Crystal and electronic structure of poly-halogenated lanthanide Schiff base complex: Insights into halogen bond from structural and theoretical analysis

With the aim to explore the electronic structure and the influence of halogen bonds to the supramolecular networks of lanthanide Schiff base complexes, halogenated salen-type Schiff-base and cerium nitrate were chosen as starting materials and isolated a new salen-type cerium(IV) complex [Ce-IV(3,5Br-salpn)(2)] ( 1 ) where 3,5Br-salpn = N,N'-bis(3,5-bromo salicylidene)-1,3-diaminopropane. The complex was investigated in the solid state by single-crystal X-ray diffraction. Structural analysis reveal the substitutional halogen atoms play an important role in tuning the molecule structure and supramolecular networks. The electronic structure of halogen bonds was confirmed by theoretical calculation, which uncovered an interesting phenomenon that the o --hole of bromine atoms of different substituents present quite different molecular electrostatic surface potential (5-Br: V-max = 6.8 kcal/mol and 3-Br: V-max = 13.2 kcal/mol). Hirshfeld surface analysis showed that bromine atoms involved intermolecular contacts donate 56.6% contribution of all the interactions, indicating the significant role of bromine atoms in crystal structures. Additionally, fluorescence experiments proved that the halogenated ligand has an important influence on the fluorescence behavior of the complex. (c) 2020 Elsevier B.V. All rights reserved.

Automated summary

The influence of halogen bonds on the supramolecular networks of lanthanide Schiff base complexes was explored in this study. It was found that substituional halogen atoms play an important role in tuning molecule structure and supramolecular networks, with different substituents on bromine atoms presenting distinct molecular electrostatic surface potential. Fluorescence experiments confirmed that halogenated ligands have a significant impact on the fluorescence behavior of the complex.