Pawel Uznanski

First Approach to Nitrogen‐Containing Fused Aromatic Hydrocarbons as Targets for Organoelectronics Utilizing a New Transformation of O‐Protected Diaryl Methanols

A new concise approach for the construction of heteroatom analogues of polycyclic aromatic benzo[g]quinoline, benzo[b]carbazole, and pyrido[b]carbazole systems via diaryl methanols is described. This transformation involves formation of a central benzene ring fused to two aromatic 5- or 6-membered rings of pyrrole and/or pyridine by using a combination of two aromatic aldehydes, of which at least one contains a ring nitrogen. Analysis of the UV and fluorescent properties, Stokes shifts, quantum yields in solution, and pi-stacking interactions in the crystal structures of the new materials was performed. These polycyclic aromatic compounds show potential as small-molecule organoelectronic materials.

Oxidation of photochromic spirooxazines by coinage metal cations. Part I. Reaction with AgNO3 : formation and characterisation of silver particles

Thermal oxidation of the zwitterionic form of two photochromic spirooxazines: 1,3-dihydro-1,3,3-trimethylspiro(2H-indole-2,3′-[3H]naphth[2,1-b]-[1,4]oxazine) (1) and 1,3-dihydro-1,3,3-trimethylspiro(2H-indole-2,3′-[3H]phenanthr[9,10-b]-[1,4]oxazine) (2) has been studied in the presence of silver ions in anaerobic conditions. The products of the reaction have been identified and a mechanism for their formation is proposed. In alcohols (MeOH, EtOH), the major degradation product is the indolinooxazole salt together with either methoxy- or ethoxy-substituted spirooxazines at the C2′ carbon atom of the C2′N1′ bond. The four new spirooxazine derivatives display no photochromic properties although X-ray diffraction studies show that the bond lengths around the spiro carbon atom are similar to those observed for compounds revealing colouration. Photophysical properties of the indolinooxazole and of its hydroxylated derivative are also presented. High quantum yield and large Stokes shifts are observed. As a consequence of the reduction of silver ions to neutral atoms, silver colloids have been prepared after either thermal- or photo-oxidation of spirooxazine. They are stabilised by poly(N-vinylpyrrolidone). The formation and growth of silver colloids have been studied by electron microscopy, photon correlation spectroscopy and UV-vis absorption spectroscopy. The growth of silver particles of different sizes and morphologies is presented and the role of a photochromic electron donor on the growth process is discussed. The average particle sizes ranged from a few to approximately one hundred nanometers. The classical plasmon absorption band at 420 nm and a broad red-shifted peak at 790 nm due to the large non-spherical particles are thus observed. Both particle size and plasmon absorption are dependent upon UV irradiation. Size enlargement upon irradiation of silver colloids brings about colour changes from yellow through green to light blue.

Synthesis and optoelectronic properties of hexahydroxylated 10-O-R-substituted anthracenes via a new modification of the Friedel-Crafts reaction using O-protected ortho-acetal diarylmethanols.

A new modification of the Friedel-Crafts type intramolecular cyclization involving O-protected ortho-acetal diarylmethanols as a new type of reactant, was carried out for the first time in a medium containing a large amount of water at room temperature and enabled synthesis of a series of electron-rich, hexahydroxylated 10-O-R-substituted anthracenes, where R is an alkyl (Me, nBu, n-C(16)H(33)) or arylalkyl group (CH(2)Ph, CH(2)-2-Napht, CH(2)C(6)H(4)CH(2)OAr) and also evaluation of their electronic and optoelectronic properties in solution, crystal, and solid thin film. In this transformation, a central 10-O-R-substituted benzene ring was formed, fused to rings originating from two independent aromatic aldehydes. The reaction proceeded via two identified mechanisms involving acetal and/or free aldehyde groups. The acid sensitive acetal and dibenzyl alkoxy functions have never been used together in the intramolecular Friedel-Crafts type cyclization. The new compounds revealed deep blue fluorescence and quantum yields in solution around 0.3. The electrical properties investigated for thin films obtained by vacuum deposition on glass were 10-O-R-substituent dependent and showed much faster transient current decay in the case of the 10-O-CH(2)Ph derivative than for the material with a 10-O-Me substituent (the lifetime of charge carriers was 25 times shorter in this case). The AFM images of thin films, Stokes shifts, and X-ray analysis of π-stacking interactions in crystals of the new materials have been also obtained.

Oxidation of photochromic spirooxazines by coinage metal cations. Part II. Oxidation by gold(III) compounds and synthesis of gold colloids

In our previous paper, we reported that colloidal silver can be prepared by thermal or photo-oxidation processes of spirooxazines (SO). Here we show that SO easily reduce gold(III) ions (1 : 1 equiv.) to monovalent gold(I) species. A salt composed of oxidized dye/AuI was isolated and fully characterised by X-ray diffraction, 1H and 13C NMR, UV-vis, fluorescence and FTIR spectroscopies. This salt was further reduced by another SO (2 : 1 equiv.) leading to gold(0) atoms that coalesce into gold powder. A mechanism for these two reactions is proposed. In the presence of a stabilising agent, such as poly(N-vinylpyrrolidone), the coalescence of Au atoms is limited and nanoparticles with an average size of 8–14 nm and a broad size distribution are formed. The colloidal solution is strongly fluorescent due to the presence of the oxidized SO in the medium. Changes in the absorption spectra from that of the sol and the free oxidized SO are interpreted as a consequence of the adsorption of the cationic dye on the gold surface.

Aurophilic complexes as gold atom sources in organic media

The decomposition, either thermal or under H2, of [O(AuIPR3)3](CF3SO3) (R = Ph 1, R = Me 2) in organic solvents has been studied by 31P(1H) NMR, UV-vis spectroscopy and TEM; during the reaction, the phosphine acts as an efficient oxygen trap and gold nanoparticles are produced which may be stabilized by PVP in acetonitrile (mean diameter 4.5 nm) or oleylamine in toluene (mean diameter 9 nm).

Solvatochromism in the visible absorption band of 4-dimethylamino-4′-nitroazobenzene in polystyrene and poly(vinyl acetate), and in model liquid solvents: Effects of temperature, medium polarity, and rigidity

Abstract Temperature-induced solvatochromism in the visible absorption band of 4-dimethylamino-4′-nitroazobenzene (diMANA) dissolved in polystyrene (PS) and poly(vinyl acetate) (PVAc), and in toluene and ethyl acetate used as model liquid solvents was investigated. In all solutions under study the absorption band maximum shifts to blue, and the magnitude of the transition moment slightly diminishes as temperature rises. In polymer solid solution the absorption band maximum is red shifted relative to the position of the band maximum in model liquid solutions. Based on solvatochromism theory, a qualitative interpretation of the changes in the spectrum induced by variation of the temperature, polarity, and rigidity of the medium is given. It is shown that orientational polarization interactions in PVAc play a significant role.

Spiropyrans as Counterions in Photochrome-Containing Polyelectrolyte

Abstract Synthesis and properties of polycation with spiropyran salt as counterion were investigated. The photochromic group was connected to the main chain of polymer (polycation bromide) by ion-exchange in polar solution. The new system shows negative photochromism. The existence of N+-cation as part of the polymer changes kinetic properties the thermocoloration. The ring closuring reaction influences thermal properties of the polyelectrolyte chain.

Application of parylene for surface (polymer) enhanced laser desorption/ionization of synthetic polymers.

RATIONALE Synthetic polymers of molecular masses up to a few kDa can be analyzed without the use of any matrix by direct laser desorption/ionization mass spectrometry (LDI-MS). In this technique, the surface of the sample plate plays a crucial role, and many attempts have been made to understand the influence of the surface on the ease of desorption. Since this technique requires no tedious sample pretreatment, it is a promising method for the rapid characterization of various synthetic polymers. METHODS Parylene (poly(p-xylylenes), PPX) was tested as a surface support for studying the molecular masses of biocompatible polymers: poly(ethylene glycol) (PEG), poly(L-lactide) (PLLA), and poly(methyl methacrylate) (PMMA). The average molecular masses of the polymers were: PEG (600.0 Da and 3.5 kDa), PMMA (2.0 kDa), and PLLA (2.8 kDa). RESULTS LDI mass spectra of polymers deposited on parylene were enhanced by a factor of two over those obtained directly from the gold target plate. CONCLUSIONS Modification of the surface of the target plate by the addition of a PPX layer extended the functionality of LDI-TOF MS, especially for the analysis of low-mass compounds. The LDI analysis using the PPX-coated target plate provided details of polymers including: end-group, composition, monomer unit, and molecular mass distribution. The average molecular weights of four tested polymers on the gold target plate and the PPX support were unchanged, indicating that sample degradation was not occurring despite the high energy of the laser beam. The LDI investigations showed that the PPX support boosted ion yields by a factor of two compared with the gold target plate.

Use of isomeric, aromatic dialdehydes in the synthesis of photoactive, positional isomers of higher analogs of o-bromo(hetero)acenaldehydes

Synthesis of the pairs of positional isomers of the title compounds is based on utilization of two isomeric o,o-dibromo dialdehydes and a selective ortho-metallation/Friedel–Crafts cyclization sequence of the corresponding diacetals. Photophysical and electrochemical properties of the new group of fluorescent and photoresistant compounds have also been performed.

Photophysical studies of functionalised polyionene complexes in solutions and in the solid state

Fluorescence steady state and time-resolved studies of hydrophobically modified polyionene systems prepared by exchange reaction with counterions of aromatic and aliphatic character in the parent polymer were conducted in DMF and water solutions as well as in solid films cast from these solvents. The effect of polyionene composition on excimer formation and energy transfer has been examined for different types of counterions, that is: 1-pyrenesulfonate, 1-pyrenebutyrate, 2-naphthalene sulphonate and sodium dodecyl sulphate. In a DMF solution, excimer formation was observed only for hydrophobically modified parent polyionene samples. In an aqueous solution, excitation spectra and instantaneous decay of fluorescence monitored at 480 nm suggest that excimer originates from paired chromophores in the ground state. For solid samples prepared from different solvents, the results indicate that various structures produced by solvent as the result of the self-organising interactions may be trapped in the solid state by polyelectrolyte. Such findings might be interesting for a variety of new optically active materials.