Tuning the Magnetoluminescence Behavior of Lanthanide Complexes Having Sphenocorona and Cubic Coordination Geometries

The reaction of the tripodal fluorophoric ligand tris(benzimidazol‐2‐ylmethyl)amine (ntbi) with two different lanthanide salts [Ln(NO3)3 and LnCl3 (Ln = Dy, Ho, Tb)] afforded two new classes of mononuclear complexes. The class 1 complexes [{Ln(ntbi)(NO3)3}2·3CH3OH; Ln = Dy (1) and Ho (3)] exhibit very rare “sphenocorona” coordination geometries around the Ln centers, whereas the class 2 complexes [{Ln(ntbi)2}5·15Cl·xH2O; Ln = Dy, x = 18 (2) and Ln = Tb, x = 27 (4)] show “cubic” coordination geometries, as revealed by single‐crystal X‐ray diffraction studies. The class 2 complexes also exhibit a unique “double‐propeller”‐type structural feature. Owing to the significant difference in the coordination geometries around the Ln centers, prominent variations in the slow magnetic relaxation behaviors as well as the luminescence intensities are observed by alternating current magnetic susceptibility and solid‐state luminescence studies, respectively. LnIII complexes (Ln = Dy, Ho, Tb) with distinctly different coordination geometries, namely, sphenocorona and cubic, are synthesized. The different coordination geometries around the LnIII centers significantly modulate the slow magnetic relaxation and photoluminescence behaviors of the complexes, as revealed from AC magnetic susceptibility and solid‐state luminescence studies, respectively.