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Kidd SR, Zhou W, Warren JJ, Leznoff DB. Inducing ring distortions in unsubstituted metallophthalocyanines using axial N-heterocyclic carbenes. Dalton Trans 2024; 53:6537-6546. [PMID: 38498318 DOI: 10.1039/d4dt00528g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
A series of metallophthalocyanine (PcM) complexes with axial N-heterocyclic carbene ligands (NHC; 1,3-diisopropylimidazol-2-ylidene (DIP) and 1,3-dimethylbenzimidazol-2-ylidene (DMB)) were prepared and structurally characterized. PcCoII(DIP), PcZnII(DIP), and PcZnII(DMB) are five-coordinate complexes with mild dome-type Pc-ring distortions, while PcFeII(DIP)2 is six-coordinate and has a very large ruffle-type ring-distortion with respect to typical PcM(L)2 systems. The distortion is induced by the highly steric axial DIP ligands. The distortions were quantified and classified by their bond lengths and torsion angles, and according to the normal-coordinate structural decomposition (NSD) analysis. Upon ligation of the NHC, the insoluble PcM materials were solublized in common organic solvents, with typical UV-visible Q-band maxima observable between 658 and 677 nm; the increased solubility is rationalized in terms of the reduced solid-state aggregation of the complexes, attributable to the axial ligation.
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Affiliation(s)
- Steven R Kidd
- Simon Fraser University, Department of Chemistry, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Wen Zhou
- Simon Fraser University, Department of Chemistry, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Jeffrey J Warren
- Simon Fraser University, Department of Chemistry, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Daniel B Leznoff
- Simon Fraser University, Department of Chemistry, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
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Senge MO, MacGowan SA, O'Brien JM. Conformational control of cofactors in nature - the influence of protein-induced macrocycle distortion on the biological function of tetrapyrroles. Chem Commun (Camb) 2016; 51:17031-63. [PMID: 26482230 DOI: 10.1039/c5cc06254c] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Tetrapyrrole-containing proteins are one of the most fundamental classes of enzymes in nature and it remains an open question to give a chemical rationale for the multitude of biological reactions that can be catalyzed by these pigment-protein complexes. There are many fundamental processes where the same (i.e., chemically identical) porphyrin cofactor is involved in chemically quite distinct reactions. For example, heme is the active cofactor for oxygen transport and storage (hemoglobin, myoglobin) and for the incorporation of molecular oxygen in organic substrates (cytochrome P450). It is involved in the terminal oxidation (cytochrome c oxidase) and the metabolism of H2O2 (catalases and peroxidases) and catalyzes various electron transfer reactions in cytochromes. Likewise, in photosynthesis the same chlorophyll cofactor may function as a reaction center pigment (charge separation) or as an accessory pigment (exciton transfer) in light harvesting complexes (e.g., chlorophyll a). Whilst differences in the apoprotein sequences alone cannot explain the often drastic differences in physicochemical properties encountered for the same cofactor in diverse protein complexes, a critical factor for all biological functions must be the close structural interplay between bound cofactors and the respective apoprotein in addition to factors such as hydrogen bonding or electronic effects. Here, we explore how nature can use the same chemical molecule as a cofactor for chemically distinct reactions using the concept of conformational flexibility of tetrapyrroles. The multifaceted roles of tetrapyrroles are discussed in the context of the current knowledge on distorted porphyrins. Contemporary analytical methods now allow a more quantitative look at cofactors in protein complexes and the development of the field is illustrated by case studies on hemeproteins and photosynthetic complexes. Specific tetrapyrrole conformations are now used to prepare bioengineered designer proteins with specific catalytic or photochemical properties.
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Affiliation(s)
- Mathias O Senge
- School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin 2, Ireland and Medicinal Chemistry, Institute of Molecular Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St. James's Hospital, Dublin 8, Ireland.
| | - Stuart A MacGowan
- School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin 2, Ireland
| | - Jessica M O'Brien
- Medicinal Chemistry, Institute of Molecular Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St. James's Hospital, Dublin 8, Ireland.
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Ikezaki A, Ono J, Ohgo Y, Fukagawa M, Ikeue T, Nakamura M. Electronic structure of low-spin six-coordinate iron(III) meso-tetrapropylchlorin complexes. J PORPHYR PHTHALOCYA 2014. [DOI: 10.1142/s1088424614500576] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Low-spin iron(III) tetrapropylchlorins [ Fe ( T n PrC ) L 2]± (L = HIm, 1-MeIm, DMAP, CN-, 4-CNPy, tBuNC) adopt the dxy-type ground state regardless of the nature of axial ligands. Among the complexes examined, [ Fe ( T n PrC )( t BuNC )2]+ has shown quite unique spectroscopic properties as described below. (1) 1 H NMR signals were extremely broad as compared with those of other complexes. In particular, 5,20- CH 2(α) signal was too broad to detect. (2) No signals except C γ were observed in 13 C NMR spectra. (3) Tetragonal splitting parameter (|Δ|) estimated by the EPR g values at 4.2 K reached as much as 12.4 λ, which is the largest |Δ| value among all the low-spin iron(III) porphyrins and porphyrinoids reported previously. On the basis of these results, we have concluded that [ Fe ( T n PrC )( t BuNC )2]+ adopts the low-spin iron(III) with (dxz, dyz)4(dxy)1 electronic ground state at 4.2–30 K where the EPR spectra are taken, while it should be expressed as the low-spin Fe ( II ) chlorin π-radical cation [ Fe II ( T n PrC .)( t BuNC )2]+ at ambient temperature where the NMR spectra are taken.
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Affiliation(s)
- Akira Ikezaki
- Department of Chemistry, School of Medicine, Toho University, Ota-ku, Tokyo 143-8540, Japan
| | - Jyunpei Ono
- Department of Chemistry, School of Medicine, Toho University, Ota-ku, Tokyo 143-8540, Japan
| | - Yoshiki Ohgo
- Department of Chemistry, School of Medicine, Toho University, Ota-ku, Tokyo 143-8540, Japan
| | - Mari Fukagawa
- Department of Chemistry, School of Medicine, Toho University, Ota-ku, Tokyo 143-8540, Japan
| | - Takahisa Ikeue
- Department of Material Science, Interdisciplinary Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
| | - Mikio Nakamura
- Department of Chemistry, School of Medicine, Toho University, Ota-ku, Tokyo 143-8540, Japan
- Department of Chemistry, Faculty of Science, Toho University, Funabashi 274-8510, Japan
- Research Center for Materials with Integrated Properties, Toho University, Funabashi 274-8510, Japan
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Cheng RJ, Ting CH, Chao TC, Tseng TH, Chen PPY. The characterization of the saddle shaped nickel(iii) porphyrin radical cation: an explicative NMR model for a ferromagnetically coupled metallo-porphyrin radical. Chem Commun (Camb) 2014; 50:14265-8. [DOI: 10.1039/c4cc06993e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ni(iii)(OETPP˙)(Br)2 is the first Ni(iii) porphyrin radical cation with structural and 1H and 13C paramagnetic NMR data for porphyrinate systems.
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Affiliation(s)
- Ru-Jen Cheng
- Department of Chemistry
- National Chung-Hsing University
- Taichung 402, Taiwan
| | - Chiao-Han Ting
- Department of Chemistry
- National Chung-Hsing University
- Taichung 402, Taiwan
| | - Ten-Chih Chao
- Department of Chemistry
- National Chung-Hsing University
- Taichung 402, Taiwan
| | - Tzu-Hsien Tseng
- Department of Chemistry
- National Chung-Hsing University
- Taichung 402, Taiwan
| | - Peter P.-Y. Chen
- Department of Chemistry
- National Chung-Hsing University
- Taichung 402, Taiwan
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