Journal of Porphyrins and Phthalocyanines

The binding mode of a porphyrin dimer to double stranded native DNA was investigated in this study using normal electric absorption, circular dichroism (CD) and linear dichroism (LD) spectroscopies. At the time of mixing, the spectral properties of the porphyrin dimer upon its association with DNA were characterized by hypochromism and a red shift in the absorption spectrum and by complicated CD and negative LD in the Soret region. As time elapsed, the CD spectrum became a negative single band and the negative LD signal increased. These spectral changes suggested that the majority of both porphyrin moieties of the dimer intercalated between the DNA base-pairs. The changes in the spectral characteristics of the DNA bound porphyrin-dimer were similar when the minor groove of DNA was saturated by 4′,6-diamidino-2-phenylindole (DAPI), which is well-known minor groove binding molecule. The spectral properties of DAPI, which can be summarized by a large positive induced CD in the DAPI absorption region (300~400 nm) and wavelength-independent positive reduced LD, remained intact when the porphyrin dimer was present. These observations indicated that both DAPI and porphyrin bind to DNA simultaneously, and furthermore, the bis-intercalation of the porphyrin dimer occurs in the major groove.

Spectrophotometric protonation titrations were performed for the trimethyl esters (TME) of chlorin e₆ (3¹,3²-didehydrorhodochlorin-15-acetic acid) and the 7¹-acetal of rhodin g₇ (3¹,3²-didehydrorhodochlorin-7¹-oxo-15-acetic acid) using HCl as the acid and methanol as the solvent. For rhodin g₇ TME, the 7¹-acetal formation could be clearly detected as the first step in the titration. Only two spectroscopically different protonated species were observed for each chlorin derivative in addition to the neutral forms. The two protonated species were assigned to the monocation and dication of each chlorin derivative. The following pK_a values were obtained: pK₃ = 4.63 and pK₄ = 0.62 for chlorin e₆ TME and pK₃ = 4.40 and pK₄ = 0.60 for the acetal of rhodin g₇ TME. The protonation titration for chlorin e₆ TME with HCl in acetic acid afforded UV-vis spectra similar to those obtained with HCl in methanol. The UV-vis spectrometric parameters are given for the neutral forms of chlorin e₆ TME, rhodin g₇ TME and its 7¹-acetal, as well as for the mono- and diprotonated species of chlorin e₆ TME and rhodin g₇ TME acetal. The protonation titration results of the chlorin e₆ derivatives are compared with those previously obtained for phytyl/methyl pyropheophorbide a.

A series of porphyrin derivatives with one to four maltohexaose moieties in their meso positions have been synthesized. Zinc or free-base m-THPP (5,10,15,20-tetrakis(m-hydroxyphenyl)-porphyrin) was used as the porphyrin platform. The reaction of m-THPP with 3-iodopropyl nonadecaacetylmaltohexaoside afforded a mixture of all possible combinations of glycoconjugated porphyrins having one to four maltohexaose moieties; monoglycosylated (Ac-1), bisglycosylated (Ac-cis-2 and Ac-trans-2), triglycosylated (Ac-3), and tetraglycosylated (Ac-4) porphyrins were obtained in 11–26% yield. Removal of acetyl groups at maltohexaose moiety afforded highly water-soluble glycoconjugated porphyrins 1–4. Zinc derivatives were synthesized in a similar manner. These maltohexaose-linked porphyrins exhibit remarkable water-solublity (530 mg/mL for 4). The singlet oxygen production ability upon visible light irradiation is not affected by the maltohexaose substitution. Photo- and dark cytotoxicities of the maltohexaose-conjugated porphyrins 1–4 and Zn-1–4 were examined against a HeLa cell line, which showed that the mono-maltohexaosylated derivative (1 and Zn-1) was the most effective photosensitizer for PDT.

The novel palladium metalated derivatives of 5,5′-[8,8′-di(thiooctyloxy)-4,4′-phenyl)]-10,10′,15,15′,20,20′-hexakis(4,4′-t-butylphenyl)diporphyrin and 5,5′-[8,8′-di(thiooctyloxy)-4,4′-phenyl)]- 10,10′,15,15′,20,20′-hexakis(3,3′,4,4′,5,5′-hexakisdecyloxyphenyl)diporphyrin, 1 and 2 respectively, have been synthesized and deposited to form self-assembled monolayer (SAM) films on gold-coated glass slides that served as substrates. The SAM films have been characterised by RAIR spectroscopy. Excitation of the molecules within the films has been achieved using the evanescent field arising when the glass substrate was used as a waveguide. Luminescence spectroscopy detected both fluorescence and phosphorescence emission from the SAM films under an argon atmosphere. Quenching of the phosphorescence emission by dioxygen was investigated for both films. Greater reproducibility of data was achieved from the SAM films of compound 2. The phosphorescence quenching from these films followed the Stern–Volmer relationship.

Pullulan conjugates (i.e. PFP1, PFP4) formed via DCC/DMAP coupling of porphyrin derivatives possessing one (P1) or four (P4) carboxylic acid moieties with folate-appended pullulans (PF) were prepared for application as photosensitizers (PS) for photodynamic therapy. To maximize the desired PS characteristics, the assembly size of PS should be less than 200 nm in water medium. In a PBS buffer solution, PFP4 forms smaller assemblies (~100 nm) than PFP1 (~320 nm) due to its enhanced intramolecular hydrophilicity.

We report a refined and expanded synthetic study of 4,4-difluoro-1,3,5,7-tetramethyl-8-(aryl)-4-bora-3a,4a-diaza-s-indacene under treatment with POCl₃/DMSO. The 2-chloro-6-methylsulfide derivative (Kim TI, Park S, Choi Y and Kim Y. Chem. Asian J. 2011; 6: 1358-61.) was one of five co-eluants, including 2,6-disulfido and -dichloro species, and mono-substituted counterparts. The 8-meso tail group modifies product distribution. The different sulfur-containing products undergo different "off-on" responses with NaOCl (10 equiv.). Compounds 4b and 2b exhibit low toxicity and were found to enter juxtanuclear regions in neuroblastoma.

We synthesized a novel discotic liquid crystalline compound, octakis[3-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)phenoxy]phthalocyaninato copper(II) (abbreviated as [m-MeO(EtO)₃PhO]₈PcCu), and established the mesomorphism by using a differential scanning calorimeter, a polarizing optical microscope, and temperature-dependent wide angle X-ray diffraction diffractometer. Very interestingly, this [m-MeO(EtO)₃PhO]₈PcCu complex showed a hexagonal ordered columnar (Col_ho) mesophase in the virgin sample, whereas it showed a rectangular ordered columnar (Col_ro(P2₁/a)) mesophase in the non-virgin sample. The Col_ho mesophase gave a dimer stacking distance at 9.26 Å, whereas the Col_ro mesophase gave a short monomer stacking distance at 3.45 Å. Furthermore, this novel Pc derivative is readily soluble in polar solvents such as acetone, ethanol and methanol. Using antagonist solubilities of the present hydrophilic [m-MeO(EtO)₃PhO]₈PcCu derivative in a polar solvent and the previous hydrophobic (C₁₀O)₁₆TzCu derivative in the non-polar solvent, a p-n junction layered thin films could be successfully prepared.

New covalent conjugates of aqua platinum(II) and octacarboxy-substituted zinc phthalocyanine, bearing one, two, three and four aqua platinum moieties on the periphery of the Pc ligand have been synthesized and characterized. The effect of the stepwise introduction of the aqua platinums on the photophysical and photochemical properties of these compounds has been investigated in dimethylsulfoxide solution. It has been found that aqua platinum moieties have only a limited effect on the dynamics of the singlet and triplet excited states, on the ability to sensitize singlet oxygen formation and on the photostability. Each conjugate has a high singlet oxygen quantum yield (Φ_Δ 0.51–0.62) and thus retains potential for use as a dual action anticancer drugs by acting as a sensitizer for PDT in addition to the likely chemotherapeutic effects of the Pt(II) complexes.

Porphyrin-modified ferrocenes were synthesized via the reductive amination reaction of ferrocenylpyrazolecarboxaldehydes and tetraphenylporphyrinamine. The steric hindrance of ferrocene moiety was found to play the key role in this reaction.