Synthesis and characterization of new molecular complexation between free base meso-tetraarylporphyrins and nitrosonium ion as π-acceptor

NOBF4 reacts with para-substituted meso-tetraarylporphyrins, H2t(4-Xp)p, at room temperature for formation of green molecular complexes, [H2t(4-Xp)p(NO)]BF4. Mole ratio for the porphyrins and nitrosonium ion in the molecular complexes was 1:1, [H2T(4-X)PP(NO)]BF4. FT-IR, UV–Vis, (1H and 13C) NMR spectral data, elemental analysis and molar conductivity indicated that NO+ (as electron acceptor) is bound to the lone electron pairs of the two pyrrolenine nitrogens in a side of the porphyrin plane. In these molecular complexes, two pyrrolic nitrogen atoms of the porphyrin core coordinate to the acceptor and two protons of the pyrrolic nitrogen atoms have been remained on the porphyrin macrocycles. Molecular complexation of meso-tetraarylporphyrins with NO+ produces a large downfield shift for the NH signal.

Graphical abstractMixing of meso-tetraarylporphyrins (H2t(4-Xp)p) and NOBF4 leads to the formation of [H2t(4-Xp)p(NO)]BF4 molecular complexes, that two nitrogen atoms of pyrrolic in the porphyrin core act as electron donors to a nitrosonium cation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► NOBF4 reacts with meso-tetraarylporphyrins, H2t(4-Xp)p, for formation of green molecular complexes, [H2t(4-Xp)p(NO)]BF4. ► Lone pairs of two pyrrolenine nitrogens of porphyrin act as the electron donors to NO+ cation in NOBF4. ► NO+ cation locates above or below the mean plane of the porphyrin. ► Two hydrogen atoms of N–H in porphyrin locate on a side of the macrocycle plane. ► There is hydrogen bonding between hydrogen atoms of N–H and one F atom of BF4− in the molecular complexes.