Synthesis, excited-state dynamics, and reactivity of a directly-linked pyromellitimide-(porphinato)zinc(II) complex

N-[5-(10,20-Diphenylporphinato)zinc(ll)]-N'-(octyl)pyromellitic diimide (PZn-Pl), a meso-pyromellitimide-substituted (porphinato)zinc(II) compound, has been fabricated from the reaction of (5-amino-10,20-diphenylporphinato)zinc(II) with pyromellitic dianhydride in the presence of octylamine. Interrogation of the photoinduced charge separation (CS) and thermal charge recombination (CR) electron-transfer (ET) dynamics for PZn-Pl in CH2Cl2 via pumpprobe transient absorption spectroscopic methods shows that tau(cs) and tau(CR) are 770 and 5200 fs, respectively. These ET dynamics differ from those elucidated previously for closely related 5-quinonyl-substituted (porphinato)metal compounds, and derive from the fact that the low-lying excited states for PZn-PI are porphyrin-localized, possessing little charge-transfer character. The synthesis of N-{5-[15-(2-(triisopropylsilyl)ethynyl)-10,20-diphenylporphinato]zinc(ll)}-N'-(octyl)pyromellitic diimide demonstrates that PZn-Pl can be halogenated at its 15-meso-position and used subsequently as a substrate in metal-catalyzed cross-coupling reactions; the reactivity of PZn-Pl is unusual with respect to many directly linked donor-acceptor compounds in that it is stable to these oxidizing and reducing reaction conditions.