Observation and Interpretation of Annulated Porphyrins: Studies on the Photophysical Properties ofmeso-Tetraphenylmetalloporphyrins

Citations Over TimeTop 10% of 2003 papers

Abstract

We present results of a joint computational and experimental study for a series of annulated metalloporphyrins in order to establish structure−property relationships. Specifically, we have examined the effects of substitution by meso-tetraphenylation, tetrabenzo and tetranaphtho annulation, and effects of changing the central metal from zinc (Zn) to palladium (Pd). Utilizing absorption and emission spectroscopy and laser flash photolysis techniques, the photophysical properties of these porphyrins have been determined. Upon the addition of benzo or naphtho groups, we observed an overall red shift in the ground state absorption spectra of both the B-bands and the Q-bands with increased conjugation and an increase in the Q-band to B-band intensity ratios. Time-dependent density functional theory calculations were performed on both series of porphyrins to identify the effects of phenyl, benzo, and naphtho substituents on the spectra. The benzo and naphtho adducts provide a larger contribution (typically 40−90%) to the observed red shifts due to increased π-conjugation, while there is a smaller contribution (typically 0−25%) from distortion of the porphyrin. Similarly, a red shift for the T1−Tn absorption spectrum and an overall general broadening in the spectrum were found with increased conjugation. An increase in the triplet molar extinction coefficient through the near-infrared region with annulation was also found. Varying the metal has an effect on the overall absorption spectra; i.e., the ground state spectra of the Zn porphyrins are red-shifted relative to the Pd porphyrins. For the triplet excited state spectra there were small effects in the spectra by changing the metal with a significant contribution to the kinetic properties by the heavy atom effect of the Pd.

Related Papers

• → Application of Flash Photolysis in the Study of the Triplet State of Organic Substances(1970)23 cited
• → A FLASH PHOTOLYSIS STUDY OF THE TRIPLET STATE OF ACRIDINE ORANGE IN BASIC SOLVENTS(1971)23 cited
• → INDICATION OF FAST TRIPLET FORMATION IN BIMOLECULAR QUENCHING OF EXCITED SINGLET STATES STUDIED BY CONVENTIONAL FLASH PHOTOLYSIS(1976)10 cited
• → CIS-TRANS isomerization of styrenes via the triplet pathway:The perpendicular triplet state observed by laser flash photolysis(1979)19 cited
• → On the triplet lifetime and triplet-triplet absorption spectra of naphthaldehydes(1988)9 cited