The Mn(II)-mediated transformation of 2-cyanopyrimidine to methylimidate in the presence of inorg... more The Mn(II)-mediated transformation of 2-cyanopyrimidine to methylimidate in the presence of inorganic azide is proven through isolation and structural characterization of a metal complex. Though the reaction conditions are favorable for a "click" reaction leading to the formation of tetrazole, as evidenced from recent studies, we are astonished to see the formation of methylimidate in MeOH instead of tetrazole, which is supposed to form only in the presence of catalytic amount of corresponding alkoxide ion as base. The catalytic nature of this transformation reaction was confirmed by performing these experiments under catalytic conditions and analyzing the products using liquid chromatography-mass spectrometry techniques, which clearly showed ∼96% and ∼60% selectivity of methylimidate along with almost 100% conversion in the presence of Mn(II) and Co(II) as catalysts, respectively. In absence or presence of other metal ions like Cu(II), Ni(II), Fe(II), Zn(II), etc. only te...
In the present work, two compartmental ligands H2L(1) and H2L(2) were in situ generated during th... more In the present work, two compartmental ligands H2L(1) and H2L(2) were in situ generated during the syntheses of new trinuclear complexes, [Cu2Ni(L(1))(2,2'-bpy)2(NO3)2][ClO4]2 (), [Cu3(L(2))(NO3)2][ClO4]2 (), and [Cu3(L(2))(NCS)2(NO3)](+) that co-crystallize in with a [Cu6(L(2))2Na2(NO3)6(NCS)4] unit to give the final molecular formula [Cu6(L(2))2Na2(NO3)6(NCS)4][Cu3(L(2))(NCS)2(NO3)]2(NO3)2·5H2O (). The magnetic property studies of revealed weak Cu(II)-Cu(II) ferromagnetic interactions in compound (JCu-Cu/kB = +1.4(1) K) and (JCu-Cu/kB = +1.6) while in intranuclear Cu(II)-Ni(II)-Cu(II) compound , the magnetic coupling between two Cu(II) ions is switched off by the diamagnetic square planar Ni(II) bridge. The catalytic epoxidation of two olefins, namely styrene and cyclooctene, by tert-BuOOH (TBHP) was also explored in the presence of a catalytic amount of , or in MeCN. For styrene oxidation, exhibited ∼57% styrene epoxide selectively (conversion ∼37%) with a TON of about 925 along with benzaldehyde (∼43%), whereas exhibited conversion up to ∼63% (TON ∼ 1575) with a good selectivity towards epoxide (∼71%). For compound , this conversion is more important (TON ∼ 8108) probably due to the presence of more active sites involved in the epoxidation. The concerted path was found to be operative for styrene oxidation while a radical path was suggested for the oxidation of cyclooctene.
ABSTRACT This study describes the solvent-dependent conversion of an oxime under identical reacti... more ABSTRACT This study describes the solvent-dependent conversion of an oxime under identical reaction conditions ([Cu(bipy)Cl2]/NaN3/5-Br-H2salox/TEA=1:2:1:2 molar ratio; bipy=2,2′-bipyridyl, 5-Br-H2salox=5-bromosalicylaldoxime, TEA=triethylamine), but in different solvents. In DMSO/CH2Cl2 (2:1 v/v) only tetrazole is formed, whereas iminoacylation in MeCN and simple complexation takes place in MeOH. The formed tetrazole and iminoacylated ligands further undergo complexation with metal ions, as evidenced from single-crystal X-ray diffraction studies and ESI-MS analyses. Mechanistic models have been proposed in which coordination-assisted bonding of sodium azide across the CNOH double bond occurs to form a tetrazole and oxime–MeCN coupling forms an iminoacylated ligand. The former is a catalytic reaction, as evidenced from a turnover number of approximately 50, whereas the latter is stoichiometric in nature. This is the first report to demonstrate the dependence of solvent polarity on oxime transformation reactions through structural elucidation.
The generation and study of metal-hydroperoxo/metal-peroxo (LCu(II)-OOH or LCu(II)-OO˙) complexes... more The generation and study of metal-hydroperoxo/metal-peroxo (LCu(II)-OOH or LCu(II)-OO˙) complexes is a fascinating area of research of many chemical and biochemical researchers, because of their involvement as active intermediates in many biological and industrial catalytic oxidation processes. For this purpose we have designed a bulky hexa-coordinating ligand with potential N4O2 donor atoms which could provide an opportunity to synthesize a mononuclear Cu(II) complex with an aim to utilize it in the catalytic oxidation of aromatic hydrocarbons by an environmentally benign oxidant, H2O2. The Cu(II) complex (1) was structurally characterized and found to have square-planar geometry with the two pyrazolyl groups remaining in dangling mode. A novel mononuclear complex [Et3NH][LCu(II)-OOH] (2) was found to form in the reaction between 1 and H2O2 in the presence of Et3N. The presence of this dangling groups favours the stability of hydroperoxo species, [LCu-OOH](-) (2) through H-bonding with the coordinated phenoxo oxygen atom, which was confirmed by ESI-MS(+) and MS(-) (m/z) mass analysis and DFT calculations. This complex was found to be thermally stable at room temperature [k(d) = (5.67 ± 0.03) × 10(-5) s(-1) at 25 °C] and may be due to the formation of O-O-H···O(phenoxo) H-bonding as delineated by the DFT calculations. Complex 1 was found to be an efficient catalyst for the oxidation of aromatic hydrocarbons to the corresponding aldehyde and alcohol in 2:1 mole ratio with TON ~300.
ABSTRACT This study describes the solvent-dependent conversion of an oxime under identical reacti... more ABSTRACT This study describes the solvent-dependent conversion of an oxime under identical reaction conditions ([Cu(bipy)Cl2]/NaN3/5-Br-H2salox/TEA=1:2:1:2 molar ratio; bipy=2,2′-bipyridyl, 5-Br-H2salox=5-bromosalicylaldoxime, TEA=triethylamine), but in different solvents. In DMSO/CH2Cl2 (2:1 v/v) only tetrazole is formed, whereas iminoacylation in MeCN and simple complexation takes place in MeOH. The formed tetrazole and iminoacylated ligands further undergo complexation with metal ions, as evidenced from single-crystal X-ray diffraction studies and ESI-MS analyses. Mechanistic models have been proposed in which coordination-assisted bonding of sodium azide across the CNOH double bond occurs to form a tetrazole and oxime–MeCN coupling forms an iminoacylated ligand. The former is a catalytic reaction, as evidenced from a turnover number of approximately 50, whereas the latter is stoichiometric in nature. This is the first report to demonstrate the dependence of solvent polarity on oxime transformation reactions through structural elucidation.
ABSTRACT A mononuclear square planar complex [CuII(Lf )] (1) was synthesized and structurally cha... more ABSTRACT A mononuclear square planar complex [CuII(Lf )] (1) was synthesized and structurally characterized by single crystal X-ray diffraction studies. Though we have started with the Schiff base H2La with two –CH2OH groups for complexation with Cu2+, the final product appears to have two formyl groups where two carbinols were oxidized during the course of the reaction with Cu2+. It opens up the possibility of using this complex as a precursor for condensation with suitable amines to give symmetric/asymmetric cyclic/acyclic Schiff base complexes. Systematic studies on catalytic oxidation of aromatic hydrocarbons like toluene and xylenes by an environmentally benign oxidant, H2O2 in the presence of 1 as a catalyst reveals that it is an efficient catalyst leading to the formation of the corresponding alcohol as the major product with TON �300 and alcohol selectivity of �72%.
... cation layer' templated by an Anderson polyoxometallate. Mahammad Ali, Daipayan Dutta, S... more ... cation layer' templated by an Anderson polyoxometallate. Mahammad Ali, Daipayan Dutta, Surajit Biswas, Jaromir Marek and Atish Dipankar Jana CrystEngComm, 2009, 11, 2608-2610. DOI: 10.1039/B910732K , Communication. ...
Hand, foot and mouth disease (HFMD) is a relatively rare viral illness, mainly affecting infants ... more Hand, foot and mouth disease (HFMD) is a relatively rare viral illness, mainly affecting infants and children. The disease causes fever and a distinctive rash involving the mouth and skin. HFMD is caused by members of the non-polio enterovirus group of viruses,[1] ...
Immune reconstitution inflammatory syndrome describes a collection of inflammatory disorders asso... more Immune reconstitution inflammatory syndrome describes a collection of inflammatory disorders associated with paradoxical deterioration of various pre-existing processes following start of highly active antiretroviral therapy (HAART) in human immunodeficiency virus ...
The Mn(II)-mediated transformation of 2-cyanopyrimidine to methylimidate in the presence of inorg... more The Mn(II)-mediated transformation of 2-cyanopyrimidine to methylimidate in the presence of inorganic azide is proven through isolation and structural characterization of a metal complex. Though the reaction conditions are favorable for a "click" reaction leading to the formation of tetrazole, as evidenced from recent studies, we are astonished to see the formation of methylimidate in MeOH instead of tetrazole, which is supposed to form only in the presence of catalytic amount of corresponding alkoxide ion as base. The catalytic nature of this transformation reaction was confirmed by performing these experiments under catalytic conditions and analyzing the products using liquid chromatography-mass spectrometry techniques, which clearly showed ∼96% and ∼60% selectivity of methylimidate along with almost 100% conversion in the presence of Mn(II) and Co(II) as catalysts, respectively. In absence or presence of other metal ions like Cu(II), Ni(II), Fe(II), Zn(II), etc. only te...
In the present work, two compartmental ligands H2L(1) and H2L(2) were in situ generated during th... more In the present work, two compartmental ligands H2L(1) and H2L(2) were in situ generated during the syntheses of new trinuclear complexes, [Cu2Ni(L(1))(2,2'-bpy)2(NO3)2][ClO4]2 (), [Cu3(L(2))(NO3)2][ClO4]2 (), and [Cu3(L(2))(NCS)2(NO3)](+) that co-crystallize in with a [Cu6(L(2))2Na2(NO3)6(NCS)4] unit to give the final molecular formula [Cu6(L(2))2Na2(NO3)6(NCS)4][Cu3(L(2))(NCS)2(NO3)]2(NO3)2·5H2O (). The magnetic property studies of revealed weak Cu(II)-Cu(II) ferromagnetic interactions in compound (JCu-Cu/kB = +1.4(1) K) and (JCu-Cu/kB = +1.6) while in intranuclear Cu(II)-Ni(II)-Cu(II) compound , the magnetic coupling between two Cu(II) ions is switched off by the diamagnetic square planar Ni(II) bridge. The catalytic epoxidation of two olefins, namely styrene and cyclooctene, by tert-BuOOH (TBHP) was also explored in the presence of a catalytic amount of , or in MeCN. For styrene oxidation, exhibited ∼57% styrene epoxide selectively (conversion ∼37%) with a TON of about 925 along with benzaldehyde (∼43%), whereas exhibited conversion up to ∼63% (TON ∼ 1575) with a good selectivity towards epoxide (∼71%). For compound , this conversion is more important (TON ∼ 8108) probably due to the presence of more active sites involved in the epoxidation. The concerted path was found to be operative for styrene oxidation while a radical path was suggested for the oxidation of cyclooctene.
ABSTRACT This study describes the solvent-dependent conversion of an oxime under identical reacti... more ABSTRACT This study describes the solvent-dependent conversion of an oxime under identical reaction conditions ([Cu(bipy)Cl2]/NaN3/5-Br-H2salox/TEA=1:2:1:2 molar ratio; bipy=2,2′-bipyridyl, 5-Br-H2salox=5-bromosalicylaldoxime, TEA=triethylamine), but in different solvents. In DMSO/CH2Cl2 (2:1 v/v) only tetrazole is formed, whereas iminoacylation in MeCN and simple complexation takes place in MeOH. The formed tetrazole and iminoacylated ligands further undergo complexation with metal ions, as evidenced from single-crystal X-ray diffraction studies and ESI-MS analyses. Mechanistic models have been proposed in which coordination-assisted bonding of sodium azide across the CNOH double bond occurs to form a tetrazole and oxime–MeCN coupling forms an iminoacylated ligand. The former is a catalytic reaction, as evidenced from a turnover number of approximately 50, whereas the latter is stoichiometric in nature. This is the first report to demonstrate the dependence of solvent polarity on oxime transformation reactions through structural elucidation.
The generation and study of metal-hydroperoxo/metal-peroxo (LCu(II)-OOH or LCu(II)-OO˙) complexes... more The generation and study of metal-hydroperoxo/metal-peroxo (LCu(II)-OOH or LCu(II)-OO˙) complexes is a fascinating area of research of many chemical and biochemical researchers, because of their involvement as active intermediates in many biological and industrial catalytic oxidation processes. For this purpose we have designed a bulky hexa-coordinating ligand with potential N4O2 donor atoms which could provide an opportunity to synthesize a mononuclear Cu(II) complex with an aim to utilize it in the catalytic oxidation of aromatic hydrocarbons by an environmentally benign oxidant, H2O2. The Cu(II) complex (1) was structurally characterized and found to have square-planar geometry with the two pyrazolyl groups remaining in dangling mode. A novel mononuclear complex [Et3NH][LCu(II)-OOH] (2) was found to form in the reaction between 1 and H2O2 in the presence of Et3N. The presence of this dangling groups favours the stability of hydroperoxo species, [LCu-OOH](-) (2) through H-bonding with the coordinated phenoxo oxygen atom, which was confirmed by ESI-MS(+) and MS(-) (m/z) mass analysis and DFT calculations. This complex was found to be thermally stable at room temperature [k(d) = (5.67 ± 0.03) × 10(-5) s(-1) at 25 °C] and may be due to the formation of O-O-H···O(phenoxo) H-bonding as delineated by the DFT calculations. Complex 1 was found to be an efficient catalyst for the oxidation of aromatic hydrocarbons to the corresponding aldehyde and alcohol in 2:1 mole ratio with TON ~300.
ABSTRACT This study describes the solvent-dependent conversion of an oxime under identical reacti... more ABSTRACT This study describes the solvent-dependent conversion of an oxime under identical reaction conditions ([Cu(bipy)Cl2]/NaN3/5-Br-H2salox/TEA=1:2:1:2 molar ratio; bipy=2,2′-bipyridyl, 5-Br-H2salox=5-bromosalicylaldoxime, TEA=triethylamine), but in different solvents. In DMSO/CH2Cl2 (2:1 v/v) only tetrazole is formed, whereas iminoacylation in MeCN and simple complexation takes place in MeOH. The formed tetrazole and iminoacylated ligands further undergo complexation with metal ions, as evidenced from single-crystal X-ray diffraction studies and ESI-MS analyses. Mechanistic models have been proposed in which coordination-assisted bonding of sodium azide across the CNOH double bond occurs to form a tetrazole and oxime–MeCN coupling forms an iminoacylated ligand. The former is a catalytic reaction, as evidenced from a turnover number of approximately 50, whereas the latter is stoichiometric in nature. This is the first report to demonstrate the dependence of solvent polarity on oxime transformation reactions through structural elucidation.
ABSTRACT A mononuclear square planar complex [CuII(Lf )] (1) was synthesized and structurally cha... more ABSTRACT A mononuclear square planar complex [CuII(Lf )] (1) was synthesized and structurally characterized by single crystal X-ray diffraction studies. Though we have started with the Schiff base H2La with two –CH2OH groups for complexation with Cu2+, the final product appears to have two formyl groups where two carbinols were oxidized during the course of the reaction with Cu2+. It opens up the possibility of using this complex as a precursor for condensation with suitable amines to give symmetric/asymmetric cyclic/acyclic Schiff base complexes. Systematic studies on catalytic oxidation of aromatic hydrocarbons like toluene and xylenes by an environmentally benign oxidant, H2O2 in the presence of 1 as a catalyst reveals that it is an efficient catalyst leading to the formation of the corresponding alcohol as the major product with TON �300 and alcohol selectivity of �72%.
... cation layer' templated by an Anderson polyoxometallate. Mahammad Ali, Daipayan Dutta, S... more ... cation layer' templated by an Anderson polyoxometallate. Mahammad Ali, Daipayan Dutta, Surajit Biswas, Jaromir Marek and Atish Dipankar Jana CrystEngComm, 2009, 11, 2608-2610. DOI: 10.1039/B910732K , Communication. ...
Hand, foot and mouth disease (HFMD) is a relatively rare viral illness, mainly affecting infants ... more Hand, foot and mouth disease (HFMD) is a relatively rare viral illness, mainly affecting infants and children. The disease causes fever and a distinctive rash involving the mouth and skin. HFMD is caused by members of the non-polio enterovirus group of viruses,[1] ...
Immune reconstitution inflammatory syndrome describes a collection of inflammatory disorders asso... more Immune reconstitution inflammatory syndrome describes a collection of inflammatory disorders associated with paradoxical deterioration of various pre-existing processes following start of highly active antiretroviral therapy (HAART) in human immunodeficiency virus ...
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