Tetrahedral molecular geometry

About: Tetrahedral molecular geometry is a research topic. Over the lifetime, 1795 publications have been published within this topic receiving 30706 citations.

Copper(II), nickel(II), cobalt(II) and oxovanadium(IV) complexes of substituted β-hydroxyiminoanilides

Abstract: Complexes of the general formula, ML2 [M = CuII, NiII, CoII and OVIV; L = 1,2,3,5,6,7,8,8a-octahydro-3-hydroxyimino-N-(4-X-phenyl)-l-phenyl-5-(phenylmethylene)-2-naphthalenecarboxamide (X = H, Me, OMe, Cl)] have been prepared and characterized on the basis of elemental analysis, magnetic moments and i.r., e.p.r. and electronic spectra. These metal complexes contain the N4 chromophore with the ligand coordinating through nitrogens of the azomethine and deprotonated anilide functions. C.v. measurements indicate that the copper(II) complexes are quasi-reversible in acetonitrile solution. Square planar and square pyramidal structures are assigned respectively to the copper(II) and oxovanadium(IV) complexes, whereas tetrahedral geometry is assigned to the nickel(II) and cobalt(II) complexes. Deprotonated anilide nitrogen is involved in coordination and the presence of an electron-donating group para to the anilide function decreases the ΔE values of the d–d transitions while the value is found to increase when electron-withdrawing groups are substituted. Line spacing in the e.p.r. spectra of the copper(II) and oxovanadium(IV) complexes increases when methyl group is para to the anilide group, and decreases when this group is replaced by methoxy or chloro. The ν(C–N) of the anilide group and the ν(C-N) of the azomethine function of the oxime metal complexes are metal-sensitive and the blue shift for the above stretching frequencies follows the order: copper(II) > oxovanadium(IV) > nickel(II) ≈ cobalt(II).

Synthesis, characterization and antimicrobial activity of transition metal complexes with the Schiff base derived from imidazole-2-carboxaldehyde and glycylglycine

Abstract: The Co(II), Ni(II) and Cu(II) complexes of the Schiff base derived from imidazole-2-carboxaldehyde and glycylglycine were synthesized and characterized by elemental analysis, PMR, molar conductance, IR, electronic, magnetic measurements, ESR, redox properties, thermal studies, XRD and SEM. Conductance measurements indicate that the complexes are 1 : 1 electrolytes. IR data show that the ligand is tetradentate with imidazole nitrogen, azomethine nitrogen, amide nitrogen and carboxylato oxygen donor groups. Electronic spectral measurements indicate tetrahedral geometry for Co(II) and Ni(II) complexes and square-planar geometry for Cu(II). Magnetic measurements show weak ferromagnetic behavior for Co(II) and Ni(II) complexes, and paramagnetic for Cu(II) complex. The X-band ESR spectral data indicate a covalent link between metal and ligand. The complexes were found to be stabilized in unusual oxidation states of metal during electrolysis. Thermal analysis of the complexes indicate that decomposition takes pl...

Temperature Dependence of the Crystal Lattice Organization of Coordination Compounds Involving Nitronyl Nitroxide Radicals: A Magnetic and Structural Investigation

Abstract: Four new mononuclear complexes of formula Cd(PN)(4)(NCS)(2) (A), Cd(PNN)(4)(N(3))(2) (B), Zn(PNN)(4)(N(3))(2) (C), and Zn(PNN)(2)(NCS)(2) (D), where PNN stands for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and PN for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl, were synthesized and structurally and magnetically characterized. The X-ray structures of compounds B and C were also determined at 90 K. Compounds A[bond]C crystallize in the triclinic space group P 1 macro (No. 2), and D crystallizes in the monoclinic space group P2(1)/m (No. 11). A[bond]C adopt a centrosymmetric distorted octahedral geometry in which the metal ions are bonded to four radical ligands through the nitrogen atom of the pyridyl rings and the azido or thiocyanato ligands occupy the apical positions. Compound D adopts a distorted tetrahedral geometry in which the zinc ion is bonded to two radicals and two thiocyanato ligands. As suggested by their magnetic behavior, the low-temperature X-ray structures of B and C show that these compounds undergo a clear structural change with respect to the room-temperature structures. The experimental magnetic behaviors were perfectly reproduced by a dimer model for A[bond]C and an alternating chain model for D while the sudden breaks observed in the chi(M)T versus T curves for B and C were well accounted for by the high- and low-temperature X-ray structures. For all these complexes the crystal structures favor significant overlap between molecular magnetic orbitals leading to rather strong intermolecular antiferromagnetic interactions.