This critical review provides an overview on the formation of π-stacks of functional dyes in solution, aiming to acquaint young researchers with this topical research field and to stimulate further advance in supramolecular dye chemistry. Different mathematical models that have been proposed and applied for the description of aggregation equilibria of π-systems in solution are discussed. The factors that have significant impact on the structural features of aggregates and the thermodynamics of π–π stacking such as electrostatic interactions, size and geometry of the dye molecules are covered in this review. A comparison of the binding strength is made for different classes of functional π-conjugated systems, from simple benzene to more extended polycyclic hydrocarbon molecules, including triphenylenes and hexabenzocoronenes, heteroaromatic porphyrins and phthalocyanines, quadrupolar naphthalene and perylene bisimides, dipolar or even zwitterionic merocyanines and squaraines, and some macrocyclic dyes. Solvent effects on binding constants are analysed by linear free energy relationships with various solvent polarity scales (98 references with multiple entries).

Self-assembled π-stacks of functional dyes in solution: structural and thermodynamic features

Several photosensitizing porphyrins are selectively retained in solid tumors and other rapidly growing tissues in humans and other mammals. On subsequent illumination with light of wavelengths absorbed by the porphyrin, tumors can be destroyed with relatively little damage to the surrounding normal tissue; it is generally assumed that tumor damage is mediated by singlet oxygen generated by the light excited sensitizer. In clinical practice the patient is injected intravenously with a few mg/kg of the porphyrin. Then, 48-72 h later (an interval necessary to attain the maximum differential concentration of porphyrin in the tumor) the tumor area is illuminated with an appropriate dose of light (25-50 J/cm); typically a dye laser tuned to an absorption peak of the porphyrin is used. The only side effect observed in patients is a skin photosensitivity that persists for a month or so. This photochemotherapeutic procedure, termed photodynamic therapy (PDT)*, has been used on several thousand patients, with generally encouraging results (Dougherty ,1984, 1985). In spite of the utility of the technique, PDT as presently used suffers from some disadvantages. The photosensitizer preparation most generally used is a complex mixture of porphyrins termed hematoporphyrin derivative (HPD). This is prepared by subjecting hematoporphyrin acetates to alkaline hydrolysis. The composition of the mixture varies in different preparations and with time of storage. The most active component has been described as a dihematoporphyrin ether (Dougherty, 1985) or ester (Kessel, 1985); however these are not available as pure chemicals. Red light, usually from a dye laser tuned to 630 nm (corresponding to the longest wavelength absorption peak of HPD), is most commonly used in PDT to permit the maximum depth of

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1751-1097.1986.tb05648.x

Phthalocyanines as photosensitizers in biological systems and for the photodynamic therapy of tumors.

Aggregation of sensitizing dyes in solution and their adsorption onto silver halides

UV−vis and CD spectroscopy reveal that a tricationic cyanine dye spontaneously assembles into a helical J-aggregate in the presence of a double-helical DNA template. The stability of the J-aggregate is strongly dependent on the dye concentration and DNA length in a manner that reflects a high degree of cooperativity in formation of the aggregate. Slight changes in environmental conditions such as temperature and ionic strength result in interconversion between J- and H-aggregates. The aggregate likely consists of dimeric units assembled in an offset, face-to-face orientation within the minor groove of the DNA template, analogous to an earlier report of H-aggregation on DNA by a related cyanine dye. A model is proposed that relates the two aggregate structures by translation of one monomer from a given dimer along the floor of the minor groove. This translation requires adjacent monomers to also translate, leading to the observed cooperativity.

DNA-Templated Formation of a Helical Cyanine Dye J-Aggregate

The photophysical properties of zinc phthalocyanine (ZnPC) andchloroaluminum phthalocyanine (AlPHCl) incorporated into lipo-somes of dimyristoyl phosphatidylcholine in the presence and absenceof additives such as cholesterol or cardiolipin were studied by time-resolved fluorescence, laser flash photolysis and steady-state tech-niques. The absorbance of the drugs changed linearly with drugconcentration, at least up to 5.0 µM in homogeneous and heteroge-neous media, indicating that aggregation did not occur in these mediawithin this concentration range. The incorporation of the drugs intoliposomes increases the dimerization constant by one order of magni-tude (for ZnPC, 3.6 x 10 4 to 1.0 x 10 5 M -1 and for AlPHCl, 3.7 x 10 4 to 1.5 x 10 5 M -1 ), but this feature dose does not rule out the use of thiscarrier, since the incorporation of these hydrophobic drugs into lipo-somes permits their systemic administration. Probe location in bio-logical membranes and predominant positions of the phthalocyaninesin liposomes were inferred on the basis of their fluorescence andtriplet state properties. Both phthalocyanines are preferentially dis-tributed in the internal regions of the liposome bilayer. The additivesaffect the distribution of these drugs within the liposomes, a fact thatcontrols their delivery when both are used in a biological medium,retarding their release. The addition of the additives to the liposomesincreases the internalization of phthalocyanines. The interaction of thedrugs with a plasma protein, bovine serum albumin, was examinedquantitatively by the fluorescence technique. The results show thatwhen the drugs were incorporated into small unilamellar liposomes,the association with albumin was enhanced when compared withorganic media, a fact that should increase the selectivity of tumortargeting by these phthalocyanines (for ZnPC, 0.71 x 10

/pdf/photophysical-studies-of-zinc-phthalocyanine-and-4ugkgzzqte.pdf

Photophysical studies of zinc phthalocyanine and chloroaluminum phthalocyanine incorporated into liposomes in the presence of additives

Dimerization of a copper(II)-phthalocyanine dye in carbon tetrachloride and benzene

Association of copper(II), vanadyl, and zinc(II) 4,4',4',4'''-tetraalkylphthalocyanine dyes in benzene

Polar Tautomer Dimerization of Ionic Arylazonaphthols in Water

Monomer-dimer-gleichgewichte des 4,4′,4′′,4′′′-tetrakis-(octadecylaminosulfonyl)-phthalocyaninato-kupfer(ii)-farbstoffes in tetrachlorkohlenstoff und benzol

Allen F. DeLuca

Papers

Dimerization of a copper(II)-phthalocyanine dye in carbon tetrachloride and benzene

Association of copper(II), vanadyl, and zinc(II) 4,4',4',4'''-tetraalkylphthalocyanine dyes in benzene

Polar Tautomer Dimerization of Ionic Arylazonaphthols in Water

Monomer-dimer-gleichgewichte des 4,4′,4′′,4′′′-tetrakis-(octadecylaminosulfonyl)-phthalocyaninato-kupfer(ii)-farbstoffes in tetrachlorkohlenstoff und benzol

Polare tautomeren-dimerisierung ionogener arylazonaphthole in wasser