Lanthanide coordination compounds with 1H-benzimidazole-2-carboxylic acid: syntheses, structures and spectroscopic properties

Abstract

A flexible multidentate ligand, 1H-benzimidazole-2-carboxylic acid, was synthesized to construct a series of lanthanide coordination polymers [Ln(HBIC) 3 ] n (Ln = Eu (1), Tb (2), Gd (3), Pr (4), Nd (5); H 2 BIC = 1H-benzimidazole-2-carboxylic acid) under hydrothermal conditions. All the compounds were fully characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, thermal analysis and various spectroscopic techniques. Structural analyses reveal that they are isostructural and feature a 2D wave-like layer structure with distorted grids, in which the adjacent Ln 3+ centers are bridged by the HBIC 2 ligands with two kinds of new coordination modes and the adjacent HBIC 2 ligands are tightly bound by two types of distinct intra-layer hydrogen bonds. The adjacent 2D layers are further interconnected by strong inter-layer hydrogen bond ring motifs R 2 2 (10)to generate a 3D supramolecular architecture. Optical studies indicate that the compounds 1, 2, 4 and 5 exhibit characteristic luminescence emission bands of the corresponding lanthanide ions in the visible or near-infrared regions at room temperature. In particular, compound 2 displays bright green luminescence in the solid state with a satisfactory 5 D 4 lifetime of 1.2 ms and a high overall quantum yield of 31%, due to an ideal energy gap between the lowest triplet state energy level of H 2 BIC ligand and the 5 D 4 state energy level of Tb 3+ . The energy transfer mechanisms in compounds 1 and 2 were also described and discussed.

Preparation of Crystalline Phases of 3D Coordination Polymers Based on Tetracarbonatodiruthenium Units and Lanthanide(III) Ions – Magnetic Characterization

“…The Ln–O bond lengths are for two oxygen atoms of a chelate ligand coordinated to the same Ln centre. These intervals for the Ln–O bond lengths are also analogous to those observed in other lanthanide compounds with O‐donor ligands , …”

Synthesis, characterisation and cytotoxic activity of organoruthenium(II)-halido complexes with 1H-benzimidazole-2-carboxylic acid

“…19.00 and 20.00 ppm attributable to the methyl groups attached to the p-cymene moiety, at ca. 22.00 ppm assigned to two methyl protons of the isopropyl groups, at around 31.00 and 31.50 ppm due to the CH resonance of the isopropyl group and in the range from 77.50 to 103.50 ppm due to aromatic carbons from p-cymene moiety. Furthermore, all complexes display signals in the range from 114.00 to 141.00 ppm related to the aromatic carbons from benzimidazole moiety, at 145.50 ppm from imidazole carbon, and at 164.00 ppm attributable to the carboxylate carbon.…”

“…The flexibility of the carboxylic group allows for various coordination modes in metal complexes, in which 1H-benzimidazole-2-carboxylate acts as a monodentate or bidentate chelating ligand. Recently, bidentate chelating, chelatingebridging, or bis(chelatingebridging) coordination modes have been reported for lanthanide complexes (Scheme 1) [22,23].…”

Structurally simple complexes of CO2

“…The added stability provided by their fused ring structures allows the N-substituents to be hydrogen atoms, as opposed to the bulky side groups utilized in most NHCs. [148][149][150][151] Gurau et al 152 found that bubbling CO2 into the ionic liquid 1-ethyl-3-methylimidazolium acetate, [EMIM]OAc, promoted the deprotonation of the cation by the acetate anion, generating acetic acid. Subsequent addition of CO2 to the generated carbene gave a complex which was crystallized as the [ 152 Finally, on a related note, N-heterocylic olefins (NHOs) have also been found to display remarkable reactivity towards CO2.…”