The kinetics of oxidation of H 2 O 2 by [Ni III (cyclam)] 3+ , [Ni III L 1 ], was studied in aqueous acidic media at 25 • C and I = 0.5 M (NaClO 4). The [Ni III L 1 ] to [Ni II L 1 ] reduction was found to be fast in the presence of Cu(II) ion than the oxidation of the cyclam ligand by • OH. The rate constant showed an inverse acid dependence on H + ion at the pH range 1-1.5. The presence of sulphate retards the reaction. Macrocylic ligand oxidation was followed spectrophotometrically by examining the oxidation of nickel(II) complexes of macrocyclic ligands such as 1,8-bis(2-hydroxyethyl)-1,3,6,8,10,13-hexaazacyclotetradecane (L 2), ms-5,7,7,12,14,14hexamethyl-1,4,8,11-tetraazacyclotetradecane (L 3), rac-Me 6 [14]-4,11-dieneN 4 (L 4) by reaction with hydrogen peroxide. The rate constant for the cross reaction is discussed in terms of Marcus relationship.

A series of sulfonic acid functionalized ordered mesoporous silica (OMS), designated as RSO3H‐OMS (R=alkyl or aryl; OMS=MCM‐41, IITM‐56 or SBA‐15), were prepared by post‐synthesis grafting method. These catalysts, in general, exhibit strong acidic sites and, therefore, yield diacetone‐D‐glucose as main product in the D‐glucose acetonation reaction. On the other hand, the functionalized catalyst can also be tuned in such a way to generate significant amount of weak‐to‐moderate acidic sites, which are in turn responsible for the formation of 1,2‐monoacetone‐D‐glucose, hitherto not reported so far. These functionalized materials also show promise as they are water tolerant catalyst as well as exhibit varying acidic strengths, which allow greater flexibility for the desired product. In addition, the uniform mesopores with high surface area permit bulkier molecules to enter the active sites, thus the catalyst offers larger pliability in terms of yield and reusability. We report here, for the first time, RSO3H‐SBA‐15, with sizable amount of weak‐to‐moderate acidic sites, as a robust heterogeneous catalyst for the formation of the targeted molecule, 1,2‐monoacetone‐D‐glucose.

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The kinetics of the oxidation of hydroquinone (H 2 Q), catechol (H 2 cat) and substituted catechols with nickel(III) macrocycle [NiL 1 ] 3? (L 1 = 1,8-bis(2-hydroxyethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) has been studied spectrophotometrically in aqueous perchloric acid in the presence of sulfate. Over the pH range 1-2.6, and at higher sulfate concentration 0.05 \ [SO 42-] \ 0.2 mol dm -3 , the decomposition of [Ni III L 1 ] in the oxidation of benzenediols via [Ni III-L 1 (OH)(H 2 O)] is small. With hydroquinone, the rate constant is almost independent of the hydrogen ion concentration and with catechols, the involvement of catechol anion (Hcat -) has been considered. The rate constants for cross reactions are discussed in terms of the Marcus relationship.

Cu(II) ion catalyzed kinetics of oxidation of H 2 O 2 by [Ni III L 2 ] (L 2 = 1,8-bis(2-hydroxyethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) was studied in aqueous acidic medium in the presence of sulphate ion. The rate of oxidation of H 2 O 2 by [Ni III L 2 ] is faster than that by [Ni III L 1 ] (L 1 = 1,4,8,11-tetraazacyclotetradecane) in sulphate medium. DFT calculations at BP86/def2-TZVP level lead to different modes of bonding between [NiL] II/III and water ligands (L = L 1 and L 2 ). In aqueous medium, two water molecules interact with [NiL] II through weak hydrogen bonds with L and are tilted by ∼23 • from the vertical axis forming the dihydrate [NiL] 2+ .2H 2 O. However, there is coordinate bond formation between [NiL 1 ] III and two water molecules in aqueous medium and an aqua and a sulphato ligand in sulphate medium leading to the octahedral complexes [NiL 1 (H 2 O) 2 ] 3+ and [NiL 1 (SO 4 )(H 2 O)] + . In the analogous [NiL 2 ] III , the water molecules are bound by hydrogen bonds resulting in [NiL 2 ] 3+ .2H 2 O and [NiL 2 (SO 4 )] + .H 2 O. As the sulphato complex [NiL 2 (SO 4 )] + .H 2 O is less stable than [NiL 1 (SO 4 )(H 2 O)] + in view of the weak H-bonding interactions in the former it can react faster. Thus the difference in the mode of bonding between Ni(III) and the water ligand can explain the rate of oxidation of H 2 O 2 by [Ni III L] complexes.