Field-Induced Single Molecular Magnetism and Photoluminescence in Rare Cocrystals of Isomorphic Lanthanide(III) Coordination Compounds with Fully Substituted Pyridine-4-carboxamide Ligand

A series of four isomorphous, 1:2 (complex/ L ) rare cocrystals of coordination compounds of Ln(III) ions as [Ln( L )(NO 3 ) 3 (H 2 O)] 2 [ L ] 2 (Ln(III) = Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), and Ho ( 4 )), were synthesized with N , N -diisobutylisonicotinamide ( L ) using a metal-to-ligand ratio of 1:1. All compounds are dimeric in nature with two cocrystallized L molecules centro-symmetrically interspersed between two dimeric units with H-bonded bridges between them to form interesting, self-assembled H-bonded tapes along the c -axis. Detailed Shape analysis and Hirshfeld analysis are done to demonstrate geometry around the metal centers and various noncovalent interactions present in the systems, respectively. Magnetic studies show that compound 3 is a field-induced single-molecule magnet (SMM) for which the magnetization relaxes through a combination of Orbach (Δ = 51 K and τ 0 = 3.1 × 10 -7 s) and Raman mechanisms. Solid-state luminescence studies reveal that compounds 1 , 2 , and 3 are photoluminescent in the visible range, while 4 exhibits luminescence in the NIR region. Compound 3 shows cold white-light emission with Commission Internationale de l'Eclairage (CIE) coordinates (0.31, 0.30) and correlated color temperature (CCT) value of 6942 K.