Synthesis, Electronic Structure, and Electron Transfer Dynamics of (Aryl)ethynyl-Bridged Donor−Acceptor Systems
摘要:
The ET dynamics of a series of donor-spacer-acceptor (D-Sp-A) systems featuring (porphinato)zinc(II), (aryl)ethynyl bridge, and arene diimide units were investigated by pump-probe transient absorption spectroscopy. Analysis of these data within the context of the Marcus-Levich-Jortner equation suggests that the pi-conjugated (aryl)ethynyl bridge plays an active role in the charge recombination (CR) reactions of these species by augmenting the extent of (porphinato)zinc(II) cation radical electronic delocalization; this increase in cation radical size decreases the reorganization energy associated with the CR reaction and thereby attenuates the extent to which the magnitudes of the CR rate constants are solvent dependent. The symmetries of porphyrin-localized HOMO and HOMO-1, the energy gap between these two orbitals, and D-A distance appear to play key roles in determining whether the (aryl)ethynyl bridge simply mediates electronic superexchange or functions as an integral component of the D and A units.
Conformational Gating of Long Distance Electron Transfer through Wire-like Bridges in Donor−Bridge−Acceptor Molecules
作者:William B. Davis、Mark A. Ratner、Michael R. Wasielewski
DOI:10.1021/ja010330z
日期:2001.8.1
influence that bridge dynamics have on electrontransferthrough these oligomers. The temperature dependence of the charge separation (CS) rates in all five molecules does not appear to obey the predictions of standard ET theories based upon the Condon approximation. All five molecules show behavior consistent with CS being "gated" by torsional motion between the tetracene donor and the first bridge phenyl
Influence of Energetics and Electronic Coupling on Through-Bond and Through-Space Electron Transfer within U−Shaped Donor-Bridge-Acceptor Arrays
作者:Emily A. Weiss、Louise E. Sinks、Aaron S. Lukas、Erin T. Chernick、Mark A. Ratner、Michael R. Wasielewski
DOI:10.1021/jp037756f
日期:2004.7.1
functionalized aromatic imide and diimide donors and acceptors arranged in rodlike linear structures and in U-shaped folded structures on xanthene scaffolds. Femtosecond and nanosecond transient absorption spectroscopy is used to explore the relative efficiency of through-bond and through-space electron transfer in these molecules. The magnitude of the electronic coupling between the oxidized donor and
我们在这里介绍了供体-桥-受体阵列中的多步电子转移机制,该阵列由功能化的芳香族酰亚胺和二酰亚胺供体和受体组成,这些供体和受体以棒状线性结构和 U 形折叠结构排列在呫吨支架上。飞秒和纳秒瞬态吸收光谱用于探索这些分子中通过键和通过空间电子转移的相对效率。氧化供体和还原受体之间电子耦合的大小通过直接测量自由基离子对内的单重态-三重态分裂 2J 来专门探测,使用磁场对自由基离子对重组产生的三重态产率的影响. 这些数据用于定量评估能量学和电子耦合对电子转移机制的影响。发现当受体减少时,空间电子转移是 U 形结构中的一种可行机制。
Synthesis of Directly Linked Zinc(II) Porphyrin–Imide Dyads and Energy Gap Dependence of Intramolecular Electron Transfer Reactions
to determine the rates of photoinducedchargeseparation, 1ZP* - Im --> ZP+ - Im-, and subsequent thermal chargerecombination ZP+ - Im- --> ZP - Im. The free-energy gap dependence (energy gap law) has been probed from the normal to the nearly top region for the chargeseparationrate alone, and only the inverted region for the chargerecombinationrate. Although both of the energy gap dependencies
The present invention pertains to a reversibly thermochromic system comprising a substituted or an unsubstituted 6,11-dihydroxy-naphthacene-5,12-dione and a base and to a reversibly thermochromic composition comprising the reversibly thermochromic system and a carrier material and to novel substituted 6,11-dihydroxy-naphthacene-5,12-diones.
Femtosecond Transient Grating Studies of Chlorophylls and a Chlorophyll-Based Electron Donor-Acceptor Molecule
作者:Gary P. Wiederrecht、Walter A. Svec、Mark P. Niemczyk、Michael R. Wasielewski
DOI:10.1021/j100021a069
日期:1995.5
Ultrafast, polarization selective, transient grating studies are performed on several chlorophylls and an electron donor-acceptor molecule, Zn DMPPH-PI, that consists of a zinc methyl 13(1)-desoxopyropheophorbide a donor covalently linked to a pyromellitimide acceptor. The covalent linkage between the donor and acceptor constrains the distance and geometric relationship between them. The ability of the experiment to determine the nature of a particular physical phenomenon through separable polarization characteristics of the diffracted signal is used to analyze photophysical and photochemical processes in these molecules. This is achieved for cases in which the observed physical processes have overlapping spectral contributions, a situation where linear dichroism experiments are very difficult to interpret. Careful analysis of the absorption grating data allows us to determine rotational anisotropy values for the molecules in solution, two-photon absorption-state symmetries, and the relative orientation of the donor and acceptor in the Zn DMPPH-PI molecule. These results demonstrate complete separation of the contributions to the time dependent diffracted signal from the two radical ion pair products formed in the electron transfer reaction.