Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409, USA.
Department of Chemistry, University of Houston, 112 Fleming Building, Houston, TX 77204, USA.
Molecules. 2021 Jan 24;26(3):603. doi: 10.3390/molecules26030603.
Herein, we report the syntheses of two lithium-vanadium oxide-fluoride compounds crystallized from the same reaction mixture through a time variation experiment. A low temperature hydrothermal route employing a viscous paste of VO, oxalic acid, LiF, and HF allowed the crystallization of one metastable phase initially, LiVO(HO)F⋅2HO (), which on prolonged heating transforms to a chemically similar yet structurally different phase, LiVOF (). Compound crystallizes in centrosymmetric space group, 2/ with = 6.052(3), = 7.928(4), = 12.461(6) Å, and = 103.99(2)°, while compound crystallizes in a non-centrosymmetric (NCS) space group, 2 with = 5.1173(2), = 8.612(3), = 9.346(3) Å. Synthesis of NCS crystals are highly sought after in solid-state chemistry for their second-harmonic-generation (SHG) response and compound exhibits SHG activity albeit non-phase-matchable. In this article, we also describe their magnetic properties which helped in unambiguous assignment of mixed valency of V (+4/+5) for LiVO(HO)F⋅2HO () and +4 valency of V for LiVOF ().
在此，我们通过时间变化实验报告了两种从相同反应混合物中结晶出来的锂钒氧化物-氟化物化合物的合成。采用低温水热路线，使用 VO、草酸、LiF 和 HF 的粘性糊状物，最初允许一种亚稳相结晶，LiVO(HO)F⋅2HO()，其在延长加热过程中转化为化学相似但结构不同的相，LiVOF()。化合物在中心对称空间群 2/中结晶， = 6.052(3)， = 7.928(4)， = 12.461(6)Å， = 103.99(2)°，而化合物在非中心对称（NCS）空间群 2 中结晶， = 5.1173(2)， = 8.612(3)， = 9.346(3)Å。在固态化学中，对 NCS 晶体的合成非常感兴趣，因为它们具有二次谐波产生（SHG）响应，而化合物尽管不满足相位匹配条件，但其具有 SHG 活性。在本文中，我们还描述了它们的磁性性质，这有助于明确确定 LiVO(HO)F⋅2HO()的混合价 V (+4/+5)和 LiVOF()的 V +4 价。
