No abstract

Five new mononuclear lanthanide complexes, [LnL 2 ][Et 3 NH]•THF/H 2 O (Ln = Nd, Tb, Dy) (H 2 L Cl = 2-bis(2hydroxy-3,5-dichloro benzyl)aminomethyl]pyridine), Ln = Nd (1), Tb (2), and Dy (3), and (H 2 L Br = 2-bis(2-hydroxy-3,5-dibromo benzyl)aminomethyl]pyridine), Ln = Nd (4, H 2 O) and Tb ( 5), were synthesized and structurally characterized by single-crystal Xray 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 threedimensional (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 singlemolecule 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.

Industrial dye effluents have emerged as significant health hazard. Laccases found in white rot fungi can degrade an assortment of dyes. Here, we explore the molecular thermodynamic origin of the substrate promiscuity in laccases using a combination of steady-state UV−visible absorption spectroscopy, molecular docking, and molecular dynamics (MD) simulation studies on the interaction of laccase with five dye molecules with varying charge, size, and shape. The spectroscopic studies confirm that all of these dyes can be degraded by laccase. Using MD simulations, we have demonstrated the presence of various distinct conformations of a loop in the protein active site that can accommodate the wide range of dye molecules. We have also shown that the diverse selection of dye molecules may exhibit surprisingly similar binding affinity due to cancellation of different thermodynamic factors. Our results highlight the potential of laccase as a multipurpose degrader for industrial dye effluents.