Modification of the porphyrin chromophore by ring fusion: identifying trends due to annelation of the porphyrin nucleus

Abstract

ABSTRACT:The effects exerted by fused aromatic rings on the UV-vis spectra of porphyrins are surveyed. Modified porphyrin chromophores with fused benzene, 1,2-naphthalene, 9,10-phenanthrene or phenanthroline rings are surprisingly little affected even when a maximum number of ring fusions are incorporated. Linearly annealed naphtho-or anthraporphyrins show large red shifts to the Q bands but the Soret absorptions are weakened and undergo only minor bathochromic shifts. Fluoranthoporphyrins give multiple bands in the Soret region, but the Q band region is virtually unaffected by this tetracyclic ring system. On the other hand, metal chelates of fluoranthoporphyrins show surprisingly strong bands near 600 nm. Benzothiadiazole rings split and weaken the Soret band, but the Q bands region is unexceptional. However, metal coordination again produces relatively intense bands near 600 nm. The most significant results were obtained for porphyrins with fused acenaphthylene rings. Monoacenaphthoporphyrins (41) have three Soret bands at 387, 431 and 454 nm, and the longest wavelength Q band is shifted to 658 nm. opp-Diacenaphthoporphyrin (43) further shifts these bands with two Soret absorbances at 443 and 470 nm, and an additional strong peak is observed at 692 nm. The metal complexes of these systems also show strong bands between 602 and 656 nm. Still larger effects are produced by tetraacenaphthoporphyrin (47), the dication for which in trifluoroacetic acid (TFA)-chloroform has a Soret absorption at 528 nm. Tetraaryltetraacenaphthoporphyrins (48) are even more red shifted, showing Soret bands between 556 and 570 nm for the free bases and 565 to 588 nm for the related dications. The lead(II) chelate for tetraphenylporphyrin (48a) shows an additional 'hyper' spectral shift that brings the Soret band to 604 nm, and this effect can also be achieved by introducing four meso-phenylethynyl substituents onto the tetraacenaphthoporphyrin nucleus (49). In addition, by combining these two factors for the lead(II) chelate of 49, a record-breaking value for the Soret band of 642 nm can be achieved. Spectral shifts due to ring annelation in porphyrin analogues are also discussed, including those for oxybenziporphyrins, oxypyriporphyrins, carbaporphyrins and sapphyrins.

TD-DFT calculations and MCD spectroscopy of porphyrin and phthalocyanine analogues: rational design of photosensitizers for PDT and NIR region sensor applications

“…In a similar manner to what has been reported in previous studies, 15,24 when benzo groups are added to the ligand periphery of porphyrin (1) or tetraazaporphyrin (7) to form tetrabenzoporphyrin (2) or Pc (8), there is a narrowing of the predicted HOMO-LUMO gap in DFT and TD-DFT calculations ( Figure 2) due to a destabilization of the a MO relative to the s, -a, and -s MOs. A similar effect is observed when the frontier π -MOs of naphthalocyanine (9) and anthracocyanine (10) are compared to those of Pc (8), but it is smaller in magnitude since the additional rings lie further from the inner perimeter where the largest MO coefficients are anticipated for the frontier π -MOs derived from the HOMO and LUMO of the parent perimeter ( Figure 3).…”

“…The trends in the MO energies of the frontier π -MOs and in the HOMO-LUMO gaps of the analogous set of fused-ring-expanded phthalonitriles (39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54), shown in Figure 7, are also broadly similar to those predicted for the corresponding Pc (1-22) and aza-BODIPY (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) analogues. The alignments of the nodal planes of the a and s MOs (Figure 8) are similar to those of the corresponding tetraazapophyrin analogues (Figure 3), as would be anticipated based on their radial symmetry and the manner in which the 4 angular nodal planes lie on alternating sets of 8 atoms on the inner perimeter due to the M L = ± 4 properties.…”

Extrovertierte Verwirrung – Linus Pauling, Melvin Calvin und Porphyrinisomere

“…[35] Es war mir nicht möglich zu klären, ob Calvins Untersuchungen Pauling bekannt waren. Beide kannten sich, trafen sich mehrmals und unterhielten eine gelegentliche Korrespondenz über andere Dinge.…”

Ein kernmodifiziertes Rubyrin mit meso‐Aryl‐Subsituenten und Phenanthren‐anellierten Pyrrolringen als hoch konjugierter NIR‐Farbstoff und Hg2+‐Sonde

“…Weil darüber hinaus die Anellierung am Kern bei Porphyrinen schon erfolgreich zur Verschiebung der optischen Spektren ins NIR angewendet wurde, [15,16] synthetisierten wir das Rubyrin 1 und untersuchten seine spektroskopischen Eigenschaften und Merkmale als Hg 2+ -Sonde. Die Synthese von 1 beginnt mit der oxidativen Kupplung von einfach lithiiertem Thiophen.…”