N‐methylporphyrins

Influence of Macrocycle Protonation on the Photophysical Properties of Porphyrins

“…The N-CH 3 substitution leads to a bathochromic shift for the 0-0-transition band, amounting to 460 cm -1 , as compared to that for H 2 OMP (Figure 1c) or H 2 OEP. [35] The ∆E(S 2 -S 1 ) splitting value for the MP molecules is 822 cm -1 , being very close to that measured for the MP species of H 2 P, but about 150 cm -1 less than for the MP form of H 2 OMP. An important point is that the hypsochromic shifts upon formation of the protonated species for H(N-CH 3 )OEP are also higher.…”

“…[50] The question then arose if this class of porphyrins showed any features for the protonated forms different from those found for the porphyrins substituted on the periphery. [35,37] The absorption spectra for the FB, MP and DP forms of H(N-CH 3 )OEP are shown in Figure 1d. The absorption spectra show similarity to those for H 2 OMP, but some differing points can be discussed.…”

“…[35,[47][48][49] This substitution strongly affects the geometry of the porphyrin macrocycle since the core cavity is too small to accommodate these bulky substituents. [4,[49][50] It was expected that even in the case of pyrrole nitrogen methylation substantial nonplanar distortions take place.…”

“…[4] The electronic absorption spectra of MP and DP forms were measured for a number of porphyrin derivatives. [1,3,4,14,[16][17][18][19][20][21][22][23][24][26][27][28]30,[35][36][37] The spectral features of the MP and DP forms for a series of porphyrins with the most common substitution patterns are presented and discussed in details below. The series includes the free base porphin (H 2 P), asymmetrically substituted free base 2,7,12,17-tetramethylporphin (H 2 TMP), free base 2,3,7,8,12,13,17,18-octamethylporphin (H 2 OMP), N-substituted free base 21-methyl-2,3,7,8,12,13,17,18-octaethylporphin (H(N-CH 3 )OEP), free base 5,10,15,20-tetraphenylporphin (H 2 TPP) and free base 5,10,15,20-tetramesitylporphin (H 2 TMesP).…”

Structural Isomerism and chirality of N‐monosubstituted protoporphyrins

“…The central N-substituent cannot fit into the inner cavity of the porphyrin macrocycle and consequently causes a distortion of the N-alkylated ring which is significantly tilted out of the porphyrin plane; this is particularly so in the Results given were obtained with the same preparation of mouse liver mitochondria (as the source of ferrochelatase) employing/>3 different concentrations of inhibitor [5 ]. The pure isomers, obtained from unresolved synthetic N-methyl protoporhyrin as in [ 3 ], were only tested once; all other results were confirmed in ~>2 additional experiments metal chelate derivatives where the space available in the centre of the porphyrin system is further reduced by the presence of a metal [13][14][15][16]. We therefore suggest that when a propionlc acid-substituted ring is N-methylated, the alignment of the 2 propionic acid chains with respect to each other may be significantly altered ( fig.l, cf.…”