Investigation on the Role of Molecular Planarity and Conjugation Effects on Physicochemical Properties of Anthracene and Pyrene Appended meso-5,15-Bis(Thien-2-yl)-10,20-Diphenylporphyrin Triads

To examine the influence of molecular planarity and conjugation effects on physicochemical properties of porphyrin π-system through meso-thienyl ring, a new class of anthracene and pyrene appended trans-ThPPZn(II)-An and trans-ThPPZn(II)-Py porphyrins have been synthesized. An efficient and facile methodology is adopted for the synthesis of trans-5NThPPM and trans-5AThPPM (where M = H2, Cu(II), Ni(II), Zn(II)) porphyrins from 5(5-nitro-2-thienyl)dipyrromethane. The 1H NMR spectra of the synthesized porphyrins showed two signals of equal intensity corresponding to the pyrrolyl β-protons, which evidenced the structure of trans-isomers. Electronic spectroscopy and cyclic voltammetry explain the near co-planarity of the thien-2-yl group with the central porphyrin π-system which can influence the electron delocalization on these molecules. The present study reveals the existence of resonance interaction between porphyrin core and anthracene/pyrene moiety in their thien-2-yl bridged conjugates.