The electronic effect in supramolecular self-assembly of para-substituted tetraphenylporphyrinatozinc(II) with imidazolyl-linked porphyrinatomanganese(III) by coordinative bonding

Abstract

The supramolecular self-assembly of para-substituted tetraphenylporphyrin complexes of zinc(II), Zn(p-X)TPP, with imidazolyl-linked porphyrinatomanganese(III), Mn(p-lmBPTPP)Cl, driven by coordinative bonding has been investigated by fluorescence spectra, electrospray mass spectrometry, 1 H-n.m.r. and u.v.-vis. spectra. The association constants of the supramolecular complexes, K c , were calculated using fluorescence spectroscopic titration data at suitable dilute concentration ranges in which the fluorescent quenching of Zn(p-X)TPP by Mn(p-ImBPTPP)Cl is a static process. The electronic effect in the supramolecular self-assembly of para-substituted . porphyrinatozinc(II) with imidazolyl-linked porphyrinatomanganese(III) is discussed. The non-linear dependence of log K c on the Hammett constants was found, which suggested that the electronic effect in para-substituents of tetraphenylporphyrin complexes of zinc(II) is an important, but not a sole factor effecting the association constants of the Zn(p-X)TPP-Mn(p-ImBPTPP)Cl supramolecular complexes. The results indicate that the closed conformation of the Zn(p-X)TPP-Mn(p-ImBPTPP)Cl supramolecular complex is another important factor effecting the association constants of the Zn(p-X)TPP-Mn(p-ImBPTPP)Cl supramolecular complexes.

Synthesis of a fluorescein–porphyrin hybrid and its supramolecular self-assembly with amino-porphyrinatocopper(II) by hydrogen bonding

“…As described above, it seems clear the observed spectroscopic changes are caused by the formation of a (Fl-PTPP)-Cu-APTPP supramolecular complex (Fig. 1) and effective photoinduced electron transfer [22,26]. Upon addition of a hydrogen-bonding solvent, such as methanol, to the Fl-PTPP/CuAPTPP system, the fluorescence intensity of Fl-PTPP was gradually restored, which further supports the conclusion that hydrogen bonding is the driving force of supramolecular self-assembly.…”

“…NMR is an important method for investigating the interaction between host and guest in supramolecular complexes [22,[28][29][30][31]. In order to look for NMR evidence for the formation of the (Fl-PTPP)-CuAPTPP supramolecular complex, the 1:1 (molar ratio) binding behavior of Fl-PTPP/CuAPTPP has been studied by using 1 H NMR in CDCl 3 (Fig.…”

“…A fluorescence strengthening character was previously observed in a fluorescence spectroscopic titration experiment for the Zn(p-CPTPP)/Cu(p-CPTPP) system (p-CPTPP = 5-(p-carboxyl) phenylene-methanamidophenyl-10,15,20-triphenylporphyrin), in which the porphyrin zinc(II)-copper(II) supramolecule was self-assembled by carboxyl-carboxyl type hydrogen bonding and the supramolecular association constant in CH 2 Cl 2 was (3.0 ± 0.3) 9 10 6 M -1 [16,22]. It is interesting that the K value of the Fl-PTPP/CuAPTPP system reported here is less than that of the Zn(p-CPTPP)/Cu(p-CPTPP) system.…”

“…There are several examples in the literature of model dimeric structures that involve conjugated bridges in the context of the donor-acceptor model system of porphyrin-fluorescein with diad-chromophores [16][17][18][19]. Various fluorescence quenching phenomena caused by photoinduced electron transfer from porphyrins or porphyrinatozinc to an electron acceptor have been observed in these systems [20][21][22][23][24][25][26]. Recently, a carboxyl porphyrin zinc(II)-copper(II) supramolecular unit, self-assembled by carboxyl-carboxyl type hydrogen bonding, that exhibits rare fluorescence strengthening character has been reported [15,16,19].…”

A novel fluorescein-porphyrinatozinc(II) hybrid: synthesis and its supramolecular self-assembly with imidazolyl-linked porphyrinatomanganese(III) by coordinative bonding

“…Because the chromophores in the photosynthesis system are all non-covalently attached to a protein scaffold, constructing non-covalently linked donor-acceptor systems to model the photosynthetic reaction center is an emerging area of supramolecular chemistry. Free bases and metalloporphyrins are known to form different aggregates, and the driving forces for these non-covalent molecular complexes can be hydrogen bonds, van der Waals, electrostatic interactions, and the hydrophobic effect [2, [5][6][7][8][9][10][11][12][13]. Some donor-acceptor supramolecular complexes assembled through porphyrin coordination chemistry have been reported [4][5][6][7][8].…”