Probing surface acidity, basicity, and dipolarity/polarizability of 12-tungstophosphoric acid by means of solvatochromic dyes

Zimmermann, Yvonne; Spange, Stefan

doi:10.1039/b204664b

Cited by 14 publications

(8 citation statements)

References 61 publications

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“…Thus, large α values are not absolutely consistent with high catalytic activity. Similar results have been found for H 3 PW as a solid acid catalyst . Because a small fraction of mobile protons interact with 1 , then a too large α results.…”

Section: Resultssupporting

confidence: 81%

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Solvent Influence on the Catalytic Activity and Surface Polarity of Inorganic Solid Acids

and

Spange

2002

J. Phys. Chem. B

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The surface-mediated hydride-transfer reaction of 1,4-cyclohexadiene with triphenylmethylium induced by two silicas, an alumina, and an aluminosilicate as solid acid catalyst, respectively, has been kinetically studied as a function of the polarity of the surrounding solvent. The specific rate constants k′ have been determined in 10 different solvents. Generally, k′ decreases with increasing polarity of the solvent. Kamlet-Taft's R (hydrogen-bond acidity) and π* (dipolarity/polarizability) parameters of the solid acid/solvent interface have been determined for alumina and aluminosilicate in various solvents. Fe(phen) 2 (CN) 2 [cis-dicyanobis(1,10phenanthroline)iron(II), ( 1)] and Michler's ketone [4,4′-bis(N,N-dimethylamino)benzophenone, (2)] were used as solvatochromic surface polarity indicators. The UV/vis spectra of the two surface polarity indicators 1 and 2 adsorbed on solid acid catalysts from the solvents were measured by the reflection mode and the UV/vis absorption maxima were used to calculate the R and π* values of the catalysts. R of the solid acid catalyst/ solvent interface decreases with increasing β term (hydrogen-bond accepting) ability of the solvent, whereas the π* term of the solvent marginally modifies the interfacial polarity. k′ increases for each individual solvent with increasing β of the catalyst solvent interface in the order series silica < alumina < aluminosilicate. It can be shown that R of the solid acid catalyst/solvent interface decreases with increasing β term (hydrogenbond accepting) ability of the solvent, whereas the π* term of the solvent marginally modifies the interfacial polarity.

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Section: Resultssupporting

confidence: 81%

“…Similar results have been found for H 3 PW as a solid acid catalyst. 38 Because a small fraction of mobile protons interact with 1, then a too large R results. In this case it does not correspond to concentration of active surface sites, which are actually responsible for the rate of the polar reaction.…”

Section: Resultsmentioning

confidence: 99%

Solvent Influence on the Catalytic Activity and Surface Polarity of Inorganic Solid Acids

and

Spange

2002

J. Phys. Chem. B

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“…The surface polarity parameters were referenced to the Kamlet-Taft solvent parameter set. 29 The a values of HY (a ¼ 1.71), DAY (a ¼ 1.43), MCM 41 (a ¼ 1.53) and MCM 48 (a ¼ 1.21) are large compared to pure silica (a ¼ 1) and in the expected order for those types of aluminosilica materials, which indicate a strong Brønsted acidity. 30 The monoprotonated cationic form of 1 (l max ¼ 570 nm), 2 (l max ¼ 600 nm), and 3 (l max ¼ 640 nm) respectively is generated by reaction of acidic surface protons of MCM 41 with the oxygen atom of the pyran ring resulting in a significant shift of the Fig.…”

Section: Resultsmentioning

confidence: 97%

Functional mesoporous aluminosilicate nanoparticles as host material to fabricate photo-switchable polymer films

et al. 2011

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Precisely nano-sized aluminosilicate particles (average diameter size 50 to 80 nm) with tailor-made internal surface polarity are suitable as host material for photochromic dyes of the chromene type in order to produce optical transparent photoswitchable polymer films. The sophisticated host material does accomplish two important requirements for a technical application, appropriate internal space for the light induced reversible switching process of the adsorbed dye and suppression of disturbing chemical reactions. The adjustment of the internal surface polarity of the host material was achieved by silane reagents which could be observed by means of specific solvatochromic probes

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“…The usefulness of 1 for the determination of the basicity of polymer films and poly(amino acids) has been already demonstrated . Recently, we were able to show that even the strong solid acid H 3 PW (phosphoric tungsten acid) can be evaluated by this probe molecule . Since 1 is a large molecule, it will not enter the channels of HY or HZSM 5 zeolites.…”

Section: Introductionmentioning

confidence: 94%

Probing Surface Basicity of Solid Acids with an Aminobenzodifurandione Dye as the Solvatochromic Probe

et al. 2005

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Solvatochromism and sorptiochromism of the dye 3-(4-amino-3-methylphenyl)-7-phenyl-benzo1,2b:4,5b‘difuran-2,6-dione (1) are studied with an extended set of solvents and various solid acids including silicas, aluminas, and alumosilicates. 1 shows a positive solvatochromism with increasing basicity and dipolarity/polarizability of the solvent; its solvent-induced bathochromic UV−vis absorption band shift ranges from formic acid (υmax = 21 630 cm-1) to hexamethylphosphoric acid triamide (υmax = 14 200 cm-1). Multiple square analyses of υmax of the solvent-dependent solvatochromic UV−vis absorption band of 1 with several empirical solvent polarity parameters prove that a composite of basicity, acidity, and dipolarity/polarizability of the environment must be taken into account. For the analysis of the solvent-dependent UV−vis shift of 1, the Kamlet−Taft and Catalán solvent parameters have been evaluated. It could be shown that the Catalán solvent parameter set is more suitable to reflect multiple solvation processes involving both strong basic and strong acidic solvents. Quantum chemical calculations indicate that an interaction of the silanol oxygen atom with the protons of the amino group is clearly favored over various acidic attacks of silanol groups upon 1. Accordingly, surface basicity of silica, alumina, and alumosilicates can be determined using the linear solvation energy relationship derived from the solvent-dependent UV−vis band of 1. An unambiguous interpretation of the UV−vis spectroscopic data of 1 adsorbed on surfaces containing Lewis-acid sites is sometimes difficult. UV−vis monitoring of 1-loaded solid acids during surface titration with 2,6-di-tert-butyl pyridine allows the discrimination of whether Brønsted- or Lewis-acid sites interfere with 1. Additionally, adsorbed water has an important influence on the actual surface basicity of solid acids. 1 is recommended as a sensitive probe for checking both basicity and acidity when directly compared with solvatochromism of the established hydrogen-bond-donating indicator (cis-dicyano)bis(1,10-phenanthroline)iron(II) (2).

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Probing surface acidity, basicity, and dipolarity/polarizability of 12-tungstophosphoric acid by means of solvatochromic dyes

Cited by 14 publications

References 61 publications

Solvent Influence on the Catalytic Activity and Surface Polarity of Inorganic Solid Acids

Solvent Influence on the Catalytic Activity and Surface Polarity of Inorganic Solid Acids

Functional mesoporous aluminosilicate nanoparticles as host material to fabricate photo-switchable polymer films

Probing Surface Basicity of Solid Acids with an Aminobenzodifurandione Dye as the Solvatochromic Probe

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