= 1 quantum materials: new twists on a seemingly old theme*

We aim to control the spatial exchange and single-ion anisotropies (D) in bespoke S = 1 Ni(II) quantum magnets. Early work led to [Ni(HF₂)(pyz)₂]SbF₆ (pyz = pyrazine) which contains Ni-FHF-Ni chains (J_FHF) cross-linked by Ni-pyz-Ni segments (J_pyz) to form a tetragonal network [1]. The material undergoes XY-AFM order below T_N = 12.2 K with collinear Ni(II) moments confined to the [Ni(pyz)₂]²⁺ plane. High-field M(H) and inelastic neutron scattering (INS) revealed D ≈ J_FHF >> J_pyz. In the related square lattices [2,3], NiX₂(pyz)₂ (X = F, Cl, Br, I, NCS), the electronegativity of X dictates the Ni(II) spin direction with XY- and Ising-like ground-states observed for X = F, Cl and X = Br, I, NCS, respectively. We used INS to determine J_pyz and J_⊥. Chemical substitution of pyz for pyrimidine (pym) affords unusual topologies and enhanced magnetic interactions along Ni-pym-Ni relative to Ni-pyz-Ni. Thus, we synthesized two new Q1D chains: staggered [Ni(pym)(H₂O)₄]SO₄●2H₂O and chiral [Ni(pym)(H₂O)₄]SiF₆●H₂O, each showing multiple field-induced phase transitions below 5 K. Lastly, we will describe a unique 3D chiral Ni(II) framework that may display spin-liquid behavior at low temperatures. Time permitting, the structural and magnetic properties of these materials will be discussed.