• Jyoti V Sawant

Articles written in Journal of Chemical Sciences

• A novel hydrogen-bonded cyclic dibromide in an organic diammonium salt

The organic diammonium salt N,N′-dibenzyl-N,N,N′,N′-tetramethylethylenediammonium dibromide dihydrate, (dbtmen)Br2.2H2O (1), was prepared by the reaction of N,N,N′,N′-tetramethyl-ethylenediamine (tmen) with benzyl bromide.1 crystallizes in the triclinic space group$$P\bar 1$$ with the following unit cell dimensions for C20H34Br2N2O2 (M = 494.31):a = 8.6672(6) Å,b = 11.7046(8) Å,c = 11.7731(8) Å, α = 76.988(8)°, β = 88.978(8)°, γ= 76.198(8)γ,V= 1129.26(13) Å3, Z=2. Three components, namely the (dbtmen)2+ dication, two bromide anions and two crystal water molecules constitute the structural arrangement of1. H2O molecules are linked to bromide anions via O-H...Br hydrogen bonding interactions resulting in the formation of a four-membered O2Br2 cyclic dibromide. The O2Br2 units and the dications are arranged as alternating layers extending in the crystallographicbc plane. The arrangement of anions and cations may be viewed as a typical lamellar structure. The crystal water molecules can be removed by heating 1 at 140°C and the anhydrous dibromide thus formed can be fully rehydrated as evidenced by IR spectra and X-ray powder patterns.

• Synthesis, spectroscopy, thermal studies and supramolecular structures of two new alkali-earth 4-nitrobenzoate complexes containing coordinated imidazole

The reaction of hydrated magnesium or calcium 4-nitrobenzoate (4-nba) generated in situ, with imidazole (Im) results in the formation of the complexes [Mg(H2O)2(Im)2(4-nba)2] 1 and [Ca(H2O)3(Im)(4-nba)2]$\cdot$Im 2, which exhibit the same metal:4-nba:Im ratio but different degrees of hydration. Complex 1 crystallizes in the triclinic $P_{\bar{i}}$ space group and the Mg atom is located on an inversion centre, while 2 crystallizes in the monoclinic $P2_1/c$ space group and all atoms are located in general positions. In 1 the Im ligands, which are trans to each other, are coordinated to Mg, while 2 contains coordinated as well as free Im. The monodentate 4-nba ligands are disposed trans to each other in 1, while they adopt a cis orientation in 2 resulting in different supramolecular structures. Complex 1 exhibits two types of H-bonding interactions namely O-H𝛬O and N-H𝛬O, while in 2 three varieties of H-bond, viz. O-H𝛬O, N-H𝛬O and O-H𝛬N are observed. The Im ligand functions as a bifurcated H-bond donor in 1 while the O atom of the nitro group functions as a H-bond acceptor. In contrast, the nitro group in 2 is not involved in any H-bonding interactions. The free Im in 2 functions as a bifurcated acceptor and forms an extended chain linking adjacent complex molecules. The chains thus formed are further cross-linked with the aid of H-donor bonds from both the free as well as the coordinated Im. Both 1 and 2 exhibit 𝜋-𝜋 stacking interactions. Complex 1 is thermally more stable as compared to 2, and both complexes can be dehydrated to the corresponding anhydrous complexes by heating at 140 and 100°C respectively. At elevated temperatures, both the complexes can be pyrolysed to the corresponding oxide. The anhydrous complexes can be rehydrated to obtain the starting hydrated materials.

• Synthesis, spectroscopy and supramolecular structures of two magnesium 4-nitrobenzoate complexes

The aqueous reaction of [Mg(H2O)6]Cl2 with the in situ generated sodium salt of 4-nitrobenzoic acid (4-nbaH) and N-methylimidazole (N-MeIm) results in the formation of the dinuclear complex [Mg(H2O)(N-MeIm)2(4-nba)2]2 1 (4-nba = 4-nitro benzoate), while the direct reaction of [Mg(H2O)6]Cl2 with sodium 4-nba leads to the formation of the mononuclear complex, [Mg(H2O)6](4-nba)2.2H2O 2. In the centrosymmetric dimer 1, each Mg atom is coordinated to an aquo ligand, two monodentate N-MeIm ligands and a monodentate 4-nba ligand. The second 4-nba ligand functions as a bridging bidentate ligand, linking the metal centers and completes the hexacoordination around each Mg(II). The dimeric molecules of 1 are linked into a one-dimensional chain along 𝑏 with the aid of intra- as well as intermolecular H-bonding interactions between the coordinated water and the free oxygen atom of the monodentate 4-nba ligand. In the mononuclear complex [Mg(H2O)6](4-nba)2.2H2O 2, the Mg(II) is located on an inversion center and its structure consists of an octahedral [Mg(H2O)6]2+ dication, a free uncoordinated 4-nba anion and a lattice water molecule. One of the H atoms attached of the lattice water is disordered over two positions. The hexaaquomagnesium(II) dication, the 4-nba anion and the lattice water molecule are linked by intra- and intermolecular H-bonding interactions resulting in the formation of alternating layers of [Mg(H2O)6]2+ dications and 4-nba anions in the crystallographic $bc$ plane. The lattice water molecules are situated between the cations, while the 4-nba anions are arranged antiparallel to each other along 𝑏.

• catena-Poly[[(pentaaqua)(4-nitrobenzoato-O,O')barium(II)] (𝜇-4-nitrobenzoato-O,O')]: A barium(II) coordination polymer showing O-H$\cdots$O and C-H$\cdots$O interactions

The reaction of barium carbonate with 4-nitrobenzoic acid (4-nbaH) results in the formation of a Ba(II) coordination polymer, catena-poly[[(pentaaqua)(4-nitrobenzoato-O,O')barium(II)](𝜇-4-nitrobenzoato-O,O')] 1. The polymeric compound [[Ba(H2O)5(4-nba-O,O')](𝜇-4-nba-O,O')]$_n$ 1 was characterized by elemental analysis, IR and UV-Vis spectra, weight loss studies, X-ray powder diffraction and its structure determined. In 1 five water molecules are coordinated to the central metal and one of the 4-nba ligands is bonded to Ba(II) in a bidentate manner (4-nba-O,O') through the carboxylate O atoms. The [(pentaaqua)(4-nitrobenzoato-O,O')barium(II)] units are linked into an infinite one-dimensional chain along 𝑏-axis with the aid of the second 4-nba anion, which functions as a bridging bidentate (𝜇-4-nba-O,O') ligand. This results in nine coordination around each Ba(II) ion in the coordination polymer. A long Ba$\cdots$Ba distance of 6.750(1) Å is observed between adjacent Ba(II) ions in the chain and the oxygen atoms of the carboxylate group and the nitro functionalities of the 4-nba ligand are involved in several O-H$\cdots$O and C-H$\cdots$O interactions.

• # Journal of Chemical Sciences

Volume 134, 2022
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