Hexadecaphyrin-(1.0.0.0.1.1.0.1.1.0.0.0.1.1.0.1): A Dual Site Ligand That Supports Thermal Conformational Changes

A new expanded porphyrin, hexadecaphyrin-(1.0.0.0.1.1.0.1.1.0.0.0.1.1.0.1), is reported. It was obtained via the condensation of a hexapyrrolic derivative prepared in turn from a bipyrrole dialdehyde and a stable quaterpyrrole precursor. This hexadecaphyrin contains eight direct α-pyrrole-to-α-pyrrole linkages in its structure. It supports the formation of bimetallic complexes of both zinc and cobalt that are characterized by different conformational structures. Furthermore, a mixed zinc/cobalt macrocycle has been prepared. The cobalt bimetallic complex shows two stable conformations with the same oxidation state that are in equilibrium. All compounds have been characterized by common spectroscopic means, and single crystal X-ray diffraction structures were obtained for all macrocyclic compounds. DFT calculations and transient absorption spectra were used to study the electronic features of the complexes and the effect of conformational changes. This system shows promise as an accumulated heat sensor.本研究报道了一种新型扩环卟啉（expanded porphyrin）：十六卟啉-(1.0.0.0.1.1.0.1.1.0.0.0.1.1.0.1)（hexadecaphyrin-(1.0.0.0.1.1.0.1.1.0.0.0.1.1.0.1)）。该化合物通过六吡咯衍生物（hexapyrrolic derivative）的缩合反应制得，而该六吡咯衍生物则由联吡咯二醛（bipyrrole dialdehyde）与稳定的四吡咯前驱体（quaterpyrrole precursor）制备得到。该十六卟啉的结构中含有8个直接的α-吡咯-α-吡咯连接键（α-pyrrole-to-α-pyrrole linkages）。该十六卟啉可与锌、钴分别形成双金属配合物（bimetallic complexes），且此类配合物呈现出各异的构象结构（conformational structures）。此外，本研究还合成了锌钴混合大环配合物（mixed zinc/cobalt macrocycle）。该钴基双金属配合物存在两种处于平衡状态且氧化态（oxidation state）一致的稳定构象。所有化合物均通过常规光谱手段（spectroscopic means）进行了表征，且所有大环化合物均获得了单晶X射线衍射（single crystal X-ray diffraction）结构。本研究通过密度泛函理论（Density Functional Theory, DFT）计算与瞬态吸收光谱（transient absorption spectra）分析，探究了配合物的电子特性以及构象变化所带来的影响。该体系具备作为累积热传感器（accumulated heat sensor）的应用潜力。