Directly Diphenylborane‐Fused Porphyrins

The enhancement of the light absorption ability of synthetic chlorophyll derivatives is demonstrated. Chlorophyll derivatives directly conjugated with a difluoroboron 1,3-diketonate group at the C3 position were synthesized from methyl pyropheophorbide-d through Barbier acylmethylation of the C3-formyl moiety, oxidation of the C3-carbinol, and difluoroboron complexation of the diketonate. Electronic absorption spectra in a diluted solution showed that the synthetic conjugates gave an absorption band at λ=400-500 nm, with a Qy band shifted to a longer wavelength of λ≈700 nm. DFT calculations demonstrated that the absorption bands and redshifts were ascribable to the coupling of the LUMO of chlorin with that of the difluoroboron diketonate moiety. The introduction of a pyrenyl group at the C3(3) -position of the conjugate afforded an additional charge-transfer band over λ=500 nm, producing a pigment that bridged the green gap in standard chlorophylls.

Section: Resultssupporting

confidence: 73%

Enhancement of Light Absorption Ability of Synthetic Chlorophyll Derivatives by Conjugation with a Difluoroboron Diketonate Group

Kinoshita

Kitagawa

Tamiaki

2016

“…The B−N bond lengths (B−N1 and B−N2) are 1.616(6) and 1.556(5) Å, which are comparable with the respective bond distances in 8 (Supporting Information Figure S29c). The C19−B bond distance in 9 is 1.626(4) Å, which is marginally larger than the respective values observed in 1 – 3 . The σ‐phenyl unit is almost perpendicular (82.80(9)°) to the plane (Figure d) as compared to other meso ‐aryl units (Supporting Information Table S2).…”

Section: Figurementioning

confidence: 76%

“…The chemistry of organoboranes (C−B) has emerged as an important class of synthetic materials due to its intriguing features such as high luminescence, large nonlinear optical responses, anionic sensors, and as potential precursors and intermediates for many organic reactions . Numerous synthetic methods have been introduced for the formation C−B bonds on aromatic frameworks, however, such bond formation in porphyrin macrocycles is in the infancy stage and recently received considerable attention . The initial reports on borylated porphyrins 1 is utilized mainly for peripheral modification of the macrocycle .…”

Section: Figurementioning

confidence: 99%

Carbatriphyrin(3.1.1)–A Distinct Coordination Approach of B^III to Generate Organoborane and Weak C−H⋅⋅⋅B Interactions

Adinarayana

Thomas

Yadav

et al. 2017

Carbatriphyrin(3.1.1) is the structural isomer of biphenylcorrole and achieved by switching the bonding mode of biphenyl unit from 3,3' to 2,3' which turns the corrole into a triphyrin analogue. The presence of a m-arene unit in the framework restricts the overall conjugation and thus leads to a nonaromatic macrocycle. The protonation experiments afford a trifluoroacetate ion complex. The coordination chemistry reveals that the bottom approach of boron(III) ion forms weak C-H⋅⋅⋅B interactions, however a top approach stabilizes the organoborane complex and the product distribution relies on the basicity of the proton scavengers. These results are unambiguously confirmed by single-crystal X-ray analyses.

“…As a different approach, a synthetic strategy of attaching a heteroatom directly at the meso position of porphyrins in a fused manner has been explored to extend the π‐conjugation networks (Scheme , left). These porphyrins displayed significantly altered optical and electronic properties owing to the effective electronic interactions of the porphyrin ring with the embedded heteroatoms, such as nitrogen, boron, carbon radicals, and silicon . In particular, nitrogen‐embedded porphyrins (X=N) are attractive in light of the electron‐donating attributes of the nitrogen atom that alter optical and electronic properties.…”

Section: Introductionmentioning

confidence: 99%

meso–meso‐Linked Diarylamine‐Fused Porphyrin Dimers

Fukui

Yorimitsu

Osuka

2016

Self Cite

A meso-meso-linked diphenylamine-fused porphyrin dimer and its methoxy-substituted analogue were synthesized from a meso-meso-linked porphyrin dimer by a reaction sequence involving Ir-catalyzed β-selective borylation, iodination, meso-chlorination, and S Ar reactions with diarylamines followed by electron-transfer-mediated intramolecular double C-H/C-I coupling. While these dimers commonly display characteristic split Soret bands and small oxidation potentials, they produced different products upon oxidation with tris(4-bromophenyl)aminium hexachloroantimonate. Namely, the diphenylamine-fused porphyrin dimer was converted into a dicationic closed-shell quinonoidal dimer, while the methoxy-substituted dimer gave a meso-meso, β-β doubly linked porphyrin dimer.