Controlled mixing of rhodamine B with fluorescent carbon dots derived from β-carotene resulted in... more Controlled mixing of rhodamine B with fluorescent carbon dots derived from β-carotene resulted in a white light emitting mixture that could be used for optical thermometry and Fe3+ ion detection in water.
An easy synthesis of pyridinium fluorochromate (PFC), C5H5NH[CrO3F], was developed by reacting Cr... more An easy synthesis of pyridinium fluorochromate (PFC), C5H5NH[CrO3F], was developed by reacting CrO3 with NH4HF2 in the presence of pyridine. The structure of PFC was determined by X-ray diffraction. The crystals are orthorhombic, space group Cmc21, with a = 8.360(3) Å, b = 7.312(4)Å, c = 12.160(5) Å, V= 743.4(6) Å, and Z = 4; R = 0.0347 for 409
ABSTRACT Graphene oxide is utilized as an environmentally friendly and efficient catalyst for an ... more ABSTRACT Graphene oxide is utilized as an environmentally friendly and efficient catalyst for an ultrasound mediated multi-component coupling reaction that involves aldehyde, amine/ethylacetoacetate and diethyl phosphite/urea, under solvent-free conditions, leading to the bioactive alpha-aminophosphonates and 3,4-dihydropyrimidin-2-ones with excellent yield.
Graphene oxide functions as an effective and reusable carbocatalyst for the multicomponent synthe... more Graphene oxide functions as an effective and reusable carbocatalyst for the multicomponent synthesis of α-aminophosphonates and 3,4-dihydropyrimidinones under solvent-free conditions using ultrasonic irradiation.
Stable crystalline organic ammonium tribromides (OATB), like Me4NBr3, Et4NBr3, Bu4NBr3, cetyltrim... more Stable crystalline organic ammonium tribromides (OATB), like Me4NBr3, Et4NBr3, Bu4NBr3, cetyltrimethylammonium tribromide, PyHBr3, can be readily synthesised from the reaction of the corresponding bromides with V205 and aqueous H202. Typically, TBATB, Bu4NBr3, brominates a variety of organic substrates rather easily under mild conditions. An activated aromatic ring is selectively brominated in the presence of an olefinic double bond.
Au@C-dot nanocomposite functions as a fluorescent turn-on sensor for the selective assay of bioth... more Au@C-dot nanocomposite functions as a fluorescent turn-on sensor for the selective assay of biothiols based on ligand exchange occurring on the Au nanoparticle surface and replacement of C-dots.
The molybdenum(VI) peroxo complex 1, synthesized from the reaction of MoO 3 with H 2 O 2 and 3,5-... more The molybdenum(VI) peroxo complex 1, synthesized from the reaction of MoO 3 with H 2 O 2 and 3,5-dimethylpyrazole (dmpz), selectively oxidizes benzylic C-H bonds of alkylbenzenes to the corresponding alcohols and ketones in moderate to good yields in the presence of H 2 O 2 in acetonitrile under reflux (ca. 80°C).
Higher-valent transition metals react with H 2 O 2 to form peroxometallates, thereby activating t... more Higher-valent transition metals react with H 2 O 2 to form peroxometallates, thereby activating the coordinated peroxide. Based on the reaction profiles of peroxometal species, environmentally acceptable newer syntheses of tetrabutylammonium tribromide (TBATB), Bu 4 NBr 3 , cetyltrimethylammonium tribromide (CTMATB), cetyl(Me) 3 NBr 3 , and tetraethylammonium tribromide (TEATB), Et 4 NBr 3 , have been developed from the reactions of the corresponding quaternary ammonium bromides with H 2 O 2 and a catalytic amount of vanadium(V) or molybdenum(VI). Other transition metals capable of activating peroxide give similar results. The quaternary ammonium tribromides (QATBs) thus produced, especially TBATB and CTMATB, very efficiently act as clean and selective brominating agents for a variety of organic substrates. Very facile bromination of organic substrates, including aromatics, is also possible by tetrabutylammonium bromide (TBAB) Bu 4 NBr, either promoted by V 2 O 5-H 2 O 2 or catalyzed by MoO 4 2-H 2 O 2. The scope of the protocols has been underscored, and the relevance to green chemistry has been highlighted. PEROXOMETALS: THE HUB OF HALIDE OXIDATION It has been a long-known fact that higher-valent transition metals interact with hydrogen peroxide to give very flamboyant reactions owing to the formation of peroxometal complexes in solution [1]. Such reactions are often very complicated particularly because of the formation of a number of complex species with varying compositions at different pH values of the reaction medium [2]. Peroxometal chemistry attracted a renewed interest some years ago especially because of an intrinsic biological interest in [3a-3e] and important catalytic activity [3f-3n] in important organic transformations [3] of peroxometallates. It was during the late 1970s through the early 1980s when solution studies engaged the attention of most of the workers in this field [4] that we began our work on the synthesis of peroxo compounds of metals such as Ti, V, Zr, and UO 2 2+ , for instance. Our attention, in particular, was drawn a little more toward the peroxovanadium compounds leading to successful synthesis of a good number of simple and heteroligand di-and triperoxovanadates [5]. In this process, the importance of pH in the synthesis of such compounds and the scope of their widely varied reactions were realized. Guided by the burgeoning knowledge about the formation and transformation of complexes several reactivity studies were conducted by us [6] and by others [7]. These aspects were very comprehensively reviewed by Butler et al. a few years ago [7]. Our reactivity studies with peroxovanadates(V) involved a number of inorganic substrates [6], including bromide. Meanwhile, there was a breakthrough in this area in the early 1980s consequent upon the isolation of the vanadium-dependent haloperoxidase [3e] (VHPO).
Fig. 1. Flow chart showing the synthesis of a new precursor of Na=Nb O 2 3 ?ெ2H 2 O for conversio... more Fig. 1. Flow chart showing the synthesis of a new precursor of Na=Nb O 2 3 ?ெ2H 2 O for conversion to NaNbO 3 .
An easy synthesis of pyridinium fluorochromate (PFC), C5H5NH[CrO3F], was developed by reacting Cr... more An easy synthesis of pyridinium fluorochromate (PFC), C5H5NH[CrO3F], was developed by reacting CrO3 with NH4HF2 in the presence of pyridine. The structure of PFC was determined by X-ray diffraction. The crystals are orthorhombic, space group Cmc21, with a = 8.360(3) Å, b = 7.312(4)Å, c = 12.160(5) Å, V= 743.4(6) Å, and Z = 4; R = 0.0347 for 409
Carbon dots were used as a reducing agent for the synthesis of Pd nanoparticles coated with ultra... more Carbon dots were used as a reducing agent for the synthesis of Pd nanoparticles coated with ultrathin carbon dot shells of ca. 4 nm. The resulting composite nanoparticles showed high catalytic activity for the Heck and Suzuki coupling reactions. Carbon nanodots (C-dots) constitute a fascinating new class of carbon structures showing size and excitation wavelength dependent photoluminescence (PL) behaviour. 1 With their high photostability and lack of known cytotoxicity, C-dots are considered to be a green alternative to fluorescent semiconductor nanoparticles and have shown potential use in optical detection, bioimaging, light emitting diodes, fluorescent ink and photocatalysts. 2 The presence of carboxylic and hydroxyl moieties at their surface endows excellent water solubility as well as biocompatibility. This optimism has led to increased interest recently in developing methods for their synthesis, involving approaches such as laser ablation, pyrolysis, wet oxidation, ultra-sound and microwave assisted synthesis, hydrothermal synthesis and electrochemical etching. 1,3 Several natural sources such as carbohydrates, proteins, amino acids, biopolymers etc. have been used for the synthesis of C-dots. 4 Recently there have been several reports on C-dots derived from food products such as orange juice, banana juice, soy milk, egg, sugar, bread, jaggery etc. 5 However the potential of C-dots remains relatively unexplored as compared to the other carbon based counterparts such as carbon nanotubes and graphene oxide. Composites of metallic nanoparticles (NPs) with carbonaceous materials have shown tremendous technological importance, ranging from catalysis, sensing, fuel cells and optoelectronics. 6 Specifically in catalysis, metal nanoparticles embedded in carbon nanotubes and graphene as supports act as excellent heterogeneous catalysts for organic † Electronic supplementary information (ESI) available: Experimental section and supporting figures. See
Controlled mixing of rhodamine B with fluorescent carbon dots derived from β-carotene resulted in... more Controlled mixing of rhodamine B with fluorescent carbon dots derived from β-carotene resulted in a white light emitting mixture that could be used for optical thermometry and Fe3+ ion detection in water.
An easy synthesis of pyridinium fluorochromate (PFC), C5H5NH[CrO3F], was developed by reacting Cr... more An easy synthesis of pyridinium fluorochromate (PFC), C5H5NH[CrO3F], was developed by reacting CrO3 with NH4HF2 in the presence of pyridine. The structure of PFC was determined by X-ray diffraction. The crystals are orthorhombic, space group Cmc21, with a = 8.360(3) Å, b = 7.312(4)Å, c = 12.160(5) Å, V= 743.4(6) Å, and Z = 4; R = 0.0347 for 409
ABSTRACT Graphene oxide is utilized as an environmentally friendly and efficient catalyst for an ... more ABSTRACT Graphene oxide is utilized as an environmentally friendly and efficient catalyst for an ultrasound mediated multi-component coupling reaction that involves aldehyde, amine/ethylacetoacetate and diethyl phosphite/urea, under solvent-free conditions, leading to the bioactive alpha-aminophosphonates and 3,4-dihydropyrimidin-2-ones with excellent yield.
Graphene oxide functions as an effective and reusable carbocatalyst for the multicomponent synthe... more Graphene oxide functions as an effective and reusable carbocatalyst for the multicomponent synthesis of α-aminophosphonates and 3,4-dihydropyrimidinones under solvent-free conditions using ultrasonic irradiation.
Stable crystalline organic ammonium tribromides (OATB), like Me4NBr3, Et4NBr3, Bu4NBr3, cetyltrim... more Stable crystalline organic ammonium tribromides (OATB), like Me4NBr3, Et4NBr3, Bu4NBr3, cetyltrimethylammonium tribromide, PyHBr3, can be readily synthesised from the reaction of the corresponding bromides with V205 and aqueous H202. Typically, TBATB, Bu4NBr3, brominates a variety of organic substrates rather easily under mild conditions. An activated aromatic ring is selectively brominated in the presence of an olefinic double bond.
Au@C-dot nanocomposite functions as a fluorescent turn-on sensor for the selective assay of bioth... more Au@C-dot nanocomposite functions as a fluorescent turn-on sensor for the selective assay of biothiols based on ligand exchange occurring on the Au nanoparticle surface and replacement of C-dots.
The molybdenum(VI) peroxo complex 1, synthesized from the reaction of MoO 3 with H 2 O 2 and 3,5-... more The molybdenum(VI) peroxo complex 1, synthesized from the reaction of MoO 3 with H 2 O 2 and 3,5-dimethylpyrazole (dmpz), selectively oxidizes benzylic C-H bonds of alkylbenzenes to the corresponding alcohols and ketones in moderate to good yields in the presence of H 2 O 2 in acetonitrile under reflux (ca. 80°C).
Higher-valent transition metals react with H 2 O 2 to form peroxometallates, thereby activating t... more Higher-valent transition metals react with H 2 O 2 to form peroxometallates, thereby activating the coordinated peroxide. Based on the reaction profiles of peroxometal species, environmentally acceptable newer syntheses of tetrabutylammonium tribromide (TBATB), Bu 4 NBr 3 , cetyltrimethylammonium tribromide (CTMATB), cetyl(Me) 3 NBr 3 , and tetraethylammonium tribromide (TEATB), Et 4 NBr 3 , have been developed from the reactions of the corresponding quaternary ammonium bromides with H 2 O 2 and a catalytic amount of vanadium(V) or molybdenum(VI). Other transition metals capable of activating peroxide give similar results. The quaternary ammonium tribromides (QATBs) thus produced, especially TBATB and CTMATB, very efficiently act as clean and selective brominating agents for a variety of organic substrates. Very facile bromination of organic substrates, including aromatics, is also possible by tetrabutylammonium bromide (TBAB) Bu 4 NBr, either promoted by V 2 O 5-H 2 O 2 or catalyzed by MoO 4 2-H 2 O 2. The scope of the protocols has been underscored, and the relevance to green chemistry has been highlighted. PEROXOMETALS: THE HUB OF HALIDE OXIDATION It has been a long-known fact that higher-valent transition metals interact with hydrogen peroxide to give very flamboyant reactions owing to the formation of peroxometal complexes in solution [1]. Such reactions are often very complicated particularly because of the formation of a number of complex species with varying compositions at different pH values of the reaction medium [2]. Peroxometal chemistry attracted a renewed interest some years ago especially because of an intrinsic biological interest in [3a-3e] and important catalytic activity [3f-3n] in important organic transformations [3] of peroxometallates. It was during the late 1970s through the early 1980s when solution studies engaged the attention of most of the workers in this field [4] that we began our work on the synthesis of peroxo compounds of metals such as Ti, V, Zr, and UO 2 2+ , for instance. Our attention, in particular, was drawn a little more toward the peroxovanadium compounds leading to successful synthesis of a good number of simple and heteroligand di-and triperoxovanadates [5]. In this process, the importance of pH in the synthesis of such compounds and the scope of their widely varied reactions were realized. Guided by the burgeoning knowledge about the formation and transformation of complexes several reactivity studies were conducted by us [6] and by others [7]. These aspects were very comprehensively reviewed by Butler et al. a few years ago [7]. Our reactivity studies with peroxovanadates(V) involved a number of inorganic substrates [6], including bromide. Meanwhile, there was a breakthrough in this area in the early 1980s consequent upon the isolation of the vanadium-dependent haloperoxidase [3e] (VHPO).
Fig. 1. Flow chart showing the synthesis of a new precursor of Na=Nb O 2 3 ?ெ2H 2 O for conversio... more Fig. 1. Flow chart showing the synthesis of a new precursor of Na=Nb O 2 3 ?ெ2H 2 O for conversion to NaNbO 3 .
An easy synthesis of pyridinium fluorochromate (PFC), C5H5NH[CrO3F], was developed by reacting Cr... more An easy synthesis of pyridinium fluorochromate (PFC), C5H5NH[CrO3F], was developed by reacting CrO3 with NH4HF2 in the presence of pyridine. The structure of PFC was determined by X-ray diffraction. The crystals are orthorhombic, space group Cmc21, with a = 8.360(3) Å, b = 7.312(4)Å, c = 12.160(5) Å, V= 743.4(6) Å, and Z = 4; R = 0.0347 for 409
Carbon dots were used as a reducing agent for the synthesis of Pd nanoparticles coated with ultra... more Carbon dots were used as a reducing agent for the synthesis of Pd nanoparticles coated with ultrathin carbon dot shells of ca. 4 nm. The resulting composite nanoparticles showed high catalytic activity for the Heck and Suzuki coupling reactions. Carbon nanodots (C-dots) constitute a fascinating new class of carbon structures showing size and excitation wavelength dependent photoluminescence (PL) behaviour. 1 With their high photostability and lack of known cytotoxicity, C-dots are considered to be a green alternative to fluorescent semiconductor nanoparticles and have shown potential use in optical detection, bioimaging, light emitting diodes, fluorescent ink and photocatalysts. 2 The presence of carboxylic and hydroxyl moieties at their surface endows excellent water solubility as well as biocompatibility. This optimism has led to increased interest recently in developing methods for their synthesis, involving approaches such as laser ablation, pyrolysis, wet oxidation, ultra-sound and microwave assisted synthesis, hydrothermal synthesis and electrochemical etching. 1,3 Several natural sources such as carbohydrates, proteins, amino acids, biopolymers etc. have been used for the synthesis of C-dots. 4 Recently there have been several reports on C-dots derived from food products such as orange juice, banana juice, soy milk, egg, sugar, bread, jaggery etc. 5 However the potential of C-dots remains relatively unexplored as compared to the other carbon based counterparts such as carbon nanotubes and graphene oxide. Composites of metallic nanoparticles (NPs) with carbonaceous materials have shown tremendous technological importance, ranging from catalysis, sensing, fuel cells and optoelectronics. 6 Specifically in catalysis, metal nanoparticles embedded in carbon nanotubes and graphene as supports act as excellent heterogeneous catalysts for organic † Electronic supplementary information (ESI) available: Experimental section and supporting figures. See
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