Characterization of the acid-base nature of metal oxides by adsorption of TCNQ

Abstract

This paper reviews the acid-base (electron donor-acceptor) interaction of 7,7,8,8-tetracyanoquinodimethane (TCNQ) with metal oxides. When TCNQ is adsorbed onto metal oxides, TCNQ anion radicals are formed as a result of electron transfer from the metal oxides to TCNQ. The measurement of the TCNQ radical concentration allows the determination of the electron donicity of single and two-component metal oxides. TCNQ adsorption is also affected significantly by the acidbase interaction between the metal oxide and solvent, the metal oxide and TCNQ, and TCNQ and the solvent. In addition, the strength and distribution of electron donor sites and enhancement of the electron donor properties of metal oxides are discussed.

Synthesis and applications of CoFe2O4nanoparticles for multicomponent reactions

“…The catalyst played the role of base to afford the product by the Knoevenagel condensation followed by a Michael addition. The Lewis basic sites originate from electrons trapped in the intrinsic defects or from surface hydroxyl groups 41 or from co-ordinatively unsaturated oxide ion associated with neighbouring hydroxyl groups. 42 Synthesis of 2,2′-arylmethylene bis(3-hydroxy-5,5-dimethyl-2cyclohexene-1-one) derivatives using CoFe 2 O 4 nanoparticles as catalyst Encouraged from the above results we also tried to synthesise 2,2′-arylmethylene bis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) derivatives by the reaction of aromatic aldehydes and 1,3-cyclic diketones (dimedone and 1,3-cyclohexanedione) in a 1 : 2 molar ratio to investigate the scope of our catalytic system.…”

Surface electron properties and catalytic activity of Sr doped lanthana

“…The ESR spectrum of these colored samples gave unresolved spectral lines with g values of 2.003 and 2.01 I for TCNQ and chloranil, respectively. The electronic spectrum of the adsorbed samples gave bands near 400, 600 and 700 nm corresponding to physically adsorbed state of neutral TCNQ [7], dimeric TCNQ radical [8], and to Chloranil anion radical [9], respectively. The data are given in Table I along Table 2 contains the data on acidity/basicitv distribution.…”

Study of cyclohexanol decomposition reaction over the ferrospinels, A1−xCuxFe2O4 (A=Ni or Co and x=0, 0.3, 0.5, 0.7 and 1), prepared by ‘soft’ chemical methods

“…Secondly, sulphating agents, being acidic species, preferentially attack the basic sites converting these to acidic sites. Both Lewis and Br nsted basic sites are present on the samples at 300 • C. At this temperature, the Lewis basic sites on metal oxides are mainly due to surface hydroxyl groups [34] and the Br nsted basic sites are due to coordinatively unsaturated oxide ions associated with neighbouring hydroxyl group. It was suggested [35] that the formation of acid sites during sulphation involved the chemical reaction between the surface hydroxyl groups of the metal hydroxide and the adsorbed H 2 SO 4 (from the sulphating agent).…”