NMR, DFT and luminescence studies of the complexation of V(<scp>v</scp>) oxoions in solution with 8-hydroxyquinoline-5-sulfonate

Ramos, M. Luísa; Justino, Licínia L. G.; Fonseca, Sofia M.

doi:10.1039/c4nj01873g

Cited by 11 publications

(18 citation statements)

References 65 publications

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“…This is suggested to be due to the presence of low-lying ligand-to-metal chargetransfer state(s). 80 However, the weakness of the emission with Crq 3 is attributed to it involving a metal based transition. Further studies are in progress to fully characterize this at room temperature and low temperature.…”

Section: Uv/visible Absorption and Luminescence Spectral Studiesmentioning

confidence: 99%

Synthesis, structure, and spectral and electrochemical properties of chromium(iii) tris-(8-hydroxyquinolinate)

et al. 2015

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The kinetically inert chromium(III) tris-(8-hydroxyquinolinate), Crq3, has been synthesized, crystallized from 90% methanol-water, and characterized by MALDI-TOF mass spectrometry, thermogravimetry, FTIR, NMR spectroscopy, and X-ray powder diffraction. It is formed as a methanol solvate, but the solvent can be removed by heating. Large paramagnetic shifts and spectral broadening in (1)H NMR spectra indicate electron delocalization between the metal and the ligand. DFT calculations show it is present as the meridional isomer, with the HOMO largely based on one of the metal 3d orbitals and the LUMO essentially localized on the ligands. Cyclic voltammetry (CV) in acetonitrile solutions shows four oxidation peaks and two, less intense reduction waves on the first scan. The HOMO energy determined from the first oxidation peak is fairly close to that obtained by DFT, in agreement with this being mainly metal based. Although the number of peaks decreases on subsequent CV scans, the complex shows markedly enhanced electrochemical stability compared with aluminium(III) tris-(8-hydroxyquinolinate). Solution UV/visible absorption and solid diffuse reflectance spectra have a weak, long wavelength band, assigned to the metal based d-d transition, in addition to the normal, ligand based bands seen in metal quinolates. The energy of the lowest energy band is identical to the HOMO-LUMO separation obtained by cyclic voltammetry, in agreement with the above description. The compound is only weakly luminescent, in contrast to many other metal quinolates, due to the lowest energy transition being metal rather than ligand based. The potential of this compound as an electron transporting/hole blocking layer in optoelectronic devices is indicated.

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Section: Uv/visible Absorption and Luminescence Spectral Studiesmentioning

confidence: 99%

Synthesis, structure, and spectral and electrochemical properties of chromium(iii) tris-(8-hydroxyquinolinate)

et al. 2015

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“…Though the five-membered chelate rings formed between the NO donors and Cr(III) metal centers have increased the π-π* conjugation and conformational coplanarity of 8-hydroxyquinolinate, it is hard to detect the fluorescent signal of the two metallocomplexes. In contrast to other complexes of 8-hydroxyquinoline and its derivatives with metal ions (e.g., Al(III), Ga(III), Zn(II), or Cd(II)), the 3 d 3 Cr(III) ion exhibits striking quenching effect, which might be attributed to the lowest energy transition being metal rather than ligand based [ 34 , 39 ]. The striking fluorescence response of the two 8-hydroxyquinolinate based ligand towards Cr 3+ both in solid and solution indicated they could serve as a good heavy metal chelating agent for Cr 3+ in a range of environmental monitoring and biomedical applications.…”

Section: Resultsmentioning

confidence: 99%

Two 8-Hydroxyquinolinate Based Supramolecular Coordination Compounds: Synthesis, Structures and Spectral Properties

et al. 2017

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Two new Cr(III) complexes based on 2-substituted 8-hydroxyquinoline ligands, namely [Cr(L1)3] (1), (HL1=(E)-2-[2-(4-nitro-phenyl)-vinyl]-8-hydroxy-quinoline) and [Cr(L2)3] (2), (HL2=(E)-2-[2-(4-chloro-phenyl)vinyl]-8-hydroxy-quinoline), were prepared by a facile hydrothermal method and characterized thoroughly by single crystal X-ray diffraction, powder X-ray diffraction, FTIR, TGA, ESI-MS, UV-Visible absorption spectra and fluorescence emission spectra. Single crystal X-ray diffraction analyses showed that the two compounds featured 3D supramolecular architectures constructed from noncovalent interactions, such as π···π stacking, C-H···π, C-H···O, C-Cl···π, C-H···Cl interactions. The thermogravimetric analysis and ESI-MS study of compounds 1 and 2 suggested that the Cr(III) complexes possessed good stability both in solid and solution. In addition, the ultraviolet and fluorescence response of the HL1 and HL2 shown marked changes upon their complexation with Cr(III) ion, which indicated that the two 8-hydroxyquinolinate based ligand are promising heavy metal chelating agent for Cr3+.

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“…With aromatic ligands, inductive effects at specific positions in the aromatic rings allow the identification of changes in the electronic environment together with insights into the nature of the metal-ligand bonds on complexation, and the structure of the chelate species, in particular the symmetry of the coordinated ligands, 57 as illustrated in our studies of the complexation of 8-HQS with Zn 2+ , Cd 2+ , Hg 2+ , Al 3+ , Ga 3+ and V(V). [35][36][37][38][39] The combination of proton, carbon-13 and metal ion NMR can provide valuable structural information, including the type of metal centre present in these complexes, and also metal oxoions of vanadate, molybdate and tungstate with relevant ligands. [37][38][39]43,44,[58][59][60][61][62][63][64][65][66][67] In previous studies we have characterized a large number of species, and have found that the 183 W and 95 Mo NMR chemical shift ranges of homologous complexes of W(VI) and Mo(VI) show a linear correlation (δ W = 1.8δ Mo − 137.3), which parallels Scheme 1 the ratio of nuclear charges.…”

Section: Resultsmentioning

confidence: 99%

“…[35][36][37][38][39] The combination of proton, carbon-13 and metal ion NMR can provide valuable structural information, including the type of metal centre present in these complexes, and also metal oxoions of vanadate, molybdate and tungstate with relevant ligands. [37][38][39]43,44,[58][59][60][61][62][63][64][65][66][67] In previous studies we have characterized a large number of species, and have found that the 183 W and 95 Mo NMR chemical shift ranges of homologous complexes of W(VI) and Mo(VI) show a linear correlation (δ W = 1.8δ Mo − 137.3), which parallels Scheme 1 the ratio of nuclear charges. 65,67 This relationship has proved to be useful in comparative studies in the identification and structural characterisation of homologous species of Mo(VI) and W(VI).…”

Section: Resultsmentioning

confidence: 99%

“…In contrast, with vanadium(V), the 8-HQS complex is only weakly fluorescent. 39 This is suggested to be due to the presence of low-lying ligand-to-metal chargetransfer (LMCT) states close to the emitting ligand-based excited state. We are interested in extending these studies to other high oxidation state transition metal ions, and have studied the complexation with Mo(VI) and W(VI) oxoions.…”

Section: Introductionmentioning

confidence: 99%

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Oxocomplexes of Mo(vi) and W(vi) with 8-hydroxyquinoline-5-sulfonate in solution: structural studies and the effect of the metal ion on the photophysical behaviour

et al. 2015

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Multinuclear ((1)H, (13)C, (95)Mo and (183)W) NMR spectroscopy, combined with DFT calculations, provides detailed information on the complexation between the Mo(VI) and W(VI) oxoions and 8-hydroxyquinoline-5-sulfonate (8-HQS) in aqueous solution. Over the concentration region studied, Mo(VI) and W(VI) oxoions form three homologous complexes with 8-HQS in water in the pH range 2-8. Two of these, detected at pH < 6, are mononuclear 1 : 2 (metal : ligand) isomers, with the metal centre (MO2(2+)) coordinated to two 8-HQS ligands. An additional complex, dominant at slightly higher pH values (5-8) for solutions with a 1 : 1 metal : ligand molar ratio, has a binuclear M2O5(2+) centre coordinated to two 8-HQS ligands. The two metal atoms are bridged by three oxygen atoms, two coming from 8-HQS, together with the M-O-M bridge of the bimetallic centre. We show that the long-range exchange corrected BOP functional with local response dispersion (LCBOPLRD), together with explicit solvent molecules, leads to geometries that readily converge to equilibrium structures having realistic bridging O8-HQS-M bonds. Previous attempts to calculate the structures of such binuclear complexes using DFT with the B3LYP functional have failed due to difficulties in treating the weak interaction in these bridged structures. We believe that the LCBOPLRD method may be of more general application in theoretical studies in related binuclear metal complexes. UV/visible absorption and luminescence spectra of all the complexes have also been recorded. The complex between Mo(vi) and 8-HQS is only weakly luminescent, in contrast to what has been observed with this ligand and many other metal ions. We suggest that this is due to the presence of low-lying ligand-to-metal charge transfer (LMCT) states close to the emitting ligand-based level which quench the emission. However, with W(VI), DFT calculations show that the LMCT states are now much higher in energy than the ligand based levels, leading to a marked increase in fluorescence.

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NMR, DFT and luminescence studies of the complexation of V(v) oxoions in solution with 8-hydroxyquinoline-5-sulfonate

Abstract: The complexation of vanadium(v) with 8-HQS is accompanied by marked changes in the multinuclear NMR and UV/visible absorption spectra of 8-HQS, but does not lead to a significant increase in fluorescence.

Cited by 11 publications

References 65 publications

Synthesis, structure, and spectral and electrochemical properties of chromium(iii) tris-(8-hydroxyquinolinate)

Synthesis, structure, and spectral and electrochemical properties of chromium(iii) tris-(8-hydroxyquinolinate)

Two 8-Hydroxyquinolinate Based Supramolecular Coordination Compounds: Synthesis, Structures and Spectral Properties

Oxocomplexes of Mo(vi) and W(vi) with 8-hydroxyquinoline-5-sulfonate in solution: structural studies and the effect of the metal ion on the photophysical behaviour

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