RE-p-halobenzoic acid–terpyridine complexes, part III: structural and supramolecular trends in a series of p-iodobenzoic acid rare-earth hybrid materials

Abstract

A series of twenty-one new rare-earth p-iodobenzoic acid complexes, [RE(L¹)₃(L²)(H₂O)]₂ (RE = La³⁺ (1) Ce³⁺ (2)), [RE(L¹)₃(L²)]₂·H₂O (RE = Ce³⁺ (2′), Pr³⁺ (3), Nd³⁺ (4), Sm³⁺ (5)), Eu³⁺ (6), Gd³⁺ (7), Tb³⁺ (8), Dy³⁺ (9), Ho³⁺ (10), Er³⁺ (11), Tm³⁺ (12), Yb³⁺ (13), Lu³⁺ (14), Y³⁺ (15)), [RE(L¹)₃(L²)(H₂O)]₂ (RE = Yb³⁺ (13′), Lu³⁺ (14′), Y³⁺ (15′)), and RE₂(L¹)₄(L²)₂(Ox) (RE = Er³⁺ (11′), Tm³⁺ (12′)); L¹: p-iodobenzoic acid; L²: 2,2′:6′,2′′-terpyridine; Ox: oxalic acid, have been hydrothermally synthesized and structurally characterized by single crystal and powder X-ray diffraction. The series includes binuclear complexes [(La³⁺–Ce³⁺), (Ce³⁺–Y³⁺)], mononuclear complexes (Yb³⁺–Y³⁺), and oxalate-bridged binuclear complexes (Er³⁺–Tm³⁺), formed as a result of in situ ligand synthesis. All twenty-one complexes feature halogen- and π-based supramolecular interactions which assemble the molecular complexes into one, two, and three dimensions. Solid-state visible and near-IR luminescence spectra were collected on complexes 5, 6, 8, 9, 12, and 13 and characteristic emission was observed. The local coordination geometry over the p-iodobenzoic acid series were analyzed and then compared to the previously described and characterized RE-p-chlorobenzoic acid and RE-p-bromobenzoic acid analogues. Additionally, structural trends and supramolecular motifs were extracted from this series of materials and compared with the previously reported p-chloro- and p-bromo materials.