Factors Influencing Self-Aggregation Tendencies of Cationic Porphyrins in Aqueous Solution

Kawasaki, Koji; Fukuda, Kazuya; Wakami, Hideo; Nishiyabu, Ryuhei; Pasternack, Robert F.

doi:10.1021/ja000738g

Cited by 323 publications

(242 citation statements)

References 39 publications

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“…It is known that the self-assembly of a porphyrin forms H-and J-type supramolecular structures in its higher level of organization: The former has a face-to-face stacking structure that shows a characteristic blue-shift of a Soret absorption band, whereas the other adopts an edge-to-edge orientation, which is responsible for the red-shift of the Soret band (37)(38)(39). A tetraphenylporphyrin is not allowed to adopt a face-to-face stacking structure because of the steric repulsion of the phenyl groups; thus, the face-to-face stacking motif of the porphyrin units of 2 can be ruled out in its assembled structure.…”

Section: Resultsmentioning

confidence: 99%

Supramolecular polymer formed by reversible self-assembly of tetrakisporphyrin

Haino

Fujii

Watanabe

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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S-shaped tetrakisporphyrin 2 forms supramolecular polymeric assemblies via a complementary affinity of its bisporphyrin units in solution. The self-association constant determined by applying the isodesmic model is >10 6 L mol ؊1 , which suggests that a sizable polymer forms at millimolar concentrations at room temperature. The electron deficient aromatic guest (TNF) binds within the molecular clefts provided by the bisporphyrin units via a chargetransfer interaction. This guest complexation completely disrupts supramolecular polymeric assembly. The long, fibrous fragments of the polymeric assemblies were characterized by atomic-force microscopy imaging of a film cast on a mica surface. The polymeric assemblies have lengths of >1m and show a coiled structure with a higher level of organization. The approach discussed in this report concerning the quick preparation of supramolecular polymeric assemblies driven by noncovalent forces sets the stage for the preparation of a previously undescribed class of macromolecular porphyrin architectures.porphyrin ͉ supramolecular chemistry S ignificant effort has been directed toward elucidating the energy transport phenomena occurring in natural lightharvesting complexes. A variety of porphyrin-based model compounds have been created to mimic natural light-harvesting complexes with the goal of applying them to artificial lightharvesting systems and molecular photonic devices (1-4). Among them, nanometric multiporphyrin arrays are the most challenging target, wherein, their covalent synthesis offers a high stability and a precisely controlled arrangement of multiporphyrin arrays (5, 6). Unfortunately, the growth of size and complexity of these systems makes their synthesis tedious and inefficient.In contrast, supramolecular self-assembly is a versatile alternative and offers the quick construction of 1-, 2-, or 3-dimensional nanometric architectures that have discrete structures, properties, and functions in which the molecular components are held together by reversible interactions (7-11). Self-assembled nanometric multiporphyrin arrays having well-defined shapes and dimensions provide unique optical and electrochemical properties for photochemical energy conversion and storage. As a consequence, their practical applications can be foreseen in the field of molecular electronics: conductive molecular wires, switches, and photovoltaic cells. These creative developments should pave the way for research directions in creating key materials for emerging field of nanotechnology and science.Coordination-driven self-assembly of porphyrin is one of the most useful approaches for developing large and elaborate molecular architectures (12, 13). Hunter and coworkers developed unique self-assembled porphyrin arrays (14-18). Giant porphyrin arrays and large porphyrin wheels via metal coordination for modeling light-harvesting antenna have been reported by . Aida and coworkers have investigated self-assembled nanometric porphyrin arrays (27-29). There are limited examples of porphyrin self...

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Section: Resultsmentioning

confidence: 99%

Supramolecular polymer formed by reversible self-assembly of tetrakisporphyrin

Haino

Fujii

Watanabe

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…This value is considerably lower in comparison to pK a values reported in the literature for the protonation of other watersoluble porphyrins. 29,30 Indeed, both the formation of strongly aggregated species and the occurrence of specific intramolecular interactions between the propionate side chain and the inner core could be responsible for this anomalous value.…”

Section: Discussionmentioning

confidence: 99%

Aggregation Behavior of Protoporphyrin IX in Aqueous Solutions: Clear Evidence of Vesicle Formation

et al. 2002

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The aggregation behavior of protoporphyrin IX in aqueous solution, as a function of pH and ionic strength, has been studied by means of UV/vis, fluorescence emission spectroscopy, and resonant light scattering (RLS) techniques. Our experimental results agree with previous literature assignments: (i) protoporphyrin IX is a monomer in the pH range 0-3, (ii) a dimer is present for pH > 8, and (iii) higher aggregates are present in the pH range 3-7. Addition of sodium chloride up to 0.3 M to a porphyrin solution at pH 12 gives a process resembling a phase transition, whereas it has little effect on acidic or neutral solutions. The apparent split Soret band observed in the intermediate pH range has been explained using a model in which dimers of porphyrins (with a slip angle R ) 38°or 52°, as derived from depolarized RLS measurements) are the basic units and they interact axially through π-π stacking and laterally by edge-to-edge hydrophobic contacts. The half neutralization of the carboxylic acid side chains is responsible for the occurrence of a network of intermolecular hydrogen bonds, which contribute to a better stabilization of the supramolecular assembly. Evaporation on a glass surface of solutions containing protoporphyrin IX aggregates from samples at intermediate pH leads to aggregates stable enough to be investigated for the first time through scanning electron (SEM) and scanning near-field optical microscopy (SNOM). These species evidence a prolate shape with an average size of 200-500 nm and a medium height of 60 nm, which is in agreement with the hydrodynamic radii as measured in solution by dynamic light scattering. On consideration of the amphiphilic character of protoporphyrin IX, these observations suggest the formation of multilamellar or onion-like vesicles. The analysis of the SNOM images points to the presence of regions in which the aggregation process resulted in a thin film covering the vesicles. An analysis of SEM experiments reveals also the contemporary presence of large regions in which the vesicles collapse in a continuum layered structure.

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“…It is well known that self-aggregation of a PS is generally a drawback in PDT since it reduces the 1 O 2 formation (DeRosa and Crutchley 2002). Self-aggregation tendencies of cationic amphiphilic porphyrins have been extensively studied, and it seems that the most important factors are electronic and structural effects that influence self-aggregation in a complex manner (Kano et al 2000). The length of the alkyl chain has a strong impact on aggregation, and pyridinium porphyrins with longer alkyl chains (C8, C12 and C18) have been shown to form micelles (Dancil et al 1997).…”

Section: Ps Distributionmentioning

confidence: 99%

Porphyrin-based cationic amphiphilic photosensitisers as potential anticancer, antimicrobial and immunosuppressive agents

2017

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Photodynamic therapy (PDT) combines a photosensitiser, light and molecular oxygen to induce oxidative stress that can be used to kill pathogens, cancer cells and other highly proliferative cells. There is a growing number of clinically approved photosensitisers and applications of PDT, whose main advantages include the possibility of selective targeting, localised action and stimulation of the immune responses. Further improvements and broader use of PDT could be accomplished by designing new photosensitisers with increased selectivity and bioavailability. Porphyrin-based photosensitisers with amphiphilic properties, bearing one or more positive charges, are an effective tool in PDT against cancers, microbial infections and, most recently, autoimmune skin disorders. The aim of the review is to present some of the recent examples of the applications and research that employ this specific group of photosensitisers. Furthermore, we will highlight the link between their structural characteristics and PDT efficiency, which will be helpful as guidelines for rational design and evaluation of new PSs.

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Factors Influencing Self-Aggregation Tendencies of Cationic Porphyrins in Aqueous Solution

Cited by 323 publications

References 39 publications

Supramolecular polymer formed by reversible self-assembly of tetrakisporphyrin

Supramolecular polymer formed by reversible self-assembly of tetrakisporphyrin

Aggregation Behavior of Protoporphyrin IX in Aqueous Solutions: Clear Evidence of Vesicle Formation

Porphyrin-based cationic amphiphilic photosensitisers as potential anticancer, antimicrobial and immunosuppressive agents

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