Effects of Core and/or Peripheral Protonation of meso-Tetra(2-, 3-, and 4-pyridyl)Porphyrin and meso-Tetra(3-methylpyridyl)Porphyrin on Their UV-vis Spectra

Table 1

UV-vis spectral data for hexaprotonation of H₂t(py)p with HCl in water (pH = 0) ^a.

Porphyrins and the dications	Soret band	Q(0,0) band
	(λ/nm)	(λ/nm)
H2t(2-py)p	417.0	642.0
[H6t(2-py)p](Cl)6	436.3	636.2
Δ𝜈 (cm^−1)^b	−106.0	142.0
H2t(3-py)p	418.0	646.4
[H6t(3-py)p](Cl)6	435.0	636.0
Δ𝜈 (cm^−1)	−935.0	253.0
H2t(4-py)p	416.0	643.0
[H6t(4-py)p](Cl)6	440.8	636.2
Δ𝜈 (cm^−1)	−1352	166.0

aSee Section  2.3 for details. The hexaprotonated species are completely insoluble in dichloromethane. ^bΔ𝜈 (cm⁻¹) = 10⁷(1/𝜆₂−1/𝜆₁), relative to the corresponding free base porphyrin.