Synthesis and characterization of oxo-bridged, trinuclear, six-coordinate mixed-carboxylato complexes of chromium (III)

Substitution reactions of thorium(IV) acetate to synthesize nano-sized carboxylate complexes

Some mixed-ligand thorium(IV) complexes with the general formula [Th(OOCCH(3))(4-n)L(n)] (L=anions of myristic, palmitic or stearic acid and n=1-4) have been synthesized by the stepwise substitution of acetate ions of thorium(IV) acetate with straight chain carboxylic acids in toluene under reflux. The complexes were characterized by elemental analyses, spectral (electronic, infrared, NMR and powder XRD) studies, electrical conductance and magnetic susceptibility measurements. Doubly and triply bridged coordination modes of the ligands were established by their infrared spectra and nano-size of the complexes by powder XRD. Room temperature magnetic susceptibility measurements revealed diamagnetic nature of the complexes. Electronic absorption spectra of the complexes showed pi-->pi*, n-->pi* and charge transfer transitions. Molar conductance values indicated the complex to be non-electrolytes. These are a new type of mixed-ligand thorium(IV) complexes for which a nano-sized, oxygen bridged polymeric structure has been established on the basis of physico-chemical studies.

Preparation and characterization of novel oxo-centered basic p-chlorobenzoic bridging trinuclear complexes

Three new oxo-centered trinuclear complexes, one of them a mixed-valence complex [Mn3O(C7H4O2Cl)6(Py)3]Py (1) and the others, mixed-metal complexes of [Fe2MnO(C7H4O2Cl)6(Py)3]NO3 (2) and [Fe2CoO(C7H4O2Cl)6(Py)3] (3) were synthesized by the direct reaction between metal nitrates and p-chlorobenzoic acid. These complexes were characterized by elemental analyses (CHN), atomic absorption spectroscopy and spectral (IR, electronic) studies. These are new type of oxo-bridged mixed-metal complexes in which the carboxylate ligand is pchlorobenzoic acid. The UV spectra of the complexes exhibited a strong band in the region 42,500 cm-1 which is related to the (? ? ?*) transitions of the pyridine ligand. The IR spectra of these compounds showed two strong stretching vibrations bands, indicating a bridging coordination mode of the carboxylic group of the ligand in the complexes.

Synthesis and characterization of novel oxo-bridged, trinuclear mixed-metal complexes of Cr(III) and Fe(III)

Two new heterotrinuclear p-chlorobenzoates, [Fe2CrO(C7H4O2Cl)6(py)3]NO3 (1) and [Cr2FeO(C7H4O2Cl)6(py)3]NO3 (2) were prepared as nitrate salts and characterized by elemental analyses (CHN), spectroscopic (infrared, electronic) studies and atomic absorption spectroscopy. These complexes are a new type of oxo-bridged mixed-metal complex in which the carboxylate ligand is p-chlorobenzoic acid. Bridging coordination modes for the carboxylates were indicated by the presence of ?asym (M2M'O) vibrations in the infrared spectra.

Spectral studies with coordination behaviour of (NO3) and (NCS) anions and EPR parameters of chromium(III) complexes which have different chromospheres macrocyclic ligands: synthesis and electronic spectroscopy

New macrocyclic ligands were prepared and chromium(III) stability in the marcrocyclic cavities are reported. Two of them have four-coordinate [N2O2]:[N4], third one has five-coordinate [N2O2S] and the last one has six-coordinate [N4O2] donor macrocyclic cavities. These macrocyclic ligands have been synthesized with their chromium(III) complexes which have mononuclear nature and their structural features have been discussed on the basis of: elemental analysis, magnetic moment, electronic, IR, 1H NMR, and EPR spectral studies. All the chromium(III) complexes show magnetic moments in the range of 3.74-3.80 B.M. corresponding to high-spin configuration. However, the interaction of oxygen to the chromium ion in complexes is much weaker than that of other donor atoms. The spin-orbit coupling parameter, z, gives no significance because the splitting of doublet transition lines are too large to be explained by spin-orbit coupling. The beta values (0.75-0.79) indicate the covalent character, which is due to the presence of sigma bond between the metal/ligand. lambda values indicate that the complexes under study have substantial covalent character and their g-values have also been calculated by using spin-orbital coupling constant (lambda).