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Sanjay K Mandal - One of the best experts on this subject based on the ideXlab platform.
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a Primary Amide functionalized heterogeneous catalyst for the synthesis of coumarin 3 carboxylic acids via a tandem reaction
Inorganic Chemistry, 2020Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:A crystalline Primary Amide-based bifunctional heterogeneous catalyst, {[Cd2(2-BPXG)(Fum)2(H2O)2]·2H2O}n (1) (where, 2-BPXG = 2,2′-((1,4-phenylenebis(methylene))bis((pyridin-2-ylmethyl)azanediyl)) ...
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design and development of a heterogeneous catalyst for the michael addition of malononitrile to 2 enoylpyridines influence of the Primary Amide decorated framework on catalytic activity and selectivity
Inorganic Chemistry, 2019Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:For the Michael addition of malononitrile to 2-enoylpyridines, we report the first heterogeneous catalyst, {[Zn2(2-bpbg)(fum)2]·4H2O·EtOH}n (1) (where 2-bpbg = N,N'-bis(2-pyridylmethyl)-1,4-diaminobutane-N,N'-diacetAmide and where fum = fumarate), which is decorated with Primary Amide side arms. It is prepared from the self-assembly of starting materials in methanol at room temperature (27 °C). Using 3 mol % of 1, greater than 99% conversion of substrates to the desired product is achieved within 1 h at 27 °C. Moreover, the catalyst is recyclable up to five consecutive cycles without significant loss of activity and structural integrity. In order to show the uniqueness of 1, the reaction under the same conditions was catalyzed by a fully pyridyl-based (i.e., having no Primary Amide group) and isostructural analogue, {[Zn2(tpbn)(fum)2]·6H2O}n (2) (where tpbn = N',N',N″,N''-tetrakis(pyridin-2-ylmethyl)butane-1,4-diamine), but resulting only in 7% conversion. This demonstrates the selective catalytic activity of 1 over 2 due to the presence of the Primary Amide side arms, where it acts as a bifunctional catalyst through the excellent hydrogen bond donating (HBD) ability in this reaction. For providing an insight into its mechanism of action involving a cyclic seven-membered hydrogen bonding motif, the reaction was performed with freshly synthesized (E)-chalcone, 3-enoylpyridine, and 4-enoylpyridine instead of 2-enoylpyridine under the same conditions. In the case of (E)-chalcone no product formation was observed, whereas for 3-enoylpyridine and 4-enoylpyridine the conversions were only 29% and 25%, respectively. Both 1 and 2 were fully characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis, and single-crystal and powder X-ray diffraction.
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novel Primary Amide based cationic metal complexes green synthesis crystal structures hirshfeld surface analysis and solvent free cyanosilylation reaction
Dalton Transactions, 2019Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:A new symmetrical and flexible Primary Amide functionalized ligand, 2,2′-(ethane-1,2-diylbis((pyridin-2-ylmethyl)azanediyl))diacetAmide (2-BPEG), has been synthesized and structurally characterized. Using this multidentate ligand, four novel metal complexes, namely [Cu(2-BPEG)](ClO4)2·0.5H2O (1), [Zn(2-BPEG)](ClO4)2 (2), [Zn(2-BPEG)](ZnCl4)·H2O (3) and [Cd(2-BPEG)(H2O)](ClO4)2·H2O (4), have been synthesized under ambient conditions and characterized by elemental, spectroscopic and thermal analysis, and single and powder X-ray diffraction. Complexes 1–3 are hexacoordinated with an N4O2 donor set (provided by the hexadentate 2-BPEG ligand), while complex 4 is heptacoordinated with an additional coordinated water molecule. In all cases, the 2-BPEG ligand acts as a hexadentate ligand. A change in the starting metal salt has resulted in the formation of 2 and 3 with different tetrahedral anions, ClO4− and ZnCl4−, respectively. This has provided an opportunity to showcase anion-directed supramolecular networks for these compounds. Compounds 1, 2 and 4 with perchlorate anions show similar and comparable intermolecular interactions in their 3D networks. On the other hand, the supramolecular self-assembly of 3 is dominated by a variety of intermolecular interactions such as C–H⋯Cl, N–H⋯Cl, O–H⋯Cl and C–H⋯O due to the presence of a tetrachlorozincate(II) ion. Moreover, the role of weak intermolecular interactions in the crystal packing has been analysed and quantified using Hirshfeld surface analysis. Furthermore, compound 4 exhibiting an open Lewis acid site has been found to be a very efficient and recyclable heterogeneous catalyst for the solvent-free cyanosilylation of various aldehydes with trimethylsilyl cyanide (TMSCN) producing the corresponding trimethylsilyl ether in high yields.
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design of a Primary Amide functionalized highly efficient and recyclable hydrogen bond donating heterogeneous catalyst for the friedel crafts alkylation of indoles with β nitrostyrenes
ACS Catalysis, 2019Co-Authors: Datta Markad, Sanjay K MandalAbstract:A Primary-Amide-functionalized metal organic framework, {[Zn2(2-BQBG)(BDC)2]·10H2O}n (1) (in which 2-BQBG = 2,2′-(butane-1,4-diylbis((quinolin-2-ylmethyl)azanediyl))diacetAmide and BDC = 1,4-benzenedicarboxylate), has been found to be a highly efficient hydrogen-bond-donating (HBD) heterogeneous catalyst for the Friedel–Crafts alkylation of indole with β-nitrostyrenes under mild reaction conditions (catalyst loading: 3 mol %; reaction conditions: 12 h and 35 °C). The catalyst can be easily separated from the reaction mixture by simple filtration for its reuse in four consecutive cycles with very little loss of activity. More importantly, the one-pot room temperature synthesis of 1 from the self-assembly of Zn(OAc)2·2H2O and 2-BQBG (in CH3OH) and Na2BDC (in H2O) can be easily scaled-up for obtaining multigram quantities in few hours. In order to showcase its versatility, the substrate scope included a variety of substituted indoles and different β-nitrostyrene derivatives forming the desired products in go...
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Design of a Primary-Amide-Functionalized Highly Efficient and Recyclable Hydrogen-Bond-Donating Heterogeneous Catalyst for the Friedel–Crafts Alkylation of Indoles with β‑Nitrostyrenes
2019Co-Authors: Datta Markad, Sanjay K MandalAbstract:A Primary-Amide-functionalized metal organic framework, {[Zn2(2-BQBG)(BDC)2]·10H2O}n (1) (in which 2-BQBG = 2,2′-(butane-1,4-diylbis((quinolin-2-ylmethyl)azanediyl))diacetAmide and BDC = 1,4-benzenedicarboxylate), has been found to be a highly efficient hydrogen-bond-donating (HBD) heterogeneous catalyst for the Friedel–Crafts alkylation of indole with β-nitrostyrenes under mild reaction conditions (catalyst loading: 3 mol %; reaction conditions: 12 h and 35 °C). The catalyst can be easily separated from the reaction mixture by simple filtration for its reuse in four consecutive cycles with very little loss of activity. More importantly, the one-pot room temperature synthesis of 1 from the self-assembly of Zn(OAc)2·2H2O and 2-BQBG (in CH3OH) and Na2BDC (in H2O) can be easily scaled-up for obtaining multigram quantities in few hours. In order to showcase its versatility, the substrate scope included a variety of substituted indoles and different β-nitrostyrene derivatives forming the desired products in good to high yields. For its catalytic action, a direct proof for the key step in the proposed mechanism, based on the interaction of a Primary-Amide group in the 2-BQBG ligand with the nitro group of β-nitrostyrene through hydrogen bonding, is provided from the enhancement in fluorescence intensity of 1 upon successive addition of β-nitrostyrene
Datta Markad - One of the best experts on this subject based on the ideXlab platform.
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a Primary Amide functionalized heterogeneous catalyst for the synthesis of coumarin 3 carboxylic acids via a tandem reaction
Inorganic Chemistry, 2020Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:A crystalline Primary Amide-based bifunctional heterogeneous catalyst, {[Cd2(2-BPXG)(Fum)2(H2O)2]·2H2O}n (1) (where, 2-BPXG = 2,2′-((1,4-phenylenebis(methylene))bis((pyridin-2-ylmethyl)azanediyl)) ...
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design and development of a heterogeneous catalyst for the michael addition of malononitrile to 2 enoylpyridines influence of the Primary Amide decorated framework on catalytic activity and selectivity
Inorganic Chemistry, 2019Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:For the Michael addition of malononitrile to 2-enoylpyridines, we report the first heterogeneous catalyst, {[Zn2(2-bpbg)(fum)2]·4H2O·EtOH}n (1) (where 2-bpbg = N,N'-bis(2-pyridylmethyl)-1,4-diaminobutane-N,N'-diacetAmide and where fum = fumarate), which is decorated with Primary Amide side arms. It is prepared from the self-assembly of starting materials in methanol at room temperature (27 °C). Using 3 mol % of 1, greater than 99% conversion of substrates to the desired product is achieved within 1 h at 27 °C. Moreover, the catalyst is recyclable up to five consecutive cycles without significant loss of activity and structural integrity. In order to show the uniqueness of 1, the reaction under the same conditions was catalyzed by a fully pyridyl-based (i.e., having no Primary Amide group) and isostructural analogue, {[Zn2(tpbn)(fum)2]·6H2O}n (2) (where tpbn = N',N',N″,N''-tetrakis(pyridin-2-ylmethyl)butane-1,4-diamine), but resulting only in 7% conversion. This demonstrates the selective catalytic activity of 1 over 2 due to the presence of the Primary Amide side arms, where it acts as a bifunctional catalyst through the excellent hydrogen bond donating (HBD) ability in this reaction. For providing an insight into its mechanism of action involving a cyclic seven-membered hydrogen bonding motif, the reaction was performed with freshly synthesized (E)-chalcone, 3-enoylpyridine, and 4-enoylpyridine instead of 2-enoylpyridine under the same conditions. In the case of (E)-chalcone no product formation was observed, whereas for 3-enoylpyridine and 4-enoylpyridine the conversions were only 29% and 25%, respectively. Both 1 and 2 were fully characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis, and single-crystal and powder X-ray diffraction.
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novel Primary Amide based cationic metal complexes green synthesis crystal structures hirshfeld surface analysis and solvent free cyanosilylation reaction
Dalton Transactions, 2019Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:A new symmetrical and flexible Primary Amide functionalized ligand, 2,2′-(ethane-1,2-diylbis((pyridin-2-ylmethyl)azanediyl))diacetAmide (2-BPEG), has been synthesized and structurally characterized. Using this multidentate ligand, four novel metal complexes, namely [Cu(2-BPEG)](ClO4)2·0.5H2O (1), [Zn(2-BPEG)](ClO4)2 (2), [Zn(2-BPEG)](ZnCl4)·H2O (3) and [Cd(2-BPEG)(H2O)](ClO4)2·H2O (4), have been synthesized under ambient conditions and characterized by elemental, spectroscopic and thermal analysis, and single and powder X-ray diffraction. Complexes 1–3 are hexacoordinated with an N4O2 donor set (provided by the hexadentate 2-BPEG ligand), while complex 4 is heptacoordinated with an additional coordinated water molecule. In all cases, the 2-BPEG ligand acts as a hexadentate ligand. A change in the starting metal salt has resulted in the formation of 2 and 3 with different tetrahedral anions, ClO4− and ZnCl4−, respectively. This has provided an opportunity to showcase anion-directed supramolecular networks for these compounds. Compounds 1, 2 and 4 with perchlorate anions show similar and comparable intermolecular interactions in their 3D networks. On the other hand, the supramolecular self-assembly of 3 is dominated by a variety of intermolecular interactions such as C–H⋯Cl, N–H⋯Cl, O–H⋯Cl and C–H⋯O due to the presence of a tetrachlorozincate(II) ion. Moreover, the role of weak intermolecular interactions in the crystal packing has been analysed and quantified using Hirshfeld surface analysis. Furthermore, compound 4 exhibiting an open Lewis acid site has been found to be a very efficient and recyclable heterogeneous catalyst for the solvent-free cyanosilylation of various aldehydes with trimethylsilyl cyanide (TMSCN) producing the corresponding trimethylsilyl ether in high yields.
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design of a Primary Amide functionalized highly efficient and recyclable hydrogen bond donating heterogeneous catalyst for the friedel crafts alkylation of indoles with β nitrostyrenes
ACS Catalysis, 2019Co-Authors: Datta Markad, Sanjay K MandalAbstract:A Primary-Amide-functionalized metal organic framework, {[Zn2(2-BQBG)(BDC)2]·10H2O}n (1) (in which 2-BQBG = 2,2′-(butane-1,4-diylbis((quinolin-2-ylmethyl)azanediyl))diacetAmide and BDC = 1,4-benzenedicarboxylate), has been found to be a highly efficient hydrogen-bond-donating (HBD) heterogeneous catalyst for the Friedel–Crafts alkylation of indole with β-nitrostyrenes under mild reaction conditions (catalyst loading: 3 mol %; reaction conditions: 12 h and 35 °C). The catalyst can be easily separated from the reaction mixture by simple filtration for its reuse in four consecutive cycles with very little loss of activity. More importantly, the one-pot room temperature synthesis of 1 from the self-assembly of Zn(OAc)2·2H2O and 2-BQBG (in CH3OH) and Na2BDC (in H2O) can be easily scaled-up for obtaining multigram quantities in few hours. In order to showcase its versatility, the substrate scope included a variety of substituted indoles and different β-nitrostyrene derivatives forming the desired products in go...
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Design of a Primary-Amide-Functionalized Highly Efficient and Recyclable Hydrogen-Bond-Donating Heterogeneous Catalyst for the Friedel–Crafts Alkylation of Indoles with β‑Nitrostyrenes
2019Co-Authors: Datta Markad, Sanjay K MandalAbstract:A Primary-Amide-functionalized metal organic framework, {[Zn2(2-BQBG)(BDC)2]·10H2O}n (1) (in which 2-BQBG = 2,2′-(butane-1,4-diylbis((quinolin-2-ylmethyl)azanediyl))diacetAmide and BDC = 1,4-benzenedicarboxylate), has been found to be a highly efficient hydrogen-bond-donating (HBD) heterogeneous catalyst for the Friedel–Crafts alkylation of indole with β-nitrostyrenes under mild reaction conditions (catalyst loading: 3 mol %; reaction conditions: 12 h and 35 °C). The catalyst can be easily separated from the reaction mixture by simple filtration for its reuse in four consecutive cycles with very little loss of activity. More importantly, the one-pot room temperature synthesis of 1 from the self-assembly of Zn(OAc)2·2H2O and 2-BQBG (in CH3OH) and Na2BDC (in H2O) can be easily scaled-up for obtaining multigram quantities in few hours. In order to showcase its versatility, the substrate scope included a variety of substituted indoles and different β-nitrostyrene derivatives forming the desired products in good to high yields. For its catalytic action, a direct proof for the key step in the proposed mechanism, based on the interaction of a Primary-Amide group in the 2-BQBG ligand with the nitro group of β-nitrostyrene through hydrogen bonding, is provided from the enhancement in fluorescence intensity of 1 upon successive addition of β-nitrostyrene
Sanford A Asher - One of the best experts on this subject based on the ideXlab platform.
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interaction enthalpy of side chain and backbone Amides in polyglutamine solution monomers and fibrils
Journal of Physical Chemistry Letters, 2018Co-Authors: David Punihaole, Ryan S Jakubek, Riley J Workman, Sanford A AsherAbstract:We determined an empirical correlation that relates the Amide I vibrational band frequencies of the glutamine (Q) side chain to the strength of hydrogen bonding, van der Waals, and Lewis acid–base interactions of its Primary Amide carbonyl. We used this correlation to determine the Q side chain carbonyl interaction enthalpy (ΔHint) in monomeric and amyloid-like fibril conformations of D2Q10K2 (Q10). We independently verified these ΔHint values through molecular dynamics simulations that showed excellent agreement with experiments. We found that side chain–side chain and side chain–peptide backbone interactions in fibrils and monomers are more enthalpically favorable than are Q side chain–water interactions. Q10 fibrils also showed a more favorable ΔHint for side chain–side chain interactions compared to backbone–backbone interactions. This work experimentally demonstrates that interAmide side chain interactions are important in the formation and stabilization of polyQ fibrils.
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uv resonance raman investigation of the aqueous solvation dependence of Primary Amide vibrations
Journal of Physical Chemistry B, 2015Co-Authors: David Punihaole, Zhenmin Hong, Ryan S Jakubek, Elizabeth M Dahlburg, Steven J Geib, Nataliya S. Myshakina, Sanford A AsherAbstract:We investigated the normal mode composition and the aqueous solvation dependence of the Primary Amide vibrations of propanAmide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanAmide. We examined the aqueous solvation dependence of the Primary Amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetAmide, all of the resonance enhanced Primary Amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar –O—C═NH2+ resonance structure over the neutral O═C—NH2 resonance structure. Thus, vibrations with large C—N stretching show increased UVRR cross sections because the C—N displacement between th...
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glutamine and asparagine side chain hyperconjugation induced structurally sensitive vibrations
The Journal of Physical Chemistry, 2015Co-Authors: David Punihaole, Zhenmin Hong, Ryan S Jakubek, Elizabeth M Dahlburg, Steven J Geib, Sanford A AsherAbstract:We identified vibrational spectral marker bands that sensitively report on the side chain structures of glutamine (Gln) and asparagine (Asn). Density functional theory (DFT) calculations indicate that the Amide IIIᴾ (AmIIIᴾ) vibrations of Gln and Asn depend cosinusoidally on their side chain OCCC dihedral angles (the χ₃ and χ₂ angles of Gln and Asn, respectively). We use UV resonance Raman (UVRR) and visible Raman spectroscopy to experimentally correlate the AmIIIᴾ Raman band frequency to the Primary Amide OCCC dihedral angle. The AmIIIᴾ structural sensitivity derives from the Gln (Asn) Cᵦ–Cᵧ (Cα–Cᵦ) stretching component of the vibration. The Cᵦ–Cᵧ (Cα–Cᵦ) bond length inversely correlates with the AmIIIᴾ band frequency. As the Cᵦ–Cᵧ (Cα–Cᵦ) bond length decreases, its stretching force constant increases, which results in an upshift in the AmIIIᴾ frequency. The Cᵦ–Cᵧ (Cα–Cᵦ) bond length dependence on the χ₃ (χ₂) dihedral angle results from hyperconjugation between the CδOϵ (CᵧOδ) π* and Cᵦ–Cᵧ (Cα–Cᵦ) σ orbitals. Using a Protein Data Bank library, we show that the χ₃ and χ₂ dihedral angles of Gln and Asn depend on the peptide backbone Ramachandran angles. We demonstrate that the inhomogeneously broadened AmIIIᴾ band line shapes can be used to calculate the χ₃ and χ₂ angle distributions of peptides. The spectral correlations determined in this study enable important new insights into protein structure in solution, and in Gln- and Asn-rich amyloid-like fibrils and prions.
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UV Resonance Raman Investigation of the Aqueous Solvation Dependence of Primary Amide Vibrations
2015Co-Authors: David Punihaole, Zhenmin Hong, Ryan S Jakubek, Elizabeth M Dahlburg, Nataliya S. Myshakina, Steven Geib, Sanford A AsherAbstract:We investigated the normal mode composition and the aqueous solvation dependence of the Primary Amide vibrations of propanAmide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanAmide. We examined the aqueous solvation dependence of the Primary Amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetAmide, all of the resonance enhanced Primary Amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar –OCNH2+ resonance structure over the neutral OCNH2 resonance structure. Thus, vibrations with large CN stretching show increased UVRR cross sections because the CN displacement between the electronic ground and excited state increases along the CN bond. In contrast, vibrations dominated by CO stretching, such as the AmI, show a decreased displacement between the electronic ground and excited state, which result in a decreased UVRR cross section upon aqueous solvation. The UVRR Primary Amide vibrations can be used as sensitive spectroscopic markers to study the local dielectric constant and hydrogen bonding environments of the Primary Amide side chains of glutamine (Gln) and asparagine (Asn)
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uv resonance raman investigation of the aqueous solvation dependence of Primary Amide vibrations
The Journal of Physical Chemistry, 2015Co-Authors: David Punihaole, Zhenmin Hong, Ryan S Jakubek, Elizabeth M Dahlburg, Steven J Geib, Nataliya S. Myshakina, Sanford A AsherAbstract:We investigated the normal mode composition and the aqueous solvation dependence of the Primary Amide vibrations of propanAmide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanAmide. We examined the aqueous solvation dependence of the Primary Amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetAmide, all of the resonance enhanced Primary Amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar –OCNH₂⁺ resonance structure over the neutral OCNH₂ resonance structure. Thus, vibrations with large CN stretching show increased UVRR cross sections because the CN displacement between the electronic ground and excited state increases along the CN bond. In contrast, vibrations dominated by CO stretching, such as the AmI, show a decreased displacement between the electronic ground and excited state, which result in a decreased UVRR cross section upon aqueous solvation. The UVRR Primary Amide vibrations can be used as sensitive spectroscopic markers to study the local dielectric constant and hydrogen bonding environments of the Primary Amide side chains of glutamine (Gln) and asparagine (Asn).
David Punihaole - One of the best experts on this subject based on the ideXlab platform.
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interaction enthalpy of side chain and backbone Amides in polyglutamine solution monomers and fibrils
Journal of Physical Chemistry Letters, 2018Co-Authors: David Punihaole, Ryan S Jakubek, Riley J Workman, Sanford A AsherAbstract:We determined an empirical correlation that relates the Amide I vibrational band frequencies of the glutamine (Q) side chain to the strength of hydrogen bonding, van der Waals, and Lewis acid–base interactions of its Primary Amide carbonyl. We used this correlation to determine the Q side chain carbonyl interaction enthalpy (ΔHint) in monomeric and amyloid-like fibril conformations of D2Q10K2 (Q10). We independently verified these ΔHint values through molecular dynamics simulations that showed excellent agreement with experiments. We found that side chain–side chain and side chain–peptide backbone interactions in fibrils and monomers are more enthalpically favorable than are Q side chain–water interactions. Q10 fibrils also showed a more favorable ΔHint for side chain–side chain interactions compared to backbone–backbone interactions. This work experimentally demonstrates that interAmide side chain interactions are important in the formation and stabilization of polyQ fibrils.
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uv resonance raman investigation of the aqueous solvation dependence of Primary Amide vibrations
Journal of Physical Chemistry B, 2015Co-Authors: David Punihaole, Zhenmin Hong, Ryan S Jakubek, Elizabeth M Dahlburg, Steven J Geib, Nataliya S. Myshakina, Sanford A AsherAbstract:We investigated the normal mode composition and the aqueous solvation dependence of the Primary Amide vibrations of propanAmide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanAmide. We examined the aqueous solvation dependence of the Primary Amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetAmide, all of the resonance enhanced Primary Amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar –O—C═NH2+ resonance structure over the neutral O═C—NH2 resonance structure. Thus, vibrations with large C—N stretching show increased UVRR cross sections because the C—N displacement between th...
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glutamine and asparagine side chain hyperconjugation induced structurally sensitive vibrations
The Journal of Physical Chemistry, 2015Co-Authors: David Punihaole, Zhenmin Hong, Ryan S Jakubek, Elizabeth M Dahlburg, Steven J Geib, Sanford A AsherAbstract:We identified vibrational spectral marker bands that sensitively report on the side chain structures of glutamine (Gln) and asparagine (Asn). Density functional theory (DFT) calculations indicate that the Amide IIIᴾ (AmIIIᴾ) vibrations of Gln and Asn depend cosinusoidally on their side chain OCCC dihedral angles (the χ₃ and χ₂ angles of Gln and Asn, respectively). We use UV resonance Raman (UVRR) and visible Raman spectroscopy to experimentally correlate the AmIIIᴾ Raman band frequency to the Primary Amide OCCC dihedral angle. The AmIIIᴾ structural sensitivity derives from the Gln (Asn) Cᵦ–Cᵧ (Cα–Cᵦ) stretching component of the vibration. The Cᵦ–Cᵧ (Cα–Cᵦ) bond length inversely correlates with the AmIIIᴾ band frequency. As the Cᵦ–Cᵧ (Cα–Cᵦ) bond length decreases, its stretching force constant increases, which results in an upshift in the AmIIIᴾ frequency. The Cᵦ–Cᵧ (Cα–Cᵦ) bond length dependence on the χ₃ (χ₂) dihedral angle results from hyperconjugation between the CδOϵ (CᵧOδ) π* and Cᵦ–Cᵧ (Cα–Cᵦ) σ orbitals. Using a Protein Data Bank library, we show that the χ₃ and χ₂ dihedral angles of Gln and Asn depend on the peptide backbone Ramachandran angles. We demonstrate that the inhomogeneously broadened AmIIIᴾ band line shapes can be used to calculate the χ₃ and χ₂ angle distributions of peptides. The spectral correlations determined in this study enable important new insights into protein structure in solution, and in Gln- and Asn-rich amyloid-like fibrils and prions.
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UV Resonance Raman Investigation of the Aqueous Solvation Dependence of Primary Amide Vibrations
2015Co-Authors: David Punihaole, Zhenmin Hong, Ryan S Jakubek, Elizabeth M Dahlburg, Nataliya S. Myshakina, Steven Geib, Sanford A AsherAbstract:We investigated the normal mode composition and the aqueous solvation dependence of the Primary Amide vibrations of propanAmide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanAmide. We examined the aqueous solvation dependence of the Primary Amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetAmide, all of the resonance enhanced Primary Amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar –OCNH2+ resonance structure over the neutral OCNH2 resonance structure. Thus, vibrations with large CN stretching show increased UVRR cross sections because the CN displacement between the electronic ground and excited state increases along the CN bond. In contrast, vibrations dominated by CO stretching, such as the AmI, show a decreased displacement between the electronic ground and excited state, which result in a decreased UVRR cross section upon aqueous solvation. The UVRR Primary Amide vibrations can be used as sensitive spectroscopic markers to study the local dielectric constant and hydrogen bonding environments of the Primary Amide side chains of glutamine (Gln) and asparagine (Asn)
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uv resonance raman investigation of the aqueous solvation dependence of Primary Amide vibrations
The Journal of Physical Chemistry, 2015Co-Authors: David Punihaole, Zhenmin Hong, Ryan S Jakubek, Elizabeth M Dahlburg, Steven J Geib, Nataliya S. Myshakina, Sanford A AsherAbstract:We investigated the normal mode composition and the aqueous solvation dependence of the Primary Amide vibrations of propanAmide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanAmide. We examined the aqueous solvation dependence of the Primary Amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetAmide, all of the resonance enhanced Primary Amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar –OCNH₂⁺ resonance structure over the neutral OCNH₂ resonance structure. Thus, vibrations with large CN stretching show increased UVRR cross sections because the CN displacement between the electronic ground and excited state increases along the CN bond. In contrast, vibrations dominated by CO stretching, such as the AmI, show a decreased displacement between the electronic ground and excited state, which result in a decreased UVRR cross section upon aqueous solvation. The UVRR Primary Amide vibrations can be used as sensitive spectroscopic markers to study the local dielectric constant and hydrogen bonding environments of the Primary Amide side chains of glutamine (Gln) and asparagine (Asn).
Sadhika Khullar - One of the best experts on this subject based on the ideXlab platform.
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a Primary Amide functionalized heterogeneous catalyst for the synthesis of coumarin 3 carboxylic acids via a tandem reaction
Inorganic Chemistry, 2020Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:A crystalline Primary Amide-based bifunctional heterogeneous catalyst, {[Cd2(2-BPXG)(Fum)2(H2O)2]·2H2O}n (1) (where, 2-BPXG = 2,2′-((1,4-phenylenebis(methylene))bis((pyridin-2-ylmethyl)azanediyl)) ...
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design and development of a heterogeneous catalyst for the michael addition of malononitrile to 2 enoylpyridines influence of the Primary Amide decorated framework on catalytic activity and selectivity
Inorganic Chemistry, 2019Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:For the Michael addition of malononitrile to 2-enoylpyridines, we report the first heterogeneous catalyst, {[Zn2(2-bpbg)(fum)2]·4H2O·EtOH}n (1) (where 2-bpbg = N,N'-bis(2-pyridylmethyl)-1,4-diaminobutane-N,N'-diacetAmide and where fum = fumarate), which is decorated with Primary Amide side arms. It is prepared from the self-assembly of starting materials in methanol at room temperature (27 °C). Using 3 mol % of 1, greater than 99% conversion of substrates to the desired product is achieved within 1 h at 27 °C. Moreover, the catalyst is recyclable up to five consecutive cycles without significant loss of activity and structural integrity. In order to show the uniqueness of 1, the reaction under the same conditions was catalyzed by a fully pyridyl-based (i.e., having no Primary Amide group) and isostructural analogue, {[Zn2(tpbn)(fum)2]·6H2O}n (2) (where tpbn = N',N',N″,N''-tetrakis(pyridin-2-ylmethyl)butane-1,4-diamine), but resulting only in 7% conversion. This demonstrates the selective catalytic activity of 1 over 2 due to the presence of the Primary Amide side arms, where it acts as a bifunctional catalyst through the excellent hydrogen bond donating (HBD) ability in this reaction. For providing an insight into its mechanism of action involving a cyclic seven-membered hydrogen bonding motif, the reaction was performed with freshly synthesized (E)-chalcone, 3-enoylpyridine, and 4-enoylpyridine instead of 2-enoylpyridine under the same conditions. In the case of (E)-chalcone no product formation was observed, whereas for 3-enoylpyridine and 4-enoylpyridine the conversions were only 29% and 25%, respectively. Both 1 and 2 were fully characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis, and single-crystal and powder X-ray diffraction.
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novel Primary Amide based cationic metal complexes green synthesis crystal structures hirshfeld surface analysis and solvent free cyanosilylation reaction
Dalton Transactions, 2019Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:A new symmetrical and flexible Primary Amide functionalized ligand, 2,2′-(ethane-1,2-diylbis((pyridin-2-ylmethyl)azanediyl))diacetAmide (2-BPEG), has been synthesized and structurally characterized. Using this multidentate ligand, four novel metal complexes, namely [Cu(2-BPEG)](ClO4)2·0.5H2O (1), [Zn(2-BPEG)](ClO4)2 (2), [Zn(2-BPEG)](ZnCl4)·H2O (3) and [Cd(2-BPEG)(H2O)](ClO4)2·H2O (4), have been synthesized under ambient conditions and characterized by elemental, spectroscopic and thermal analysis, and single and powder X-ray diffraction. Complexes 1–3 are hexacoordinated with an N4O2 donor set (provided by the hexadentate 2-BPEG ligand), while complex 4 is heptacoordinated with an additional coordinated water molecule. In all cases, the 2-BPEG ligand acts as a hexadentate ligand. A change in the starting metal salt has resulted in the formation of 2 and 3 with different tetrahedral anions, ClO4− and ZnCl4−, respectively. This has provided an opportunity to showcase anion-directed supramolecular networks for these compounds. Compounds 1, 2 and 4 with perchlorate anions show similar and comparable intermolecular interactions in their 3D networks. On the other hand, the supramolecular self-assembly of 3 is dominated by a variety of intermolecular interactions such as C–H⋯Cl, N–H⋯Cl, O–H⋯Cl and C–H⋯O due to the presence of a tetrachlorozincate(II) ion. Moreover, the role of weak intermolecular interactions in the crystal packing has been analysed and quantified using Hirshfeld surface analysis. Furthermore, compound 4 exhibiting an open Lewis acid site has been found to be a very efficient and recyclable heterogeneous catalyst for the solvent-free cyanosilylation of various aldehydes with trimethylsilyl cyanide (TMSCN) producing the corresponding trimethylsilyl ether in high yields.
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engineering a nanoscale Primary Amide functionalized 2d coordination polymer as an efficient and recyclable heterogeneous catalyst for the knoevenagel condensation reaction
ACS Applied Nano Materials, 2018Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:This work reports the design, structural characterization, and catalytic behavior of the first example of Primary Amide-functionalized coordination polymers (CPs), namely, {[Cd2(2-bpbg)(fum)2(H2O)2]·8.5H2O}n (1) (where 2-bpbg = N,N′-bis(2-pyridylmethyl)-1,4-diaminobutane-N,N′-diacetAmide and fum = fumarate). CP 1 is synthesized from a one-pot self-assembly of starting materials in methanol under ambient conditions in excellent yield and purity, allowing an easy access to multigram quantities of it within few hours. As an example, CP 1 was used as a highly efficient heterogeneous catalyst in the carbon–carbon bond-forming Knoevenagel condensation reaction for the conversion of benzaldehyde to benzylidene malononitrile. CP 1 possesses both Lewis acidic and Bronsted basic character for the presence of unsaturated metal sites and Primary Amide groups, respectively, making it a highly competent bifunctional catalyst for such type of reactions. Surprisingly, on the one hand, 100% conversion was observed using o...
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Engineering a Nanoscale Primary Amide-Functionalized 2D Coordination Polymer as an Efficient and Recyclable Heterogeneous Catalyst for the Knoevenagel Condensation Reaction
2018Co-Authors: Datta Markad, Sadhika Khullar, Sanjay K MandalAbstract:This work reports the design, structural characterization, and catalytic behavior of the first example of Primary Amide-functionalized coordination polymers (CPs), namely, {[Cd2(2-bpbg)(fum)2(H2O)2]·8.5H2O}n (1) (where 2-bpbg = N,N′-bis(2-pyridylmethyl)-1,4-diaminobutane-N,N′-diacetAmide and fum = fumarate). CP 1 is synthesized from a one-pot self-assembly of starting materials in methanol under ambient conditions in excellent yield and purity, allowing an easy access to multigram quantities of it within few hours. As an example, CP 1 was used as a highly efficient heterogeneous catalyst in the carbon–carbon bond-forming Knoevenagel condensation reaction for the conversion of benzaldehyde to benzylidene malononitrile. CP 1 possesses both Lewis acidic and Brønsted basic character for the presence of unsaturated metal sites and Primary Amide groups, respectively, making it a highly competent bifunctional catalyst for such type of reactions. Surprisingly, on the one hand, 100% conversion was observed using only 2 mol % catalyst within 1 h at 27 °C in methanol. On the other hand, 2 mol % and 3 mol % catalyst loadings but without a solvent gives 93% and 100% conversions, respectively, in 1 h at 27 °C. CP 1 is far better than those reported in the literature. To prove the uniqueness and efficiency of the Primary Amide-based ligand, a similar compound with a pyridyl-based ligand was also synthesized, {[Cd2(tpbn)(fum)2]·6H2O}n (2) (where tpbn = N′,N′,N″,N″-tetrakis(pyridin-2-ylmethyl)butane-1,4-diamine). With CP 2 under the same catalyst loading and conditions (2 mol %, 27 °C, 1 h), only 28% conversion was observed. This demonstrates that selective heterogeneous catalytic properties of 1 over 2 are due to the presence of the Primary Amide moieties and open metal sites. Moreover, CP 1 can easily be separated from the reaction mixture and reused for five consecutive cycles without significant loss of its activity. Both 1 and 2 were fully characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal and powder X-ray diffraction. These crystallize in the triclinic P1̅ space group, showing their isostructural nature and three-connected, uninodal {63} honeycomb net topology
