Clausen C, Gryko DT, Yasseri AA, Diers JR, Bocian DF, Kuhr WG, Lindsey JS
Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, and Department of Chemistry, University of California, Riverside, California 92521-0403, USA.
J Org Chem. 2000 Nov 3;65(22):7371-8. doi: 10.1021/jo000489e.
Our prior designs for molecular-based information storage devices have employed multiple redox-active units organized in weakly coupled, covalently linked arrays. To explore a simpler design, we report here the synthesis of porphyrin arrays where porphyrins with identical oxidation potentials are directly linked to one another instead of joined via a molecular linker. Oxidative coupling with AgPF(6) of zinc(II)-5,15-bis(4-tert-butylphenyl)-10-phenylporphyrin, obtained by a rational synthesis, afforded the expected dimer joined by a meso-meso linkage and an unexpected trimer joined by meso-meso linkages. For attachment to an electroactive surface we synthesized a meso-linked porphyrin dimer with a thiol-linker in one of the meso positions. The S-acetyl protecting group was used to avoid handling free thiol groups. Coupling of zinc(II)-5,10,15-tris(3, 5-di-tert-butylphenyl)porphyrin ("upper half") and zinc(II)-5-[4-(S-acetylthio)phenyl]-10,20-bis(3, 5-di-tert-butylphenyl)porphyrin ("lower half") afforded three different meso-linked dimers with the desired dimer as the main product. Electrochemical examination of the meso-linked dimer in solution shows that the first two oxidation potentials of the array differ by approximately 0.15 V and straddle the value exhibited by the monomeric constituents. The third and fourth oxidation potentials of the array are also split although to a lesser extent ( approximately 0.08 V) than the first and second. For the meso-linked trimer, the first three oxidation waves are also split; however, these waves are severely overlapped. The electrochemical behavior of the dimers and trimer is indicative of strong electronic interactions among the porphyrins. The thiol-derivatized meso-linked dimers form self-assembled monolayers (SAMs) on gold via in situ cleavage of the S-acetylthio protecting group. The porphyrin SAM exhibits four well-resolved oxidation waves. Regardless, the meso-meso linkage is relatively unstable upon formation of the pi-cation radical(s). This characteristic indicates that the structural motif is of limited utility for molecular information storage elements.
我们之前基于分子的信息存储设备设计采用了多个氧化还原活性单元，这些单元以弱耦合、共价连接的阵列形式组织。为了探索一种更简单的设计，我们在此报告卟啉阵列的合成，其中具有相同氧化电位的卟啉彼此直接相连，而不是通过分子连接体连接。通过合理合成得到的锌（II）-5,15-双（4-叔丁基苯基）-10-苯基卟啉与AgPF(6)进行氧化偶联，得到了通过中位-中位键连接的预期二聚体和通过中位-中位键连接的意外三聚体。为了连接到电活性表面，我们合成了一种在其中一个中位位置带有硫醇连接体的中位连接卟啉二聚体。使用S-乙酰基保护基团来避免处理游离硫醇基团。锌（II）-5,10,15-三（3,5-二叔丁基苯基）卟啉（“上半部分”）与锌（II）-5-[4-（S-乙酰硫基）苯基]-10,20-双（3,5-二叔丁基苯基）卟啉（“下半部分”）偶联得到了三种不同的中位连接二聚体，其中所需的二聚体为主要产物。对溶液中的中位连接二聚体进行电化学检测表明，该阵列的前两个氧化电位相差约0.15 V，并且跨越了单体成分所表现出的值。该阵列的第三和第四氧化电位也有分裂，尽管程度比第一和第二氧化电位小（约0.08 V）。对于中位连接的三聚体，前三个氧化波也有分裂；然而，这些波严重重叠。二聚体和三聚体的电化学行为表明卟啉之间存在强烈的电子相互作用。硫醇衍生的中位连接二聚体通过S-乙酰硫基保护基团的原位裂解在金上形成自组装单分子层（SAMs）。卟啉SAM表现出四个分辨良好的氧化波。无论如何，在形成π-阳离子自由基时，中位-中位键相对不稳定。这一特性表明该结构基序对于分子信息存储元件的用途有限。
