Journal of Porphyrins and Phthalocyanines

Organic self-assemblies of meso-tetra (4-carboxyphenyl)porphine (TCPP) prepared in trifluoroacetic acid (TFA) and hydrochloric acid solutions at pH < 1 were studied by X-ray photoelectron spectroscopy (XPS) in order to determine the protonation state of the porphyrin building blocks present in the solid self-assembled nanostructures. XPS measurements were conducted both at room and at elevated temperatures. Room temperature N 1s spectra showed two bands with a 3:1 intensity ratio consistent with three protonated and one unprotonated nitrogen in the structures prepared in both TFA and HCl solutions. We attribute this result to TCPP existing as a 50:50 mixture of the free-base and diacid forms of the porphyrin core in the self-assembled state. Upon heating to 150 °C the TCPP/TFA and TCPP/HCl nanomaterials exhibit loss of pyrrolic hydrogens and retain different amounts of their respective counter ions. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of the nanostructures showed that these systems have different morphologies depending on the acid employed during fabrication and the post preparation temperature treatment. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) of the TCPP nanostructures indicate that those prepared in HCl are crystalline while the nanoassemblies made in TFA are polycrystalline or amorphous.

A new method of preparation and the properties (solubility, aggregation, spectralluminescent properties, singlet oxygen and photobleaching quantum yields) of non-metal 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine are reported. The influence of ionization state on photophysicochemical properties of this dye is also presented.

This study describes the application of porphyrin-embedded porous organosilicate materials to the adsorption of ammonia gas. Organosilicate scaffolds were synthesized through a surfactant-templating process combined with a phase separation technique. The structure offers a macro-textured scaffold to facilitate flow through the sorbent material and provide enhanced access to the available surface area provided by a combination of micro- and mesopores distributed over a range of sizes. The materials were grafted post-synthesis to provide sites for covalent immobilization of porphyrins. These porphyrins were utilized for incorporation of metal sites into the organosilicate materials. The removal of ammonia was evaluated for a number of materials incorporating copper metalloporphyrins of varied structure at varied loading levels. Results have been compared to removal of ammonia by a carbon material. Copper deuteroporphyrin IX bis-ethylene glycol provided the strongest interactions with ammonia. High loading levels of this porphyrin within the sorbent structure showed increasing evidence of stacking and did not improve the performance of the material.

In previous work, we successfully synthesized the first columnar liquid crystalline 1:1 phthalocyanine(Pc)-fullerene(C₆₀) dyad, C₁₂(OMalC₆₀)PcCu (4), showing spontaneous homeotropic alignment, by using Bingel reaction. However, it gave undesirable 2:1 and 3:1 Pc-C₆₀ by-products at the same time, so that the 1:1 Pc-C₆₀ dyad (4) could be obtained in a very low yield (20%). On the other hand, in this work we have prepared novel Pc-C₆₀ dyads, C₁₂(OFbaC₆₀)PcM (8: M = Co (a), Ni (b) and Cu (c)), by using Prato reaction. Very interestingly, it gave almost only the target 1:1 Pc-C₆₀ dyads 8a–8c in very high yields (81–96%) with negligible amount of Pc-C₆₀ by-products. These dyads 8a–8c and the precursor Pc derivatives were characterized by polarizing microscope, differential scanning calorimeter and temperature-dependent X-ray diffractometer. Thus, it was revealed that each of the dyads and precursors shows spontaneous homeotropic alignment in their Col_tet mesophase.

The first hyperpolarizabilities, β_HRS, of corrole derivatives have been measured by using Hyper–Rayleigh Scattering technique. The results showed that β_HRS of corroles could be greatly enhanced by modifying its periphery with donor–acceptor groups. Maximum value reaches 354 × 10^-30 esu at an incident wavelength of 1500 nm. β_HRS of investigated corroles were also calculated with the Zerner's intermediate neglect of differential overlap/configuration interaction/sum-over-states method. The calculated and experimental results are in good agreement and conclude that β_HRS arises mainly from the charge transfer along molecule's non-symmetrical axis and strong coupling between two different excited states of the Soret band.

A water-soluble porphyrin bearing multi-dentate ligands was prepared, and its aggregation behavior in solution under various conditions (temperature, pH, metal ion, chiral compound) was investigated using UV-vis absorption spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy. Upon the addition of Ca²⁺, Ba²⁺, or Sr²⁺ to a solution of porphyrin, the porphyrin first forms an H-aggregate and is then transformed to a J-aggregate at 25 °C in buffered aqueous solution (pH 7.4). On the other hand, the porphyrin forms a self-aggregate (H-aggregate) at 25 °C in buffered aqueous solution (pH 6.0), and the H-aggregate does not form the J-aggregate upon the addition of the group II metal ions. The measurement of CD spectra revealed that the H-aggregate that forms right after the addition of Ba²⁺ to the porphyrin solution in the presence of D- or L-phenylalanine does not show an induced CD signal, while the J-aggregate formed from the H-aggregate shows induced CD signals in the Soret region.

The preparation and physico-chemical characteristics of zinc(II) porphyrin and phthalocyanine derivatives with biphenyl units are reported. These compounds have been prepared as components for molecular electronics systems and rotor-based molecular machines, where the biphenyl units can act as paddles because they are oriented quasi-perpendicularly to the plane of the aromatic macrocycles which would be coordianted through the transition metal ion by an axial ligand. The minimalist design along with the absence of solubilizing groups leads to a low solubility of the compounds in organic solvents; the phthalocyanines is only sparingly soluble while the porphyrin is more easily manipulated, but in any case the concentration of both compounds is sufficient for surface deposition. The luminescence of the compounds is characteristic of the central unit, although it is clear in the absorption spectra that the phthalocyanine derivative has a particularly strong tendency to aggregate non-specifically. The porphyrin forms microcrystals while the phthalocyanines which bears eight biphenyl units forms amorphous aggregates from 1,2-dichlorobenzene reminiscent of glasses of other biphenyl derivatives, which is interesting for the preparation of amorphous materials for optics applications.

One of the porphyrin moieties of the porphyrin dimer intercalates rapidly between the DNA base-pairs, followed by the slow intercalation of the other. The slow intercalation of the second porphyrin moiety of porphyrin dimer to poly[d(G-C)₂] was investigated by normal absorption and circular dichroism spectroscopy. The change in absorbance in the Soret band of porphyrin upon association with poly[d(G-C)₂] can be best elucidated by the combination of the two single exponential curves, suggesting the intercalation occurred via two independent first order reactions. Activation energies of these two first order reactions were calculated to be 0.37 kcal/mol and 3.19 kcal/mol, respectively. The intercalation associated with lower activation energy can be assigned to the intercalation of second porphyrin moiety to 5′CG3′ site while that with higher activation energy to 5′GC3′ intercalation site. Increasing the flexibility of poly[d(G-C)₂] by adding Na⁺ ion resulted in an enhancement of the reaction rate for both steps in an exponential manner.