trans-cis Photoisomerization of Azobenzene-Conjugated Dithiolato-Bipyridine Platinum(II) Complexes: Extension of Photoresponse to Longer Wavelengths and Photocontrollable Tristability
trans-cis Photoisomerization of Azobenzene-Conjugated Dithiolato-Bipyridine Platinum(II) Complexes: Extension of Photoresponse to Longer Wavelengths and Photocontrollable Tristability
复制标题
DOI：
10.1002/chem.200801593
复制
发表时间：
2009-01-01
影响因子：
4.3
通讯作者：
Nishihara, Hiroshi
中科院分区：
文献类型：
--
作者：
Sakamoto, Ryota;Kume, Shoko;Nishihara, Hiroshi
合成了偶氮苯衍生物与二硫羟联吡啶铂（II）配合物修饰，揭示了它们在长波长范围内的高度扩展的光响应以及独特的光控三稳定性。反式-1和反式-2与一个偶氮苯基团上的二硫杂环戊烯和联吡啶配体，分别，覆盖范围从300至700 nm。通过含时密度泛函（TD）计算，这些跃迁归因于二硫杂环戊烯（pi）到联吡啶（pi *）的跃迁，即偶氮苯单元的配体间电荷转移（CT）、pi-pi * 和n-pi * 跃迁，以及联吡啶配体的pi-pi * 跃迁.此外，只有反式-1显示出独特的电子带，可归属于从二硫杂环戊烯（pi）到偶氮苯（pi *）的跃迁，定义为配体内CT。配合物1显示出与偶氮苯相反的光异构化行为：反式至顺式和顺式至反式的转化在405和312 nm照射下进行，这分别对应于偶氮苯和联吡啶单元的intraligand CT和pi-pi * 带的激发。与此相反，配合物2显示类似的偶氮苯的光异构化：反式到顺式和顺式到反式转换发生与365和405 nm的照射，分别。照射在578 nm，对应于激发的interligand CT转换，结果在顺式到反式转换的I和2，这是有史以来最长的波长报道影响的偶氮苯基团的光异构化。4的吸收和光致变色性，它具有偶氮苯基团上的二硫代和联吡啶配体，具有非常相似的1和2，这使4在一个单一的分子中，使用光在365，405，和578 nm的光可控三稳定性的特性。我们还阐明了1和2具有高的光异构化效率，以及顺式形式的良好的热稳定性。配合物3和5具有与它们的位置异构体配合物2和4几乎相同的光响应。
Azobenzene derivatives modified with dithiolato-bipyridine platinum(II) complexes were synthesized, revealing their highly extended photoresponses to the long wavelength region as well as unique photocontrol-lable tristability. The absorptions of trans-1 and trans-2 with one azobenzene group on the dithiolene and bipyridine ligands, respectively, cover the range from 300 to 700 nm. These absorptions are ascribed, by means of time-dependent (TD)DFT calculations, to transitions from dithiolene(pi) to bi-pyridine(pi*), namely, interligand charge transfer (CT), pi-pi*, and n-pi* transitions of the azobenzene unit, and pi-pi* transitions of the bipyridine ligand. In addition, only trans-1 shows distinctive electronic bands, assignable to transitions from the dithiolene(pi) to azobenzene(pi*), defined as intraligand CT. Complex 1 shows photoisomerization behavior opposite to that of azobenzene: trans-to-cis and cis-to-trans conversions proceed with 405 and 312 nm irradiation, which correspond to excitation with the intraligand CT, and pi-pi* bands of the azobenzene and bipyridine units, respectively. In contrast, complex 2 shows photoisomerization similar to that of azobenzene: trans-to-cis and cis-to-trans transformations occur with 365 and 405 nm irradiation, respectively. Irradiation at 578 nm, corresponding to excitation of the interligand CT transitions, results in cis-to-trans conversion of both I and 2, which is the longest wavelength ever reported to effect the photoisomerization of the azobenzene group. The absorption and photochromism of 4, which has azobenzene groups on both the dithiolato and bipyridine ligands, have characteristics quite similar to those of 1 and 2, which furnishes 4 with photocontrollable tristability in a single molecule using light at 365, 405, and 578 nm. We also clarified that 1 and 2 have high photoisomerization efficiencies, and good thermal stability of the cis forms. Complexes 3 and 5 have almost the identical photoresponse to those of their positional isomers, complexes 2 and 4.