Self-Organized Porphyrin Dimer as a Highly Specific Receptor for Pyrazine Derivatives

Abstract

Complex formation between pyrazine derivatives and dimeric self-assembly of αααα-isomer of meso-tetrakis(2-carboxy-4-nonylphenyl)porphyrin Zn complex (1·Zn) was investigated. Thermal atropisomerization of 1·Zn in a nonpolar solvent such as toluene gives the αααα-atropisomer exclusively. Vapor pressure osmometry for the resultant αααα-atropisomer solubilized in CHCl3 shows molecular weight of 2650 ± 200, indicating formation of dimeric self-assembly of 1·Zn. 1H NMR and UV/vis titration experiments for this dimeric assembly with pyrazine derivatives show highly specific 1:2 complex formation of pyrazine and 1·Zn. The equilibrium constants for 1·Zn dimer/pyrazine complex formation are estimated to be over 107 M-1. The most characteristic feature of the present ternary system, (1·Zn)2 ·pyrazine, is that the pyrazine derivative, having a large side moiety such as benzoyl group, can coordinate two zinc atoms inside the dimer cavity by sticking the side moiety out of a window formed between hydrogen-bond pillars of the complex.

Supramolecular Organization of Porphyrins and Phthalocyanines by Use of Biomimetic Coordination Methodology

“…Kuroda and coworkers prepared pyrazine-appended free-base porphyrin 98 as a multiple binding site for porphyrin tetrabenzoic acid 99, which forms dimer 99 2 with quadruple hydrogen bonding interaction. 147,148 Photoexcitation energy of peripheral Zn-porphyrin was transferred with 61% efficiency, resulting in fluorescence emission from the central free-base porphyrin 98 core (Scheme 48).…”

Novel meso-substituted porphyrins: Synthesis, characterization and photocatalytic activity of their TiO2-based composites

“…However, the overall molecular set-up may be rearranged by either introducing axial ligands and/or other substituents attached to the carbon bridges (meso position) or replacing the hydrogens of the pyrrole units. Such modified porphyrin systems have shown a range of interesting physicochemical features, including photoactivity, optoelectronic and electrochemical properties, and hence they are supposed to find application in hi-tech materials [4][5][6][7][8][9][10][11], medical treatment [12][13][14][15][16][17], molecular recognition [18,19], photosensitizers and photocatalysts [20][21][22][23][24][25][26] as well as in different areas of modern technology.…”

Hydrogen bond-directed aggregation of diazadibenzoperylene dyes in low-polarity solvents and the solid state

“…For most examples, this interaction relies on hydrogen-bonding, which is a directionalreversible interaction with adjustable binding strength (4,5). Within the family of hydrogen-bonded systems, the association of carboxylic acids and pyridines has received special attention and includes work on defined molecular assemblies (6)(7)(8)(9), supramolecular polymers and networks (4,5,(10)(11)(12)(13)(14), and hydrogen-bonded liquid crystals (15)(16)(17)(18). However, the lowbinding constant between pyridines and carboxylic acids precludes high degrees of polymerization in solution between dicarboxylic acid and dipyridine building blocks, which, up to now, limited this supramolecular synthon to applications in solid-state materials.…”