间隔基在共面双卟啉单重态-单重态能量转移机制（福斯特与德克斯特）中的作用。

Role of the spacer in the singlet-singlet energy transfer mechanism (Förster vs Dexter) in cofacial bisporphyrins.

作者信息

Faure Sébastien, Stern Christine, Guilard Roger, Harvey Pierre D

机构信息

LIMSAG UMR 5633, Université de Bourgogne, 6 bd Gabriel, 21100 Dijon, France.

出版信息

J Am Chem Soc. 2004 Feb 4;126(4):1253-61. doi: 10.1021/ja0379823.

DOI:10.1021/ja0379823

PMID:14746498

Abstract

The cofacial bisporphyrins H4DPS (DPS = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzothiophene), H4DPO (DPO = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzofuran), H4DPX (DPX = 4,5-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]-9,9-dimethylxanthene), H4DPA (DPA = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]anthracene), and H4DPB (DPB = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]biphenylene) have been monometalated by Zn(OAc)2.2H2O and by GaCl3 to explore the singlet-singlet energy transfer from the photoexcited metal porphyrin center to the linked free base porphyrin. The spectroscopic (UV-vis and fluorescence) and photophysical properties (fluorescence lifetimes, tauF, and quantum yields, phiF) have been investigated at 298 and 77 K in degassed 2-MeTHF for the donor-acceptor systems, (Zn)H2DPS, (Zn)H2DPO, (Zn)H2DPA, (Zn)H2DPX, and (Zn)H2DPB, as well as for the bis-zinc complexes, (Zn)2DPS, (Zn)2DPO, (Zn)2DPX, and (Zn)2DPB, respectively, and the monoporphyrin derivatives, H2P, (Zn)P, and (Ga-OMe)P (P2- = 5-phenyl-2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrin-dianion). The singlet-singlet energy transfer rate constants (KET) were obtained using KET = (1/tauF -1/tauFo), where tauFo is the fluorescence lifetime of the corresponding bis-zinc(II) systems (or (Zn)P and (Ga-OMe)P) where no energy transfer occurs. The tauF value for three bis-zinc(II) compounds varies from 1.69 to 2.01 ns and is 1.84 (at 298 K) and 3.20 ns (at 77 K) for (Ga-OMe)P. In the donor-acceptor bismacrocycles, depending on the spacer and the temperature, the fluorescence lifetimes decrease down to 50-240 ps. The KET values range from approximately 4 to approximately 21 (ns(-1)) and have been analyzed considering both the Förster and the Dexter mechanisms. Using the C(meso)-C(meso) distance parameters in the calculations, the Förster and Dexter mechanisms operate for DPS and DPO, and for DPA, DPX, and DPB spacer systems, respectively. The limit distance where one mechanism dominates over the other is estimated to be around 5-6 A.

摘要

共面双卟啉H4DPS（DPS = 4,6 - 双[5 - (2,8,13,17 - 四乙基 - 3,7,12,18 - 四甲基卟啉基)]二苯并噻吩）、H4DPO（DPO = 4,6 - 双[5 - (2,8,13,17 - 四乙基 - 3,7,12,18 - 四甲基卟啉基)]二苯并呋喃）、H4DPX（DPX = 4,5 - 双[5 - (2,8,13,17 - 四乙基 - 3,7,12,18 - 四甲基卟啉基)] - 9,9 - 二甲基呫吨）、H4DPA（DPA = 1,8 - 双[5 - (2,8,13,17 - 四乙基 - 3,7,12,18 - 四甲基卟啉基)]蒽）和H4DPB（DPB = 1,8 - 双[5 - (2,8,13,17 - 四乙基 - 3,7,12,18 - 四甲基卟啉基)]联苯撑）已通过Zn(OAc)2·2H2O和GaCl3进行单金属化，以探索从光激发的金属卟啉中心到相连的游离碱卟啉的单重态 - 单重态能量转移。在298 K和77 K下，于脱气的2 - 甲基四氢呋喃中，对供体 - 受体体系(Zn)H2DPS、(Zn)H2DPO、(Zn)H2DPA、(Zn)H2DPX和(Zn)H2DPB，以及双锌配合物(Zn)2DPS、(Zn)2DPO、(Zn)2DPX和(Zn)2DPB，还有单卟啉衍生物H2P、(Zn)P和(Ga - OMe)P（P2 - = 5 - 苯基 - 2,8,13,17 - 四乙基 - 3,7,12,18 - 四甲基卟啉二价阴离子）的光谱（紫外 - 可见和荧光）及光物理性质（荧光寿命，τF，和量子产率，φF）进行了研究。单重态 - 单重态能量转移速率常数（KET）使用KET = (1/τF - 1/τFo)获得，其中τFo是相应的双锌(II)体系（或(Zn)P和(Ga - OMe)P）的荧光寿命，在这些体系中不发生能量转移。三种双锌(II)化合物的τF值在1.69至2.01 ns之间变化，对于(Ga - OMe)P，在298 K时为1.84 ns，在77 K时为3.20 ns。在供体 - 受体双大环化合物中，根据间隔基和温度的不同，荧光寿命降至50 - 240 ps。KET值范围约为4至约21（ns⁻¹），并已从Förster和Dexter机制两方面进行了分析。在计算中使用C(meso) - C(meso)距离参数时，Förster机制适用于DPS和DPO体系，而Dexter机制分别适用于DPA、DPX和DPB间隔基体系。一种机制优于另一种机制的极限距离估计约为5 - 6 Å。