Ru(II) polypyridine complexes: photophysics, photochemistry, eletrochemistry, and chemiluminescence

Great attention is currently paid to the synthesis of polynuclear transition metal complexes and the study of their photochemical, photophysical, and electrochemical properties. This interest is stimulated, in particular, by attempts to design and construct multicomponent systems (often called supramolecular species) capable of performing useful lightand/or redox-induced functions.1-16 A great deal of investigations on mononuclear transition metal complexes had previously shown that several families of these compounds are very interesting from the electrochemical, photochemical, and photophysical viewpoints.17-22 The metalligand interaction, in fact, is often (i) weak enough to allow the manifestation of intrinsic properties of metal and ligands (e.g., ligand-centered and metalcentered absorption bands and redox waves) and, at the same time, (ii) strong enough to cause the appearance of new properties, characteristic of the whole compound (e.g., metal-to-ligand or ligand-tometal charge-transfer bands). On passing from mononuclear to polynuclear transition metal complexes, the situation becomes even more interesting because in the latter (supramolecular) compounds one can find, besides properties related to each metal-based component, properties related to the structure and composition of the whole array. A suitable choice of the mononuclear building blocks and bridging ligands and an appropriate design of the (supramolecular) structure can in fact allow the occurrence of very interesting and potentially useful processes such as energy transfer along predetermined pathways, photoinduced charge separation, multielectron exchange at a predetermined potential, etc. The knowledge on the luminescence and redox properties of polynuclear transition metal complexes is rapidly accumulating, but it is disperse in a great number of journals. We have made an attempt to collect the available results, and we present them together with some fundamental introductory concepts and a few comments. One of the main problems, of course, was to delimit the field of this review. Using personal criteria which are related to our own research interests, we decided to consider only polynuclear transition metal complexes that can be defined as supramolecular species (section 2.2) and that are reported to exhibit luminescence. For such compounds only, the electrochemical properties have also been reviewed. Furthermore, we decided to include only classical (Werner-type) polynuclear transition metal compounds where the number of metal-based units is exactly known and the connection between the metal centers is provided only by bridging ligands. Thus, a number of interesting systems such as polymer-appended metal † In memoriam of Mauro Ciano. 759 Chem. Rev. 1996, 96, 759−833

Luminescent and Redox-Active Polynuclear Transition Metal Complexes.

A sensor designed to determine the amount and concentration of analyte in a sample having a volume of less than about 1 μL. The sensor has a working electrode coated with a non-leachable redox mediator. The redox mediator acts as an electron transfer agent between the analyte and the electrode. In addition, a second electron transfer agent, such as an enzyme, can be added to facilitate the electrooxidation or electroreduction of the analyte. The redox mediator is typically a redox compound bound to a polymer. The preferred redox mediators are air-oxidizable. The amount of analyte can be determined by coulometry. One particular coulometric technique includes the measurement of the current between the working electrode and a counter or reference electrode at two or more times. The charge passed by this current to or from the analyte is correlated with the amount of analyte in the sample. Other electrochemical detection methods, such as amperometric, voltammetric, and potentiometric techniques, can also be used. The invention can be used to determine the concentration of a biomolecule, such as glucose or lactate, in a biological fluid, such as blood or serum. An enzyme capable of catalyzing the electrooxidation or electroreduction of the biomolecule is provided as a second electron transfer agent.

Small volume in vitro analyte sensor

Communication between iron(II) building blocks in cooperative spin transition phenomena

Spin crossover in iron(II)-complexes

Synthesis and electrochemical and photoemission properties of mononuclear and binuclear ruthenium(II) complexes containing 2,2'-bipyridine, 2,9-dimethyl-1,10-phenanthroline, 2,2'-bipyrimidine, 2,2'-biimidazole, and 2-pyridinecarboxaldimine ligands

Contrary to previous reports, the tris(2-(2-pyridyl)imidazole)iron(II) ((Fe((py)imH)/sub 3/)/sup 2 +/) and tris(2-(2-pyridyl)benzimidazole)iron(II) ((Fe((py)bimH)/sub 3/)/sup 2 +/) cations have been shown to be spin-equilibrium species in solution by variable-temperature magnetic and electronic spectral studies. Laser Raman temperature-jump kinetics has been used to directly measure the forward (k/sub 1/ = 1.1 x 10/sup 7/s/sup -1/) and reverse (k/sub -1/ = 1.0 x 10/sup 7/s/sup -1/) intersystem crossing rate constants for the dynamic spin-interconversion process in (Fe((py)imH)/sub 3/)/sup 2 +/. The results are compared to similar kinetic data available for other iron(II) spin-forbidden/conversion processes in bis(pyrazolylborate)iron(II) and (Fe(6-Mepy)/sub n/(py)/sub m/tren)/sup 2 +/. 2 tables, 3 figures, 36 references.

Solution-state spin-equilibrium properties of the tris[2-(2-pyridyl)imidazole]iron(II) and tris[2-(2-pyridyl)benzimidazole]iron(II) cations

Dynamics of intersystem crossing processes in solution for six-coordinate d5, d6, and d7 spin-equilibrium metal complexes of iron(III), iron(II), and cobalt(II)

Synthesis and spin-state studies in solution of .gamma.-substituted tris(.beta.-diketonato) iron(III) complexes and their spin-equilibrium .beta.-ketoimine analogues derived from triethylenetetramine

Bis(N-methylethylenediaminesalicylaldiminato)iron(III) complexes, (Fe(X-Salmeen)/sub 2/)(PF/sub 6/), with their FeN/sub 4/O/sub 2/ cores have been shown by variable-temperature magnetic susceptibility (10 to 300 K) and Moessbauer spectroscopy to be new (low-spin, S = /sup 1///sub 2/) reversible (high-spin, S = /sup 5///sub 2/), spin-squilibrium compounds in the solid state. From the Moessbauer spectra, an upper limit of approximately 10/sup 7/s/sup -1/ has been established for the rate of intersystem crossing in the solid state. The spin equilibria are also supported in the solution state, as verified by variable-temperature (200 to 300 K) magnetic susceptibility and electronic spectroscopy measurements. In solution, laser Raman temperature-jump kinetics has been employed to directly measure the forward (k/sub 1/) and reverse (k/sub -1/) rate constants for the intersystem crossings with 2 x 10/sup 7/s/sup -1/ < or approximately k < or approximately 2 x 10/sup 8/s/sup -1/. Intersystem crossing rate constant data for these bis-tridentate (Fe/sup III/(X-Salmeen)/sub 2/)/sup +/ complexes are discussed and compared to data already available for the electronically similar (same FeN/sub 4/O/sub 2/ core) but structurally different (hexadentate ligand) spin-equilibrium species, (Fe/sup III/(Sal)/sub 2/trien)/sup +/. 4 tables, 6 figures, 40 references.

Bis(N-methylethylenediminesalicylaldiminato)iron(III) complexes. Magnetic, Moessbauer, and intersystem crossing rate studies in the solid and solution states for a new (S = /sup 1///sub 2/) in equilibrium (S = /sup 5///sub 2/) spin-equilibrium case

Eric V. Dose

Papers

Synthesis and electrochemical and photoemission properties of mononuclear and binuclear ruthenium(II) complexes containing 2,2'-bipyridine, 2,9-dimethyl-1,10-phenanthroline, 2,2'-bipyrimidine, 2,2'-biimidazole, and 2-pyridinecarboxaldimine ligands

Solution-state spin-equilibrium properties of the tris[2-(2-pyridyl)imidazole]iron(II) and tris[2-(2-pyridyl)benzimidazole]iron(II) cations

Dynamics of intersystem crossing processes in solution for six-coordinate d5, d6, and d7 spin-equilibrium metal complexes of iron(III), iron(II), and cobalt(II)

Synthesis and spin-state studies in solution of .gamma.-substituted tris(.beta.-diketonato) iron(III) complexes and their spin-equilibrium .beta.-ketoimine analogues derived from triethylenetetramine

Bis(N-methylethylenediminesalicylaldiminato)iron(III) complexes. Magnetic, Moessbauer, and intersystem crossing rate studies in the solid and solution states for a new (S = /sup 1///sub 2/) in equilibrium (S = /sup 5///sub 2/) spin-equilibrium case