Glycine‐Induced Unique Crystal Packing of Octacyanidetungstates With Strong Intermolecular Antiferromagnetic Interaction, Near‐Infrared Emission, and Second Harmonic Generation

We report a supramolecular assembly of octacyanidetungstates ( S = 1/2) with glycine, Cs 3 [W V (CN) 8 ](glycine), featuring a one‐dimensional columnar structure with a remarkably strong intermolecular antiferromagnetic superexchange interaction of J = −42.41(2) K between adjacent octacyanidetungstates due to their effective packing close to van der Waals contacts. This represents the strongest intermolecular spin‐spin interaction reported to date among cyanidemetallates. When exposed to 470 nm light, this compound exhibits a near‐infrared emission with a peak at 763 nm originating from the ligand‐to‐metal charge‐transfer excited state of [W V (CN) 8 ] 3− . Such emission is notably rare for d 1 metal complexes. Additionally, the noncentrosymmetric crystal structure of this compound enables second harmonic generation, emitting second harmonic light at 650 nm when irradiated with 1300 nm incident light.