Olejnik Adrian, Kopec Wioletta, Maskowicz Dominik, Sawczak Mirosław
Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, 11/12 G. Narutowicza Street, 80-233 Gdansk, Poland.
Centre for Plasma and Laser Engineering, The Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14 Street, 80-231 Gdańsk, Poland.
ACS Appl Mater Interfaces. 2023 Mar 29;15(12):15848-15862. doi: 10.1021/acsami.2c22626. Epub 2023 Mar 17.
Paramount spin-crossover properties of the 3D-Hoffman metalorganic framework (MOF) [Fe(pz)Pt(CN)] are generally described on the basis of the ligand field theory, which provides adequate insight into theoretical and simulation analysis of spintronic complexes. However, the ligand field approximation does not take into account the 3D periodicity of the actual complex lattice and surface effects and therefore cannot predict a full-scale periodic structure without utilizing more advanced methods. Therefore, in this paper, the electronic properties of the exemplar MOF were analyzed from the band structure perspective in low-spin (LS) and high-spin (HS) states. The density-of-states spectra determined for both spin-up and spin-down electrons of Fe d orbitals indicate spin-orbital splitting and delocalization for HS due to spin polarization in the iron atom ligand field. Presence of the surface states in the real crystal causes a red shift of the metal-metal charge transfer (MMCT) and metal-ligand charge transfer (MLCT) peaks for both HS and LS states. The addition of residual water molecules and disorder among the pyrazine rings reveal additional influences on the positions of the pyrazine band and, therefore, on the absorption spectra of the crystal. The results show a magnification of the peak correlated with the MLCT in the HS state and a significant red shift of the LS characteristic absorption band. The presented approach involving band structure analysis delivers a more complete image of the electronic properties of the [Fe(pz)Pt(CN)] crystalline network and can be a landmark for insightful studies of other MOFs.
三维霍夫曼金属有机框架（MOF）[Fe(pz)Pt(CN)]卓越的自旋交叉特性通常基于配体场理论进行描述，该理论为自旋电子复合物的理论和模拟分析提供了充分的见解。然而，配体场近似没有考虑实际复合晶格的三维周期性和表面效应，因此在不使用更先进方法的情况下无法预测完整规模的周期性结构。因此，在本文中，从能带结构的角度分析了典型MOF在低自旋（LS）和高自旋（HS）状态下的电子特性。对Fe d轨道的自旋向上和自旋向下电子确定的态密度光谱表明，由于铁原子配体场中的自旋极化，HS状态下存在自旋轨道分裂和离域现象。真实晶体中表面态的存在导致HS和LS状态下金属-金属电荷转移（MMCT）和金属-配体电荷转移（MLCT）峰发生红移。残留水分子的添加和吡嗪环之间的无序性揭示了对吡嗪能带位置以及晶体吸收光谱的额外影响。结果表明，HS状态下与MLCT相关的峰被放大，LS特征吸收带发生显著红移。所提出的涉及能带结构分析的方法为[Fe(pz)Pt(CN)]晶体网络的电子特性提供了更完整的图像，并且可以成为对其他MOF进行深入研究的一个里程碑。
