In this work we report the obtention of a tetrabutylammonium hydroxide (TBAOH) solution in acetonitrile in a one pot process in order to study the interaction ironporphyrinOH- in non-aqueous systems. All the reactions were carried out under dry argon atmosphere to prevent the contamination of the solution with CO2, which leads to the formation of (TBA)2CO3.

Life on earth depends on the absorption and conversion of solar energy into chemical bonds, i.e. photosynthesis. In this process, sun light is employed to oxidize water into oxygen and reducing equivalents used to produce fuels. In artificial photosynthesis, the goal is to develop relatively simple systems able to mimic photosynthetic organisms and promote solar-to-chemical conversion. The aim of the present review was to describe recent advances in the application of coordination compounds as catalysts in some key reactions for artificial photosynthesis, such as water splitting and CO2 reduction.

Spin crossover is a property found in some coordination compounds formed by the first series of transition metals with d4-d7 configuration. These complexes, when stimulated by an external factor (temperature, light, etc.), can be converted from their low spin states to high spin states, or vice versa. However, this issue is not addressed in the Inorganic Chemistry literature used in undergraduate courses. In this work, the Density Functional Theory is used to predict which complexes may present the Spin Cross Over property. In addition to establish a methodology to predict in which situations this process will occur, this computational tool can also be used in undergraduate or postgraduate classes to explore this property in the study of coordination compounds.

Copper(II) (3d9, S = 1/2) complexes are stable and widely investigated by electron paramagnetic resonance (EPR) spectroscopy. In contrast, isoelectronic nickel(I) is much less common and much less investigated. Nickel(I), however, is of biological interest as the active site of methyl coenzyme M reductase (MCR) contains a tetraaza macrocyclic ligand, F430, which coordinates NiI in its active form, MCRred1. As result, the redox behavior and spectroscopy of tetraaza macrocyclic complexes of nickel is of importance in biomimetic chemistry. Such efforts are complicated by the difficulty in generating NiI from their stable, NiII, precursors. Reduction of NiII macrocyclic complexes can afford NiI in certain cases, but in many other cases can lead instead to reduction of the macrocycle to generate an organic radical anion. Previous studies on the formation of tetraaza macrocyclic complexes of NiI are discussed in terms of the competition between metal-centered and ligand-centered reduction. EPR results are particularly important in making the distinction between these two reduction processes, as formation of NiI gives characteristic EPR spectra similar to those for CuII, while ligand-centered reduction gives narrow EPR spectra at g = 2.00, typical of organic radicals. Even if metal-centered reduction occurs, the geometry of the resulting NiI macrocyclic complex is highly variable and, as a result, the EPR spectral appearance is highly variable. In this case, the comparison is between the extremes of spectra typical for tetragonally distorted complexes (<img src="/img/revistas/jbchs/v21n7/a02img11.gif" align=absmiddle> ground state, which includes tetragonally distorted octahedral, square pyramidal and square planar geometries) and those for trigonal bipyramidal complexes (<img src="/img/revistas/jbchs/v21n7/a02img12.gif" align=absmiddle> ground state). Previous work on CuII was related to the situation for NiI. The different types of EPR spectra for such systems are specifically discussed using previously unpublished examples of several tetraaza macrocyclic complexes of nickel, including F430 and MCR itself.

Homo and heterotrinuclear acetates are unique compounds having μ3-oxo bridge and many interesting properties of such compounds are derived from this structure. Some undergraduate inorganic textbooks discuss several aspects of these compounds and we present here an undergraduate experiment for the high-yield synthesis of [Fe2MO(CH3CO2)6(H 2O)3], with M = Fe3+, Co2+ and Ni2+, as well as their characterization using infrared spectroscopy and cyclic voltametry. The proposed experiment gives the opportunity to discuss several concepts of coordination chemistry that follow the characterization techniques, such as: types of acetate coordination, reversibility of electrochemical processes, quelate and trans effects and lability.

Coordination compounds of the radioactive element technetium are well established in diagnostic nuclear medicine, and various complexes of the gamma-emitting nuclide 99mTc are routinely used for organ imaging. Modern trends in the radiopharmaceutical chemistry of technetium focus on the 'labeling' of biologically active molecules such as peptides, steroids or other receptor-seeking units. This requires more knowledge about the coordination chemistry of the artificial transition metal, particularly with regard to stable or kinetically inert coordination spheres, which allow couplings to biomolecules following a bioconjugate approach. The dominant role of technetium compounds in diagnostic procedures recommends the beta--emitting rhenium isotopes 186Re and 188Re for applications in nuclear-medical therapy. 188Re is readily available from an 188W/188Re radionuclide generator system and general synthetic approaches can be adopted from the established technetium chemistry.

This paper describes in a somewhat personal way an overview of the use of electron paramagnetic resonance (EPR) spectroscopy, including high-frequency and -field EPR (HFEPR) to unravel the electronic structure of transition metal ion complexes. The spin Hamiltonian parameters obtained from EPR experiments, namely the g matrix for systems with S =1/2 and the g and D (zero-field splitting) matrices for systems with S > 1/2 provide information on d orbital energy levels. This information can be combined with ligand-field theory (LFT) to provide information on the overall electronic structure of the paramagnetic transition metal complex. As has been discussed by others, LFT is still useful in providing such a quantitative understanding of these complexes, even in the day of advanced computational methods, such as density functional theory (DFT). The discussion is illustrated by examples across the d n configuration.

An efficient synthetic access to new cationic porphyrin-bipyridine iridium(III) bis-cyclometalated complexes was developed. These porphyrins bearing arylbipyridine moieties at β-pyrrolic positions coordinated with iridium(III), and the corresponding Zn(II) porphyrin complexes were spectroscopically, electrochemically, and electronically characterized. The features displayed by the new cyclometalated porphyrin-bipyridine iridium(III) complexes, namely photoinduced electron transfer process (PET), and a remarkable efficiency to generate 1O2, allowing us to envisage new challenges and opportunities for their applications in several fields, such as photo(catalysis) and photodynamic therapies.