(Invited) Catalytic and Biocatalytic Iron Porphyrin Carbene Formation: Effects of Binding Mode, Carbene Substituent, Porphyrin Substituent, and Protein Axial Ligand

2016 ◽  
Keyword(s):  
Binding Mode ◽  
Axial Ligand ◽  
Iron Porphyrin

Stable Iron Porphyrin Intramolecularly Coordinated by Alcoholate Anion: Synthesis and Evaluation of Axial Ligand Effect of Alcoholate on Spectroscopy and Catalytic Activity

2019 ◽  
Vol 58 (7) ◽  
pp. 4268-4274
Author(s):  
Yoshinori Shirakawa ◽  
Yuuki Yano ◽  
Yuki Niwa ◽  
Kanako Inabe ◽  
Naoki Umezawa ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Axial Ligand ◽  
Iron Porphyrin ◽  
Ligand Effect

scholarly journals Multireference Ground and Excited State Electronic Structures of Free- versus Iron Porphyrin-Carbenes

2019 ◽  
Author(s):  
Gautam Stroscio ◽  
Martin Srnec ◽  
Ryan Hadt
Keyword(s):  
Excited State ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Closed Shell ◽  
Axial Ligand ◽  
Iron Porphyrin ◽  
Functional Theory ◽  
Reaction Coordinates ◽  
Ligand Charge Transfer ◽  
Energy Surfaces

Iron porphyrin carbenes (IPCs) are important reaction intermediates in engineered carbene transferase enzymes and homogeneous catalysis. However, discrepancies between theory and experiment complicate the understanding of IPC electronic structure (i.e., open- vs. closed-shell singlet (OSS vs. CSS)). Here we investigate the structurally dependent ground and excited spin state energetics of a free carbene and its IPC analogs. Only multireference <i>ab initio</i> wave function methods are consistent with experiment and predict a CSS ground state (Fe(II)←{:C(X)Y}<sup>0</sup>), contrary to density functional theory (DFT). The OSS is a high-lying metal-to-ligand charge transfer (MLCT) excited state that is sensitive to the nature of the axial ligand. Furthermore, potential energy surfaces (PESs) along the Fe–C bond elongation coordinate exhibit strong mixings between CSS/OSS characters, which can be an important feature for describing reaction mechanisms. Future studies on IPC reaction coordinates should evaluate contributions from ground and excited state multireference character. <br>

Primary photoprocesses in cationic 5,10,15,20-meso-tetrakis(4-N-methylpyridiniumyl)porphyrin and its transition metal complexes bound with nucleic acids

2003 ◽  
Vol 07 (11) ◽  
pp. 766-774 ◽  
Author(s):  
Vladimir S. Chirvony
Keyword(s):  
Excited States ◽  
Transition Metal Complexes ◽  
Photophysical Properties ◽  
Binding Mode ◽  
Axial Ligand ◽  
Guanosine Monophosphate ◽  
Groove Binding ◽  
Base Pairs ◽  
Excited Complex ◽  
Groove Binding Mode

Photophysical properties of meso-tetrakis(4-N-methylpyridiniumyl)porphyrin ( TMpyP 4) and its metallocomplexes M (II) TMpy P4 ( M = Zn , Cu , Ni , Co ) bound to natural DNA and synthetic poly-, oligo- and mononucleotides are considered with a primary emphasis placed upon intermolecular interaction of the photoexcited porphyrins with the nearest environment. Quenching of the fluorescent S 1 (but not triplet T 1) state due to guanine to porphyrin electron transfer is observed for TMpyP 4 intercalated between GC base pairs of the double-strand helixes, whereas in the case of TMpyP 4 complexed with guanosine monophosphate (GMP) both S 1 and T 1 states of the porphyrin are quenched. Furthermore, a dependence of the efficiency of TMpyP 4 triplet state quenching by the dissolved molecular oxygen from air on the porphyrin localization enables one to readily distinguish porphyrin groove binding mode from intercalation. Excited states of the TMpyP 4 complexes with transition metals, in spite of their very short lifetimes, also interact with nucleic acid components by means of an axial ligand binding/release to/from the metal. A possible structure of the five-coordinate excited complex (“exciplex”) formed in case of CuTMpyP 4 groove binding to some single- and double-strand polynucleotides is discussed.

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