Anirban Karmakar

Zinc(II) and cobalt(II) complexes of (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid: a structural study

Different types of cyclic polynuclear complexes and one-dimensional coordination polymers of zinc(II) derived from (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (LH2) are synthesised and characterised. The macrocyclic effect of ligand L leads to the formation of a coordination polymer having composition {[Na2Zn2(L)2(OH)2]}n and a binuclear zinc complex having composition [Zn2Na2(L)2(CH3COO)2(Pyz)2(MeOH)2] (where Pyz = pyrazole). A tetranuclear cyclic zinc(II) metallacycle with two dimethylformamide molecules in two different environments is synthesized and it has two symmetry non-equivalent cyclic molecules in its unit cell. The mononuclear complexes of zinc with L and the bidentate ligands such as 2,2′-bipyridine or 1,10-phenanthroline ancillary ligands are structurally characterised.

Variations in product in reactions of naphthoquinone with primary amines.

Reaction of 1,2-naphthoquinone with primary amines gives a 2-amino-1,4-naphthoquinone derivative which is equivalent to 1,2 to 1,4 carbonyl transposition. For example the reaction of 1,2-naphthoquinone with 4-methoxyaniline gives 2-(4-methoxyanilino)-naphthoquinone-1,4-(4-methoxyanil) (1) and with n-butylamine gives 2-(butylamino)-naphthoquinone-1,4-butylimine (2) respectively. The compounds 1 and 2 are characterized by X-ray crystallography; they have hydrogen-bonded dimeric structures. Similar reaction of 1,4-naphthoquinone with 3-picolylamine and 4-picolylamine gives the corresponding 2-amino 1,4-naphthoquinones; two products are characterized by X-ray crystallography. The reaction of 1,4-naphthoquinone with 4-aminothiophenol and 1,4-naphthoquinone with 4-aminophenol are compared. The former leads to C-S and the latter to C-N bond formation. The reaction of 1,4-naphthoquinone with 4-aminothiophenol in an NMR tube is studied to explain that 2-(4-anilinothiolato) 1,4-naphthoquinone derivative to be the sole product in the reaction.

Solvent induced symmetry non-equivalence in the crystal lattice of 7-carboxymethyl-1,3,6,8-tetraoxo-3,6,7,8-tetrahydro-1H-benzo[lmn][3,8]phenathrolin-2-yl) acetic acid

In the assembly of 7-carboxymethyl-1,3,6,8-tetraoxo-3,6,7,8-tetrahydro-1H-benzo[lmn][3,8]phenathrolin-2-yl) acetic acid, the weak interactions with solvent molecules can generate symmetry non-equivalent molecules in an unit cell.

Manganese and Cadmium Benzoate Complexes Having 8-Aminoquinoline Ancillary Ligand

Simple synthetic methods for synthesis of trinuclear manganese(II) benzoate complexes having 8aminoquinoline as ancillary ligand are reported. The crystal structure of two trinuclear manganese(II) complexes, [Mn3(2NO2C6H4COO)6(AQ)2] (I) and [Mn3(3-CH3C6H4COO)6(AQ)2].NPD (II) is reported (where AQ = 8-aminoquinoline, NPD = 1,5 dihydroxynaphthalene). In solution, the degradation of trinuclear complex I leads to a dinuclear complex [Mn2(2NO2C6H4COO)4(AQ)2 (H2O)2] (III) and structure of complex III is reported. A solution phase synthetic method for the synthesis of the dinuclear manganese(II) complex III is also reported. This complex has a Mn2O2 bridge originating from the carboxylate ligand. Synthesis of a cadmium 2-nitrobenzoate co-ordination polymer [Cd(2-NO2C6H4COO)2(AQ)]n (IV) having eight co-ordination number is reported and its structure is explained as aggregation of multiple numbers of six coordinated mononuclear cadmium complexes.

Structural aspects and properties of salt and inclusion compounds of 8-hydroxyquinoline based amides

The structural aspects of two amide containing isoquinoline derivatives namely N-cyclohexyl-2-(quinolin-8-yloxy) acetamide (1) and N-(2,6-dimethylphenyl)-2-(quinolin-8-yloxy) acetamide (2) are studied. On treatment with mineral acids such as sulfuric acid, hydrochloric or phosphoric acid N-cyclohexyl-2-(quinolin-8-yloxy) acetamide forms gels whereas on treatment with nitric acid it forms crystalline solid. Acids having non-planar anions facilitate the gel formation and the acids having planar anion such as nitrate and carboxylate were not suitable for gelation of 2. N-(2,6-Dimethylphenyl)-2-(quinolin-8-yloxy) acetamide forms crystalline salts on treatment with mineral acids. The crystal structure of compounds 1, 2 and two salts are reported. Compound 2 forms 2 : 1 host–guest complexes with 1,4-dihydroxybenzene as well as with 1,5-dihydroxynaphthalene. The crystal structures of both compounds are reported. These host–guest complexes have much stronger fluorescence emission at lower wavelength than the parent compound, however, the protonated state of compound 2 is not fluorescence active. The compound 1 on protonation shows fluorescence at much higher wavelength than the parent compound, whereas compound 1 on interaction with 1,4-dihydroxybenzene fluorescence occurs at a lower wavelength. The crystal structure of N-[3-(4-methoxy-phenyl)propyl]-2-(quinolin-8-yloxy)acetamide is determined and found to have parallel sheet structure.

N-oxides in metal-containing multicomponent molecular complexes.

Syntheses and structures of three-component rare cocrystals of 4-nitrobenzoic acid, aromatic N-oxides, and aqua complexes of manganese and zinc and their transformation to metal complexes as well as coordination polymers are presented.

N-[2-(4-Methoxy-phenyl)-ethyl]-2-(quinolin-8-yloxy)acetamide: a receptor for acid binding

Different hydrates of the receptor, N-[2-(4-methoxy-phenyl)-ethyl]-2-(quinolin-8-yloxy)acetamide (I), and its co-crystals with acetic acid and l(+)α-hydroxy-phenylacetic acid are synthesised and their structures are studied. The acids such as acetic acid, l(+)α-hydroxy-phenylacetic acid quench fluorescence of I. The receptor I shows a fluorescence quenching on interaction with perchloric acid in benzene, whereas in methanol the solution of I results in the generation of a new fluorescence emission at higher wavelengths. The crystal structure of the perchlorate salt is determined to explain the protonation behaviour of the receptor I and the perchlorate salt in methanol leads to fluorescence emission at a place different from that of the parent compound.

Crystal packing in some flexible carboxylic acids and esters attached to a naphthalene ring

A structural study of four dicarboxylic acids and four esters attached to a naphthalene ring is presented. (4-Carboxymethoxy-naphthalen-2-yloxy)-acetic acid (1) has a chain structure in the lattice while (6-carboxymethoxy-naphthalen-1-yloxy)-acetic acid (2) and (7-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (3) adopt a sheet-like structure through weak intermolecular interactions, C–H⋯O and C–H⋯π hydrogen bonds. (3-Carboxymethylsulfanyl-1,4-dihydroxy-naphthalen-2-ylsulfanyl)-acetic acid has two symmetrically non-equivalent molecules per unit cell. The asymmetry is caused by weak C–H⋯S interactions. The packing pattern of the methyl esters differs significantly from the parent carboxylic acids and the packing patterns in each case were found to be determined by the C–H⋯O and C–H⋯π interactions.

Zinc Complexes with Cyanoxime: Structural, Spectroscopic, and Catalysis Studies in the Pivaloylcyanoxime–Zn System

Reaction of 2-hydroxyimino-4,4-dimethyl-3-oxo-pentanenitrile (common abbreviation HPiCO, pivaloyl-cyanoxime) with zinc sulfate in an aqueous solution results in the formation of the two new complexes: [Zn(PiCO){H(PiCO)2}(H2O)] (I) and tetranuclear Zn complex [Zn4(μ3-OH)2(PiCO)6 (H2O)4] (II). Both complexes were characterized by elemental analysis, IR- and UV-visible spectra, DSC/TGA studies, and X-ray analysis. In complex II, the PiCO- cyanoxime anion adopts three bidentate binding modes: O-monodentate, chelating (κ2), and bridging (η2) coordinations. Also, the ligand represents the mixture of two diasteromers (cis-anti and cis-syn) that form five- and six-membered chelate rings with Zn atoms and cocrystallize in one unit cell at population of 0.57-0.43. There are two crystallographically different Zn-centers in the ASU, and two μ3-bridging hydroxo-groups arrange via inversion center the formation of an elegant tetranuclear complex. Each Zn atom has a molecule of coordinated water and is in the distorted octahedral environment. Because of the structural flexibility and multidentate propensity of the pivaloyl-cyanoxime, complex II may act as a structural model of naturally occurring Zn-containing enzymes. Indeed, compound I exhibits an efficient catalytic performance for transesterification reaction of various esters in ethanol under mild reaction conditions. Therefore, obtained results allow assignment of observed activity as green catalysis.