Univ. Grenoble-Alpes, CNRS, Département de Chimie Moléculaire, 38400, Grenoble, France.
University of Thi-Qar, College of Science, Department of Chemistry, 64001, Nassiria, Iraq.
Chemistry. 2018 Sep 3;24(49):12961-12969. doi: 10.1002/chem.201802088. Epub 2018 Jul 27.
We report the study of stimuli-responsive Zn and Fe coordination polymers (MC3 or MC2 with M=Fe or Zn ). These soluble metallopolymers were formed spontaneously by reaction of an organic ligand (C3 or C2 ) with one molar equivalent of metal ions. The C3 and C2 ligands incorporate two chelating terpyridine groups bridged by a redox responsive hinge featuring two viologen units (viologen=N,N'-dialkyl-4,4'-bipyridinium) linked either with propyl (C3 ) or ethyl (C2 ) chains. The viologen units in the polymer chains were reduced (1 e per viologen group) either by bulk electrolysis or by visible-light irradiation carried out in the presence of a photosensitizer. The 1 e reduction of the viologen units in the MC2 polymers induced a slight decrease in the viscosity of the solutions due to a modification of the overall charge carried by the metallopolymers. In strong contrast, reduction of coordination polymers involving propyl linkers (MC3 ) led to a remarkable increase (≈+400 %) in observed viscosity. This reversible effect was attributed to a folding of the polymer chains triggered by π-dimerization of the photo-generated viologen cation radicals.
我们报告了对刺激响应型 Zn 和 Fe 配位聚合物（MC3 或 MC2，其中 M=Fe 或 Zn）的研究。这些可溶性金属聚合物是通过有机配体（C3 或 C2）与等摩尔当量的金属离子反应自发形成的。C3 和 C2 配体包含两个螯合三吡啶基团，由一个氧化还原响应的铰链桥接，该铰链具有两个联吡啶单元（viologen=N，N'-二烷基-4,4'-联吡啶），通过丙基（C3）或乙基（C2）链连接。聚合物链中的联吡啶单元通过体相电解或在光引发剂存在下进行可见光照射被还原（每个联吡啶基团 1e）。MC2 聚合物中联吡啶单元的 1e 还原导致溶液粘度略有降低，这是由于金属聚合物所携带的总电荷发生了变化。相比之下，涉及丙基连接体的配位聚合物（MC3）的还原导致观察到的粘度显著增加（≈+400%）。这种可逆效应归因于光生联吡啶阳离子自由基的π-二聚化触发的聚合物链折叠。
