Spectroscopic and electrochemical investigations of 5, 10, 15, 20 tetra(N-ethyl-3-carbazoyl) porphyrins for use in optical data storage.

摘要

The objective of this research is to demonstrate new optical recording processes for use in future information storage or processing devices. The focus of the research is to design new chromophores with response times less than one microsecond with the ultimate goal of nanosecond response. One design used was to synthesize chromophores in which the electron donor was covalently attached to the molecule rather than in the polymer matrix. This gives an intramolecular electron transfer as opposed to an intermolecular transfer and was achieved in part by the synthesis of 5, 10, 15, 20 tetra(N-ethyl-3-carbazoyl) porphyrin, TECP, where carbazole is an electron donating group covalently attached to the porphyrin in the meso positions. Manganese, cobalt, nickel, copper, and zinc complexes of TECP were also prepared.;The newly prepared TECP was characterized by 1H NMR, UV-visible spectrophotometry, and electrochemistry. The non-metallated porphyrin displayed an extinction coefficient of 2.8 x 105 cm-1 M-1 for the Soret band at 433 nm. Three Q bands were also observed at 523 nm, 563 nm, and 655 nm with corresponding extinction coefficients given as 1.3 x 104 cm -1M-1, 1.1 x 104 cm -1M-1, and 5.6 x 103 cm-1M-1. In the electronic absorption spectra of the metallated porphyrins a shift in the Soret band and the disappearance of some of the Q bands could be expected and was observed. The values obtained for the TECP complexes correspond well with those found in the literature for the TPP complexes. Trends observed in the oxidation and reduction potentials were consistent with the nature of the porphyrin. That is, the electron donating group in TECP enhances oxidation and inhibits reduction.;Thin films of the porphyrin were prepared in a polycarbonate matrix. Electronic absorption spectra were taken and were compared with electronic absorption spectra of the porphyrin in chloroform. The absorption peaks were found to have similar energies and intensity. Ellipsometry was used for further characterization. Stability studies of the TECP/PC films were carried out. Here the change in absorption was monitored using UV-visible spectrophotometry. Results of this experiment indicate that all the porphyrin samples are photoactive.