by geometry optimizations at the DFT level. The derived compounds were characterized by using IR, electronic, and magnetic circular dichroism (MCD) spectroscopy, and by electrochemical methods. Frequency calculations at the DFT level correctly reproduced the experimental IR spectra and, in particular, distinguished between the three isomers of the TAiBCs. In the electronic absorption and MCD spectra of the TAC and TABC species, the Q-band splits into two intense components similarly to the 2,3-naphthalene-fused derivatives described in our preceding paper, although no significant spectral differences were observed from species to species. On the other hand, the spectra of the TAiBCs showed moderate differences depending on the structure of the isomer. The spectroscopic properties as well as the electrochemical behavior of these chlorins resemble those of the corresponding benzene-fused derivatives rather than the 2,3-naphthalene-fused derivatives. Molecular-orbital and configuration-interaction calculations within the framework of the ZINDO/S method were helpful in the discussions of the above observations.

Spectral and luminescent properties of triareno-substituted tetraazachlorins

“…This was a consequence of the expansion of the π-conjugation [12,13]. New benzo-and naphtho-condensed derivatives of H 2 TAC that were stabilized by methyls were synthesized in order to resolve partially the problem of chemical stability [10,11]. Compounds with two methyls on each of the two quaternary C atoms of the hydrogenated pyrrole ring are more stable to oxidation and prevent conversion of the macrocycle into the corresponding H 2 TAP derivatives.…”

“…Hydroporphyrazines with an expanded conjugated system of benzene and naphthalene fragments annelated to a tetraazachlorin macrocycle (angular and linear annelation) were recently synthesized for the first time [10,11]. Areno-substituted hydroporphyrazines form a class of hydrogenated tetraazaporphyrins with unique spectral properties that is interesting for developing new light-sensitive media.…”

“…The syntheses of the compounds have been published [10,11]. Thus, H 2 TBTAC was isolated by extraction of the crude product with hot chlorobenzene followed by chromatography over silica gel with elution by CHCl 3 .…”

“…All three of these factors were combined in the sample that we studied. It is noteworthy that quantum-chemical calculations of the electronic and vibrational states have been performed [10,11].…”

Phosphorescence of palladium and platinum complexes of benzo-fused hydroporphyrazines

“…and E.A.M.) prepared new compounds of the hydroporphyrazine subclass (porphyrazine is a synonym for meso-tetraazaporphine, H 2 PA H 2 TAP) with benzene and naphthalene aromatic rings fused to the nonhydrogenated pyrrole rings as the nickel and vanadium complexes and several free bases [1][2][3][4].…”