Synthesis and Photophysical and Electrochemical Study of Tyrosine Covalently Linked to High‐Valent Copper(III) and Manganese(IV) Complexes

Abstract

As bio-inspired chemical model of the oxygen-evolving complex (OEC) in photosystem II, a new tyrosine-modified corrole ligand 3 and its high-valent copper and manganese complexes 3a and 3b were synthesized and characterized. The copper complexes 1a and 2a of corrole 1 and 2 were also prepared for comparison. The emission property indicates that the emission of ligands 2 and 3 is located at 670 nm, but no emission is observed for their metal complexes due to its suppression by the metal center. The electrochemical study shows that 3a might dimerize at the first two reversible oxidations, a behavior which was not observed in the case of 1a and 2a. The corrolato manganese(IV) complex 3b shows one reversible reduction and one quasireversible oxidation at À 0.17 and 0.77 V vs. Ag/Ag þ , respectively.Introduction. -The four-electron oxidation of water in photosynthetic organisms is achieved by an oxygen-evolving complex (OEC) in photosynthesis, which is one of the most important and fundamental chemical processes in nature [1 -3]. A series of X-ray structure analysis of photosystem II (PS II) [4 -6] indicated that the active site in a photosynthetic OEC protein contains a Mn 4 Ca cluster [5] [6], and a neighboring ltyrosine (Tyr z ) is linked between P 680 and OEC. By light absorption of the primary electron donor P 680 consisting of chlorophyll a molecules, electron transfer occurs from the excited P 680 * to a primary electron acceptor, pheophytin, and subsequently to two quinines, forming a P 680 radical cation. The electrons produced by oxidation of water at the Mn 4 Ca cluster are transferred through redox-active Tyr z to P

Energy- and Electron-Transfer Processes in Corrole−Perylenebisimide−Triphenylamine Array

“…Synthesis of complex corroles can be accomplished via the preparation of complex aldehydes followed by the corrole-forming reaction , or via a postfunctionalization of simple corroles bearing desired functional groups (NH 2 , COOH, OH, etc.) . From the point of view of minimalization of operations on the corroles, the first route is more attractive.…”

Reactivity and Mechanism Studies of Hydrogen Evolution Catalyzed by Copper Corroles

“…Dry solvents, including acetonitrile, dichloromethane, and chloroform, were purified by passage through activated alumina. Corrole ligands, 5,15-pentafluorophenyl-10-(4-nitrophenyl)­corrole, 5,10,15-tris-pentafluorophenylcorrole, and 5,15-pentafluorophenyl-10-(4-methoxyphenyl)­corrole, were synthesized using modified methods reported previously. ,,− 1 H NMR spectroscopic measurements were made on a Brüker spectrometer operating at 400 MHz. Electronic absorption spectra were acquired on a Cary 50 spectrophotometer.…”

Electrochemistry of Corroles in Nonaqueous Media

“…Almost two dozen papers (refs , , , , − , , , , , , and − ) have been published on the electrochemistry of manganese corroles since the initial electrochemical characterization of (OEC)Mn in 1998 . Some of the published papers have elucidated the redox properties of air stable compounds with a Mn­(III) center (refs , , , − , , , , and − ), while others have involved characterization of synthesized corroles with Mn­(IV) (refs , , , , , , , , and − ) or Mn­(V) (refs , , and ) central metal ions. Most of the elucidated redox processes have been oxidations, in large part because of the quite negative potential needed to access the singly reduced form of the compounds.…”

“…In the initial study of (OEC)Mn by Kadish, Vogel, and their co-workers, it was stated that the first oxidation of (OEC)Mn “unambiguously leads to a Mn­(IV) complex as ascertained by the ESR spectrum” . Assignments of a Mn­(IV) oxidation state were also made in a follow-up study of (OEC)Mn by Ou and co-workers, as well as in a number of later studies from other laboratories involving a characterization of manganese corroles with different skeletal structures (see refs , , , , , , , , and − ). However, if the examined (OEC)Mn derivative were actually present in solution as a Mn­(II) π-cation radical, i.e., (OEC +• )­Mn II , then the reductions and oxidations in nonaqueous media might both involve the conjugated macrocycle and lead to an initial formation of [(OEC)­Mn II ] − and [(OEC 2+ )­Mn II ] + prior to generation of a final Mn­(III) and Mn­(IV) corrole, respectively.…”

“…Numerous copper corroles have been characterized as to their electrochemical properties in nonaqueous media (see refs , − , − , , , , , , , , − , , , , , , and − ). The examined compounds include numerous β-pyrrole-substituted corroles, meso-substituted triarylcorroles, β,β′-benzotriarylcorroles, and bis-copper corrole dyads. ,, …”