Crystal Structure, Multiplex Photoluminescence, and Magnetic Properties of a Series of Lanthanide Coordination Polymers Based on Quinoline Carboxylate Ligand

A series of novel one-dimensional
(1D) lanthanide coordination polymers, [Ln­(pqc)­(Hpqc)­(NO3)2]n (Ln = Sm (1), Eu (2), Gd (3), Tb (4),
Dy (5), Ho (6), Er (7), Tm
(8), Yb (9), or Lu (10); Hpqc
= 2-phenyl-4-quinolinecarboxylic acid), have been synthesized via
solvothermal reaction at low temperature and then characterized by
single-crystal X-ray diffraction. Polymers 1–10 are isostructural and feature a 1D chain based on binuclear
units in which Ln3+ polyhedra are interconnected by bridging
Hpqc ligands and terminal nitrates. The infinite chains are further
extended to a three-dimensional supramolecular framework through π···π
stacking and hydrogen bonding interactions. This series affords an
opportunity to study the lanthanide contraction effect, demonstrating
that the sum of Ln–O distances proportional to this contraction
follow a quadratic decay as a function of the number n of f electrons. The photoluminescence spectra show that these complexes
are highly sensitized by Hpqc and exhibit characteristic Ln3+ (Sm (1), Eu (2), Tb (4),
Er (7), and Yb (9)) and ligand centered
(Dy (5), Ho (6), Tm (8), and
Lu (10)) luminescence in both visible and near-infrared
(NIR) regions. The magnetic properties of 4–7 have also been investigated.