In-situ spectroelectrochemistry (EPR, UV-visible) and aggregation behavior of H-2 BDCP and Zn(II)BDCP [BDCP = {5,10,15,20-tetrakis[3,4-(1,4-dioxan)phenyl]porphyrin}(2-)]

Abstract

In-situ UV-visible and EPR Spectroelectrochemistry of a free base porphyrin, 5,10,15,20-tetrakis[3,4-(1,4-dioxan)phenyl]porphyrin, and its zinc derivative, 5,10,15,20-tetrakis[3,4-(1,4-dioxan)phenyl]porphyrinatozinc(10 were performed. On one-electron oxidation of the free base porphyrin in dichloromethane/0.1 M BuN4PF6 using an optically transparent thin layer cell, the initial Soret band retains its intensity and an equally intense new band appears at 453 nm. The initial Q bands disappear, and new bands appear at 516, 555 and 694 nm. At 295 K, it exhibits an isotropic EPR signal with a peak to peak separation of about 6 G and centered at g = 2.004. On one-electron oxidation of the zinc-porphyrin in similar conditions, the Soret band loses its intensity, and a new band appears at 466 nm. The in-situ generated one-electron oxidized species exhibits an isotropic EPR signal at 295 K which is centered at g = 2.0035. The formations of aggregates/self-assemblies of zinc-porphyrin were monitored by UV-vis spectroscopy, fluorescence imaging by confocal microscope, TEM, SEM and DLS measurements. A tentative mechanism has been also proposed for the generation of different aggregates, with varying size and shape, in water-DMF binary mixtures. (C) 2014 Elsevier Ltd. All rights reserved.