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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Intramolecular Energy Transfer in Molecular Dyads Comprising Free-base Porphyrin and Ruthenium(II) Bis(2,2':6',2'-terpyridine) Termini
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Intramolecular Energy Transfer in Molecular Dyads Comprising Free-base Porphyrin and Ruthenium(II) Bis(2,2':6',2'-terpyridine) Termini

机译：包含游离碱卟啉和钌（II）双（2,2'：6'，2“-叔吡啶）特米尼的分子染料中的分子内能量转移

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摘要

A molecular dyad has been synthesized in which free-base porphyrin and ruthenium(II) bis(2,2':6',2"-terpyridine) subunits are linked via a meso-phenylene group.The distal terpyridine ligand bears a single phenylethynylene group.Selective illumination into the metal complex is followed by rapid intramolecular triplet-triplet energy transfer from the metal-to-ligand charge-transfer (MLCT) triplet to the lowest-energy pi,pi triplet state localized on the porphyrin.This process is characterized by a reorganization energy of 0.14 eV and an electronic coupling matrix element of 76 cm~(-1).Because of the alkynylene substituent,the initially produced MLCT state is centered on the distal terpyridine.Therefore,triplet energy transfer must cross the proximal terpyridine ligand.At low temperature,nuclear tunneling renders the rate of triplet energy transfer activationless.Upon selective illumination into the lowest-energy singlet (S_1) state localized on the porphyrin,fast singlet-triplet energy transfer occurs,to populate the MLCT triplet with high efficiency.This process happens by way of Dexter-type electron exchange at room temperature,and the MLCT triplet can be identified as a reaction intermediate at low temperature.The activation energy for singlet-triplet energy transfer is only 0.05 eV,because of the smaller energy gap,and the electronic coupling matrix element is decreased to 11 cm~(-1),because energy transfer is spin-forbidden.At low temperature,dipole-dipole energy transfer becomes the main mechanism for decay of the porphyrin S_1 state.Excitation into the Soret band of the porphyrin is followed by rapid internal conversion to S_1 without energy or electron transfer to the appended metal complex.
机译：合成了一种分子二联体，其中游离碱卟啉和钌（II）双（2,2'：6'，2“-吡啶基）亚基通过间亚苯基连接。远端的吡啶吡啶配体带有一个苯基亚乙炔基选择性照射到金属络合物中，随后分子内三重态-三重态三重态能量快速转移，从金属到配体的电荷转移（MLCT）三重态转变为卟啉上最低的pi，pi三重态。其特征在于重组能量为0.14 eV，电子耦合基质元素为76 cm〜（-1）。由于亚炔基取代基，最初产生的MLCT状态以远端的吡啶为中心，因此三重态能量转移必须穿过近端三联吡啶配体。在低温下，核隧穿使三重态能量转移速率无活化作用。选择性照明进入卟啉中最低能量的单重态（S_1）状态，快速的单重态-三重态能量t发生转移，从而高效率地填充了MLCT三重态。该过程通过室温下的Dexter型电子交换发生，并且可以将MLCT三重态识别为低温下的反应中间体。转移仅0.05 eV，由于能隙较小，并且电子耦合矩阵元素减小至11 cm〜（-1），因为禁止自旋能量转移。在低温下，偶极-偶极能量转移成为主要激发卟啉的Soret带后，快速内部转化为S_1，而没有能量或电子转移到所附着的金属络合物。

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