Association Complexes between Cationic Metallophthalocyanines and Anionic Metalloporphyrins II: Ultrafast Studies of Excited State Dynamics
详细信息 查看全文
- 作者：Alexey V. Gusev ; Evgeny O. Danilov ; and Michael A. J. Rodgers
- 刊名：Journal of Physical Chemistry A
- 出版年：2002
- 出版时间：March 14, 2002
- 年：2002
- 卷：106
- 期：10
- 页码：1993 - 2001
- 全文大小：900K
- 年卷期：v.106,no.10(March 14, 2002)
- ISSN：1520-5215
文摘
Femtosecond transient absorption studies were conducted for self-assemblies between oppositely chargedmetal-substituted 18-crown-6 tetrasubstituted phthalocyanines (McrPc) and metal-substituted meso-(4-sulfophenyl)-porphine (MTPPS) or meso-(4-carboxylphenyl)-porphine (MTPPC). Excitation could be carriedout at 400 nm (Ti-Sapphire second harmonic), which populates the porphyrin-localized S2 state or directlyinto the CT band (690), and was achieved by changing the pump pulse wavelength with an optical parametricamplifier. Each complex showed the transient features and kinetics that were independent of the excitationwavelength. After 400 nm excitation, all complexes displayed rapid conversion to the low-lying charge-transfer state. Studies of the CuP/CuPc complex showed no significant decay of the transients on thesubnanosecond time scale. However, investigations of the complexes containing different transition metalsshowed that deactivation of the complex excited state occurs through metal-centered (d,d) states. For themixed metal/free-base complexes, the excited-state relaxation occurred through the metallotetrapyrrolecomponent regardless of whether it was porphyrin or phthalocyanine. In these compounds, the charge transferstate deactivated to form the metal-centered (d,d) state within 2 ps, with lifetimes that varied somewhat withthe metal center. This latter state repopulated the ground state with a lifetime of ca. 13 ps (NiP/NiPc), 200ps (NiP/CuPc), 8 ps (CuP/NiPc), and 7 ps (FbP/CoPc). These metal-to-ground state rates were similar tothose measured for the monomeric metallotetrapyrroles.