Rohith P. John

1, 5-Bis (2-hydroxyacetophenone)thiocarbohydrazone: A novel colorimetric and fluorescent dual-mode chemosensor for the recognition of fluoride

1,5-Bis (2-hydroxyacetophenone)thiocarbohydrazone (H4L) has been synthesized and characterized by means of spectroscopic and single crystal X-ray diffraction methods. Interactions of the H4L with a variety of anions were investigated using a combination of UV-visible and fluorescence spectroscopic methods in a biological competing solvent DMSO. The H4L has a high degree of selectivity for fluoride over other anions. (1)H NMR titration experiments indicate that a deprotonation process is involved in the chemo sensing process.

A discrete self-assembled palladium nano-cage catalyses Suzuki–Miyaura coupling heterogeneously and Heck–Mizoroki coupling homogeneously

A coordination driven Pd2L4 self-assembly has been synthesized using a new semi rigid dipodal ligand L. The palladium(II) self assembly was characterized by multinuclear NMR and ESI-mass spectroscopic techniques and elemental analysis. The size of the assembly was determined by HR-TEM analysis and the results are in agreement with theoretical calculations. The assembly shows applicability as an effective heterogeneous reusable catalyst for the Suzuki–Miyaura coupling reaction without losing its catalytic activity in aqueous ethanol under mild and phosphine free conditions. It shows equally high efficiency for arylboronic acid and bromoarenes having electron-poor and electron-rich functional groups. Besides, it also shows efficient catalytic activity as a homogeneous catalyst in the Heck–Mizoroki coupling reaction in an aqueous DMF medium. The heterogeneous and homogeneous nature of the catalysis was monitored by ICP-AES measurements, poison test and three-phase test. The integrity of the catalyst was evaluated by FE-SEM/EDX analysis.

A coordination driven self-assembled Pd6L8 nanoball catalyses copper and phosphine-free Sonogashira coupling reaction in both homogeneous and heterogeneous formats

A Pd6L8 type coordination driven self-assembly was constructed using a tripodal ligand L (L = N1,N3,N5-trimethyl-N1,N3,N5-tris[(pyridin-4-yl)methyl]-1,3,5-benzene tricarboxamide) and palladium nitrate. The self-assembly was fully characterised using one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance spectroscopy, electrospray ionization-mass spectroscopy, thermogravimetric analysis, energy-dispersive X-ray spectroscopy and elemental analysis. Use of high resolution transmission electron microscopy (HR-TEM) analysis confirms the discrete nature of the assembly with a dimension of ∼2.8 nm, consistent with the density functional theory optimised structure. The assembly acts as an efficient homogeneous catalyst for a copper and phosphine free Sonogashira reaction under mild and aerobic conditions in aqueous medium. The catalyst shows equal efficiency for both electron deficient and electron rich aryl iodides and bromides and is also suitable for use with aliphatic alkynes. The utility of the catalyst as a reusable heterogeneous catalyst in toluene was assessed up to the 3rd cycle without any significant loss of catalytic activity.

Self-assembled Pd6L4 cage and Pd4L4 square using hydrazide based ligands: synthesis, characterization and catalytic activity in Suzuki–Miyaura coupling reactions

A discrete Pd6L4 Td-symmetric molecular cage and a discrete Pd4L4 square assembly were obtained using a coordination-driven self-assembly technique. The assembly, Pd6L4, was prepared via a face-directed method, utilising a ‘cis-clipped’ palladium(II) species and a new C3 symmetric tripodal hydrazinic ligand. The Pd4L4 square assembly was prepared via an edge directed method, using the ‘cis-clipped’-palladium(II) species and a new C2 symmetric dipodal hydrazinic ligand. Both assemblies were characterised using multinuclear NMR and ESI-MS spectroscopic techniques and elemental analysis. The size of the assemblies were assigned from HR-TEM measurements, while DOSY NMR analysis established the presence of single component species in solution. Optimised structures obtained using Hartree–Fock calculations are in conformity with the experimental results. Both the assemblies show significant catalytic activity as heterogeneous catalysts for Suzuki–Miyaura coupling reactions under mild, aerobic and phosphine free conditions in aqueous ethanolic medium.

A double stranded metal-organic assembly accommodating a pair of water trimers in the host cavity and catalysing Glaser coupling.

A supramolecular compound, catena-poly{[Cu2(1,3-μ2-(1a))2(μ2-ter)2(H2O)2]n·(6H2O)n} (1) has been synthesized using (1a) [(1a = N(1),N(3),N(5)-trimethyl-N(1),N(3),N(5)-tris((pyridin-4-yl)methyl)-1,3,5-benzene tricarboxamide] and terephthalate (ter) as the pillaring unit by self-assembly. The terephthalate units are connected by copper(II) ions forming a single strand, while a pair of such strands are then linked by (1a) via two pyridyl terminal arms bound to copper(II) nodes on either side forming a one-dimensional double stranded assembly propagating along the c axis. The compound crystallizes in the Fdd2 space group. The cavity created in the interior of this double strand assembly trap six water molecules and are stabilized by hydrogen bonding with the host. The arrangement of the pair of acyclic water trimers in isolated cavities of (1) is such that it resembles a closed-bracket-like formation. The Hirshfeld surface analysis of (1) reveals the presence of strong intermolecular hydrogen-bonding interactions between one-dimensional ladder-like units and with the water trimer in the host cavity. The copper(II)-containing coordination polymer also acts as an efficient catalyst for the Glaser-Hay homo-coupling reaction.

RETRACTED ARTICLE: Investigation on Adsorption and the Corrosion Inhibition Effect of Some Novel Hydrazide Derivatives for Mild Steel in HCl Solution

Two hydrazide derivatives, namely, N′-(thiophene-2-ylmethylene)nicotinic hydrazone (TNH) and N′-(pyrrol-2-ylmethylene)nicotinic hydrazone (PNH), have been synthesized and investigated as corrosion inhibitors for mild steel in 1 M HCl solution by electrochemical, weight loss, field emission–scanning electron microscope (FE-SEM), atomic force microscope (AFM), and quantum chemical calculation methods. The experimental results show that both the compounds are good inhibitors for mild steel in 1 M HCl. They act as mixed type inhibitors with predominating cathodic character. The adsorption of inhibitors obeys the Langmuir adsorption isotherm. Correlation between quantum chemical parameters and experimental results is discussed.

CCDC 288222: Experimental Crystal Structure Determination

Related Article: R.P.John, Kyungjae Lee, Beom Jin Kim, Byoung Jin Suh, Hackjune Rhee, Myoung Soo Lah|2005|Inorg.Chem.|44|7109|doi:10.1021/ic050891h

CCDC 298634: Experimental Crystal Structure Determination

Related Article: R.P.John, Jaejoon Park, Dohyun Moon, Kyungjin Lee, Myoung Soo Lah|2006|Chem.Commun.||3699|doi:10.1039/b607675k