A Novel Electrochromic Polymer Synthesized through Electropolymerization of a New Donor−Acceptor Bipolar System

Synthesis and electrochemical characterization of new linear conjugated arylamine copolymers

New conjugated copolymers having linear structures were synthesized by palladium catalyzed cross-coupling reactions of bis(4-bromophenyl)phenylamine or 4-hydroxymethyl-N,N’-bis(4-bromophenyl)aniline and two bisboronic acids of fluorene or thiophene. The copolymers were obtained as fully or partially soluble materials, in chlorinated and aprotic polar solvents. Having a hydroxymethyl group attached to the para position of the triphenylamine units, the synthesized copolymers can be viewed as functional polymers which were transformed into new ones by employing suitable chemical reactions. A new copolymer was obtained by coupling the hydroxymethyl group of triphenylamine of P35 copolymer, with phenyl isocyanate. The chemical structures and the properties of copolymers were investigated by spectroscopic methods such as 1H nuclear magnetic resonance, Fourier transform infrared, ultraviolet-Vis and photoluminescence spectroscopy. Cyclic voltammetry was performed in order to obtain information about the electrochemical stability and reversibility of the redox processes of copolymers. Electrochemical studies were carried out on films cast on glassy carbon electrode (GCE) or In-Tin oxide (ITO) glass-coated electrode.

Rational design, synthesis, and optical properties of film-forming, near-infrared absorbing, and fluorescent chromophores with multidonors and large heterocyclic acceptors

A new series of film-forming, low-bandgap chromophores (1 a,b and 2 a,b) were rationally designed with aid of a computational study, and then synthesized and characterized. To realize absorption and emission above the 1000 nm wavelength, the molecular design focuses on lowering the LUMO level by fusing common heterocyclic units into a large conjugated core that acts an electron acceptor and increasing the charge transfer by attaching the multiple electron-donating groups at the appropriate positions of the acceptor core. The chromophores have bandgap levels of 1.27-0.71 eV, and accordingly absorb at 746-1003 nm and emit at 1035-1290 nm in solution. By design, the relatively high molecular weight (up to 2400 g mol(-1)) and non-coplanar structure allow these near-infrared (NIR) chromophores to be readily spin-coated as uniform thin films and doped with other organic semiconductors for potential device applications. Doping with [6,6]-phenyl-C(61) butyric acid methyl ester leads to a red shift in the absorption only for 1 a and 2 a. An interesting NIR electrochromism was found for 2 a, with absorption being turned on at 1034 nm when electrochemically switched (at 1000 mV) from its neutral state to a radical cation state. Furthermore, a large Stokes shift (256-318 nm) is also unique for this multidonor-acceptor type of chromophore, indicating a significant structural difference between the ground state and the excited state. Photoluminescence of the film of 2 a was further probed at variable temperatures and the results strongly suggest that the restriction of bond rotations certainly helps to diminish non-radiative decay and thus enhance the luminescence of these large chromophores.

Photodynamic properties and photoantimicrobial action of electrochemically generated porphyrin polymeric films

Spectroscopic and photodynamic properties of polymeric films bearing porphyrin units have been studied in both solution containing photooxidizable substrates and in vitro on Escherichia coli and Candida albicans microorganisms. The films were formed by electrochemical polymerization of 5,10,15,20-tetra(4-N,N-diphenylaminophenyl)porphyrin (H2P-film) and its complex with Pd(II) (PdP-film) on optically transparent indium tin oxide (ITO) electrodes. Absorption spectroscopic studies show the characteristic Soret and Q bands of the porphyrin in the visible region and a band at approximately 350 nm corresponding to the tetraphenylbenzidine units. Upon excitation, the H2P-film exhibits two bands of fluorescence emission from porphyrin, while it is not detected using PdP-film. The singlet molecular oxygen, O2(1Deltag), productions of these surfaces were evaluated using 9,10-dimethylanthracene in N,N-dimethylformamide. Also, the photodynamic activity was compared in solutions of L-tryptophan. Under these conditions, oxidation of these substrates takes place indicating an efficient photodynamic action of both polymeric films. In vitro investigations show that these films produce photosensitized inactivation of microbial cells in aqueous suspensions. These films exhibit a photosensitizing activity causing a approximately 3 log decrease of E. coil and approximately 2.5 log of C. albicans cellular survival after 30 min of irradiation with visible light. The photodynamic effect of the surfaces was also tested by growth delay experiments. The results indicate that porphyrins immobilized on electropolymeric films are interesting and versatile photodynamic surfaces to inactivate microorganisms in liquid suspensions.

Spray Processable Green to Highly Transmissive Electrochromics via Chemically Polymerizable Donor-Acceptor Heterocyclic Pentamers

Electrochromic polymers (ECPs) of tunable green: Two symmetrical donor-acceptor based oligomers were designed, synthesized and chemically polymerized affording solution-processable conjugated polymers of distinct green hues in their neutral state. The polyheterocyclic hybrids exhibited highly transmissive oxidized states, excellent optical contrasts both in the visible and in the near infrared, fast switching times and long-term redox switching stability as expected for practical ECP devices.

Synthesis and Properties of Dumbbell-Shaped Dendrimers Containing 9-Phenylcarbazole Dendrons

We report the synthesis and structural characterization of two dumbbell-shaped dendrimers incorporating 9-phenylcarbazole units as dendrons, as well as their thermal, morphological, photophysical, and electrochemical properties.