An adjacent dibenzotetraazaporphyrin, in which two benzene units are fused to the adjacent pyrrole rings of tetraazaporphyrin skeleton, has been synthesized as a copper complex for the first time and characterized by electronic absorption and magnetic circular dichroism spectroscopy, by cyclic voltammetry and spectroelectrochemistry using an optically transparent thin layer electrochemical cell. The results were compared with those of tetraazaporphyrin and phthalocyanine analogues. The title compound shows intermediate characteristics between those of normal tetraazaporphyrins and phthalocyanines; the Q-band shifts to the red and becomes more intense while the Soret band broadens with increasing the size of the pi-system. With the expansion of the pi-system, the first reduction potential does not change significantly, while the first oxidation potential shifts negatively, indicating that the LUMO level remains almost constant while the HOMO level destabilizes significantly. These spectroscopic properties and redox potentials were reproduced by molecular orbital calculations within the framework of the Pariser-Parr-Pople approximation. Thermogravimetry analysis suggests that the skeleton of the adjacent dibenzotetraazaporphyrin complex decomposes at about 95 degrees lower than that of the tetra-tert-butylated phthalocyanine analogue.
Some phthalonitriles and 1H-isoindole-1,3(2H)-diimines containing silicon(s) in their alkoxy substituent groups are prepared and used for phthalocyanine formation reactions. Silicon–carbon bonds often survive under the reaction conditions using K2CO3 in N,N-dimethylformamide (DMF), but are often broken in the presence of sodium hydride. Silicons in the alkoxy groups do not affect the electronic absorption spectra of phthalocyanines in solution significantly. The Q band of films of phthalocyanines (Pcs) with alkyl or alkoxy groups attached to benzene carbons furthest from the Pc core lies to the blue compared to the Pcs in solution, while films of Pcs with eight alkoxy groups closest to Pc core have a Q band shifted to the red.
Tetra-2,3-pyridoporphyrazinatosilicon ( SiPyD ) containing bis(tri-n-hexylsiloxy) (1) or bis(n-heptylcarbonyloxy) (2) axial ligands have been prepared and characterized by NMR, IR and electronic absorption spectroscopies and by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). These SiPyDs are soluble in common organic solvents, and face-to-face-type stacking is prevented in solution and films. Accordingly, their NMR spectra could be reasonably assigned. Their electronic absorption spectra in solution appear to the blue and red compared with those of the corresponding Si phthalocyanines ( SiPcs ) and Si tetrapyrazinoporphyrazines ( SiPyZs ) respectively. These characteristics are reproduced by molecular orbital calculations in the framework of the Pariser-Parr-Pople approximation. On formation of films, the Q bands shift to the red of those in solution by ca 20 nm, suggesting that other similar tetravalent metallophthalocyanines with two long axial ligands can be used for shifting the Q band to the red. TGA and DTA experiments show that the thermal stability of the macrocycles is markedly influenced by the type of axial ligands.
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