A series of bis(pyridine)cobalt corroles with one or three nitrophenyl groups on the meso positions of the corrole macrocycle were synthesized and characterized as to their electrochemical and spectroscopic properties in dichloromethane, benzonitrile, and pyridine. The potentials for each electrode reaction were measured by cyclic voltammetry and the electron-transfer mechanisms evaluated by analysis of the electrochemical data combined with UV-visible spectra of the neutral, electroreduced, and electroxidized forms of the corroles. The proposed electronic configurations of the initial compounds and the prevailing redox reactions involving the electroactive central cobalt ion, the electroactive conjugated macrocycle, and the electroactive meso-nitrophenyl groups are all discussed in terms of solvent binding and the number of the nitrophenyl groups and other substituents on the meso-nitrophenyl rings of the compounds.

Four bis-ammonia ligated cobalt corroles and four mono-DMSO ligated cobalt corroles with different meso-aryl substituents on the macrocycle (A 2 B-and A 3 -corroles) were synthesized and investigated as to their electrochemical and spectroscopic properties under different solution conditions. The complexation energies of the investigated cobalt corroles were [a] Scheme 2. Structures of the investigated bis-ammonia and mono-DMSO meso-aryl cobalt corroles. dinated form of A 3 -and/or A 2 B-cobalt corroles) which will bind CO. Very recently, concentrations of CO as low as a few hundred ppb were measured by SAW sensors emphasizing the interest of such sensors for the detection of carbon monoxide. [4] Scheme 3. Synthesis of mono-DMSO and bis-NH 3 cobalt corroles.The eight cobalt corroles 1DMSO-4DMSO and 1NH 3 -4NH 3 were prepared according to the synthetic procedure shown in Scheme 3. The A 3 -and A 2 B-free-base corroles 1H-4H were synthesized according to published procedures described by Gryko and co-workers, [5] and metallated with Co(OAc) 2 in DMSO to give the cobalt complexes 1DMSO-4DMSO, each with a single DMSO molecule as axial ligand. These mono-DMSO adducts were then treated with an aqueous ammonia solution to give the bis-ammonia derivatives 1NH 3 -4NH 3 in 79-94 % yield. Spectroscopic Characterization1DMSO-4DMSO were measured at a concentration of 10 -3 M in both CH 2 Cl 2 and DMSO containing 0.1 M TBAP (Figure 2). In CH 2 Cl 2 the spectra are characterized by a Soret band at 379-387 nm and a single less intense band at 562-566 nm. There is also a shoulder on the Soret band at about 414-417 nm. These spectra are similar to previously reported UV/Vis spectra for a related series of mono-DMSO ligated cobalt nitrophenylcorroles under the same solution conditions. [3] Similar spectral patterns are seen for 2DMSO, 3DMSO and 4DMSO in the two solvents but this is not the case for 1DMSO as seen in Figure 2. The spectrum in CH 2 Cl 2 (Figure 2a) is assigned to the mono-DMSO adduct while in DMSO a mixture of the five-and six-coordinate derivatives are proposed to exist, the hexa-coordinate DMSO adduct having bands at 417, 442, 453 and 618 nm as described on the following pages. It should be noted that 1DMSO is the only cobalt corrole among the currently investigated compounds which possesses six electronwithdrawing substituents on the meso-phenyl rings, and this seems to facilitate the binding of a second DMSO molecule to the cobalt center of the neutral compound. Stronger pyridine binding constants were also earlier reported for cobalt corroles with electron-withdrawing substituents on the meso-phenyl rings. [3] UV/Visible spectra of the bis-ammonia complexes 1NH 3 -4NH 3 were also measured at a concentration of 1 × 10 -3 M un-Eur.(CO 2 MePh)Mes 2 CorCo(DMSO) (2DMSO): 88 % yield (211 mg). UV/ Visible (toluene, 1 % DMSO): λ max (ε × 10 -3 L·mol -1 cm -1 ) 383 (62.9), 563 (13.1) nm. 1 H NMR [500 MHz, CDCl 3 + NH 3 (g)]: δ = 8.98 (d,

A novel solid contact type for all-solid-state ion-selective electrodes is introduced, yielding high stability and reproducibility of potential readings between sensors as well as improved analytical performance. The transducer phase herein proposed takes advantage of the presence of porphyrinoids containing the same metal ion at different oxidation states. In contrast to the traditional approach, the compounds of choice are not a redox pair; although they have different oxidation states, they cannot be electrochemically driven one to another. The compounds of choice were cobalt(II) porphyrin and cobalt(III) corrole-both characterized by a high stability of the coordinated metal ions in their respective redox states and electrical neutrality, as well as relatively high lipophilicity. The porphyrinoids were used together with carbon nanotubes to yield transducer layers for ion-selective electrodes. As a result, we obtained a high stability of potential readings of the resulting ion-selective electrodes together with good reproducibility between different sensor batches. Moreover, advantageously the presence of porphyrinoids in the transducer phase results in improvement of the analytical performance of the sensors: linear response range and selectivity due to interactions with membrane components, resulting in tailoring of ion fluxes through the membrane phase. Thus, carbon nanotubes with the cobalt(II) porphyrin/cobalt(III) corrole system are promising alternatives for existing transducer systems for potentiometric sensors.