Cyanobuta-1,3-dienes as novel electron acceptors for photoactive multicomponent systems.
Cyanobuta-1,3-dienes as novel electron acceptors for photoactive multicomponent systems.
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Cyanobuta-1,3-diene 作为光敏多组分系统的新型电子受体。
作者：
F. Tancini;F. Monti;Kara Howes;Abdelhalim Belbakra;A. Listorti;W. Schweizer;Philippe Reutenauer;J. Alonso;C. Chiorboli;L. Urner;J. Gisselbrecht;C. Boudon;N. Armaroli;F. Diederich
报道了五种多组分体系的合成、电化学和物理化学性质，这些体系的特征在于Zn（II）卟啉（ZnP）与一个或两个苯胺基供体取代的五氰基-（PCBD）或四氰基丁-1，3-二烯（TCBD）连接，有和没有发色团间的桥接间隔基（S）：ZnP-S-PCBD（1）、ZnP-S-TCBD（2）、ZnP-TCBD（3）、ZnP-（S-PCBD）2（4）和ZnP-（S-TCBD）2（5）。通过稳态和时间分辨的吸收和发光光谱（RT和77 K），光诱导的分子内能量和电子转移过程的证明，在激发的卟啉单元。 在装有最强受体多氯联苯和间隔物的系统中（1，4），在甲苯中没有发现电子转移的证据，表明ZnP→多氯联苯能量转移，然后是多氯联苯部分的超快（<10 ps）固有失活。在具有较弱受体TCBD（2，5）的类似系统中，苯甲腈发生光诱导电子转移，产生持续2.3 μs的电荷分离（CS）态。如此长的寿命，鉴于电荷复合的高吉布斯自由能（ΔG（CR）=-1.39 eV），表明在所谓的马库斯反转区发生了背电子转移过程。值得注意的是，在缺乏发色团间间隔物的系统3中，在20 ps内发生光致电荷分离，随后发生电荷重组。这是一个结果的供体-受体合作伙伴和一个几乎activationless电子转移过程的紧密相邻。这些结果表明，强电子接受氰基丁-1，3-二烯可能成为有前途的替代品醌，perylenediimide，和富勒烯衍生受体的多组分模块具有光诱导电子转移。
The synthesis, electrochemical, and photophysical properties of five multicomponent systems featuring a Zn(II) porphyrin (ZnP) linked to one or two anilino donor-substituted pentacyano- (PCBD) or tetracyanobuta-1,3-dienes (TCBD), with and without an interchromophoric bridging spacer (S), are reported: ZnP-S-PCBD (1), ZnP-S-TCBD (2), ZnP-TCBD (3), ZnP-(S-PCBD)2 (4), and ZnP-(S-TCBD)2 (5). By means of steady-state and time-resolved absorption and luminescence spectroscopy (RT and 77 K), photoinduced intramolecular energy and electron transfer processes are evidenced, upon excitation of the porphyrin unit. In systems equipped with the strongest acceptor PCBD and the spacer (1, 4), no evidence of electron transfer is found in toluene, suggesting ZnP→PCBD energy transfer, followed by ultrafast (<10 ps) intrinsic deactivation of the PCBD moiety. In the analogous systems with the weaker acceptor TCBD (2, 5), photoinduced electron transfer occurs in benzonitrile, generating a charge-separated (CS) state lasting 2.3 μs. Such a long lifetime, in light of the high Gibbs free energy for charge recombination (ΔG(CR)=-1.39 eV), suggests a back-electron transfer process occurring in the so-called Marcus inverted region. Notably, in system 3 lacking the interchromophoric spacer, photoinduced charge separation followed by charge recombination occur within 20 ps. This is a consequence of the close vicinity of the donor-acceptor partners and of a virtually activationless electron transfer process. These results indicate that the strongly electron-accepting cyanobuta-1,3-dienes might become promising alternatives to quinone-, perylenediimide-, and fullerene-derived acceptors in multicomponent modules featuring photoinduced electron transfer.