Dielectric resonator aided sensitivity-enhancing electron paramagnetic resonance was successfully applied to small single crystals of the previously reported metal-organicin a conventional X-band EPR spectrometer at 7 K sample temperature to reveal the nature of mononuclear Cu 2+ ion defect species. We found that these paramagnetic defects are not related to an impurity phase or extraframework species of the parent metal-organic framework material but are formed within the framework. Novel angular resolved single crystal continuous wave electron paramagnetic resonance supported by powder measurements and single crystal X-ray diffraction on this metal-organic framework compound identified defective copper paddle wheel units with one missing Cu 2+ ion as the observed mononuclear paramagnetic species in this compound. The sensitivity enhancement by an estimated factor of 8.6 for the single crystal electron paramagnetic resonance spectroscopy is required to efficiently record the Cu 2+ ion signals in single crystals of typical sizes of 200 × 50 × 50 µm 3 at X-band frequencies. The results demonstrate that conventional electron paramagnetic resonance spectrometers operating at X-band frequencies and equipped with dielectric resonators can successfully be used to perform single crystal studies of these porous, low density materials with very small volume samples at low temperatures.

We report synthesis and composite study of a novel metal–organic framework (MOF) compound of chemical formula ∞ 3[Cu2 ICu2 II{H2O}2{(Me–trz–mba)2thio}2]Cl2, where (Me–trz–mba)2thio2– stands for 3,3-(5,5-(thiophene-2,5-diyl)bis(3-methyl-4H-1,2,4-triazole-5,4-diyl))dibenzoate. This coordination polymer was synthesized by solvothermal synthesis. The crystal structure was determined using single crystal X-ray diffraction. The main building block of this compound is a so-called Cu2 paddle-wheel (PW) unit, which contains two Cu2+ ions connected via four carboxylate groups. Magnetic properties of the investigated MOF were studied by continuous-wave electron paramagnetic resonance (EPR) spectroscopy at X- and Q-band frequencies in a wide temperature range. Mononuclear Cu2+ ions were observed in the EPR spectra and characterized by spectral simulations. In addition, the obtained EPR data allowed us to detect and investigate three distinct magnetic interactions related to the Cu2+ pairs. At higher temperatures the fine structure pattern was observed in the EPR spectra and the spin–spin interaction tensor D was determined. The origin of this pattern was assigned to the thermally populated excited triplet states of the Cu2+ pairs. It was found that two Cu2+ ions within a single PW unit couple antiferromagnetically with the exchange coupling constant J = −258 cm–1. Moreover, the EPR spectra of dehydrated MOF samples show a broad, poorly resolved spectral feature, the origin of which is an exchange of the spin triplets between neighboring Cu2 PW units. By simulating the powder pattern of this interdinuclear exchange line, we estimated the exchange coupling between neighboring PW units (|J′| = 4.9 cm–1). It was also found that the interdinuclear exchange gradually disappears, if the dehydrated samples are allowed to interact with air, demonstrating that this exchange can be rather easily manipulated in the investigated MOF.

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Corrosion data provided under high-temperature and high-humidity conditions as well as tin whisker growth studies are explained by differences in the surface energy of lattice planes within the crystal structure of β-tin. For this purpose, electrodeposited tin finishes were investigated regarding their microstructure utilizing X-ray diffraction, cross-sectional SEM and EBSD analysis. The corrosion as well as the tin whisker propensity strongly depends on the preferred orientation of the surface finishes. With an increasing texture along the (211) lattice plane a decreasing corrosion and whisker propensity was observed, in contrary, the presence of the (101) and (112) textures results in an increased corrosion and whisker propensity. The maximum whisker length was reduced by one order of magnitude by changing the preferred orientation towards the (211) lattice plane of the tin finish. Modified embedded-atom method simulations of tin surfaces demonstrate the minimization of the surface energy of (211) surfaces, whereas the surface energies of the (101) and (112) Miller planes are increased. We find a strong connection between the minimization of surface energy and the corrosion and tin whisker propensity of electrodeposited tin finishes. To our best knowledge, this is the first study connecting the influence of the electrodeposition parameters on the corrosion and whisker propensity explained by calculations of the surface energies of