Spin-Induced Switching of Electronic State Populations in Transition Metal Polyphthalocyanines

Polyphthalocyanines (PPCs) are a new and promising class of two dimensional materials offering versatile avenues for next generation electronic devices. For organic spintronic devices, PPCs can be engineered to tailor the electric and magnetic properties. In this work, we investigate PPC's monolayers with embedded transition metal atoms (TM = Fe, Ni, Cu), utilizing first principle calculations based on spin-polarized generalized gradient approximation (SGGA). PPC sheets with central TM atoms are simulated for the dispersion curves, electronic density of states (DOS), and projected density of states (PDOS) using quantum atomistic toolkit (Quantum ATK) software. According to simulations, the FePPC supercell with four magnetic moments of Fe, aligned in a parallel ferromagnetic (FM) configuration, show the conductive FM state, while in the case of the anti-parallel antiferromagnetic (AFM) order of the magnetic moments, the material exhibits semiconducting non-magnetic behavior. FM-ordered NiPPC displays a metallic state, which is partly suppressed for AFM-ordered NiPPC. In contrast, non-magnetic CuPPC is found to be the best conductor due to its larger PDOS at the Fermi level among all considered systems.

Synthesis, properties, and remarkable 2 D Self-Assembly at the Liquid/Solid interface of a series of triskele-shaped 5,11,17-triazatrinaphthylenes (TrisK)

A series of 5,11,17-triazatrinaphthylene (TrisK) derivatives, large disk-like π-conjugated molecules with C3h symmetry, has been synthesised by following an optimised synthetic pathway. The synthesis was performed by a four-step protocol based on the N-arylation of 1,3,5-tribromobenzene with appropriate anthranilate derivatives. This strategy permits the generation of either chlorinated (TrisK-Cl-OCn) or non-chlorinated (TrisK-H-OCn) alkoxy-substituted derivatives (OCn H2n+1 with n=3, 10, 12 and 16), thus providing additional versatility in the control of the structure-property relationships. The electronic properties of the various TrisK compounds have been characterised in solution by absorption and emission spectroscopies as well as cyclic voltammetry. The crystal structure of 2,8,14-propyloxy-5,11,17-triazatrinaphthylene TrisK-H-OC3 has been determined by X-ray diffraction analysis, which revealed the presence of stabilising weak intermolecular H bonds. Scanning tunnelling microscopy (STM) at the liquid/solid interface has revealed the remarkable 2D self-assembling properties of the TrisK compounds. In particular, it has shown that TrisK-H-OC12 forms three concomitant self-organised 2D phases with different row-packing arrangements. This 2D polymorphism arises from slow ordering due to the presence of three long dodecyloxy chains on the molecular backbone. Individual molecules can be imaged with spectacular intramolecular resolution, thus providing the possibility of correlating the STM features with the calculated charge density distribution.