Layered hybrid metal-halide perovskites with non-centrosymmetric crystal structure are predicted to show spin-selective band splitting from Rashba effects. Thus, fabrication of metal-halide perovskites with defined crystal symmetry is desired to control the spin-splitting in their electronic states. Here, we report the influence of halogen parasubstituents on the crystal structure of benzylammonium lead iodide perovskites (4-XC 6 H 4 CH 2 NH 3 ) 2 PbI 4 (X = H, F, Cl, Br). Using X-ray diffraction and second-harmonic generation, we study structure and symmetry of single crystal and thin film samples. We report that introduction of a halogen atom lowers the crystal symmetry such that the chlorine-and bromine-substituted structures are non-centrosymmetric. The differences can be attributed to the nature of the intermolecular interactions between the organic molecules. We calculate electronic band structures and find good control of Rashba splittings. Our results present a facile approach to tailor hybrid layered metal halide perovskites with potential for spintronic and non-linear optical applications.

The investigation of the mechanisms of mechanochromic luminescence is of fundamental importance for the development of materials for photonic sensors, data storage, and luminescence switches. The structural origin of this phenomenon in phosphorescent molecular systems is rarely known and thus the formulation of structure-property relationships remains challenging. Changes in the M-M interactions have been proposed as the main mechanism with d coinage metal compounds. Herein, we describe a new mechanism-a mechanically induced reversible formation of a cation-anion exciplex based on Cu-F interactions-that leads to highly efficient mechanochromic phosphorescence and unusual large emission shifts from UV-blue to yellow for Cu complexes. The low-energy luminescence is thermo- and vaporesponsive, thus allowing the generation of white light as well as for recovering the original UV-blue emission.

The electronic structure of organic/metal interfaces and thin films is essential for the performance of organic-molecule-based field effect transistors and solar cells. Here, we investigated the adsorption and electronic properties of the N-heteropolycyclic aromatic compound 6,13-diazapentacene (DAP), a potential electron-transporting semiconductor on Au(111), using temperature-programmed desorption, vibrational and electronic high-resolution electron energy loss spectroscopy, two-photon photoemission spectroscopy, and state-of-the-art quantum chemical methods. In the mono- and multilayer regime DAP adsorbs in a planar fashion with the molecular backbone oriented parallel to the gold substrate. The energetic position of transport levels (electron affinities and ionization potentials) and singlet (S) as well as triplet (T) transition energies are quantitatively determined. The lowest affinity level is located at 3.48 eV, whereas the energetic position of the first excitonic state is at 4.00 eV, resulting in an exciton binding energy of 0.52 eV. Compared to pentacene, the optical gap is reduced by 0.1 eV and the α-band gains substantially in intensity, which is explained by a detailed analysis of the electronic structure. The optical gap, i.e., the S1 excitation energy, is determined to be 2.0 eV, and the T1 transition energy is 0.9 eV, making an exothermic singlet fission process relevant in organic photovoltaics feasible.

By sequencing the control region of mitochondrial DNA, the majority of human DNA samples can be differentiated. A further increase in differentiation probability may be possible, e.g. by extending the sequenced region to coding regions of the mitochondrial genome. Restriction to those positions that do not result in a change of the amino acids guarantees that the information thus obtained does not refer to phenotypically relevant information. In the present study the sequence data of the mitochondrial genes MTATP6, MTATP8 and MTND4 were collected from 109 subjects and analyzed in order to define variable positions suitable for identification purposes. There were 32 variable base positions among 850 bases studied from MTATPase genes and 1,200 bases of the MTND4 gene showed 28 variable positions. "Hot spots" for base exchanges were found in both regions and one position (position 11719 in the MTND4 gene) seems to be suitable for SNP investigation for forensic purposes.

Molecular photoswitches are widely used in material sciences, physics, chemistry, and biology. As needs grow more complex, materials have to react more than one‐dimensionally. The use of multiple photoswitches at once opens manifold opportunities for further improved and more complicated systems. However, this requires independent addressability, i.e., orthogonality, and reversible processes. Herein, the first study on ultrafast excited state dynamics of two orthogonal photoswitches, a push‐pull azobenzene and a donor‐acceptor Stenhouse adduct is reported. In order to gain detailed insight in their interactions and mutual influences on their photoswitching behavior, they are addressed individually and simultaneously via transient absorption spectroscopy supported by quantum chemical calculations. They show reversible photoswitchability and in addition, can be used in 4D printing to provide easy access to a plethora of functional devices. Furthermore, environmental influences on the excited state dynamics are examined using different solvents and thin films. Both compounds photoisomerize independently when addressed individually or simultaneously and only little impacts on the excited state dynamics are found. Especially the vibrational relaxation is affected by different surroundings changing the energy dissipation while hardly affecting the electronic states involved. The orthogonal and simultaneous addressability is thereby crucial for their usage in 4D printed microactuators.