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Polymer-incarcerated, carbon-stabilized gold nanoclusters were found to be highly active in heterogeneous catalysis for the oxidation of secondary alcohols using molecular oxygen in aqueous medium. After optimization of catalyst preparation methods, highly loaded and highly effective catalysts were obtained, and a broad range of secondary alcohols could be oxidized by using these catalysts under mild conditions. The catalysts could be recovered and reused several times without significant loss of activity. Moreover, kinetics of the oxidation reaction with (AE )-1-phenylethanol was investigated.

Aerobic oxidation reaction of amines to imines catalyzed by polymer-incarcerated Au nanoclusters (PI-Au) was developed. The effect of cluster size for this oxidation reaction was carefully examined using the same polymer support. We have succeeded in preparation of various PI-Au catalysts containing different size clusters by modification of standard preparation methods. The size of clusters and their distribution were analyzed by electron microscopy. Interestingly, catalysts containing relatively larger clusters (>5 nm) showed higher activity in aerobic oxidation of amines than catalysts containing smaller clusters (13 nm) that showed much better activity for aerobic oxidation of alcohols. In addition, novel Au nanocluster catalysts immobilized on newly prepared polymer with tertiary amine groups were developed and they showed excellent activity for aerobic oxidation of amines to imines. The relation between cluster size and catalytic activity and role of tertiary amine in polymer were discussed. These catalysts could be applied to aerobic oxidative deprotection of p-methoxybenzyl groups.Since Haruta's discovery, aerobic oxidation reactions catalyzed by gold nanoclusters have been widely investigated. 1,2There are two important factors for the activity of gold nanocluster catalysts, cluster size and a support. 24 Cluster size affects the activity of the catalysts by both surface area and quantum size effect. 4,5 Cluster size is also influenced by the support, and some metal oxide supports can activate Au clusters by electronic effects. In other cases, the support itself sometimes works as a cocatalyst with Au clusters. 4,6 In general, smaller clusters show higher activity than larger clusters because of their high surface area to volume ratio. Moreover, the catalytic activity normalized by the number of surface atoms of smaller Au cores is known to be higher than that of larger clusters in the oxidation of CO, glucose, and alcohols. 4,5 Recently, aerobic oxidation of amines to imines catalyzed by various sizes of Au, such as bulk, microsize, nanosize, and homogeneous Au, have been widely reported.7 Interestingly, 1050 nm size Au clusters sometimes show very high activity in these reports, 7g7i although over 10 nm Au clusters hardly catalyze other aerobic oxidation reactions. In some cases in this amine oxidation, it was concluded that smaller Au clusters have higher activity; 7d,7h however, there is no clear and direct evidence that smaller clusters have higher activity for aerobic oxidation of amines to imines because there are no reports that compare systematically the activity of different sizes of Au clusters using the same support.We recently reported that gold nanocluster catalysts immobilized on polystyrene-based polymers with crosslinking moieties, 8 polymer-incarcerated gold nanocluster catalysts (PI-Au), were effective for aerobic oxidation of alcohols to ketones, aldehydes, and esters and hydroquinones to quinones under mild conditions. 9,10 Moreover, PI-Au could be reused several times by simp...

DNA hybridization biosensors offer considerable promise for obtaining sequence information of genes in a fast and simple manner. Various DNA probes that give signals in a sequencespecific fashion, as represented by molecular beacons, have been widely used. [1][2][3] However, there are very few DNA probes that release functional molecules on recognition of the target sequence. [4,5] The sequence-specific molecule-releasing system that is triggered by external stimulation, such as irradiation would be a very powerful tool for gene analysis.Herein we report for the first time a molecule-releasing system controllable by an intramolecular quenching based on a molecular-beacon strategy by using photoactive probe oligodeoxynucleotides (ODNs). The photoreaction of the probe ODN containing a photoactive group and a triplet quencher at both ends of the strand was very inefficient when it was in the closed-form ODN (a stem-and-loop structure), whereas irradiation of the open-form ODN hybridized with the complementary DNA resulted in a rapid release of the functional molecule from the ODN (see Figure 1).ODN sequences for the molecule-releasing system were designed according to the molecular-beacon strategy.[1] Phenacyl ester [6][7][8] as a photocleavable group via a triplet excited state, and substituted naphthalene [9,10] as a triplet quencher were incorporated into the 3'-and 5'-ends of the ODN, respectively. The stem of the closed-form ODN keeps a phenacyl ester and a naphthalene ring in close proximity to each other, causing the efficient triplet quenching, as in the case of a molecular beacon. In contrast, when the probe ODN is transformed to the open form by hybridization with target DNA, [1] photocleavage of the phenacyl ester proceeds very smoothly under irradiation, because the photoactive phenacyl ester is far away from the naphthalene quencher.The synthetic route for the functionalized ODN is shown in Scheme 1. The photocleavable phenacyl ester 3, which has both a maleimide functional group to be connected to thiolmodified DNA and a biotin unit as a leaving functional molecule, was prepared from 4-hydroxyacetophenone (1). Naphthalene phosphoramidite, 6, was prepared from 1-naphthylacetic acid (4) in four steps. ODNs containing both a naphthalene unit at the 5' end and a disulfide unit at the 3' end were synthesized by using a DNA synthesizer by a conventional phosphoramidite method. The disulfide group of the given ODNs 7 was reduced to thiol by dithiothreitol, and then coupled with 3 to give ODNs 9 a and 9 b that were equipped with a photoactive group and a quencher at each end.We initially investigated the efficiency of the photoreaction of ODN 9 a by irradiation at 312 nm before and after hybridization with the complementary target DNA 5'-d(CAT-AGGTCTTAACTT)-3'. The irradiation of a solution of 9 a in 15 mm sodium cacodylate (pH 7.0) and 2-propanol (2:1) was Figure 1. Outline for the phototriggered drug release from functionalized oligonucleotides by a molecular beacon strategy. Scheme 1. Reagents and condition...