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Photodynamic therapy (PDT) has drawn a great scientific attention to cancer treatment over the last decades. However, the bottleneck for the PDT is to find good photosensitizers (PSs) with greater water solubility, no aggregation, and fast discharge from the body. Therefore, there are still a big scientific desire for the synthesizing new rational PSs for treatment of cancer by PDT technique. In favor of improving the competence of PDT, an axially bis[4-(diphenylamino-1,1′-biphenyl-4-ol)] substituted silicon(IV) phthalocyanine (3) was converted to its water-soluble quaternized derivative (3Q). Their structures were fully characterized by single-crystal X-ray diffraction, elemental analysis, and different spectroscopic methods such as FT-IR, UV–Vis, MALDI-TOF, and 1H-NMR. The photophysical properties such as fluorescence quantum yields and lifetimes, and the photochemical properties such as singlet oxygen generation of both phthalocyanines were investigated. Ground and excited-state calculations were performed to explain the observed electronic absorption spectra. The addition of the 4-diphenylamino-1,1′-biphenyl-4-ol groups on the axially positions of the silicon(IV) phthalocyanine increased the singlet oxygen quantum yield from 0.15 to around 0.20. Especially quaternized compound 3Q showed high singlet oxygen quantum yield of 0.26 in water solution. In addition, a spectroscopic investigation of the binding behavior of the quaternized silicon (IV) phthalocyanine complex to bovine serum albumin (BSA) is also studied in this work, confirming the possible interaction. Further theoretical calculations were carried out to find out the plausible-binding regions of the BSA protein. [ABSTRACT FROM AUTHOR]

This article is focused on the design and photophysical properties of a series of novel porphyrin and metalloporphyrin dendrimers containing cationic η6-chloroarene-η5-cyclopentadienyliron(II) complexes functionalized with naphthalene and capped with ferrocene. The incorporation of cationic η6-chloroarene-η5-cyclopentadienyliron moieties into the dendrimer structures enhances solubility, and facilitates nucleophilic aromatic substitution and addition reactions due to the intense electron-withdrawing ability of the iron center. Divergent approaches were employed to yield highly symmetrical branched materials, with interesting and potentially useful properties. The preparation of these dendrimers was achieved via metal-mediated nucleophilic aromatic substitutions and Steglich esterifications. These dendrimers and their precursors were characterized through nuclear magnetic resonance spectroscopy, infrared spectroscopy, and UV-Visible and fluorescence spectroscopy. Substitution on the porphyrin core with various side chains and terminal functional groups and chromophores had little impact on the porphyrin emission properties, allowing for a wide variety of fluorescent macromolecules to be prepared which retain this characteristic emission. Also, the presence or absence of the organopyrene moieties also had little effect on the emission from these compounds. Complexation of a metal cation, such as Zn2+, by these compounds, did however result in a significant blue shift in the observed fluorescence; this interesting result has the potential for applications in the development of fluorescent-based cation sensors. [ABSTRACT FROM AUTHOR]

Photochromic dihydroindolizines (DHIs) 4a,5-dihydropyrrolo[1,2-b]pyridazine based tripodal-linker systems with adamantane core and ethyl benzoate tripods as anchoring groups have been successfully synthesized. In addition, new spirocyclopropene precursors have been prepared through both chemical and photochemical processes. The photochromic properties of the newly synthesized DHIs derivatives have been optimized and fine-tuned by the incorporation of various substituents on the fluorene (region A) and pyridazine (region C) moieties. Several alternative routes for the synthesis of the DHIs under investigation have been established. The Sonogashira crosscoupling reaction was utilized for fragment coupling between DHIs and the phenylacetylene tether of the adamantane core. Several reaction conditions of this key reaction were surveyed to obtain optimal yields of a new series of coupling products targeted for anchoring to semiconductor nanoparticles. The chemical structures of the newly synthesized materials were elucidated by both analytical and spectroscopic tools. Irradiation of the photochromic DHIs with polychromatic light resulted in ring opened colored betaines which underwent cycloreversion reactions via thermal 1,5-electrocyclization processes. The kinetic of the thermal 1,5-electrocyclization was studied by using a UV/VIS/NIR spectrophotometer. The kinetic measurements showed the half-lives of the colored betaines to be in the second domain. A pronounced increase in the half-lives of betaines bearing dimethyl-substituted pyridazine was noted compared with non-substituted pyridazine betaines. A strong effect of solvent polarity on the λ and half-lives of the betaines was observed. The further adjustment of the absorption maxima and the kinetic properties via the manipulation of substituents on the fluorene (region A) and pyridazine moieties (region C) should yield more refined systems for application as supports onto metal-oxide surfaces which remains an active area of our ongoing research. Copyright © 2010 John Wiley & Sons, Ltd. Photochromic DHI-tripodal linker towards anchoring on the metal-oxide nanoparticles have been synthesized. Tuning of the photochromic behavior by structure changes was recorded. [ABSTRACT FROM AUTHOR]

Multi-addressable photophysical properties of new synthesized photochromic materials based on photochromic dihydroindolizine system (DHI) covalently linked to N-acyl-11 aminoundecanoic acid (AUDA) or to its sodium salt or to its ester, through an amidic or urethane linkage have been studied. The DHI skeleton in these compounds is substituted in both the fluorene part (region A) or in the heterocyclic base (region B) with the gelling moieties. These molecules have been designed to respond to their environment. Interestingly, they are shown to act as efficient gelators for polar organic fluids, water and obviously they exhibit a thermosensitive answer as low molecular mass organogelators. In these fluids, the aggregative properties are totally suppressed upon conversion to neutral carboxylic species. The gels of these carboxylate sodium salts are shown to be markedly affected by light irradiation. Supramolecular gelating assemblies can be disrupted by the photoinduced ring opening of the DHI subunit, so that the macroscopic flowing property is recovered. Upon a further thermal treatment, the system is reversibly converted back to the supramolecular network. Controlled gelation could be achieved using temperature, light, or acidity as external stimuli. These new synthesized photochromic gels with their multi-addressable properties will find their applications as super photoresponsive materials. Developing and tuning of the photophysical properties of the synthesized compounds by the amide and urethane substituents in the 4-position of the fluorene and pyridazine regions have been achieved. The absorption maxima (λmax) and the half-lives (t1/2) of the colored betaines were detected in all cases using UV/VIS spectrophotometric measurements. Irradiation of DHI 12-20 in CH2Cl2 or in acetonitrile solutions at ambient temperature with polychromatic light leads to the formation of red to red-violet colored betaines 12′-20′. The kinetics of the bleaching process of betaines 12′-20′ to DHIs 12-20 were found to take place in the second range (96-218 s) and fit well the first order thermal back reaction. Some of these DHIs showed a photostability higher than that of the standard one. These interesting photophysical properties will help this family of compounds to find useful applications. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The phase change in metal-free 1,4,8,11,15,18,22,25-octahexylphthalocyanine compound with eight non-peripheral hexyl chains was investigated under non-isothermal conditions by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Two endothermic changes were reported. The first one between 332 and 350 K relates to the transition from the hexagonal columnar mesophase to a less ordered crystalline phase, P1. The second endothermic transition from 408 to 417 K is due to the transition to the discotic columnar mesophase, P2. The isoconversional methods of Friedman, and Kissinger, Akahira and Sunose (KAS) were used to determine the variation of the activation energy for crystallisation with temperature, E α(T). Using the Friedman method the average values of E α(T) were 121.31 and 352.77 kJ mol-1 for the first and second peaks, respectively. The KAS method gave higher values of E α(T) with averages of 173.25 and 411.44 kJ mol-1, respectively. The specific heat was measured and found to vary with temperature. [ABSTRACT FROM AUTHOR]

Abstract: Thin films of 1, 4, 8, 11, 15, 18, 22, 25-octahexylphthalocyanine were deposited on glass substrates by the thermal evaporation and spin coating techniques. The structure of the both types of films was found to be in α form. The crystallite size assumed the values of 88.65 and 44.32 nm for thermal and spin coated films, respectively. The surface morphology of the thin films was investigated by atomic force microscopy and showed that the molecules of 1, 4, 8, 11, 15, 18, 22, 25-octahexylphthalocyanine grew in stacks of parallel rows. The optical properties of thermally evaporated and spin coated films are reported here. The spectrophotometric measurements of transmittance and reflectance were carried out at UV–Vis–NIR region for the films that showed two absorption bands, namely the Q-and Soret bands. The mechanism of the optical absorption follows the indirect transitions. Almost there was no remarkable difference was observed between the two types of films. Other optical parameters, such as absorption coefficient α, the absorption index, k, and refractive index, n, were also determined. [Copyright &y& Elsevier]