Journal of the American Chemical Society, Vol.117, No.50, 12514-12527, 1995
EPR Spectroscopy and Photophysics of the Lowest Photoactivated Triplet-State of a Series of Highly Conjugated (Porphinato)Zn Arrays
The lowest photoexcited metastable triplet state of a family of highly conjugated (porphinato)zinc(II) arrays in which ethyne or butadiyne units bridge the macrocycle carbon frameworks, along with their ethyne- and butadiyne-elaborated monomeric porphyrinic building blocks, and parent (porphinato)zinc(II) precursor molecules were studied by electron paramagnetic resonance (EPR), transient triplet-triplet absorption, and phosphorescence emission. All EPR spectra of the excited monomeric precursors and dimeric and trimeric porphyrin arrays reflect symmetries of rhombic distortion (D greater than or equal to 3E) at 4 K and exhibit electron spin polarization patterns verifying that intersystem crossing from the first excited singlet state occurs predominantly through the T-z> spin state sublevel. The zero field splitting (ZFS) parameters of the (porphinato)zinc monomers that beat ethynyl and butadiynyl groups as well as the conjugated porphyrin arrays are essentially temperature independent over a 4-100 K temperature range.
Keywords:RHODOBACTER-SPHAEROIDES R-26;PARAMAGNETIC-RES SPECTROSCOPY;ELECTRON-SPIN-RESONANCE;PORPHYRIN DIMERS;RHODOPSEUDOMONAS-VIRIDIS;MOLECULAR-STRUCTURE;LATTICE RELAXATION;OPTICAL-PROPERTIES;REACTION CENTERS;TRANSFER RATES