Papers by Venkatachalam Ramkumar
Acta Crystallographica Section E Structure Reports Online, 2008
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Crystal Growth & Design, 2019
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Acta Crystallographica Section E Structure Reports Online, 2009
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Dalton transactions (Cambridge, England : 2003), Jan 21, 2017
A series of novel mononuclear (1a-7a and 1b-6b) as well as tetranuclear (8a and 9a) niobium (Nb) ... more A series of novel mononuclear (1a-7a and 1b-6b) as well as tetranuclear (8a and 9a) niobium (Nb) and tantalum (Ta) complexes of benzotriazole or benzoxazole phenoxide pro-ligands bearing different substituents at the ortho and para positions of the phenol rings were synthesized and characterized. The reaction of NbClor TaClwith one equivalent of benzotriazole or benzoxazole phenoxide pro-ligands (L1H-L6H) in dry toluene or chloroform produced the corresponding chloride (1a-6a and 1b-6b) and ethoxy (7a) mononuclear Nb and Ta complexes in high yields. Furthermore, from the mononuclear Nb complexes (1a or 4a), a new structural form of tetrameric niobium complexes (8a and 9a) was synthesized through a controlled hydrolysis reaction. The molecular structures of complexes 1b, 4b, 7a, 8a and 9a were unambiguously confirmed by single crystal X-ray diffraction analyses. Furthermore, all these complexes (1a-9a and 1b-6b) were tested as catalysts for the ring-opening polymerisation (ROP) of gl...
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Inorganic chemistry, Jan 5, 2018
Synthesis and structural elucidation of various electron precise group 5 dimetallaheteroboranes h... more Synthesis and structural elucidation of various electron precise group 5 dimetallaheteroboranes have been described. Room temperature reaction of [CpVCl] with Li[BH(EPh)], generated from the treatment of LiBH·THF and PhE(E = S or Se), for 1 h in toluene, followed by thermolysis, led to the formation of bimetallic complexes [{CpV(μ-EPh)}{μ-η:η-BHE}], 1 and 2 (1: E = S and 2: E = Se), and [{CpV(μ-SePh)}{μ-η:η-BH(OCH)Se}], 3. One of the striking features of these compounds is that they represent a rare class of distorted tetrahedral clusters having bridging hydrogens. Evaluating the skeletal electron pairs and bonding types, compounds 1, 2, and 3 may be considered as isoelectronic with our earlier reported [(CpV)(BH)]. In an attempt to synthesize the Nb analogues of 1-3, room temperature reactions of [CpNbCl] and Li[BH(EPh)] (E = S or Se) were carried out that afforded compounds [{CpNb(μ-EPh)}{μ-η:η-BHE}], 4 and 5 (4: E = S and 5: E = Se). The solid-state X-ray structures of both 4 and...
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Chemistry - A European Journal
A design approach that incorporates structural requirements for the formation of a 1D assembly, f... more A design approach that incorporates structural requirements for the formation of a 1D assembly, fibril stability, and fibril-fibril interactions for gelation was attempted by using amino acid-based sulfamides with the general structure Aa-NH-SO-NH-Aa (Aa=amino acid). A preference for 1D assembly alone was not a sufficient condition for gelation, which became evident from studies involving sulfamide esters 1-5. Reducing the crystallization tendency without hindering unidirectional growth was executed through diacids of the sulfamide precursors with various amines that form an envelope around the sulfamide core through salt bridges. This strategy was fruitful, and gels of a wide variety of solvents could be formed by varying the acid and amine components. The use of dodecylamine or benzylamine, which could stabilize the molecular layers through alkyl-chain segregation or π-π interactions improved the gelation tendency, whereas the nature of the amino acid side chain, especially the rotational freedom and hydrophobicity, had a direct role in dictating the solvent preference. Crystallographic studies of these two-component systems gave molecular-level insight into the assembly and showed the importance of anisotropy in the distribution of secondary interactions in gelation.
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ChemInform
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European Journal of Organic Chemistry, 2016
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RSC Adv., 2016
A series of new dinuclear group 4 complexes containing [NNO]-type ligands are utilized as catalys... more A series of new dinuclear group 4 complexes containing [NNO]-type ligands are utilized as catalysts for polymerization reactions.
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Acta Crystallographica Section E Structure Reports Online, 2007
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Journal of Macromolecular Science, Part A, 2010
A novel initiator containing pyrene, a fluorescent moiety, was prepared by reacting 1-aminopyrene... more A novel initiator containing pyrene, a fluorescent moiety, was prepared by reacting 1-aminopyrene and 2-bromoisobutyl bromide. The structure elucidation of the new initiator was carried out using various spectroscopic tools, as well as through single crystal X-ray diffraction studies. Novel, fluorescent amphiphilic block copolymers with a pyrene end-group, poly(styrene-b-acrylic acid) [P(S-b-AA)], poly(methyl methacrylate-b-dimethylaminoethyl methacrylate) [P(MMA-b-DMAEMA)], poly(styrene-b-tert-butyl acrylate) [P(S-b−t-BA)], poly(styrene-b-dimethylaminoethyl methacrylate)
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Chemistry - A European Journal, 2000
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European Journal of Organic Chemistry, 2016
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Crystal Growth Design, 2010
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Acta Crystallographica Section E Structure Reports Online
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CrystEngComm, 2014
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RSC Adv., 2015
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Polymer, 2015
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Tetrahedron Letters, 2009
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Polyhedron, 2010
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Papers by Venkatachalam Ramkumar