Shailendra Tripathi

Electron spin resonance studies on some copper(II) complexes with a few nitrogen donors derived from pyridine

Abstract Electron spin resonance spectral studies have been made on copper(II) chloride, bromide, thiocyanate and sulphate complexes with some pyridine derivatives, viz. nicotinic acid (NA), nicotinamide (NICA) and isonicotinamide (INA) in solid and DMF-solution states to see the effect of different anions on the Spin-Hamiltonian parameters at the paramagnetic site for a particular ligand. The spectra of the complexes for a particular anion are almost comparable suggesting the same local symmetry for them. Analysis of the ESR data reveals axial symmetry for all the complexes, except Cu(NA) 2 SO 4 for which a rhombic symmetry is suggested. The study shows the interaction of solvent (DMF) molecules with copper(II) ion in the axial plane as evident from the differences in 295 and 77 K g | values. Moreover, the spectra are consistent with the complete absence or negligbly small copper(II)—copper(II) interactions (in few cases) in these complexes. The various Spin-Hamiltonian parameters calculated from ESR data indicate the presence of an unpaired electron in the d x 2 − y 2 orbital of the copper(II) ion with the additional possibility of a d xy ground state for Cu(NA) 2 SO 4 .

Coordination polymers of cobalt (II) involving 4,4'-bipyridyl and its dioxide

SummaryAnalytical data, room temperature magnetic moment values, electronic and i.r. spectral measurements down to 200 cm−1 on the coordination compounds formed by the interaction of cobalt(II) chloride, bromide, thiocyanate, acetate and nitrate with 4,4′-bipyridyl and 4,4′-bipyridylN,N′-dioxide indicate that the isolated compounds are coordination polymers having tetrahedral or octahedral stereochemistry around cobalt(II) involving bridging 4,4′-bipyridyl/4,4′-bipyridylN,N′-dioxide molecules. Terminally bonded acetato- and nitrato-ligands and bridging or terminally bonded chloro-, bromo- and thiocyanato-groups in the solid state.

Spectroscopic studies on copper(II) halide complexes with isomeric benzoylpyridines: Electronic and electron spin resonance spectral evidence for five-coordinate copper(II) species in solution

Abstract Coordination compounds formed by copper(II) chloride and bromide with 2-, 3- and 4-benzoylpyridines (BOP)Cu(2-BOP)Cl 2 , Cu(3-BOP) 2 Cl 2 , Cu(4-BOP)Cl 2 , Cu(2-BOP) 2 Br 2 , Cu(3-BOP) 2 Br 2 and Cu(4-BOP) 2 Br 2 —have been characterized by elemental analyses, molar conductance, magnetic moments, electronic, IR and ESR spectral studies. It is suggested that Cu(2-BOP)Cl 2 is monomeric tetrahedral, Cu(3-BOP) 2 Cl 2 and Cu(4-BOP)Cl 2 are dimeric octahedral and tetrahedral structures, respectively, bridging through chlorines while all the bromo complexes are polymeric octahedral structures with bridging bromine atoms in the solid state. Powder ESR data reveal rhombic symmetry for all the chloro complexes. Cu(2-BOP) 2 Br 2 is suggested to have an axial symmetry while the other bromo complexes are isotropic in nature. Electronic and ESR spectral studies in DMSO solution suggest the interaction of solvent molecules with copper(II) ions in the axial plane. The solution spectral data are almost comparable suggesting same local symmetry for all the compounds consistent with five-coordinate square pyramidal geometry in each case. ESR spectra also suggest considerable CuCu interactions in Cu(3-BOP) 2 Cl 2 . Various Spin—Hamiltonian parameters calculated from ESR data indicate the presence of an unpaired electron in the d x 2 − y 2 orbital of the copper(II) ion in an axial symmetry.

Synthesis and Characterization of Silver(I) Nitrate Complexes with 2-, 3-, and 4- Cyano- Pyridines and Anilines

Abstract Coordination compounds formed by the interaction of silver(I) nitrate with 2-, 3- and 4- cyano- pyridines and anilines have been prepared and characterized on the basis of analytical data, molar conductanoes and infrared spectral measurements down to 200 cm−1 in the solid state. The complexes isolated are Ag(2-cyanopyridine)NO3 and AgL2·O3, where L - 3- or 4- cyanopyridine, 2-, 3- or 4- cyanoaniline. Molar conduotanoe measurements indicate that these complexes are non-electrolytes in ethanol but 1:1 electrolytes in aqueous solutions. Infrared spectral studies show that (i) the cyano- pyridines and anilines, though potentially bidentate ligands, act as monodentate ones bonding via the pyridine ring nitrogen (cyanopyridines) or NH2 nitrogen (cyanoanilines) and (ii) the nitrate groups are present as terminally bonded monodentate ligands in all the compounds except in the 2-cyanopyridine complex which is ionia. Coordination numbere and etereochemistries for ailver(1) are proposed.

Some Neutral Three-Coordinate Complexes of Mercury(II)

Abstract The preparation of 1:2 and 1:1 mercury(II) chloride and bromide complexes with 2- and 4- cyanoanilines is described. These compounds are freely soluble in ethanol in which they behave as non-electrolytes. Molecular weight measurements in molten camphor indicate the 1:1 complexes as monomeric structures. Based on molar conductance values, molecular weight determinations and infrared spectral features down to 200 cm−1, the 1:2 (metal:ligand) complexes are considered as neutral 4-coordinated tetrahedral structures while the 1:1 complexes appear to be neutral species having monomeric, three-coordinated environments around mercury(II).

Synthesis and Characterization of Bis(2-Pyridyl-N-Oxide)Disulphide Complexes with Some Uranyl Salts

Abstract Coordination compounds formed by uranyl chloride, thiocyanate, nitrate, sulphate and acetate with bis(2-pyridyl-N-oxide)di-sulphide have been prepared and characterized on the basis of analytical data, molar conductance, electronic and infrared spectral measurements down to 200 om−1. Bis(2-pyridyl-N-oride)disulphide acts as a bidentate ligand through its oxygen atoms resulting in 9-membered rings. Coordination numbers and stereochemical environments around uranium(VI) are proposed.

4-Cyanoaniline complexes with transition metal(II) halides

SummaryCoordination compounds formed by the interaction of manganese(II), cobalt(II), nickel(II) and copper(II) chloride and bromide with 4-cyanoaniline (4-CA) have been prepared and characterized by molar conductance, magnetic susceptibilities, electronic and i.r. spectral measurements down to 200 cm−1 in the solid state. The isolated complexes are M(4-CA)2X2 except for nickel(II) bromide which is NI(4-CA)4Br2. I.r. spectra, indicate that 4-CA, though a potentially bidentate ligand, nevertheless acts only as a terminally aniline (NH2) bonded monodentate ligand in all the complexes. Tentative stereochemistries of the complexes have been suggested in the solid state.

Synthetic and Spectral Studies on Copper(II) Chloride and Bromide Complexes with Isomeric Aminobenzonitriles

Abstract Syntheses of the coordination compounds formed by the interaction of copper(II) chloride and bromide vith 2-, 3- and 4- amino-benzonitrilee (ABN) has been described. The compounds isolated have been characterized on the basis of elemental analyses, electrical conductance, magnetic moments, electronic and electron spin resonance studies in the solid and DMF solution states to study the steric effects caused by the nitrile substitution, at different positions, on the nature of copper(II)—nitrogen bond. The spectra of the complexes for a particular halide are closely comparable suggesting that they have the same local symmetry. Analysis of the polycrystalline ESR data indicate rhombic symmetry for the chloro complexes. Axial symmetry is, however, suggested for the bromo complexes. The solution ESR as well as electronic spectral studies show the interaction of solvent (DMF) molecules with copper(II) ion in the axial plane. Various spin—Hamiltonian parameters calculated from the ESR data indicate the ...

Neutral Three-Coordinate Complexes of Mercury(II) Involving Coordinated Thiocyanato Groups

Abstract The preparation of 1:1 (metal:ligand) complexes of mercury(II) thiocyanate with several substituted pyridines — 4-benzyl-pyridine, 3- and 4- benzoylpyridines, nicotinamide and N-methyl-nicotinamide — is described. All the complexes are soluble in dimethylformamide or methanol in which they behave as non-electrolytes. Based on molar conductance values and infrared spectral features down to 200 cm−1, the complexes described herein are considered as neutral species exhibiting coordination number three around mercury(II) in the solid state.

Some neutral three-coordinate complexes of mercury(II) halides and pseudohalides with N-methylnicotinamide

Coordination compounds of mercury(II) chloride, bromide, cyanide and thiocyanate with N-methylnicotinamide, a potentially bidentate ligand, have been prepared. The complexesisolated have 1∶1 (metal:ligand)stoichiometry. Molecular weight measurements in molten camphor indicate that the mercury (II) chloride and bromide complexes are monomeric. Based on conductance values, molecular weight determinations and infrared spectral data, it is inferred that in the solid state in all these complexes the metal ion has a coordination number three and is bonded to the N-methylnicotinamide via its pyridine ring nitrogen, and is terminally bonded to the halogen/pseudohalogens.