Hung Ling-I, Hsieh Dai-Yi, Hsieh Tsung-Hsiu, Chen Pei-Lin, Lin Chia-Her, Wang Sue-Lein
Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan.
Inorg Chem. 2022 Jan 24;61(3):1327-1334. doi: 10.1021/acs.inorgchem.1c02685. Epub 2022 Jan 7.
Titanium phosphorus oxides (TiPOs) are promising energy-conversion materials, but most are of tetravalent titanium (Ti), with the trivalent TiPOs less explored because of instability and obstacles in synthesis. In this study, we used a simple synthetic strategy and prepared three new TiPOs with different phosphorus oxoanions: the phosphate CaTi(HPO)(PO)·HO (), the phosphite CaTi(HO)(HPO)·HO (), and the hypophosphite Ti(HPO) (). Each possesses different structures in one, two, and three dimensions, yet they are related to one another because of their infinite chains. Compound exhibits proton-coupled electron transfer (PCET) reactivity in a solid state, losing one proton from its own HPO in oxidation to yield CaTi(HPO)(PO)·HO (designated as ), while compound also exhibits PCET reactivity in which the octahedral core [Ti(HO)] gives off two protons to become a titanyl unit [Ti═O] under oxidation, yielding CaTiO(HPO)·HO (). Both and retain their original frameworks from before oxidation, but there are some changes in the hydrogen and Ti-O bonds that affect the IR absorption and powder X-ray diffraction patterns. Compound represents the first titanium hypophosphite, and two polymorphs were discovered that show structures related to and . This work demonstrates a simple strategy that is effective for preparing titanium(III) compounds in a pure phase; further, new findings in the pathways of solid-state PCET reactions promote a greater understanding of the self-sustaining oxidation behavior for TiPO solid materials.
钛磷氧化物（TiPOs）是很有前景的能量转换材料，但大多数是四价钛（Ti）的，三价TiPOs由于其不稳定性和合成过程中的障碍而较少被研究。在本研究中，我们采用了一种简单的合成策略，制备了三种具有不同磷含氧阴离子的新型TiPOs：磷酸盐CaTi(HPO)(PO)·HO（）、亚磷酸盐CaTi(HO)(HPO)·HO（）和次磷酸盐Ti(HPO)（）。它们在一维、二维和三维中各自具有不同的结构，但由于其无限链而相互关联。化合物在固态下表现出质子耦合电子转移（PCET）反应活性，在氧化过程中从自身的HPO失去一个质子，生成CaTi(HPO)(PO)·HO（命名为），而化合物也表现出PCET反应活性，其中八面体核心[Ti(HO)]在氧化时释放出两个质子成为钛氧基单元[Ti═O]，生成CaTiO(HPO)·HO（）。和在氧化前后都保留了其原始骨架，但氢和Ti - O键有一些变化，这影响了红外吸收和粉末X射线衍射图谱。化合物代表了首例钛次磷酸盐，并且发现了两种多晶型物，其结构与和相关。这项工作展示了一种在纯相中有效制备三价钛化合物的简单策略；此外，固态PCET反应途径中的新发现促进了对TiPO固体材料自持氧化行为的更深入理解。
