Unique 1∶2 adduct formation of meso-tetraarylporphyrins and meso-tetraalkylporphyrins with BF₃: a spectroscopic and ab initio study

New Cationic Sandwich-type Intermediate Sitting-atop Complexation between meso-Tetraarylporphyrins and Tantalum(V) Chloride: Synthesis, Spectroscopic Characterization and Photoluminescence Study

“…Tantalum atom had high oxidation number and enough empty d-orbitals for acception of four electron pairs of the pyrrolic nitrogen atoms in two porphyrin molecules and formation of complexes with 1:2 (acceptor:donor) mole ratio in contrast known 2:1 or 1:1 (acceptor:donor) complexes. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Several evidences confirm that the complexes of free base meso-tetraarylporphyrins with tantalum(V) chloride are formed. Changes in the 1 H NMR spectrum of H 2 tpp after mixing of different equivalents of TaCl5 (0, 0.25, 0.5, 0.75) are presented in Figure 2.…”

“…This work presents the first example for the ionic sandwich-type sitting-atop complexation between free base porphyrins and acceptors. The similarity of results of UV-Vis and ( 1 H and 13 C) NMR spectroscopy between the obtained complexes and known SAT complexes of mesotetraarylporphyins with various acceptors, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] suggested the saddled porphyrin core structures with one tantalum atom bonded to four pyrrolic nitrogens of two porphyrin macrocycles. Tantalum atom had high oxidation number and enough empty d-orbitals for acception of four electron pairs of the pyrrolic nitrogen atoms in two porphyrin molecules and formation of complexes with 1:2 (acceptor:donor) mole ratio in contrast known 2:1 or 1:1 (acceptor:donor) complexes.…”

Sandwich Intermediate Sitting-atop Complexation between Free Base meso-tetraarylporphyrins and Tellurium(IV) chloride

“…These results show that the effect of ring current have been lost in the complexed porphyrin. [2][3][4][5][6][7][8][9][10][12][13][14][15][16][17][18] Further, the observed downfield shifts of the aryl ring hydrogens could result from a direct increase in ring current of aryl groups. This has been produced by extension in the π-system of the aryl rings.…”

“…This has been produced by extension in the π-system of the aryl rings. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] In the i-SAT complexes the pyrrole rings are not equivalent and in result existence of a singlet for β-protons of meso-tetraarylporphyrin is not corresponding with unsymmetrical pyrrole rings in the proposed structure of the i-SAT complexes, Figure 2. This sym- metry is produced because the ring inversion of the saddled core conformation of the porphyrin is probably fast on the NMR time scale.…”

“…This deformation allows a strong interaction between the aryl rings and porphyrin π-system. [2][3][4][5][6][7][8][9][10][12][13][14][15][16][17][18] The UV-vis spectral data for other i-SAT complexes of meso-tetraarylporphyrins and tellu- [2][3][4][5][6][7][8][9][10] lead to the proposition of distorted porphyrin cores in all of the species. In the proposed structure four nonocoplanar pyrrole rings tilted alternately up and down and the lone pairs of pyrrolenine nitrogens of two porphyrin core act as the electron donors to one tellurium atom and so, two hydrogen atoms of pyrroles (N-H) remained still on the porphyrins.…”