“Blackening” Porphyrins by Conjugation with Quinones

Panchromatic π‐Extended Porphyrins from Conjugation with Quinones

“…Solutions of the metal‐free naphthoquinonoporphyrins 2 ‐ 2H to 6 ‐ 2H in CH 2 Cl 2 exhibited weak luminescence, if excited, for example, near the longest wavelength absorption band (see Figure and the Supporting Information). This observation contrasts with the lack of luminescence of the corresponding Zn complexes 2–Zn to 6–Zn . Apparently, fluorescence quenching in the metal‐free 2 ‐ 2H to 6 ‐ 2H was less complete.…”

“…Symmetrical β,β′‐tetrasulfolenoporphyrins have been prepared in a metal‐free form ( 1 ‐ 2H ) and as the Zn II , Ni II and Cu II complexes 1–Zn , 1–Ni and 1–Cu (Scheme ) . They were proposed to be versatile, reactive building blocks, “programmed” for further covalent attachment of functional units . The synthesis of 1–Zn was first developed in conjunction with the attachment of C 60 fullerene units by [4+2] cycloaddition reactions .…”

“…The synthesis of 1–Zn was first developed in conjunction with the attachment of C 60 fullerene units by [4+2] cycloaddition reactions . 1–Zn undergoes thermal release of SO 2 at 140 °C to form reactive porphyrindienes in situ, which are trapped efficiently by dienophiles, such as C 60 fullerene and benzoquinone, or which cyclodimerise into a chiral spiro‐dimer . By making use of the dienophilic and oxidative properties of benzoquinone in a synthetic “add‐and‐lock” strategy, an effective irreversible attachment of up to four electronically conjugated quinone units to the Zn II –porphyrin 1–Zn resulted in the unprecedented black Zn II –porphyrin 6–Zn , which was effectively non‐luminescent (Scheme ) .…”

“…1–Zn undergoes thermal release of SO 2 at 140 °C to form reactive porphyrindienes in situ, which are trapped efficiently by dienophiles, such as C 60 fullerene and benzoquinone, or which cyclodimerise into a chiral spiro‐dimer . By making use of the dienophilic and oxidative properties of benzoquinone in a synthetic “add‐and‐lock” strategy, an effective irreversible attachment of up to four electronically conjugated quinone units to the Zn II –porphyrin 1–Zn resulted in the unprecedented black Zn II –porphyrin 6–Zn , which was effectively non‐luminescent (Scheme ) . We have expanded on these original studies, prepared the corresponding Ni II complexes ( 2–Ni to 6–Ni ) and metal‐free porphyrins ( 2 ‐ 2H to 6 ‐ 2H ), and studied their spectroscopic features (Schemes and ).…”

Photochemical Transformations Involving Porphyrins and Phthalocyanines

“…A series of "black" (tris-and tetra-β-quinonoporphyrinato)zinc(II) chelates was prepared via thermolysis of a tetra-β-sulfolenoporphyrin in the presence of excess benzoquinone followed by oxidation with dicyanodichlorobenzoquinone in up to 86 % yield. Surprisingly, the absorption spectra of these tetrapyrroles represent broad and intense electronic transitions covering the whole range of visible wavelengths region (Banala et al 2009). <Chemical Structure 4> While most studies utilized quinones as acceptor compounds, these studies almost exclusively used p-quinones.…”