NiII Porphyrin Research Articles

A DFT study of the second-order nonlinear optical properties of [22]smaragdyrin-BF2-NiII porphyrin fused hybrids

Nonlinear optical response of four [22]smaragdyrin-BF2 (S)-NiII porphyrin (P) fused hybrids were explored by using DFT at CAM-B3LYP/6–31 + G(d)/SDD level of theory. We choose two types of hybrids, SP and PSP fused hybrids, for our study. Calculations indicate that these fused hybrids might be promising candidates for NLO materials based on considerable static and dynamic hyper-Rayleigh scattering (HRS) hyperpolarizability. The PSP fused hybrids possess larger first hyperpolarizabilities values compared to SP hybrids. Further analysis of hyperpolarizability density reveals the nature of the large first hyperpolarizability of the PSP fused hybrids. For all compounds, HRS hyperpolarizability at λ = 1907 nm is higher than the static value. After the interpretation of dipolar and octupolar character of βHRS, these hybrids show the high dipolar character.

22]Pentaphyrins(2.0.1.1.0) Displaying N-Fusion, Pyrrole-Rearrangement, and Dimerization Reactions Upon Oxidation and Metalation.

Exploration of expanded porphyrins with unprecedented reactivities has remained important. Here [22]pentaphyrins(2.0.1.1.0) were synthesized as a constitutional isomer of sapphyrin by acid-catalyzed cyclization of 1,14-dibromo-5,10-diaryltripyrrin with 1,2-di(pyrro-2-ly)ethenes. These pentaphyrins display roughly planar structures and varying aromaticities depending upon the vinylene structures. The 19,20-ditolyl pentaphyrin gave an N-fused product and an unprecedented pyrrole-rearranged product, depending upon the oxidation conditions. Remarkably, upon the metalation with CuCl, the N-fused product and the pyrrole-rearranged product afforded an inner β-β coupled face-to-face CuII complex dimer and an outer β-β coupled lateral CuII complex dimer, respectively, in fairly good yields. Further, [22]pentaphyrin(2.0.1.1.0) fused with a NiII porphyrin was effectively dimerized upon oxidation with MnO2 to give a 16-16' directly linked dl-dimer.

22]Pentaphyrins(2.0.1.1.0) Displaying N‐Fusion, Pyrrole‐Rearrangement, and Dimerization Reactions Upon Oxidation and Metalation

AbstractExploration of expanded porphyrins with unprecedented reactivities has remained important. Here [22]pentaphyrins(2.0.1.1.0) were synthesized as a constitutional isomer of sapphyrin by acid‐catalyzed cyclization of 1,14‐dibromo‐5,10‐diaryltripyrrin with 1,2‐di(pyrro‐2‐ly)ethenes. These pentaphyrins display roughly planar structures and varying aromaticities depending upon the vinylene structures. The 19,20‐ditolyl pentaphyrin gave an N‐fused product and an unprecedented pyrrole‐rearranged product, depending upon the oxidation conditions. Remarkably, upon the metalation with CuCl, the N‐fused product and the pyrrole‐rearranged product afforded an inner β‐β coupled face‐to‐face CuII complex dimer and an outer β‐β coupled lateral CuII complex dimer, respectively, in fairly good yields. Further, [22]pentaphyrin(2.0.1.1.0) fused with a NiII porphyrin was effectively dimerized upon oxidation with MnO2 to give a 16–16’ directly linked dl‐dimer.

Synthesis of Pyrrole‐Sharing Fused Porphyrinoid Hybrids by Post‐fabrication of Ni(II) Porphyrins

AbstractPyrrole‐sharing fused hybrids of NiII porphyrin with PdII N‐confused(NC)‐corrole and PdII NC‐oxaporphyrin were synthesized by post‐fabrication of NiII porphyrins. Specifically this consists of Friedel–Crafts type aromatic substitution reaction of meso‐free NiII porphyrin with α,α′‐dibromotripyrrin and Pd(OAc)2 assisted cyclization, and final heating to induce a Pd−C bond formation. NiII porphyrins fused with PdII NC‐corrole and with PdII NC‐oxaporphyrins show coplanar structures with a shared pyrrole unit. In these hybrids, the PdII NC‐oxaporphyrin is aromatic and the PdII NC‐corrole is moderately antiaromatic and these local electronic properties interact to influence the whole network.

Synthesis of Pyrrole-Sharing Fused Porphyrinoid Hybrids by Post-fabrication of Ni(II) Porphyrins.

Pyrrole-sharing fused hybrids of NiII porphyrin with PdII N-confused(NC)-corrole and PdII NC-oxaporphyrin were synthesized by post-fabrication of NiII porphyrins. Specifically this consists of Friedel-Crafts type aromatic substitution reaction of meso-free NiII porphyrin with α,α'-dibromotripyrrin and Pd(OAc)2 assisted cyclization, and final heating to induce a Pd-C bond formation. NiII porphyrins fused with PdII NC-corrole and with PdII NC-oxaporphyrins show coplanar structures with a shared pyrrole unit. In these hybrids, the PdII NC-oxaporphyrin is aromatic and the PdII NC-corrole is moderately antiaromatic and these local electronic properties interact to influence the whole network.

Synthesis of NiII porphyrin-NiII 5,15-diazaporphyrin hybrid tapes.

NiII porphyrin (P) and NiII 5,15-diazaporphyrin (DAP) hybrid tapes were synthesized by Suzuki-Miyaura cross-coupling reactions of meso- or β-borylated P with β-brominated DAP followed by intramolecular oxidative fusion reactions. Meso-β doubly linked hybrid tapes were synthesized by oxidation of singly linked precursors with DDQ-FeCl3. Synthesis of triply linked hybrid tapes was achieved by oxidation with DDQ-FeCl3-AgOTf with suppression of peripheral β-chlorination. In these tapes, DAP segments were present as a 20π-electronic unit, but their local antiaromatic contribution was trivial. Remarkably, these hybrid tapes were stable and exhibited extremely enhanced absorption bands in the NIR region and multiple reversible redox waves. A pentameric hybrid tape showed a remarkably sharp and red-shifted band at 1168 nm with ε = 5.75 × 105 M-1 cm-1. Singly linked P-DAP dyads were oxidized with DDQ-FeCl3 to give stable radicals, which were oxidized further to afford dimeric hybrid tapes possessing a nitrogen atom at the peripheral-side meso-position.

Post-Installation of Fused Benzoheptagons at the Periphery of NiII Porphyrins: Helical Structures and Conformation-Adjustable Fullerenes Binding.

Fused-benzoheptagon-installed NiII porphyrins were synthesized by a protocol consisting of (2-formyl)arylation at the meso-position(s) of NiII porphyrins, conversion of formyl group to methoxyethene group by Wittig reaction, and final Bi(OTf)3 -catalyzed cyclization. The structures of these porphyrins have been revealed by X-ray analysis. Owing to the installed heptagon ring(s), these porphyrins show curved structures with conformational flexibility. Dimer has been shown to have a small activation barrier for inversion and to capture C60 and C70 with large association constants with adjustable conformational changes.

Doubly N-confused and ring-contracted [24]hexaphyrin Pd-complexes as stable antiaromatic N-confused expanded porphyrins

As isomers of the regular porphyrins, N-confused porphyrins have attracted extensive attention of chemists because of their unique chemical structures, chemical reactivities, and physical properties, which result in their promising applications in the fields of catalytic chemistry, biochemistry and material science. Typically, N-confused porphyrins are synthesized via acid catalyzed condensation and following oxidation during which lactams are often formed as the byproducts. Here we report doubly N-confused and ring-contracted [24]hexaphyrin(1.1.0.1.1.0) mono- and bis-Pd-complexes as stable antiaromatic N-confused expanded porphyrins, which are synthesized through Pd-catalyzed Suzuki-Miyaura coupling of 1,14-dibromotripyrrin. These macrocycles show a paratropic ring currents, an ill-defined Soret band, a red-shifted weak absorption tail, and a small HOMO-LUMO gap. NBS bromination of the bis Pd-complex give its mono- and dibromides regioselectively, which are effectively used to synthesize a [24]hexaphyrin dimer and a NiII porphyrin-[24]hexaphyrin-NiII porphyrin triad, respectively.

Synthesis of Directly‐Linked Porphyrin−Pyricorrole Hybrid via Rearrangement of Internally‐bridged Octaphyrin(1.1.1.1.1.1.1.1) Upon Ni(II) Metalation

AbstractA directly‐linked NiII porphyrin−NiII pyricorrole hybrid was obtained upon NiII complexation of internally‐bridged octaphyrin(1.1.1.1.1.1.1.1). The structure has been unambiguously revealed by X‐ray diffraction analysis. The pyricorrole skeleton is different from that reported earlier with regard to the position of the pyridine moiety. The new pyricorrole macrocycle was characterized as an aromatic molecule sustaining a complex current density. The thermodynamic stability of the NiII pyricorrole skeleton indicated by DFT calculation may drive this rearrangement.

A Quadruply Bridged Non-Offset Face-to-Face Porphyrin Dimer and Cross-Shaped Pentameric Porphyrin Tapes Based on 2,7,12,17-Tetrakis(pinacolatoboryl) NiII Porphyrin.

2,7,12,17-Tetrakis(pinacolatoboryl) NiII porphyrin 5 Ni was synthesized in 75 % yield by Ir-catalyzed borylation of porphine followed by NiII metalation and has been demonstrated to be a useful synthon, giving 2,7,12,17-tetraaryated NiII porphyrins 6 a-d, peripherally octaarylated NiII porphyrins 8 a-d, quadruply bridged face-to-face non-offset NiII -porphyrin dimer 12, and cross-shaped β-meso singly linked porphyrin pentamers and nonamers. Oxidation of cross-shaped β-meso singly linked porphyrin pentamers 14 Ni and 14 Zn gave fused pentameric tapes 15 Ni and 15 Zn. The structures of 12, 14 Zn, and 15 Ni have been revealed by X-ray diffraction analysis. Optical separation of 12 has been accomplished, showing a bisignate coupling pattern for exciton-coupled blue-shifted Soret band. Pentameric porphyrin tape 15 Zn exhibits a red-shifted absorption band at 1156 nm and seven reversible redox waves.

A Quadruply Bridged Non‐Offset Face‐to‐Face Porphyrin Dimer and Cross‐Shaped Pentameric Porphyrin Tapes Based on 2,7,12,17‐Tetrakis(pinacolatoboryl) NiII Porphyrin

Abstract2,7,12,17‐Tetrakis(pinacolatoboryl) NiII porphyrin 5 Ni was synthesized in 75 % yield by Ir‐catalyzed borylation of porphine followed by NiII metalation and has been demonstrated to be a useful synthon, giving 2,7,12,17‐tetraaryated NiII porphyrins 6 a–d, peripherally octaarylated NiII porphyrins 8 a–d, quadruply bridged face‐to‐face non‐offset NiII‐porphyrin dimer 12, and cross‐shaped β‐meso singly linked porphyrin pentamers and nonamers. Oxidation of cross‐shaped β‐meso singly linked porphyrin pentamers 14 Ni and 14 Zn gave fused pentameric tapes 15 Ni and 15 Zn. The structures of 12, 14 Zn, and 15 Ni have been revealed by X‐ray diffraction analysis. Optical separation of 12 has been accomplished, showing a bisignate coupling pattern for exciton‐coupled blue‐shifted Soret band. Pentameric porphyrin tape 15 Zn exhibits a red‐shifted absorption band at 1156 nm and seven reversible redox waves.

Cover Feature: Heptagon/Octagon‐Fused Diporphyrins or Spiro‐Pentagon‐Bridged Dichlorin from p‐Terphenylene‐Bridged Diporphyrin (Chem. Asian J. 6/2023)

The cartoon figure on the cover image is Monkey King, who is a character in the classical Chinese novel “Journey to the West”. He has 72 polymorphic transformations. As shown in the cartoon, he only needs to blow a breath and can create a lot of little monkeys. p-Terphenylene-bridged NiII porphyrin dimer, which is similar to Monkey King, gave syn- and anti-doubly heptagon-fused NiII porphyrin dimers, a spiro-pentagon-bridged NiII chlorin dimer, and a doubly octagon-fused NiII porphyrin dimer depending on the different reaction conditions. The Chinese characters represent the abbreviation of Hunan Normal University. More information on this study can be found in the Research Article by Jianxin Song et al.

Heptagon/Octagon-Fused Diporphyrins or Spiro-Pentagon-Bridged Dichlorin from p-Terphenylene-Bridged Diporphyrin.

Intramolecular fusion reactions of a p-terphenylene-bridged NiII porphyrin dimer gave different products, depending upon reaction conditions. Oxidation with Fe(OTf)3 provided syn- and anti-doubly heptagon-fused NiII porphyrin dimers showing enlarged π-electronic networks, probably via a radical mechanism, while treatment with methanesulfonic acid provided a spiro-pentagon-bridged NiII chlorin dimer via acid-catalyzed Friedel-Crafts type cyclization. Further, a doubly octagon-fused NiII porphyrin dimer was synthesized via a sequence of double meso-formylation, reduction to corresponding diol, and BF3 -catalyzed cyclization.

The Effect of Hydrogenation on the Contest between Aromaticity and Antiaromaticity in Norcorrole.

Magnetic shielding studies demonstrate that successive hydrogenation of NiII norcorrole (NiNc), a stable molecule combining aromatic and antiaromatic features, first weakens and then eliminates the central antiaromatic region, even though the NiNc antiaromatic "core", a 14-membered conjugated cycle with 16 π electrons, is formally preserved throughout the H2 NiNc-H8 NiNc series. The differences between aromatic and non-aromatic isotropic shielding distributions and nucleus-independent chemical shift (NICS) values in these hydrogenated porphyrin analogues are highlighted by comparing the results for the members of the H2 NiNc-H8 NiNc series to those for the aromatic NiII porphyrin complex. The results strongly support the unexpected and counterintuitive conclusion that H8 NiNc will be nonaromatic, without even a trace of antiaromaticity. Based on these findings, H8 NiNc is predicted to be the most stable member of the H2 NiNc-H8 NiNc series.

Earring Porphyrins Bearing 1,9‐Di(pyrid‐2‐yl)dipyrromethene Unit and Their BODIPY Conjugates

AbstractSuzuki–Miyaura coupling reactions of 2,18‐di(6‐bromopyrid‐2‐yl)‐substituted NiII porphyrin and 2,8,12,18‐tetrakis(6‐bromopyrid‐2‐yl)‐substituted NiII porphyrin with 1,9‐biboryl‐5‐mesityl dipyrromethene and subsequent oxidation with p‐chloranil gave single earring and double earring NiII porphyrins, respectively, which bear 1,9‐(dipyrid‐2‐yl)dipyrromethene unit. These NiII complexes were converted to free base porphyrins and then to ZnII porphyrins. Treatment of earring NiII and earring ZnII porphyrins with BF3⋅Et2O afforded the corresponding BODIPY (boron dipyrrin) conjugates and the ZnII porphyrin‐BODIPY conjugates were converted to free base porphyrin‐BODIPY conjugates. Bent structures of earring NiII porphyrins and the corresponding BODIPY conjugates have been revealed by X‐ray diffraction analysis. ZnII porphyrin‐BODIPYs show efficient fluorescence quenching, which is ascribed to fast intramolecular electron transfer from the ZnII porphyrin to the BODIPY moiety.

Efficient Synthesis of Multiply Seven‐Membered‐Ring Fused Porphyrins by Rhodium‐Catalyzed [5+2] Annulation

Rhodium-catalyzed reaction of meso-pyrrol-2-yl Ni(II) porphyrins with internal alkynes proceeded smoothly to give singly, doubly, and quadruply seven-membered-ring fused Ni(II) porphyrins as the first example of [5+2] annulation reaction for porphyrin substrates, where the meso-appended pyrrole unit serves as a directing group. These reactions are operationally quite simple and easy. A plausible reaction mechanism was proposed on the basis of the isolation of a key intermediate. The structures of the representative products have been revealed to be considerably bent owing to the implemented seven-membered rings. Doubly fused Zn(II) and Ni(II) porphyrins possessing an unsubstituted meso-position were dimerized to meso-meso linked dimers by aerobic oxidation with Zn(OAc)2·2H2O and electrochemical oxidation, respectively. The optical and electrochemical highest occupied molecular orbital (HOMO) - lowest unoccupied molecular orbital (LUMO) gaps, as well as the aromatic characters of the fused porphyrins decrease as the fusion parts increases.

Efficient Synthesis of Multiply Seven-Membered-Ring Fused Porphyrins by Rhodium-Catalyzed [5+2] Annulation.

Rhodium-catalyzed reaction of meso-pyrrol-2-yl NiII porphyrins with internal alkynes proceeded smoothly to give singly, doubly, and quadruply seven-membered-ring fused NiII porphyrins as the first example of [5+2] annulation reaction for porphyrin substrates, where the meso-appended pyrrole unit serves as a directing group. These reactions are operationally quite simple and easy. A plausible reaction mechanism was proposed on the basis of the isolation of a key intermediate. The structures of the representative products have been revealed to be considerably bent owing to the implemented seven-membered rings. Doubly fused ZnII and NiII porphyrins possessing an unsubstituted meso-position were dimerized to meso-meso linked dimers by aerobic oxidation with Zn(OAc)2 ⋅2 H2 O and electrochemical oxidation, respectively. The optical and electrochemical highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps, as well as the aromatic characters of the fused porphyrins decrease as the fusion parts increases.

Fused Hybrids of a [22]Smaragdyrin BF2 Complex with a NiII Porphyrin.

[22]Smaragdyrin BF2 complex (S)-NiII porphyrin (P) fused hybrids were synthesized through Suzuki-Miyaura coupling of brominated S with borylated P and subsequent oxidative fusion reaction with FeCl3 as the first example of directly fused porphyrinoids bearing cycloheptatriene linkage. These fused hybrids have been fully characterized, including their X-ray structural analysis. Owing to the cycloheptatriene linkage, these fused hybrids adopt waving structures. These fused hybrids display red-shifted and enhanced Q-like bands and characteristic redox potentials, depending upon the constitution and the linking position.

Fused Hybrids of a [22]Smaragdyrin BF2 Complex with a NiII Porphyrin

Abstract[22]Smaragdyrin BF2 complex (S)‐NiII porphyrin (P) fused hybrids were synthesized through Suzuki–Miyaura coupling of brominated S with borylated P and subsequent oxidative fusion reaction with FeCl3 as the first example of directly fused porphyrinoids bearing cycloheptatriene linkage. These fused hybrids have been fully characterized, including their X‐ray structural analysis. Owing to the cycloheptatriene linkage, these fused hybrids adopt waving structures. These fused hybrids display red‐shifted and enhanced Q‐like bands and characteristic redox potentials, depending upon the constitution and the linking position.

Towards Photoswitchable Contrast Agents for Absolute 3D Temperature MR Imaging

AbstractTemperature can be used as clinical marker for tissue metabolism and the detection of inflammations or tumors. The use of magnetic resonance imaging (MRI) for monitoring physiological parameters like the temperature noninvasively is steadily increasing. In this study, we present a proof‐of‐principle study of MRI contrast agents (CA) for absolute and concentration independent temperature imaging. These CAs are based on azoimidazole substituted NiII porphyrins, which can undergo Light‐Driven Coordination‐Induced Spin State Switching (LD‐CISSS) in solution. Monitoring the fast first order kinetic of back isomerisation (cis to trans) with standard clinical MR imaging sequences allows the determination of half‐lives, that can be directly translated into absolute temperatures. Different temperature responsive CAs were successfully tested as prototypes in methanol‐based gels and created temperature maps of gradient phantoms with high spatial resolution (0.13×0.13×1.1 mm) and low temperature errors (<0.22 °C). The method is sufficiently fast to record the temperature flow from a heat source as a film.