Relations between Structural and Luminescence Properties of Novel Lanthanide Nitrate Complexes with Bis-phosphoramidate Ligands

Abstract

Five new bisphosphoramide-based LnIII nitrate complexes [La2(NO3)6L3 I] n (1), [Ce2(NO3)6L3 I] n (2), [Sm2(NO3)6L3 II] n (3), Sm2(NO3)6L3 III (4), and Er­(NO3)3L2 III (5) [L I = piperazine-1,4-diylbis­(diphenyl phosphine oxide), L II = N,N′-(ethane-1,2-diyl)­bis­(N-methyl-P,P-diphenylphosphinic amide, and L III = N,N′-(ethane-1,2-diyl)­bis­(P,P-diphenylphosphinic amide)] have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), and single crystal X-ray and powder diffractions. The results of the X-ray diffraction analysis revealed the new polymorph of L III , and the structural diversity of the synthesized complexes in the solid state. Complexes 1–3 display two-dimensional coordination polymers (2D-CP), containing layers with honeycomb (6, 3) topology. In these 2D-CPs, each Ln center (La, Ce, and Sm in 1, 2, and 3, respectively) could be considered as a triconnected node, linked by three bridging bisphosphoramide ligands as two-connecting linkers. In contrast, 4 is a discrete binuclear complex, in which bidentate L III ligand has two entirely different conformations: the syn chelating and the anti bridging. Cationic complex 5 shows the monomeric structure, where bidentate L III adopts the syn-chelating conformation. A comprehensive luminescence investigation has been performed on free ligands and their corresponding complexes as well. The synthesized compounds display a variety of luminescence behavior, including the ligand-centered fluorescence in 1, 2, and 5, two distinct emission peaks in 1 and 2, characteristic Sm-centered f–f emission in 3 and 4, and excitation-dependent emission in L III , 1, and 2. Furthermore, the time-dependent density functional theory (TD-DFT) study was carried out on the reported compounds to understand the nature of the emission peaks and the observed luminescence properties. The solid-state emission quantum yields of lanthanide complexes were also determined at different excitation wavelengths.

Luminescent lanthanide complexes based on 4,5-di(3,5-dicarboxylphenoxy)phthalic acid as enhanced fluorescence probes for highly selective detection of lead(ii) ions in water

“…S4 in ESI †), and they all exhibit a broad peak near 3430 cm −1 attributed to the O-H stretching vibration peak of water molecules and hydroxyl groups. 49,50 The peak at 1715 cm −1 for the ligand is attributed to the stretching vibration of the protonated carboxyl group, which is weakened in complexes 2-6 and completely absent in complex 1, suggesting that the carboxyl group in complexes 2-6 is not fully deprotonated, whereas the carboxyl group in complex 1 is completely deprotonated, which is consistent with the results of the single crystal structure analysis.…”

Seven Ln(iii) coordination polymers with two kinds of geometric coordination but the same 3D topological property: luminescence sensing and magnetic property

“…The peaks ranging from 3649 to 3519 cm −1 are the stretching vibrations of O–H bonds of crystalline waters and the 3402–3118 cm −1 are the vibrations of O–H bonds from coordination water molecules. 17 The symmetric stretching frequencies of COO − groups are between 1664 and 1364 cm −1 and the COC symmetric stretching vibrations are observed in the range of 1280–1133 cm −1 . In addition, the peaks at 972–785 cm −1 are assigned to the bending frequencies of O–CO.…”

“…With further cooling, a sharp increase of χ M T is observed, reaching to 23.14 cm 3 K mol −1 at 2 K. The gradual decrease above 10 K is mostly caused by the thermal depopulation of the excited states of Er(III), whereas the rapid increase at low temperature could be attributed to ferromagnetic intramolecular dipolar interactions. 46 At a very low temperature, the increase of χ M T indicates that the weak intramolecular ferromagnetic interaction between the Er(III) ions overwhelm the thermal depopulation of the excited states of the Er(III) ions. 47,48…”