Halogen Bond Mediated Self-Assembly of Mononuclear Lanthanide Complexes: Perception of Supramolecular Interactions, Slow Magnetic Relaxation, and Photoluminescence Properties

Sushila; Rafia Siddiqui; Sayan Patra; Kumar Shivam; Arnab Sil; Biswajit Guchhait; Haiquan Tian; Ramesh Kataria; Soumyabrata Goswami; Paloth Venugopalan; Ranjan Patra

doi:10.1021/acs.inorgchem.2c02004

Halogen Bond Mediated Self-Assembly of Mononuclear Lanthanide Complexes: Perception of Supramolecular Interactions, Slow Magnetic Relaxation, and Photoluminescence Properties

Inorg Chem. 2022 Jul 25;61(29):11484-11496. doi: 10.1021/acs.inorgchem.2c02004. Epub 2022 Jul 8.

Authors

Affiliations

¹ Department of Chemistry and Centre for Advance Studies in Chemistry, Panjab University, Chandigarh 160014, India.
² Amity Institute of Click Chemistry Research & Studies (AICCRS), Amity University, Noida 201303, India.
³ Department of Chemistry, Amity Institute of Applied Sciences, Amity University, Kolkata 700135, India.
⁴ Department of Chemistry, School of Natural Sciences, Shiv Nadar University, Dadri 201314, Uttar Pradesh, India.
⁵ Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, P. R. China.

PMID: 35801575
DOI: 10.1021/acs.inorgchem.2c02004

Abstract

Five new mononuclear lanthanide complexes, [LnL₂][Et₃NH]·THF/H₂O (Ln = Nd, Tb, Dy) (H₂L^Cl = 2-bis(2-hydroxy-3,5-dichloro benzyl)aminomethyl]pyridine), Ln = Nd (1), Tb (2), and Dy (3), and (H₂L^Br = 2-bis(2-hydroxy-3,5-dibromo benzyl)aminomethyl]pyridine), Ln = Nd (4, H₂O) and Tb (5), were synthesized and structurally characterized by single-crystal X-ray diffraction analyses. Being isostructural in all the five cases, the metal center is octa-coordinated with a triangular dodecahedron (D_2d symmetry) geometry, and it is independent of the halogen substitution (Cl/Br). This close similarity is due to the composite interplay of hydrogen/halogen bond interactions that control the overall crystal packing, yet notable differences in association patterns among the individual ones arise from the subtle stereo-electronic requirement of individual molecules in the three-dimensional (3D) architecture. Hirshfeld surface and density functional theory (DFT) calculations clearly vouch for the importance of the hydrogen bond and halogen bond interactions observed in the structure. Detailed magnetic measurements using direct-current and alternating-current susceptibility measurements show slow magnetic relaxation in 3, a characteristic feature of the single-molecule magnets (SMMs), which is not shown by 1 and 2. Steady-state and time-resolved photoluminescence of Tb(III) complexes shows a strong ligand-to-metal energy transfer that can be modulated by changing the substitution on phenolic ligands. The results from these analyses indicate that it may be advantageous to consider the subtle role of hydrogen bond (HB)/halogen bond (XB) intermolecular interactions judiciously for the design of SMMs and luminescent materials based on halogen-substituted ligands.