Palacios-Corella Mario, García-López Víctor, Waerenborgh Joao Carlos, Vieira Bruno J C, Mínguez Espallargas Guillermo, Clemente-León Miguel, Coronado Eugenio
Instituto de Ciencia Molecular (ICMol), Universitat de València C/Catedrático José Beltrán 2 46980 Paterna Spain
Centro de Ciências e Tecnologias Nucleares, DECN, Instituto Superior Técnico, Universidade de Lisboa 2695-066 Bobadela LRS Portugal.
Chem Sci. 2023 Feb 22;14(11):3048-3055. doi: 10.1039/d2sc05800f. eCollection 2023 Mar 15.
A bifunctionalized polyoxometalate (POM), [VO(CHNO)], which contains a redox active hexavanadate moiety covalently linked to two tridentate 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) ligands, has been prepared and characterized. Reaction of this hybrid molecule with Fe(ii) or Zn(ii) ions produces crystalline neutral 1D networks of formula Fe[VO(CHNO)]·solv (2) and Zn[VO(CHNO)]·solv (3) (solv = solvent molecules). Magnetic properties of 2 show an abrupt spin-crossover (SCO) with the temperature, which can be induced by light irradiation at 10 K (Light-Induced Excited Spin-State Trapping, LIESST effect). Interestingly, this porous and flexible structure enables reversible exchange of solvents in 2, which allows tuning the temperature of the thermal SCO. In 2 and 3, the hexavanadate unit can be reduced by electrochemical or chemical means in a reversible way. Chemical reduction and reoxidation by a postsynthetic method is accompanied by the insertion in the structure of the reductant and oxidant molecules (cobaltocene and tribromide, respectively), which provokes drastic changes in the spin state of Fe(ii). This leads to an elegant switching multifunctional material in which SCO properties of the Fe(ii) complexes coexist with the redox properties of the POM and can be tuned by a variety of stimuli such as temperature, light, solvent exchange or electron transfer. During the reduction process, 3 undergoes a single-crystal-to-single-crystal one-electron reduction, which confirms the presence of cobaltocenium cations by single crystal X-ray diffraction.
一种双功能化多金属氧酸盐（POM），[VO(CHNO)]，已被制备并表征，它包含一个与两个三齿2,6-双（吡唑-1-基）吡啶（1-bpp）配体共价连接的氧化还原活性六钒酸盐部分。该杂化分子与Fe(ii)或Zn(ii)离子反应生成式为Fe[VO(CHNO)]·solv (2)和Zn[VO(CHNO)]·solv (3)（solv = 溶剂分子）的晶体中性一维网络。2的磁性显示出随温度的突然自旋交叉（SCO），这可以在10 K下通过光照射诱导（光诱导激发自旋态捕获，LIESST效应）。有趣的是，这种多孔且灵活的结构使得2中的溶剂能够可逆交换，这允许调节热SCO的温度。在2和3中，六钒酸盐单元可以通过电化学或化学方法以可逆方式还原。通过后合成方法进行的化学还原和再氧化伴随着还原剂和氧化剂分子（分别为二茂钴和三溴化物）插入结构中，这引发了Fe(ii)自旋态的剧烈变化。这导致了一种优雅的开关多功能材料，其中Fe(ii)配合物的SCO性质与POM的氧化还原性质共存，并且可以通过温度、光、溶剂交换或电子转移等多种刺激进行调节。在还原过程中，3经历单晶到单晶的单电子还原，通过单晶X射线衍射证实了二茂钴阳离子的存在。
