20-(N-Methylpyridiniumyl)ethynylated chlorophyll-a derivative with an intense Qx absorption band at a green to orange region

Synthesis of Cationic Pyridinium‐(Bacterio)Chlorophyll Conjugates Bearing a Bacteriochlorin, Chlorin, or Porphyrin π‐Skeleton and their Photophysical and Electrochemical Properties

“…To confirm the effect of cationic pyridinium group on the optical properties, time‐dependent (TD) density functional theory (DFT) calculations were performed using the Gaussian09 program. First, the optimized structure and their molecular orbitals of synthetic compounds were calculated at the B3LYP/6‐31G(d) level, and the electronic transitions were estimated by TD‐DFT calculations at the same level for the optimized structures. The red‐shift values of the longest wavelength absorption band of BChl‐1/2 , Chl‐1/2 , and Por‐1/2 were estimated to be 340, 240, and 30 cm –1 , respectively, which are in good agreement with the experimental values (390/180/0 cm –1 ) (Figure S16 and Table S1).…”

“…Typically, the Qy maxima are bathochromically shifted in the order of porphyrin < chlorin < bacteriochlorin. Notably, the peripheral functional groups directly π‐conjugated to the core π‐systems also affect the absorption bands , , , . For example, the introduction of electron‐withdrawing groups at the 3‐position on the molecular y ‐axis moves the Qy maxima to longer wavelengths…”

Efficient Synthesis of Long‐wavelength Absorbing Cyanochlorophyll a Derivatives via Stereoselective Horner–Wadsworth–Emmons Reaction

“…It is well known that structural changes, induced by the peripheral substituents conjugated with the chlorin chromophore, remarkably affect the photophysical properties of these porphyrins, especially their electronic absorptions . Various long‐wavelength absorbing chlorins have been synthesized by introducing electron‐withdrawing groups including nitro, keto, carboxyl, pyridyl, quinolyl and cationic N ‐heteroaromatic groups, most of which are prepared from 3‐formyl chlorins via classical CC bond‐forming reactions such as the Wittig, Knoevenagel, Henry, Grignard, and the aldol and aldol‐like condensation reactions …”