Porphyrazines with Annulated Diazepine Rings. 2. Alternative Synthetic Route to Tetrakis-2,3-(5,7-diphenyl-1,4-diazepino)porphyrazines: New Metal Complexes, General Physicochemical Data, Ultraviolet−Visible Linear and Optical Limiting Behavior, and Electrochemical and Spectroelectrochemical Properties

Following a previous report on the synthesis and physicochemical characterization of a novel class of porphyrazines carrying peripherally annulated seven-membered rings, i.e., tetrakis-2,3-(5,7-diphenyl-1,4-diazepino)porphyrazine [Ph8DzPzH2]·4H2O and its metal derivatives [Ph8DzPzM]·xH2O (x = 2−7, M = MgII(H2O), CuII, and ZnII), a new more convenient procedure is reported here, allowing the preparation in high yields of the LiI and NaI derivatives of formulas [Ph8DzPzLi2]·5H2O and [Ph8DzPzNa2]·6H2O, which can be directly converted into other metal derivatives under mild conditions (room temperature) and in good yields. The series studied has been extended to include the MnII and CoII complexes also reported here for the first time. Physicochemical characterization of the new “diazepinoporphyrazines” was based on fast atom bombardment (FAB) mass spectrometry and X-ray powder patterns, infrared (IR), electron paramagnetic resonance (EPR), and room-temperature magnetic susceptibility measurements. A detailed discussion of the UV−vis spectra emphasizes the role played by the external diazepine rings in electron delocalization through their tautomeric or protonated forms present in neutral, basic, and acidic media. The nonlinear optical effect of optical limiting for the different species [M = 2H, MgII(H2O), MnII, CoII, CuII, and ZnII] has also been measured. It has been observed that the extent of the optical limiting depends on the specific M center. The observed nonlinear optical features are analyzed and discussed in terms of the electronic and magnetic properties exhibited by some of the metal ions and taking into account the model of the excited-state absorption in which the nature of M determines the kinetics of formation of the highly absorbing state of the specific complex examined. As evidenced by the detailed electrochemical and spectroelectrochemical study carried out on this new class of macrocycles, one of the most important aspects is the facilitated electron delocalization for the oxidized and reduced species allowed by a 1H−6H tautomerism taking place on the peripheral diazepine rings.