An Unorthodox Conformation of [18]porphyrin-(1.1.1.1) Heteroanalogue—21,23-Ditelluraporphyrin with a Flipped Tellurophene Ring

Pacholska, Ewa; Latos‐Grażyński, Lechosław; Ciunik, Z.

doi:10.1002/1521-3757(20011203)113:23<4598::aid-ange4598>3.0.co;2-f

Cited by 30 publications

(24 citation statements)

References 34 publications

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“…By contrast, porphyrin analogues display versatile structures, especially in the expanded porphyrin families where an inverted arrangement of the pyrrole rings is frequently observed 2. The inversion of the tellurophene ring in the heteroporphyrin analogue ditelluraporphyrin ( 2 ) was demonstrated by Latos‐Grażyński and co‐workers;3 however, such ring inversion has been rarely observed and remains unproven for the tetrapyrrolic framework (Scheme ).…”

Section: Methodsmentioning

confidence: 98%

Inverted N‐Confused Porphyrin Dimer

2004

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Porphyrin (1) is a well-known tetrapyrrolic macrocycle that has four nitrogen atoms arranged inside the core that are able to co-ordinate a variety of metal ions. Normally, the porphyrin core is considered to be planar because of the resonance stabilization resulting from the 18-p electron aromatic system.[1] By contrast, porphyrin analogues display versatile structures, especially in the expanded porphyrin families where an inverted arrangement of the pyrrole rings is frequently observed.[2] The inversion of the tellurophene ring in the heteroporphyrin analogue ditelluraporphyrin (2) was demonstrated by Latos-Grażyń ski and co-workers; [3] however, such ring inversion has been rarely observed and remains unproven for the tetrapyrrolic framework (Scheme 1).Previously, we reported the formation of the N-fused porphyrin (NFP) 4 [4] from an N-confused porphyrin (NCP) 3, [5] which should proceed by ring inversion within the confused pyrrole and bond formation. In addition to this, we suggested the involvement of the inverted conformation of the confused pyrrole ring during the NH tautomerism of NCP.[6] Furthermore, density functional theory (DFT) calculations indicate that the energy difference between the inverted and normal conformations is much smaller than that of porphyrin.[7] The tilted angles were increased by the introduction of substituents at the inner carbon atom of the confused pyrrole. This observation led to the question of what would happen if a larger substituent, such as porphyrin, was introduced into the core. Would it induce pyrrole inversion and stabilize the inverted conformation of the confused pyrrole ring? To examine this possibility, we planned to synthesize an NCP dimer where the two NCP molecules are connected at both of the inner-carbon atoms. The synthetic strategy involved the initial preparation of an NFP dimmer followed by the nucleophilic, bond-cleavage reaction necessary to generate a covalently bonded NCP dimer. Both the structures have been elucidated by X-ray diffraction analysis. The confused pyrrole rings in the NCP dimer keep the inverted conformation and each NCP ring exhibits aromaticity, despite the highly distorted structure.The NFP dimer was synthesized in a similar method to that used for the meso-meso porphyrin dimer, [8] in which a Ag(I)-promoted, oxidative-coupling reaction is employed. Briefly, N-fused tetrakis-(p-tolyl)porphyrin (NFTTP, 4 a) was treated with silver(i) trifluoroacetate in CHCl 3 at reflux for 24 hours to afford the NFP dimer 5, in which the NFP units were covalently bonded to each other at the C2 carbon atoms of the fused rings, in a yield of 61 % (Scheme 2).The structure of 5 was elucidated by X-ray diffraction analysis (Figure 1).[9a] The asymmetric nature of NFP and the axial chirality of dimer 5 results in the unit cell, as determined from the crystallography data, contains an enantiomeric pair of molecules of 5. The bridging bond (1.476(9) ) was formed between C2 and C2'. Each of the NFP units was almost planar and the mean deviations from ...

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Section: Methodsmentioning

confidence: 98%

Inverted N‐Confused Porphyrin Dimer

2004

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“…A seesaw motion of this moiety is fast on the 1 H NMR scale and gives rise to averaging of the inner and outer protons chemical shifts at 295 K. The molecule is diatropic, contrary to meta-benziporphyrin, where the macrocyclic aromaticity is absent as a consequence of incompatibility between the porphyrinoid and benzenoid delocalization modes [37]. In fact the structural motif of -CH CHfragment directed into the porphyrin cavity was originally discovered for 21,23-ditelluraporphyrin 16 [38].…”

Section: Heteroporphyrins and Carbaporphyrinoidsmentioning

confidence: 99%

“…The DFT-calculated cadmium-proton distances are equal 4.14 and 3.19 Å for H1 and H2 respectively. The highly nonplanar structure of 1 B -M with an inverted conformation of the annulene fragment has precedence in 21,23-ditelluraporphyrin 16 [38]. The relevant structural motive can be also seen in an appropriate reference model i.e.…”

Section: Photochemical Isomerization Bent Isomermentioning

confidence: 99%

Aza-deficient porphyrin as a ligand

Pacholska‐Dudziak¹,

Latos‐Grażyński²

2009

Coordination Chemistry Reviews

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“…Latos-Grażyński and co-workers [176] synthesized 21,23ditelluraporphyrin with a flipped tellurophene ring 211 in 11% yield by following standard synthetic methodology used for 21,23-diheteroporphyrins (Scheme 42). The 211 was the first example of the inverted structure of the 18--electron porphyrinlike frame with four five-membered rings linked by four methane carbon atoms.…”

Section: Unusual Reactivity Of Telluraporphyrinsmentioning

confidence: 99%

“…The X-ray structure solved for 211 ( Fig. 30) showed a remarkable distortion of the porphyrin, which was attributed to the size of the tellurium atoms [176]. One of the tellurophene moieties (Te23) was coplanar with the two adjacent pyrrole rings while the second tellurophene ring (Te21) was directed away from the center of the macrocycle (Fig.…”

Section: Unusual Reactivity Of Telluraporphyrinsmentioning

confidence: 99%