Cl^– Complexation Induced H- and J-Aggregation of meso-Tetrakis(4-sulfonatothienyl)porphyrin Diacid in Aqueous Solution

Abstract

Various porphyrin diacids are known to show controlled self-assembly by inorganic anions. Following the unexpected finding that meso-tetrakis(4-sulfonatothienyl)porphyrin diacid shows Cl(-) specific aggregation in spite of having the anionic substituents, the aggregation behavior of the diacid in aqueous solution with Cl(-) was investigated in detail. We found that Cl(-) induces the H-aggregate, followed by the transformation into the J-aggregate with increasing Cl(-) concentration. For the J-aggregate formation, negatively charged sulfonic acid groups were suggested to be of minor influence. The J-aggregate forms nanoscale macrostructures composed of highly oriented molecules on substrate. To our knowledge, this is the first report of both H- and J-type aggregate formation of a porphyrin diacid in the presence of an aqueous inorganic anion. These results would open the gate for controlling the chromophore packing structure of a porphyrin diacid complexed with an inorganic anion by varying the composition.

Molecular Engineering of Free‐Base Porphyrins as Ligands—The N−H⋅⋅⋅X Binding Motif in Tetrapyrroles

“…Fore xample,5 ,10,15,20-tetrakis(4sulfonatothienyl)porphyrind ihydrochloride showed chloride-specific aggregation in aqueous solution. [99] Thepresence of Cl À induced H-aggregation followed by conversion into Jaggregates with increasing chloride concentration. Nakanishi et al investigated the photoconductivity of nanochannels composed of sad-type porphyrin dications and electron donors.…”

“…In such studies, the role of the H‐bound counterions is often crucial. For example, 5,10,15,20‐tetrakis(4‐sulfonatothienyl)porphyrin dihydrochloride showed chloride‐specific aggregation in aqueous solution . The presence of Cl − induced H‐aggregation followed by conversion into J‐aggregates with increasing chloride concentration.…”

Polyelectrolyte‐Assisted Noncovalent Functionalization of Carbon Nanotubes with Ordered Self‐Assemblies of a Water‐Soluble Porphyrin

“…Taking the energy blueshift (1800 cm −1 ) for N agg =2, we obtain approximately 7 Å, which is significantly larger than the normal π–π stacking distance of porphyrins (3.5 Å). This could indicate that the geometry involved is a slipped stack (54.7< θ <90°), as proposed for the H‐aggregate of the diacid meso ‐tetrakis(4‐sulfonatothienyl)porphyrin in aqueous solution 30. Considering the ionic diameter of Cl − (3.4 Å), the involvement of a counterion intercalated between the porphyrin planes could be speculated.…”

A study on the interactions of cationic porphyrin with nano clay platelets in Layer-by-Layer (LbL) self assembled films

“…Porphyrins form aggregates under certain concentrations, pH, ionic strength, counter ions of organic salts, etc [8][9][10][11][12]. Aggregation of these molecules have their potential applications in electronic devices, such as bio-mimic membranes [9] and in nonlinear optics [13].…”