Study of structure and two-dimension correlation infrared spectroscopy on three rare-earth/3-methylbenzoic acid complexes

Three rare-earth complexes with 3-methylbenzoic acid (HL) have been hydrothermally synthesized directly: Yb(C8H7O2)31 and Ln(C8H7O2)3·(4,4′-bipy)0.5 (Ln = Eu 2, Gd 3) (4,4′-bipy = 4,4′-bipyridine).The crystal structures were determined by single crystal X-ray diffraction with the following data: 1: monoclinic, P21/n, a = 13.574(3), b = 8.0438(2), c = 20.652(4) Å, β = 96.14(3)°; 2: triclinic, P-1, a = 8.1788(2), b = 12.952 (3), c = 12.968(3) Å, α = 94.400(3)°, β = 92.260(4), γ = 101.360(4); the complex 1 is a one-dimensional chain. However, due to the existence of the second ligand-4,4′-bipy, the complexes 2 and 3 are a two-dimensional layer, the Lanthanide contraction makes the difference of the structure between the complexes at the same time. Additionally, in order to explore the structural characteristic, the 2D-IR correlation spectroscopy containing the temperature-induced structural variations and magnetism-induced structural variations is used. Photo-luminescent properties of 1 and 2 are discussed in detail.