Modulation of the Singlet-Singlet Through-Space Energy Transfer Rates in Cofacial Bisporphyrin and Porphyrin-Corrole Dyads

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• 作者：Claude P. Gros ; Fr&eacute ; d&eacute ; ric Brisach ; Anastasia Meristoudi ; Enrique Espinosa ; Roger Guilard ; Pierre D. Harvey
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：January 8, 2007
• 年：2007
• 卷：46
• 期：1
• 页码：125 - 135
• 全文大小：473K
• 年卷期：v.46,no.1(January 8, 2007)
• ISSN：1520-510X

文摘

A new series of relatively flexible cofacial donor-acceptor dyads for singlet-singlet energy transfer with the corroleor etio-porphyrin free base and zinc porphyrin as the acceptor and donor, respectively, were synthesized andcharacterized (represented as (PMes₂COx)ZnH₃ (13), (PMes₂CO)ZnH₃ (14), and (PMes₂CX)ZnH₃ (15)) where (PMes₂COx = [2-[5-(5,15-dimesitylcorrol-10-yl)-diphenylether-2'-yl]-13,17-diethyl-2,3,7,8,12,18-hexamethylporphyrin]), (PMes₂CO = [5-[5-(5,15-dimesitylcorrol-10-yl)-dibenzofuran-4-yl]-13,17-diethyl-2,3,7,8,12,18-hexamethylporphyrin]), and(PMes₂CX = [5-[5-(5,15-dimesitylcorrol-10-yl)-9,9-dimethylxanthen-4-yl)]-13,17-diethyl-2,3,7,8,12,18-hexamethylporphyrin]), respectively) along with the homobismacrocycles (DPOx)ZnH₂ (17) and (DPOx)Zn₂ (18) (where (DPOx =2,2'-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]diphenylether) as comparison standards. The ratefor energy transfer (k_ET) extracted by the measurements of fluorescence lifetimes are of the same order of magnitudeas those recently reported for the rigidly held face-to-face dyads ((DPB)ZnH₂ (1), (DPX)ZnH₂ (2), (DPA)ZnH₂ (3),(DPO)ZnH₂ (4), and (DPS)ZnH₂ (5) where (DPB = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]biphenylene), (DPX = 4,5-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]-9,9-dimethylxanthene), (DPA= 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]anthracene), (DPO = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzofuran), and (DPS = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzothiophene), respectively), but for the first time, it is shown that the presence of a bulky grouplocated between the acceptor and the donor moiety influences the transfer rate. The presence of perpendicularmesityl groups on the acceptor macrocycle prevents the two macrorings from interacting strongly; therefore, k_ET isslower. On the other hand, by rendering the rigid spacer flexible (i.e., changing the dibenzofuran rigid spacer to theflexible diphenylether assembling fragment), k_ET increases due to stronger intermacrocycle interactions. This studyis complemented by DFT computations (B3LYP/3-21G*) as a molecular modeling tool where subtle structural featuresexplain the changes in k_ET. During the course of this study, X-ray structures of 17 and 18 were investigated andexhibit a linear stacking of the bismacrocycles where intermolecular porphyrin-porphyrin interactions are observed(d_{inter(Zn···Zn)} = 4.66 and 4.57 Å, for 17 and 18, respectively).