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Non-covalent interactions are rapidly gaining interest as they are often crucial in determining the properties of materials, and key to supramolecular chemistry and to biochemistry. Non-covalent Polycyclic Aromatic Hydrocarbon (PAH) complexes are in particular relevant to astrochemistry and combustion chemistry where they are involved in the initial steps of condensation and soot formation, respectively. Here, we investigated non-covalent π-π stacking and CH-π interactions in naphthalene and acenaphthene clusters using high-resolution IR-UV spectroscopy in combination with quantum chemical calculations. We identified spectral shifts that occur upon complexation and thereby evaluated predicted potential energy surfaces. Although theory predicts a blueshift, a redshift is observed for the aliphatic CH-π interactions in the experimental spectrum of acenaphthene upon dimerization, indicating that CH-π interaction indeed affects the aliphatic bonds, while a blueshift is predicted, consequently theory deserves attention here. The results provide strong indications for a prevalent parallel naphthalene dimer, showing that π-π stacking interactions become significant for bicyclic and larger PAHs. [ABSTRACT FROM AUTHOR]

Controlling the microscopic organization of active components is crucial for the performance of organic photovoltaic (OPV) cells. In this work, (001) muscovite mica was used as a growth template to study the formation of PC61BM crystallites in the active layer structure of OPV cells. The structures were spin-coated from a PC61BM : P3HT solution and subsequently annealed. The parameter range to produce layers with high surface density of (sub)micrometer sized PC61BM crystallites was significantly larger for mica than for other substrates. The enhanced PC61BM nucleation is attributed to an epitaxial relation between the mica surface and PC61BM, which was found to crystallise in a hexagonal crystal structure. Through a float-off procedure, the active layer was transferred from the mica substrate to a conductive substrate, which formed the basis of the transferred inverted solar cell. A power conversion efficiency of 2.1% was obtained for this transferred device, which with a 22% higher short-circuit current density outperforms its conventional counterpart that was directly produced on the conductive substrate. A set-up for simultaneous laser beam induced current (LBIC) and surface reflection analysis revealed that the increased current density originates from large circular areas with a radius of about 10 μm around the PC61BM crystallites. [ABSTRACT FROM AUTHOR]

Isolated 2‐phenylallyl radicals (2‐PA), generated by pyrolysis from a nitrite precursor, have been investigated by IR/UV ion dip spectroscopy using free electron laser radiation. 2‐PA is a resonance‐stabilized radical that is considered to be involved in the formation of polycyclic aromatic hydrocarbons (PAH) in combustion, but also in interstellar space. The radical is identified based on its gas‐phase IR spectrum. Furthermore, a number of bimolecular reaction products are identified, showing that the self‐reaction as well as reactions with unimolecular decomposition products of 2‐PA form several PAH efficiently. Possible mechanisms are discussed and the chemistry of 2‐PA is compared with the one of the related 2‐methylallyl and phenylpropargyl radicals. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electrical discharge of the PAH naphthalene and acetonitrile was investigated by IR-UV ion dip spectroscopy with the free electron laser FELIX in the 550–1800 cm−1 frequency range. • New –CH 3 and –CN substituted aromatic species have been identified and their IR spectra characterized. • The NEARIR feature recently implemented in the ORCA software has been used to predict overtones and combination bands. • The results provide insight on new species which could be the object of radio astronomical searches. The formation and dissociation mechanisms of polycyclic aromatic hydrocarbons (PAHs) as well as their reactivity with other interstellar molecules are elusive. In this work, we have investigated the electrical discharge chemistry of the PAH naphthalene and acetonitrile, a molecule known to be present in interstellar environments, using a combination of mass-selective IR-UV ion dip spectroscopy with the free electron laser FELIX in the mid-IR frequency region (550 – 1800 cm−1) and quantum chemical calculations. In addition to the species known to be produced in the electrical discharge of pure naphthalene, –CH 3 and –CN substituted unsaturated hydrocarbons have been identified. Most of them, in particular those containing a nitrogen atom in the molecular framework, such as 7H-benzo[7]annulenecarbonitrile, have a substantial dipole moment and, therefore, can be considered as potential candidates for radio astronomical searches. Among the species observed, the two isomers 1- and 2-cyanonaphthalene, which have been recently detected in the TMC-1, have been identified in our experiment, thus continuing to highlight the use of electrical discharge sources as a valuable tool to produce astronomically relevant species. [ABSTRACT FROM AUTHOR]