粉末晶体结构解析实例-MOF粉末结构

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    这是用粉末结合量化的方式定的结构，与JANA等均不同。对于这种复杂结构，JANA等粉末解析软件基本没有可能解决，即使是微晶电子衍射也是需要晶粒达到一定尺度，粉末衍射对晶粒尺寸要求更低。有兴趣的参看这个文献：
Lei Wang, Si-Bo Qiao, Yan-Ting Chen, Xun Ma, Wei-Ming Wei, Jun Zhang, Lin Du, Qi-Hua Zhao. [2 + 2] cycloaddition and its photomechanical effects on 1D coordination polymers with reversible amide bonds and coordination site regulation [J]. Chem. Sci., 2024, 15(11): 3971-3979. DOI: 10.1039/d3sc06098e


A single crystal of 1 was irradiated by UV light and converted into [Cd2(L1) (MeOip)2(H2O)4]n (1a) in a single-crystal to singlecrystal manner (Fig. 2). Due to the weak diffraction of the 1a crystal for SCXRD **ysis, the structure determination was performed by quantum mechanics calculation. This showed that 1a was in the triclinic P¯i space group, with one [Cd2(L1) (MeOip)2(H2O)4] in the asymmetric unit. The central atom of 1a, namely the Cd2+ ion, was pentacentate, which formed a twisted
triangular bipyramidal [CdNO4] coordination configuration with one N atom (L1 molecule) and four O atoms (two MeOip2−and two water molecules). The acquisition of 1a confirmed the head-to-tail photodimerization of the ligand.

Simulation details
The data of powder x-ray diffraction were recorded on Bruker D8 advance diffractometer (40 kV, 40 mA) with step of 0.01 degree from 3° to 55° at room temperature, using graphite monochromator and Cu-Kα radiation (λ=1.5418 Å). The positions of the peaks were picked up from the diffraction pattern excluding the weak peaks agreeing with the reactant, they were further applied to index and yield the unit cell parameters by TOPAS 4, 5 program, subsequently an empty cell was constructed according to the enforced unit cell parameters, and the atoms were added to it and refined to find their ideal positions by TD-DFT method using GGA-PBE function. The final structure was checked through comparing the x-ray diffraction pattern between the experimental line and theoretical one (figure S3), their positons matched each other well and revealed the correction for the final structure.

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