Diamagnetic Carrier-Doping-Induced Continuous Electronic and Magnetic Crossover in One-Dimensional Coordination Polymers

The potential to introduce tunable electrical conductivity and molecular magnetism through carrier doping in metal-organic coordination polymers is particularly promising for nanoelectronics applications. Precise control of the doping level is essential for determining the electronic and magnetic properties. In this study, we present a series of one-dimensional coordination polymers, {(HNEt₃)_0.5[Cu_xCo_(1-x)(L)]}_n (HNEt₃ = triethylammonium, L = 1,2,4,5-tetrakis(methanesulfonamido)benzene), doped with diamagnetic Cu¹⁺ carriers. Through comprehensive characterization of the structural, optical, and magnetic properties, we observed continuous electronic and magnetic crossover as the doping level was gradually increased. When x < 0.5, the doped compounds exhibit ferromagnetic insulating behavior with very high energy barriers (U_eff up to 560 K) and excellent slow relaxation of magnetization. At x = 0.5, {(HNEt₃)_0.5[Cu_0.5Co_0.5(L)]}_n functions as a paramagnetic semiconductor at high temperatures and a single-molecule magnet at low temperatures. When x > 0.5, the doped compounds act as diluted antiferromagnetic semiconductors with narrow band gaps (E_a = 0.2 eV). The emergence of such rich electronic and magnetic crossovers is ascribed to the cooperation of the strong electron-donating ability of the ligand and the pronounced crystal-field effects. Our findings indicate that one-dimensional (1D) coordination polymers are promising for the design of novel low-dimensional magnetic semiconductors.