Stepwise Fusion of Porphyrin β,β′-Pyrrolic Positions to Imidazole Rings (original) (raw)
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Physical chemistry chemical physics : PCCP, 2015
Here, we report the effects of ring fusion, which causes expansion of the π-conjugation circuits of the porphyrin derivatives to the fused meso-aryl groups, on the aromaticity and the magnetic properties of porphyrin derivatives. These studies revealed the facts that the ring fusion with five-membered rings causes not only the remarkable red shifts of the absorption bands and narrowed HOMO-LUMO gaps, but also the contribution of anti-aromatic resonance forms to the magnetic properties as observed in the (1)H NMR spectra. The optical absorption and magnetic circular dichroism (MCD) spectroscopies indicate that the increase in the number of the fused rings causes stabilization of the LUMO level of the porphyrin derivatives and as a result induces the loosening of the LUMO degeneracy that is generally observed for porphyrins. The electronic structure of a quadruply fused porphyrin derivative was experimentally clarified by the ESR studies on the 1e(-)-oxidized and 1e(-)-reduced species...
Chemistry - A European Journal, 2012
FULL PAPER relative influence of the heavy-atom effect and core modification on the emission properties could be compared. The effect of forming ABAB structures with differing types of peripheral-fused-ring expansion has been explored by synthesizing core-modified diphenanthro-(P 1 and P 1-Bz y) and diacenaphthoporphyrins (P 3 and P 3-Bz y ; Figure 1 and the Supporting Information, Figure S1), which have fused bicycloA C H T U N G T R E N N U N G [2.2.2]octadiene (BCOD) and benzene rings along the y axis. Synthesis of core-modified porphyrins: The synthesis of monohetero-and diheteroporphyrins was pioneered by Ulman and Manassen in the mid-1970s, based on a reaction between a diarylfuran/diarylthiophene diol and a pyrrole to form a porphyrinoid compound. [21] In recent years, Ono and co-workers developed a breakthrough synthesis of pure pexpanded porphyrinoids [22] and benzo[c]heterocyclic oligo-A C H T U N G T R E N N U N G mers [23, 24] that was based on the tetramerization of BCODfused pyrroles to afford peripherally substituted porphyrins, which can subsequently be converted into tetrabenzoporphyrins in quantitative yield by heating at 200 8C. [25] A series of core-modified tetrabenzoporphyrins, in which one or both of the protonated pyrrole nitrogen atoms were replaced with oxygen/sulfur atoms by using BCOD-fused furan and thiophene, respectively, were successfully synthesized. [23, 26] The same synthetic approach is adopted herein to synthesize P 1-Bz y and P 3-Bz y based on the retro-Diels-Alder reaction of P 1 and P 3 , respectively, which are formed from a BCOD-fused diarylthiophene diol with either a phenanthroor acenaphtho-fused pyrrole. The replacement of pyrrole moieties by other heterocycles, such as furans, thiophenes, selenophenes, or tellurophenes, leads to the formation of new classes of core-modified porphyrinoids.
Substitution, dimerization, metalation, and ring-opening reactions of N-fused porphyrins
Tetrahedron, 2008
A variety of reactions such as substitution, dimerization, rhenium(I) metalation, and ring-opening reactions of N-fused porphyrin (NFP) and optical properties of the products are presented. Palladium-catalyzed cross-coupling reactions under Suzuki or Stille conditions afford aryl and arylethynyl-substituted NFPs (12, 14) and an ethynyl-bridged dimer (15) from 3-bromo-substituted NFP (3b) in 40e98% yields. Treatment of NFP with silver(I) trifluoroacetate in CHCl 3 affords a dimer (22) linked at both C21-positions of the fused rings and its bis-Re(I) metal complex (24) is synthesized. X-ray structures of the 3-trifluoromethyl and 3-phenyl NFP derivatives (9e and 12a) reveal the three-center hydrogen bondings in the core. All the new NFP derivatives display unique absorption spectra, and particularly, ethyne-bridged NFP-dimer (15) shows a remarkable bathochromic shift into a near-infrared region showing an absorption band at 1020 nm with tailing up to 1100 nm. Moreover, alkoxide nucleophiles convert NFP into NCP derivatives by the cleavage of CeN bond in the fused ring, which is useful for the preparation of various C3-substituted NCPs and C21,C21 0-linked NCP dimers from NFPs.
Porphyrin Macrocycle Modification: Pyrrole Ring-Contracted or -Expanded Porphyrinoids
Molecules, 2016
In recent years, several synthetic strategies aiming at the peripheral functionalization of porphyrins were developed. Particularly interesting are those involving the modification of β-pyrrolic positions leading to pyrrole-modified porphyrins containing four-, five-, six-or seven-membered heterocycles. Azeteoporphyrins, porpholactones and morpholinoporphyrins are representative examples of such porphyrinoids. These porphyrin derivatives have recently gained an increasing interest due to their potential application in PDT, as multimodal imaging contrast agents, NIR-absorbing dyes, optical sensors for oxygen, cyanide, hypochlorite and pH, and in catalysis.
Efficient Regiospecific Conjugated Ring Fusion in N-Confused Porphyrin
European Journal of Organic Chemistry, 2009
Acid-catalyzed exocyclic ring formation in meso-tetrakis(3Ј,5Ј-dimethoxyphenyl)-2-aza-21-carbaporphyrin takes place regioselectively between the external carbon atom of the confused pyrrole and the ortho-carbon atom of the adjacent meso-aryl group. The ring fusion strongly alters the spectroscopic properties of the macrocycle, but its aromaticity is preserved, as shown by NMR spectroscopy as well as DFT calculations. A tendency to self-associate is observed for [a]
5,10,15,20-tetrakis(N-protected-imidazol-2-yl)porphyrins
Tetrahedron, 1996
it is shown that examples of the title porphyrins can be prepared from suitably N-protected imidazole-2-carboxaldehydes and pyrrole in refluxing propionic acid: subsequent deprotection, affords a synthetic route to 5,10,15,20-tetrakis(substituted-imidazol-2-yl)porphyrins (TIPs).
Macroheterocycles, 2009
A convenient and straightforward approach to the synthesis of linearly annelated extended porphyrins of tetrabenzoand tetranaphthoporphyrin series was developed. 4,7-Dihydroisoindole and its benzoannelated derivative, being the closest stable precursors of unstable 2H-isoinsoles, are used in this method. Key features for this approach are its unprecedented synthetic versatility, tolerance for sensitive functional groups and the convenient introduction of meso-substituents. Aromatization of the annelated rings is conducted under mild conditions at the final stage of the synthesis. Tetraaryltetrabenzo-and tetranaphthoporphyrins are obtained using standard well-established procedures of porphyrin synthesis using common synthons.
J. Chem. Soc., Perkin Trans. 1, 1998
3,4-Diarylpyrroles (1) have been directly prepared in 20-50% yield by the reaction of -nitrostyrenes with aqueous TiCl 3 in 1,4-dioxane. Pyrroles 1 were also prepared via Barton-Zard pyrrole synthesis using the reaction of -nitrostilbenes with ethyl isocyanoacetate followed by de-ethoxycarbonylation. 3,4-Diarylpyrroles have been converted into dodecaarylporphyrins by reaction with aromatic aldehydes. Various aryl groups are readily introduced at the periphery of porphyrins by this method. Phenyl substitution at any of the positions of pyrroles decreases E ox 1/2 , while E 1/2 red is almost unchanged. On the other hand, substitution of the 2-thienyl group affects both the HOMO and LUMO energies, and the UV-vis spectra of dodeca-2-thienylporphyrins (4f or 4i) are extremely red-shifted.
Porphyrin “Lego Block” Strategy To Construct Directly meso-β Doubly Linked Porphyrin Rings
Angewandte Chemie International Edition, 2010
Electronically interacting multiporphyrinic systems have received much attention in light of their potential applications in optoelectronic devices, sensors, photovoltaic devices, nonlinear optical (NLO) materials, and photodynamic therapy (PDT) pigments. [1] To achieve desirable electronic and photophysical properties, the manipulation of interporphyrinic interactions is often essential. [2] Along this line, we reported Ag I-promoted meso-meso coupling reactions of 5,15-diaryl substituted Zn II porphyrins and a subsequent DDQ/Sc(OTf) 3induced oxidative fusion reaction (DDQ = 2,3-dichloro-5,6dicyano-1,4-benzoquinone; Tf = trifluoromethanesulfonyl) into porphyrin tapes, [3] which yielded extremely long molecules, [3b] extensively p-conjugated molecules, [3c] directly linked porphyrin rings, [3e] and an antiaromatic porphyrin sheet. [3f] These examples showed that the directly linked porphyrin arrays have a strong advantage of precise control in the large electronic interactions. As another effective synthetic protocol, we explored Ircatalyzed b-borylation reaction of meso-free meso'-aryl-type porphyrins. [4] These borylated porphyrins have been used for the construction of various functional oligomeric porphyrinoids, including doubly b-to-b bridged diporphyrins 1 a and
Heptaphyrins: Expanded porphyrins with seven heterocyclic rings
Journal of Chemical Sciences, 2003
Expanded porphyrins containing seven pyrrole/heterocyclic rings linked in a cyclic fashion are termed heptaphyrins. The number of π-electrons in heptaphyrins depends on the number of meso carbon bridges used to link the heterocyclic rings, accordingly heptaphyrins with 28π-electrons and 30 π-electrons are reported to date. Both condensation reactions of the appropriate precursors and acid-catalysed oxidative coupling reactions have been utilized to synthesise the heptaphyrins. The 30π heptaphyrins exhibit rich structural diversity where some of the heterocyclic rings in the macrocycle undergo a 180° ring flipping. An overview of the synthetic methods employed for the synthesis of heptaphyrins, their spectroscopic properties, structural behaviour and aromatic properties are highlighted in this paper.