Infrared photodissociation (IRPD) spectra of mass-selected clusters composed of protonated aniline (C6H8N+ = AnH+) and a variable number of neutral ligands (L = Ar, N2) are obtained in the N-H stretch range. The AnH+ -Ln complexes (n < or = 3) are produced by chemical ionization in a supersonic expansion of An, H2, and L. The IRPD spectra of AnH+-Ln feature the unambiguous fingerprints of at least two different AnH+ nucleation centers, namely, the ammonium isomer (5) and the carbenium ions (1 and/or 3) corresponding to protonation at the N atom and at the C atoms in the para and/or ortho positions, respectively. Protonation at the meta and ipso positions is not observed. Both classes of observed AnH+-Ln isomers exhibit very different photofragmentation behavior upon vibrational excitation arising from the different interaction strengths of the AnH+ cores with the surrounding neutral ligands. Analysis of the incremental N-H stretch frequency shifts as a function of cluster size shows that microsolvation of both 5 and 1/3 in Ar and N2 starts with the formation of intermolecular H bonds of the ligands to the acidic NH protons and proceeds by intermolecular pi bonding to the aromatic ring. The analysis of both the photofragmentation branching ratios and the N-H stretch frequencies demonstrates that the N-H bonds in 5 are weaker and more acidic than those in 1/3, leading to stronger intermolecular H bonds with L. The interpretation of the spectroscopic data is supported by density functional calculations conducted at the B3LYP level using the 6-31G* and 6-311G(2df,2pd) basis sets. Comparison with clusters of neutral aniline and the aniline radical cation demonstrates the drastic effect of protonation and ionization on the acidity of the N-H bonds and the topology of the intermolecular potential, in particular on the preferred aromatic substrate-nonpolar ligand recognition motif.

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A new donor‐acceptor copolymer consisting of triazoloquinoxaline and 9,9‐dialkylfluorene units on the main chain has been synthesized, characterized and evaluated as donor material in bulk heterojunction solar cells using PC61BM as an acceptor. The resulting polymer PTQF showed good thermal stability and solubility in common organic solvents. Cyclic Voltammetry measurements showed that the PTQF has HOMO–LUMO energy levels of −5.13 and −3.62 eV, respectively. DFT calculations revealed that the HOMO is delocalized all over the thiophene and fluorene units and the LUMO is localized mainly on the triazole and pyrazine units. PTQF absorbs broadly in the visible region and exhibits a bandgap of 1.4 eV. Photovoltaic devices exhibited 1.7% efficiency for 1:2 PTQF:PC61BM blend ratio using Ca/Ag electrodes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

The synthesis and the optical and electrochemical properties of 2-aryl-2H-benzotriazole based thiophene oligomers with chemical modifications either on the phenyl side group or on the backbone are presented. All data, supported by DFT calculations, show that modification on the backbone has a major impact on the electronic properties while the side groups can fine-tune the electronic properties. In addition, one compound exhibits a thermotropic mesophase.

An alternating copolymer comprising a 2,7functionalized carbazole donor and a 2-phenyl-2H-benzotriazole acceptor with an octyldodecyloxy substituent was synthesized. The polymer was blended with [6,6]-phenyl C 71-butyric acid methyl ester (PC 71 BM) and incorporated as absorber layer into solution processed organic solar cells. By adding the processing additive 1,8-diiodooctane (DIO) to the host solvent 1,2dichlorobenzene (DCB), the solar cell fill factor increased to remarkable 70% and the power conversion efficiency approached 4.6%. Low-energy scanning transmission electron microscopy (low-keV STEM) investigations indicated a finer bulk morphology of the active layer upon deposition from DCB:DIO. Further, the low-energy shoulder of the absorption spectrum was enhanced, indicating stronger polymer aggregation. According to external quantum efficiency measurements, the enhanced absorption also promoted better photon harvesting. Grazing incidence X-ray diffraction experiments revealed face-on polymer aggregates being beneficial for the vertical hole transport.