Lanthanide Coordination Polymers with Soft-Base Ditopic Bisthiazolate Ligands

Abstract

In order to prepare the first lanthanide coordination polymers (CPs) based on ditopic sulfide ligands, benzo [1,2d:4,5-d′]bisthiazole-2,6(3H,7H)-dithione (H 2 L) was used as a linker. The reactions of lanthanide silylamides Ln[N(SiMe 3 ) 2 ] 3 (Ln = Nd, Gd, Er, and Yb) with H 2 L result in the formation of soluble dimethyl sulfoxide (DMSO) ionic salts [Ln(DMSO) 8 ][L] 1.5 [Ln = Nd (1), Gd (2), Er (3), and Yb ( 4)]. Due to the lack of coordination of anionic ligands, compounds 1, 3, and 4 do not show sensitized metal-centered photoluminescence (PL), while Gd compound 2 shows weak phosphorescence at 77 K. It was found that the heating of 1 in a 1:9 DMSO/1,4-dioxane mixture leads to the formation of large crystals of 2D CP [Nd(DMSO) 3 L 1.5 •0.5diox] n (5), where deprotonated dithione H 2 L plays the role of a ditopic linker. This linker acts as an "antenna" in compound 5, providing an intense near-infrared (NIR) PL of Nd 3+ ion upon near-UV and blue-light excitation. The application of a synthetic protocol similar to that of compounds 2−4 led to the formation of amorphous compounds [Ln(DMSO) 3 L 1.5 •0.5diox] n [Ln = Gd (6), Er (7), and Yb (8)], whose PL properties significantly differ from those of the parental ionic salts. In the case of Yb polymer 8, the PL excitation spectra are shifted to the red region due to a low-energy ligand-to-metal charge-transfer state. The synthesized compounds 5−8 are the first examples of lanthanide CPs using soft-base ditopic linkers in their structures.

Valence tautomeric interconversion of bis-dioxolene cobalt complex with imino-pyridine functionalized by TEMPO moiety in solid solutions with isostructural nickel analogue: phase transitions and monocrystal destruction

“…This experimental–theoretical approach has proven itself in studying electron density topology from a low-resolution experimental data set. 52–56 Based on the resulting electron density distribution, we found all intermolecular pair interactions between the considered molecules in the asymmetric unit and its neighbors and then calculated the energy of these interactions according to EML correlation. 57 As expected, the total energy of all intermolecular interactions for one molecule (lattice energy) in a 1 : 8 solid solution at 240 K turned out to be the lowest (33 kcal mol −1 ) compared to crystals of both “pure” cobalt (34 kcal mol −1 ) and “pure” nickel (36 kcal mol −1 ) at 240 K (Table S4†).…”