Synthesis and luminescence properties of novel 8‐hydroxyquinoline derivatives and their Eu(III) complexes

Abstract

Six novel 8-hydroxyquinoline derivatives were synthesized using 2-methyl-8-hydroxyquinoline and para-substituted phenol as the main starting materials, and were characterized by H nuclear magnetic resonance (NMR), mass spectrometry (MS), ultraviolet (UV) light analysis and infra-red (IR) light analysis. Their complexes with Eu(III) were also prepared and characterized by elemental analysis, molar conductivity, UV light analysis, IR light analysis, and thermogravimetric-differential thermal analysis (TG-DTA). The results showed that the ligand coordinated well with Eu(III) ions and had excellent thermal stability. The structure of the target complex was EuY (NO ) .2H O. The luminescence properties of the target complexes were investigated, the results indicated that all target complexes had favorable luminescence properties and that the introduction of an electron-donating group could enhance the luminescence intensity of the corresponding complexes, but the addition of an electron-withdrawing group had the opposite effect. Among all the target complexes, the methoxy-substituted complex (-OCH ) had the highest fluorescence intensity and the nitro-substituted complex (-NO ) had the weakest fluorescence intensity. The results showed that 8-hydroxyquinoline derivatives had good energy transfer efficiency for the Eu(III) ion. All the target complexes had a relatively high fluorescence quantum yield. The fluorescence quantum yield of the complex EuY (NO ) .2H O was highest among all target complexes and was up to 0.628. Because of excellent luminescence properties and thermal stabilities of the Eu(III) complexes, they could be used as promising candidate luminescent materials.

Transition metal/Brønsted acid cooperative catalysis enabled facile synthesis of 8-hydroxyquinolines through one-pot reactions of ortho-aminophenol, aldehydes and alkynes

“…To our delight, when AgOTf decreased to 0.5 mol%, a parallel yield was also observed (entry 14-16). Solvent and temperature optimization revealed that other medias are not suitable in terms of yield comparable to that in DCE at 80 C (entry [17][18][19][20][21].…”

“…[1][2][3][4][5][6][7][8][9] Moreover, 8hydroxyquinolines have been gaining attention in metallocene complex catalyzed transformations, in which they are utilized as effective multidentate ligands. [10][11][12][13][14][15][16][17][18][19][20][21] In view of the remarkable importance of this class of heterocyclic compounds, the eld of 8-hydroxyquinoline synthesis is continuously gaining attention. Although 8-hydroxyquinolines could be prepared by hydrolysis of 8-haloquinolines 22 or 8-aminoquinolines, 23 the latter two quinolone derivatives were not easily accessible.…”

Theoretical and experimental studies on the fluorescence properties of aluminum(III), cadmium(II), zinc(II), and copper(II) complexes of substituted 8-hydroxyquinoline

“…The measurement of relative fluorescence quantum yields has exclusively been done by optical methods, most prominently using a spectrofluorometer and the comparative method as proposed by Parker and Rees. 25 In this paper, the ɸ f was calculated by a comparative method using the following equation 6,26,27 Φ Φ . .…”

“…The addition of substituents at the C-2 position of the pyridine ring, such as in ligands 1b, 1c, 1g, 1i, 1l, 1n, 1o, 1p, 1q, and 1r (Table 5, entries [3][4][5][6][7][8][9][10][11], results in a certain spatial steric resistance to the complex structure, which was not conducive to the formation of a stable five-membered ring structure. If electron-donating groups were introduced at ortho positions, the distribution of the electron cloud would change, which might significantly alter the LUMO value and expand the HOMO and LUMO gaps, such as in the zinc, cadmium, and aluminum complexes 1o, 1p, and 1q (Table 7), which resulted in a significant blue shift of the fluorescence emission wavelength.…”

“…[1][2][3][4][5] 8-Hydroxyquinoline, which possesses a heterocyclic conjugated planar structure, was used in multiple areas because of its chelating performance, luminescence properties, and coordination abilities. 6 Despite many efforts having been made on the preparation of 8-hydroxyquinoline derivatives and their metal complexes, [7][8][9][10][11][12] only a limited number of comparative studies are available on the influence of different substituents on the 8-hydroxyquinoline framework and different metals on the fluorescence properties of the corresponding complexes. Recently, we reported the synthesis of 55 different substituted 8-hydroxyquinolines ( Figure 1) along with preliminary studies on the fluorescent properties of their zinc complexes.…”