Polycyclic aromatic hydrocarbons with an open-shell singlet biradical ground state are of fundamental interest and have potential applications in materials science. However, the inherent high reactivity makes their synthesis and characterization very challenging. In this work, a convenient synthetic route was developed to synthesize two kinetically blocked heptazethrene (HZ-TIPS) and octazethrene (OZ-TIPS) compounds with good stability. Their ground-state electronic structures were systematically investigated by a combination of different experimental methods, including steady-state and transient absorption spectroscopy, variable temperature NMR, electron spin resonance (ESR), superconducting quantum interfering device (SQUID), FT Raman, and X-ray crystallographic analysis, assisted by unrestricted symmetry-broken density functional theory (DFT) calculations. All these demonstrated that the heptazethrene derivative HZ-TIPS has a closed-shell ground state while its octazethrene analogue OZ-TIPS with a smaller energy gap exists as an open-shell singlet biradical with a large measured biradical character (y = 0.56). Large two-photon absorption (TPA) cross sections (σ((2))) were determined for HZ-TIPS (σ((2))(max) = 920 GM at 1250 nm) and OZ-TIPS (σ((2))(max) = 1200 GM at 1250 nm). In addition, HZ-TIPS and OZ-TIPS show a closely stacked 1D polymer chain in single crystals.

The effect of the magnetic field on the magnetic properties of NiFe/Cu composite wires electroplated under a longitudinal magnetic controlling field is presented. Composite wire samples of 20-μm-diameter Cu electroplated with a layer of Permalloy™ (Ni80Fe20) under the influence of a longitudinal magnetic field of intensities ranging from 0 to 400 Oe were produced, and the microstructure and magnetic properties were measured. The results showed that the longitudinal magnetic field in the composite wire plating makes the packing of the crystals in the plated layer more orderly, and thus increases the uniformity and magnetic softness of the plated material. It also shifts the magnetic anisotropy of the plated layer from circumferential to longitudinal, and increases the critical frequency of the plated composite wire in magnetoimpedance effect testing, at which the magnetoimpedance ratio reaches the maximum.

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