, a Molecular Framework Material*

Low dimensional magnetic materials with spin-1/2 moments can host a range of exotic magnetic phenomena due to the intrinsic importance of quantum fluctuations to their behaviour. In this work we report the structure, magnetic structure and magnetic properties of copper(II) thiocyanate, Cu(NCS)2, a one-dimensional coordination polymer which displays low-dimensional quantum magnetism. Magnetic susceptibility, electron paramagnetic resonance spectroscopy, ¹³C magic angle spinning nuclear magnetic resonance spectroscopy, and density functional theory investigations indicate that Cu(NCS)₂ behaves as a two dimensional array of weakly coupled antiferromagnetic spin chains (J₂=133(1)K, α=J₁/J₂=0.08). Powder neutron diffraction measurements confirm that below T_N=12 K Cu(NCS)₂ orders as a commensurate G-type antiferromagnet with a strongly-reduced ordered moment (0.3 μB) due to quantum fluctuations.