ABSORPTION STUDY OF AN AGGREGATED PORPHYRIN UNDER HIGH-PRESSURE

The N,N'-diacid of meso-tetrakis(4-sulfonylphenyl)porphin forms both J - and H-aggregates. Both the B-and Q-transitions exhibit a J-band. Und er typical experimental conditions, the monomer and H-bands are also o bserved. We have measured the pressure dependence of the various spect ral bands up to 40 kbar. All data show linear dependence of spectral r ed shift with pressure. The monomer Soret band has the highest pressur e sensitivity. The pressure slope of the B-band is 3.6 times greater t han that for the e-band for the J-aggregates. A simple excitonic theor y predicted a ratio of nearly Il. It appears that there is a substanti al solvent shift contribution to these pressure derivatives. (C) 1997 American Institute of Physics.