Shestimerova Tatiana A, Yelavik Natallia A, Mironov Andrei V, Kuznetsov Alexey N, Bykov Mikhail A, Grigorieva Anastasia V, Utochnikova Valentina V, Lepnev Leonid S, Shevelkov Andrei V
Department of Chemistry , Lomonosov Moscow State University , Leninskie Gory 1-3 , Moscow 119991 , Russia.
N.S. Kurnakov Institute of General and Inorganic Chemistry , RAS , 119991 Moscow , Russia.
Inorg Chem. 2018 Apr 2;57(7):4077-4087. doi: 10.1021/acs.inorgchem.8b00265. Epub 2018 Mar 22.
We report the synthesis, crystal structures, and optical properties of two new compounds, KBiI(I)·14HO (1) and (NH)BiI(I)·4.5HO (2), as well as the electronic structure of the latter. They crystallize in tetragonal space group P4/ mmm with the unit cell parameters a = 12.974(1) and c = 20.821(3) Å for 1 and a = 13.061(3) and c = 15.162(7) Å for 2. Though 1 and 2 are not isomorphous, their crystal structures display the same structural organization; namely, the BiI octahedra are linked by I units to form disordered layers in 1 and perfectly ordered chains in 2. The I-I bond distances in the thus formed I-I-I-I linear links are not uniform; the central bond is only slightly longer than in a standalone I molecule, whereas the peripheral bonds are significantly shorter than longer bonds typical for various polyiodides, which is confirmed by Raman spectroscopy. The analysis of the electronic structure shows that the atoms forming the I-I-I-I subunits transfer electron density from their occupied 5p orbitals onto their vacant states as well as onto 6s orbitals of bismuth atoms that center the BiI octahedra. This leads to low direct band gaps that were found to be 1.57 and 1.27 eV for 1 and 2, respectively, by optical absorption spectroscopy. Luminescent radiative relaxation was observed in the near-IR region with emission maxima of 1.39 and 1.24 eV for 1 and 2, respectively, in good agreement with the band structure, despite the strong quenching propensity of I moieties.
我们报告了两种新化合物KBiI(I)·14H₂O (1)和(NH₄)BiI(I)·4.5H₂O (2)的合成、晶体结构和光学性质，以及后者的电子结构。它们结晶于四方晶系空间群P4/mmm，对于1，晶胞参数a = 12.974(1) Å和c = 20.821(3) Å，对于2，晶胞参数a = 13.061(3) Å和c = 15.162(7) Å。尽管1和2不是同构的，但它们的晶体结构显示出相同的结构组织；即，BiI八面体通过I单元相连，在1中形成无序层，在2中形成完美有序的链。在由此形成的I-I-I-I线性连接中，I-I键长不均匀；中心键仅比孤立的I分子中的键略长，而外围键明显短于各种多碘化物典型的较长键，这通过拉曼光谱得到证实。电子结构分析表明，形成I-I-I-I亚基的原子将电子密度从其占据的5p轨道转移到其空态以及以BiI八面体为中心的铋原子的6s轨道上。通过光吸收光谱发现，这导致了低的直接带隙，对于1和2分别为1.57和1.27 eV。在近红外区域观察到发光辐射弛豫，对于1和2，发射最大值分别为1.39和1.24 eV，尽管I部分有很强的猝灭倾向，但与能带结构吻合良好。
