Sharma Meenakshi, Ticho Alexander L, Samankumara Lalith, Zeller Matthias, Brückner Christian
Department of Chemistry, University of Connecticut , Unit 3060, Storrs, Connecticut 06269-3060, United States.
Department of Chemistry, Youngstown State University , One University Plaza, Youngstown, Ohio 44555-3663, United States.
Inorg Chem. 2017 Oct 2;56(19):11490-11502. doi: 10.1021/acs.inorgchem.7b00799. Epub 2017 Jun 26.
The macrocycle conformation of [meso-tetraarylporphyrinato]metal complexes is metal-dependent. Furthermore, hydroporphyrins and some of their analogues are known to be more conformationally flexible than the parent porphyrins, but the extent to which this is reflected in their metal-dependent conformations was much less studied. meso-Tetraarylmorpholinochlorins are intrinsically nonplanar chlorin analogues in which the five-membered pyrroline moiety was replaced by a six-membered morpholine moiety. The metal complexes (M = Ni, Cu, Zn, Pd, Ag) of meso-aryl-2,3-dimethoxychlorins and meso-arylmorpholinochlorins were prepared. Their conformations were determined using X-ray crystal structure diffractometry and compared against those of their free bases, as well as against the conformations of the corresponding metalloporphyrins. Out-of-plane displacement plots visualized and quantified the conformational changes upon stepwise conversion of a pyrrole moiety to a dimethoxypyrroline moiety and to a dialkoxymorpholine moiety, respectively. The generally nonplanar macrocycle conformations were found to be central-metal-dependent, with the smaller ions showing more nonplanar conformations and with the metallomorpholinochlorins generally showing a much larger conformational range than the corresponding metallochlorins, which, in turn, were more nonplanar than the corresponding porphyrins. This attests to the larger conformational flexibility of the morpholinochlorin macrocycle compared to that of a chlorin or even a porphyrin macrocycle. The degree of nonplanarity affects the electronic structure of the metal complexes, as can also be seen in a comparison of their UV-vis spectra. We thus further define the conformational and electronic effects governing pyrrole-modified porphyrins.
[中-四芳基卟啉inato]金属配合物的大环构象取决于金属。此外，氢化卟啉及其一些类似物已知比母体卟啉具有更大的构象灵活性，但这在其金属依赖性构象中的体现程度却鲜有研究。中-四芳基吗啉二氢卟吩是本质上非平面的二氢卟吩类似物，其中五元吡咯啉部分被六元吗啉部分取代。制备了中-芳基-2,3-二甲氧基二氢卟吩和中-芳基吗啉二氢卟吩的金属配合物（M = Ni、Cu、Zn、Pd、Ag）。使用X射线晶体结构衍射法确定了它们的构象，并与它们的游离碱的构象以及相应金属卟啉的构象进行了比较。面外位移图分别可视化并量化了吡咯部分逐步转化为二甲氧基吡咯啉部分和二烷氧基吗啉部分时的构象变化。发现一般非平面的大环构象取决于中心金属，较小的离子显示出更多的非平面构象，并且金属吗啉二氢卟吩通常显示出比相应的金属二氢卟吩大得多的构象范围，而相应的金属二氢卟吩又比相应的卟啉更非平面。这证明了吗啉二氢卟吩大环相比二氢卟吩甚至卟啉大环具有更大的构象灵活性。非平面程度影响金属配合物的电子结构，这在它们的紫外可见光谱比较中也可以看出。因此，我们进一步定义了控制吡咯修饰卟啉的构象和电子效应。
