Solvatochromism of dodecaphenylporphyrin and its derivatives

Solvatochromism of dodecaphenylporphyrin (H 2 DPP) and its derivative (H 2 DPP-NH[Formula: see text], to the latter of which an amino group is introduced at the [Formula: see text]-position of one of the meso-aryl groups, and their diprotonated forms (H 4 DPP[Formula: see text], H 4 DPP[Formula: see text]-NH[Formula: see text] have been investigated. Saddle-type distortions of H 2 DPP and H 4 DPP[Formula: see text] lead to non-symmetric electron density distribution of the frontier orbitals, which causes the solvatochromism. The introduction of the amino group to H 2 DPP and H 4 DPP[Formula: see text] causes the transition having charge-transfer character involving the aniline moiety and the porphyrin center, in which the aniline moiety becomes electron deficient in the excited state and the acidity of N-H protons of the amino group increases; thus, the hydrogen bonds with the solvent molecules are strengthened in the excited state. This also contributes to the solvatochromism of the amino derivatives.