Near-IR sensitization of wide band gap oxide semiconductor by axially anchored Si-naphthalocyanines

Near-IR dye sensitized solar cells are very interesting due to their potential applications in panchromatic cells, semi-transparent windows and in tandem cells. In this work we show the utilization of axially anchored Si-naphthalocyanine dye in the spectral sensitization of TiO2 nanostructured photoelectrodes. We report the first successful evaluation of a naphthalocyanine in the production of sensitized photocurrent with maximum incident photon to current efficiency (IPCE) at λ 790 n

Synthesis of 5-(4-X-Phenyl)-10,15,20-tris(Substituted Phenyl) Porphyrins Using Dipyrromethanes

5-(4-X-Phenyl)-10,15,20-tris(substituted phenyl) porphyrins (4-6) were synthesized from meso-(substituted phenyl) dipyrromethanes (1-3), which in turn were prepared in yields of 75-92 %. This synthetic pathway was compared with the binary mixed aldehyde and pyrrole condensation method. The reported dipyrromethane approach is advantageous for porphyrins substituted by –OCH3 (4) and -F (6) groups (12-14 %), while the yield of porphyrins bearing –N(CH3)2 (5) groups was similar (~0.3 %) by both methods

Porphyrin Polymers Bearing N,N′-Ethylene Crosslinkers as Photosensitizers against Bacteria

The appearance of microbes resistant to antibiotics requires the development of alternative therapies for the treatment of infectious diseases. In this work two polymers, PTPPF16-EDA and PZnTPPF16-EDA, were synthesized by the nucleophilic aromatic substitution of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin and its Zn(II) complex with ethylenediamine, respectively. In these structures, the tetrapyrrolic macrocycles were N,N′-ethylene crosslinked, which gives them greater mobility. The absorption spectra of the polymers showed a bathochromic shift of the Soret band of ~10 nm with respect to the monomers. This effect was also found in the red fluorescence emission peaks. Furthermore, both polymeric materials produced singlet molecular oxygen with high quantum yields. In addition, they were capable of generating superoxide anion radicals. Photodynamic inactivation sensitized by these polymers was tested in Staphylococcus aureus and Escherichia coli bacteria. A decrease in cell viability greater than 7 log (99.9999%) was observed in S. aureus incubated with 0.5 μM photosensitizer upon 30 min of irradiation. Under these conditions, a low inactivation of E. coli (0.5 log) was found. However, when the cells were treated with KI, the elimination of the Gram-negative bacteria was achieved. Therefore, these polymeric structures are interesting antimicrobial photosensitizing materials for the inactivation of pathogens

Antimicrobial Photosensitizing Material Based on Conjugated Zn(II) Porphyrins

The widespread use of antibiotics has led to a considerable increase in the resistance of microorganisms to these agents. Consequently, it is imminent to establish new strategies to combat pathogens. An alternative involves the development of photoactive polymers that represent an interesting strategy to kill microbes and maintain aseptic surfaces. In this sense, a conjugated polymer (PZnTEP) based on Zn(II) 5,10,15,20-tetrakis-[4-(ethynyl)phenyl]porphyrin (ZnTEP) was obtained by the homocoupling reaction of terminal alkyne groups. PZnTEP exhibits a microporous structure with high surface areas allowing better interaction with bacteria. The UV-visible absorption spectra show the Soret and Q bands of PZnTEP red-shifted by about 18 nm compared to those of the monomer. Also, the conjugate presents the two red emission bands, characteristic of porphyrins. This polymer was able to produce singlet molecular oxygen and superoxide radical anion in the presence of NADH. Photocytotoxic activity sensitized by PZnTEP was investigated in bacterial suspensions. No viable Staphylococcus aureus cells were detected using 0.5 µM PZnTEP and 15 min irradiation. Under these conditions, complete photoinactivation of Escherichia coli was observed in the presence of 100 mM KI. Likewise, no survival was detected for E. coli incubated with 1.0 µM PZnTEP after 30 min irradiation. Furthermore, polylactic acid surfaces coated with PZnTEP were able to kill efficiently these bacteria. This surface can be reused for at least three photoinactivation cycles. Therefore, this conjugated photodynamic polymer is an interesting antimicrobial photoactive material for designing and developing self-sterilizing surfaces

Singlet Molecular Oxygen Quenching Ability of Carotenoids in a Reverse-micelle Membrane Mimetic System

ABSTRACT The influence of the medium heterogeneity upon the bimolecular rate constants for the physical quenching, k q , and chemical quenching, k r , of singlet molecular oxygen O 2 ( 1 ⌬ g ) by seven natural and three synthetic carotenoids (CAR) with different substituent patterns was studied in a reverse micelle system of sodium bis(2-ethylhexyl)sulfosuccinate, hexane and water. Because O 2 ( 1 ⌬ g ) was generated inside the water pools of the reverse micelles by photosensitization of the water-soluble dye rose bengal and the CAR are mainly located in the external hexane pseudophase, the quenching process was interpreted using a pseudophase model for the partition of O 2 ( 1 ⌬ g ) between the water pools and the organic pseudophases. The k q values were mainly dependent on the extent of the double-bond conjugation of the CAR, as demonstrated by a good empirical relationship between log(k q ) and the energy E(S) of the longest wavelength transition →* of the CAR. In contrast, the k r values were almost independent of the extent of the double-bond-conjugated system and about four orders of magnitude lower than k q . However, in all cases, CAR photobleaching was observed with the formation of various oxidation products, depending on the photosensitization time. Chromatographic and spectroscopic product analysis for the reaction products of ␤-carotene with O 2 ( 1 ⌬ g ) indicated the Dedicated to Professor Silvia E. Braslavsky on the occasion of her 60th birthday

Synthesis of Porphyrins with ABAB Symmetry from Dipyrromethanes as Potential Phototherapeutic Agents

Asymmetrically meso-substituted porphyrins were synthesized with ABAB symmetry patterns. The approach required the formation of dipyrromethanes, which were obtained from the condensation of an aldehyde (pentafluorobenzaldehyde, 4-nitrobenzaldehyde or N,N-diphenylaminobenzaldehyde) with a large excess of pyrrole (1:47 aldehyde/pyrrole mol ratio), catalyzed by trifluoroacetic acid in 70–94% yields. Then, acid-catalyzed condensation of these dipyrromethanes with an aldehyde (N,N-dimethylaminobenzaldehyde, 4-carboxymethyl benzaldehyde or N-ethyl-3-carbazolecarbaldehyde) (1:1 mol ratio) in dichloromethane, followed by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone affords the diseased porphyrins in 10–42% yields. These ABAB-porphyrins are interesting starting materials to obtain photoactive molecular structures as potential phototherapeutic agents