M. Sundaralingam

Bio: M. Sundaralingam is an academic researcher. The author has contributed to research in topics: Salicylic acid. The author has an hindex of 1, co-authored 1 publications receiving 132 citations.

Cytotoxicity and antiviral activity of transition-metal salicylato complexes and crystal structure of Bis(diisopropylsalicylato)(1,10-phenanthroline)copper(II)

Abstract: Complexes of CuII, FeIII, CoII, NiII, TiIV and ZnII with 3,5-disubstituted salicylates, and ternary complexes of CuII containing substituted phenanthrolines have been prepared and characterised. The crystal structure of bis(diisopropylsalicylato)(1,10-phenanthroline)copper(II), [Cu(phen)(Hdips)2], has been determined; CuII is in a tetragonal co-ordination environment with in-plane bonds to 2 nitrogens from phen[Cu–N 2.014(4)A] and 2 oxygens from the carboxylates of Hdips [Cu–O 1.951(3)A], with weaker off-axial bonds to carboxylate oxygens [Cu–O 2.557(3)A]. The hydroxyl oxygen of Hdips is not co-ordinated. These complexes have been tested for antiviral and cytotoxic activity. Most are potently cytotoxic, especially [Cu(dmphen)(Hdips)2], where dmphen is 2,9-dimethylphenanthroline.

Improving the hydrogen-adsorption properties of a hydroxy-modified MIL-53(Al) structural analogue by lithium doping.

Abstract: Lithium makes the difference: A simple strategy for the synthesis of lithium-doped porous metal-organic frameworks (MOFs) is developed (see structure; C black, O red, AlO(6) blue octahedra), thus paving the way for the facile preparation of lithium-doped MOFs. Moreover, the significant increase in hydrogen adsorption predicted by theoretical calculations is observed.

Solubility and Melting Properties of Salicylic Acid

Abstract: The solubility of salicylic acid has been investigated in methanol, acetonitrile, acetic acid, acetone, water, and ethyl acetate from (10 to 50) °C. No new polymorphs or solvates of salicylic acid were found. The melting properties of salicylic acid were determined by differential scanning calorimetry. A correlation was observed between the solubility and the van't Hoff enthalpy of solution. A higher solubility was related to a lower van't Hoff enthalpy of solution. Water differed from the organic solvents in terms of solubility and its correlation to the van't Hoff enthalpy of solution. In addition, the morphology of salicylic acid crystals recrystallized from water differed from the other solvents.

Intra- and intermolecular interactions in small bioactive molecules: cooperative features from experimental and theoretical charge-density analysis.

Abstract: The topological features of the charge densities, ρ(r), of three bioactive molecules, 2-thiouracil [2,3-dihydro-2-thioxopyrimidin-4(1H)-one], cytosine [4-aminopyrimidin-2(1H)-one] monohydrate and salicylic acid (2-hydroxybenzoic acid), have been determined from high-resolution X-ray diffraction data at 90 K. The corresponding results are compared with the periodic theoretical calculations, based on theoretical structure factors, performed using DFT (density-functional theory) at the B3LYP/6-31G** level. The molecules pack in the crystal lattices via weak intermolecular interactions as well as strong hydrogen bonds. All the chemical bonds, including the intra- and intermolecular interactions in all three compounds, have been quantitatively described by topological analysis based on Bader's quantum theory of `Atoms In Molecules'. The roles of interactions such as C—H⋯O, C—H⋯S, C—H⋯π and π⋯π have been investigated quantitatively in the presence of strong hydrogen bonds such as O—H⋯O, N—H⋯O and N—H⋯S, based on the criteria proposed by Koch and Popelier to characterize hydrogen bonds and van der Waals interactions. The features of weak intermolecular interactions, such as S⋯S in 2-thiouracil, the hydrogen bonds generated from the water molecule in cytosine monohydrate and the formation of the dimer via strong hydrogen bonds in salicylic acid, are highlighted on a quantum basis. Three-dimensional electrostatic potentials over the molecular surfaces emphasize the preferable binding sites in the structure and the interaction features of the atoms in the molecules, which are crucial for drug–receptor recognition.

Ground and Excited State Intramolecular Proton Transfer in Salicylic Acid: an Ab Initio Electronic Structure Investigation

Abstract: Energetics of the ground and excited state intramolecular proton transfer in salicylic acid have been studied by ab initio molecular orbital calculations using the 6-31G** basis set at the restricted Hartree -Fock (RHF) and configuration interaction-single excitation (CIS) levels and also using the semiempirical method AM1 at the RHF level as well as with single and pair doubles excitation configuration interaction spanning eight frontier orbitals (PECI ) 8). The ab initio potential energy profile for intramolecular proton transfer in the ground state reveals a single minimum corresponding to the primary form. In the first excited singlet state, however, there are two minima corresponding to the primary and tautomeric forms, separated by a barrier of 6 kcal/mol, thus accounting for dual emission in salicylic acid. Electron density changes with electronic excitation and tautomerism indicate no zwitterion formation. Changes in spectral characteristics with change in pH, due to protonation and deprotonation of salicylic acid, are also accounted for, qualitatively. Although the AM1 calculations suggest a substantial barrier for proton transfer in the ground as well as the first excited state of SA, it predicts the transition wavelength in near quantitative accord with the experimental results for salicylic acid and its protonated and deprotonated forms.