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Ishizuka T, Grover N, Kingsbury CJ, Kotani H, Senge MO, Kojima T. Nonplanar porphyrins: synthesis, properties, and unique functionalities. Chem Soc Rev 2022; 51:7560-7630. [PMID: 35959748 DOI: 10.1039/d2cs00391k] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Porphyrins are variously substituted tetrapyrrolic macrocycles, with wide-ranging biological and chemical applications derived from metal chelation in the core and the 18π aromatic surface. Under suitable conditions, the porphyrin framework can deform significantly from regular planar shape, owing to steric overload on the porphyrin periphery or steric repulsion in the core, among other structure modulation strategies. Adopting this nonplanar porphyrin architecture allows guest molecules to interact directly with an exposed core, with guest-responsive and photoactive electronic states of the porphyrin allowing energy, information, atom and electron transfer within and between these species. This functionality can be incorporated and tuned by decoration of functional groups and electronic modifications, with individual deformation profiles adapted to specific key sensing and catalysis applications. Nonplanar porphyrins are assisting breakthroughs in molecular recognition, organo- and photoredox catalysis; simultaneously bio-inspired and distinctly synthetic, these molecules offer a new dimension in shape-responsive host-guest chemistry. In this review, we have summarized the synthetic methods and design aspects of nonplanar porphyrin formation, key properties, structure and functionality of the nonplanar aromatic framework, and the scope and utility of this emerging class towards outstanding scientific, industrial and environmental issues.
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Affiliation(s)
- Tomoya Ishizuka
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan.
| | - Nitika Grover
- School of Chemistry, Chair of Organic Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin 2, Ireland
| | - Christopher J Kingsbury
- School of Chemistry, Chair of Organic Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin 2, Ireland
| | - Hiroaki Kotani
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan.
| | - Mathias O Senge
- Institute for Advanced Study (TUM-IAS), Technical University of Munich, Focus Group - Molecular and Interfacial Engineering of Organic Nanosystems, Lichtenbergstrasse 2a, 85748 Garching, Germany.
| | - Takahiko Kojima
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan.
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Nikitin K, O'Gara R. Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy. Chemistry 2019; 25:4551-4589. [PMID: 30421834 DOI: 10.1002/chem.201804123] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Indexed: 12/31/2022]
Abstract
Detailed mechanistic information is crucial to our understanding of reaction pathways and selectivity. Dynamic exchange NMR techniques, in particular 2D exchange spectroscopy (EXSY) and its modifications, provide indispensable intricate information on the mechanisms of organic and inorganic reactions and other phenomena, for example, the dynamics of interfacial processes. In this Review, key results from exchange NMR studies of small molecules over the last few decades are systemised and discussed. After a brief introduction to the theory, the key types of dynamic processes are identified and fundamental examples given of intra- and intermolecular reactions, which, in turn, could involve, or not, bond-making and bond-breaking events. Following that logic, internal molecular rotation, intramolecular stereomutation and molecular recognition will first be considered because they do not typically involve bond breaking. Then, rearrangements, substitution-type reactions, cyclisations, additions and other processes affecting chemical bonds will be discussed. Finally, interfacial molecular dynamics and unexpected combinations of different types of fluxional processes will also be highlighted. How exchange NMR spectroscopy helps to identify conformational changes, coordination and molecular recognition processes as well as quantify reaction energy barriers and extract detailed mechanistic information by using reaction rate theory in conjunction with computational techniques will be shown.
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Affiliation(s)
- Kirill Nikitin
- School of Chemistry, University College Dublin, Belfield, Dublin, Ireland
| | - Ryan O'Gara
- School of Chemistry, University College Dublin, Belfield, Dublin, Ireland
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Zhou Z, Zhang X, Liu Q, Yan Z, Lv C, Long G. Geometry and Temperature Dependence of meso-Aryl Rotation in Strained Metalloporphyrins: Adjustable Turnstile Molecules. Inorg Chem 2013; 52:10258-63. [DOI: 10.1021/ic4001208] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Zaichun Zhou
- School of Chemistry and Chemical
Engineering, Key Laboratory of Theoretical
Chemistry and Molecular Simulation of Ministry of Education, and Hunan Provincial University Key Laboratory of QSAR/QSPR, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Xi Zhang
- School of Chemistry and Chemical
Engineering, Key Laboratory of Theoretical
Chemistry and Molecular Simulation of Ministry of Education, and Hunan Provincial University Key Laboratory of QSAR/QSPR, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Qiuhua Liu
- School of Chemistry and Chemical
Engineering, Key Laboratory of Theoretical
Chemistry and Molecular Simulation of Ministry of Education, and Hunan Provincial University Key Laboratory of QSAR/QSPR, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Ziqiang Yan
- School of Chemistry and Chemical
Engineering, Key Laboratory of Theoretical
Chemistry and Molecular Simulation of Ministry of Education, and Hunan Provincial University Key Laboratory of QSAR/QSPR, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Chengjin Lv
- School of Chemistry and Chemical
Engineering, Key Laboratory of Theoretical
Chemistry and Molecular Simulation of Ministry of Education, and Hunan Provincial University Key Laboratory of QSAR/QSPR, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Ge Long
- School of Chemistry and Chemical
Engineering, Key Laboratory of Theoretical
Chemistry and Molecular Simulation of Ministry of Education, and Hunan Provincial University Key Laboratory of QSAR/QSPR, Hunan University of Science and Technology, Xiangtan 411201, China
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Yatsunyk LA, Ann Walker F. Synthesis and characterization of the iron(III) complexes of tetra-(β,β'-tetramethylene)tetraphenylporphyrin, (TC6TPP)FeCl and (TC6TPP)FeONO2. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424605000289] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The synthesis, NMR and EPR spectroscopic investigation as well as two crystal structures of ( TC 6 TPP ) FeX , where X - = chloride and nitrate are reported. The crystal structure of ( TC 6 TPP ) FeCl reveals an almost equal mixture of saddled and ruffled distortion of the porphyrin as judged by the coefficients of the lowest-frequency vibrational modes (calculated from Normal-Coordinate Structural Decomposition), while ( TC 6 TPP ) FeONO 2 is mainly saddled and more distorted overall. This difference in core structure indicates high conformational flexibility of the TC 6 TPP porphyrin ligand. Overall, both ( TC 6 TPP ) FeX structures have smaller deviation from planarity as compared to five coordinate ( OMTPP ) FeCl and ( OETPP ) FeCl . Therefore, the nature and number of peripheral substituents as well as the axial ligand(s) control geometry and conformation of the porphyrins and fine-tune their spectroscopic properties. EPR data (4.2 K) indicate a predominantly high-spin ( S = 5/2, 97.3%) ground state for ( TC 6 TPP ) FeCl and less pure high-spin state ( S = 5/2, 80%) for ( TC 6 TPP ) FeONO 2. The NMR results support an ideally saddled structure or rapid switching between saddled and ruffled conformations of ( TC 6 TPP ) FeX in solution. The flexibility of the porphyrin core was addressed by using dynamic NMR spectroscopy. The following kinetic parameters for ring inversion were obtained: Δ H ‡ = 24(1) kJ . mol −1, Δ S ‡ = −37(3) J . mol −1. K −1 and Δ H ‡ = 36(1) kJ . mol −1, Δ S ‡ = 20(4) J . mol −1. K −1 for ( TC 6 TPP ) FeCl and ( TC 6 TPP ) FeONO 2, respectively. This results in low free energies of activation, Δ G 298‡ = 35(2) and 30(2) kJ.mol−1, respectively, indicating extremely high flexibility of the porphyrin core in solution (kex298 > 4.2 × 106 and 3.8 × 107 s−1).
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Affiliation(s)
- Liliya A. Yatsunyk
- Department of Chemistry, University of Arizona, Tucson, AZ 85721-0041, USA
| | - F. Ann Walker
- Department of Chemistry, University of Arizona, Tucson, AZ 85721-0041, USA
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Roquette P, Maronna A, Reinmuth M, Kaifer E, Enders M, Himmel HJ. Combining NMR of Dynamic and Paramagnetic Molecules: Fluxional High-Spin Nickel(II) Complexes Bearing Bisguanidine Ligands. Inorg Chem 2011; 50:1942-55. [DOI: 10.1021/ic102420x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Pascal Roquette
- Contribution from the Department of Inorganic Chemistry, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Astrid Maronna
- Contribution from the Department of Inorganic Chemistry, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Matthias Reinmuth
- Contribution from the Department of Inorganic Chemistry, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Elisabeth Kaifer
- Contribution from the Department of Inorganic Chemistry, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Markus Enders
- Contribution from the Department of Inorganic Chemistry, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Hans-Jörg Himmel
- Contribution from the Department of Inorganic Chemistry, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
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Patra R, Chaudhary A, Ghosh SK, Rath SP. Modulation of Metal Displacements in a Saddle Distorted Macrocycle: Synthesis, Structure, and Properties of High-Spin Fe(III) Porphyrins and Implications for the Hemoproteins. Inorg Chem 2008; 47:8324-35. [DOI: 10.1021/ic800944q] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Ranjan Patra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India
| | - Arvind Chaudhary
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India
| | - Sudip Kumar Ghosh
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India
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Cai S, Shokhireva TK, Lichtenberger DL, Walker FA. NMR and EPR studies of chloroiron(III) tetraphenyl-chlorin and its complexes with imidazoles and pyridines of widely differing basicities. Inorg Chem 2006; 45:3519-31. [PMID: 16634582 PMCID: PMC2504473 DOI: 10.1021/ic0515352] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The NMR and EPR spectra of two bisimidazole and three bispyridine complexes of tetraphenylchlorinatoiron(III), [(TPC)Fe(L)2]+ (L = Im-d4, 2-MeHIm, 4-Me2NPy, Py, and 4-CNPy), have been investigated. The full resonance assignments of the [(TPC)Fe(L)2]+ complexes of this study have been made from correlation spectroscopy (COSY) and nuclear Overhauser enhancement spectroscopy (NOESY) experiments and Amsterdam density functional (ADF) calculations. Unlike the [(OEC)Fe(L)2]+ complexes reported previously (Cai, S.; Lichtenberger, D. L.; Walker, F. A. Inorg. Chem. 2005, 44, 1890-1903), the NMR data for the [(TPC)Fe(L)2]+ complexes of this study indicate that the ground state is S = 1/2 for each bisligand complex, whereas a higher spin state was present at NMR temperatures for the Py and 4-CNPy complexes of (OEC)Fe(III). The pyrrole-8,17 and pyrroline-H of all [TPCFe(L)2]+ show large magnitude chemical shifts (hence indicating large spin density on the adjacent carbons that are part of the pi system), while pyrrole-12,13-CH2 and -7,18-CH2 protons show much smaller chemical shifts, as predicted by the spin densities obtained from ADF calculations. The magnitude of the chemical shifts decreases with decreasing donor ability of the substituted pyridine ligands, with the nonhindered imidazole ligand having slightly larger magnitude chemical shifts than the most basic pyridine, even though its basicity is significantly lower (4-Me2NPyH+ pKa = 9.7, H2Im+ pKa = 6.65 (adjusted for the statistical factor of 2 protons)). The temperature dependence of the chemical shifts of all but the 4-Me2NPy bisligand complexes studied over the temperature range of the NMR investigations shows that they have mixed (dxy)2(dxz,dyz)3/(dxzdyz)4(dxy)1 electron configurations that cannot be resolved by temperature-dependent fitting of the proton chemical shifts, with an S = 3/2 excited state in each case that in most cases lies at more than kT at room temperature above the ground state. The observed pattern of chemical shifts of the 4-CNPy complex and analysis of the temperature dependence indicate that it has a pure (dxzdyz)4(dxy)1 ground state and that it is ruffled, because ruffling mixes the a(2u)(pi)-like orbital of the chlorin into the singly occupied molecular orbital (SOMO). This mixing accounts for the negative chemical shift of the pyrroline-H (-6.5 ppm at -40 degrees C) and thus the negative spin density at the pyrroline-alpha-carbons, but the mixing is not to the same extent as observed for [(TPC)Fe(t-BuNC)2]+, whose pyrroline-H chemical shift is -36 ppm at 25 degrees C (Simonneaux, G.; Kobeissi, M. J. Chem. Soc., Dalton Trans. 2001, 1587-1592). Peak assignments for high-spin (TPC)FeCl have been made by saturation transfer techniques that depend on chemical exchange between this complex and its bis-4-Me2NPy adduct.
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Affiliation(s)
- Sheng Cai
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041, USA
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Hoshino A, Ohgo Y, Nakamura M. Synthesis and inversion barriers of undeca- and dodeca-substituted saddle shaped porphyrin complexes. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.05.100] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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