RESUMO
Fullerenes have been long investigated for application as singlet oxygen sources. Even though they possess high photosensitizing efficiency, their practical use is still limited, mostly because of insufficient absorption of visible and/or near-infrared light. This limitation can be overcome by introducing organic chromophores that absorb longer-wavelength light, either by covalent attachment to C60 or by its encapsulation in a polymeric matrix. In this work, we investigated the photosensitizing properties of the C60 molecule functionalized with organic units comprising thiophene or selenophene rings. The chemical structures of the synthesized dyads were characterized by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. The influence of the S/Se atoms and vinyl linkage between the organic unit and C60 on the absorptive and emissive properties of the dyads was investigated and correlated with their photosensitizing activity. For the latter, we used a standard chemical singlet oxygen trap. A selected dyad C60ThSe2 was also applied as a source of singlet oxygen in a model photocatalyzed synthesis of the fine chemical juglone from 1,5-dihydroxynapthalene.
RESUMO
Within the presented work, we propose a complex photoemission-based approach for the investigation of the C60ThSe2 dyad (C60ThSe2)/indium-tin oxide (ITO) interface formation. For surface topography and basic morphology determination, atomic force microscopy was utilized, and the results showed that C60ThSe2 agglomerated into close-to-spherical crystallites and the island-like growth was the dominant type for fullerene growth on the ITO substrate. Further, detailed X-ray and UV-photoelectron spectroscopies (XPS, UPS) were used for thorough characterization of the chemical and electronic properties of the investigated structures. Experiments were conducted by means of cyclic voltammetry and UV-VIS techniques for both deposition purposes and for determination of the basic electronic structure. As a result, we present the detailed characterization of the chemical and energy structures with a clear designation of the mutual influence of both materials on their counterparts. Among others, the accurate photoemission signal decomposition of the overlapping signals was done with respect to obtaining the energy-related information depth. The obtained data clearly showed that an interface dipole (0.56 eV) was created between the ITO substrate and organic overlayer at the ultrathin coverage stage. Since our results point out the most probable charge-carrier relocation in the vicinity of the interface, this together with the dipole existence should be taken into account while creating energy-level cascades for various (e.g., photovoltaic or organic electronic) applications. The work may also provide insights for engineers working with a vast range of organic-based electronics while designing devices based on fullerene/ITO hybrid structures.
RESUMO
A series of novel donor-acceptor D-π-A-π-D compounds were synthesized and characterized in order to determine the influence of different acceptor units on their properties. The introduction of acceptor moieties had a direct impact on the HOMO and LUMO energy levels. Fluorescence spectra of compounds can be changed by the choice of an appropriate acceptor and were shifted from the green to the near-infrared part of spectra. Due to observed concentration induced emission quenching, the green exciplex type host was used to evaluate the potential of synthesized molecules as emitters in organic light emitting diodes (OLEDs).
RESUMO
We present the synthesis and selected physicochemical properties of several novel symmetrical and unsymmetrical alpha,omega-nucleobase mono- and bis-amide conjugated systems containing aliphatic, aromatic or saccharidic linkages. The final stage of the synthesis involves condensation of a subunit bearing carboxylic group with an amine subunit. 4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) was found to be a particularly effective condensing agent. The subunits containing carboxylic groups were obtained by acidic hydrolysis of N-1 Michael adducts of uracils or N-9 Michael adducts of 6-chloropurine with methyl acrylate. The amines used were aliphatic/aromatic diamines, adenine, 5-substituted 1-(ω-aminoalkyl)uracils and 5'-amino-2',5'-dideoxythymidine. The title compounds may find application as antiprotozoal agents. Moreover, preliminary microscopy TEM studies of supramolecular behaviour showed that target molecules with bolaamphiphilic structures were capable of forming highly ordered assemblies, mainly nanofibres.
