Aromaticity of biphenylene networks.

Magnetically induced ring-currents and magnetic susceptibilities have been calculated for the series of biphenylene sheets and biphenylene nanoribbons with armchair and zigzag edges with hydrogen atoms, as well as with bromine and fluorine atoms. Calculations have been performed at the density functional level of theory. It has been shown that biphenylene sheets and nanoribbons are characterized by dominant paratropic ring current, resulting in antiaromatic character. The global electron delocalization in biphenylene networks favors the edges of molecular structures, passing through cyclobutadiene units avoiding the outer contour of benzene. Replacing the hydrogen atoms with bromine and fluorine atoms slightly reduces the global ring-current strength and increases the diamagnetic property. The B3LYP functional overestimates the paramagnetic contribution of magnetic susceptibility in large molecular structures, compared with the BHandHLYP functional, which is recommended for magnetic property calculations.