The observation of a subpicosecond bottleneck state in an iron porphyrin.

Iron (III) tetraphenylporphine chloride (FeTPP) displayed a 0.75 +- .15 ps transient absorbance at 625 nm following excitation with 0.15 ps laser pulses at either 625 nm or 312.5 nm. We suggest that this transient corresponds to a hitherto unobserved singlet charge transfer bottleneck state. Relaxation into this state following excitation at either 16,000 cm(-1) or 32,000 cm(-1) occurred in less than 30 fs.