biostudies-literatureLi YMinistry of Science and ICTMinistry of Science and ICT, South KoreaNational Research Foundation of Koreae202500849https://www.ebi.ac.uk/biostudies/studies/S-EPMC12089917biostudies-literatureUnknown31(28)Birefringence, a vital property of anisotropic crystals, is indispensable for advanced optical technologies. Quasi-1D structures, with their inherent structural anisotropy, offer fertile ground for discovering materials with exceptional optical anisotropy. In this work, we report four metal-free quasi-1D crystals-(C₅H₆NO)⁺(NO₃)^-(4HPN), (C₅H₆NO)⁺(HC₂O₄)^-(4HPO), (C₄N₃H₆)⁺(NO₃)^-(2APMN), and (C₄N₃H₆)⁺(HC₂O₄)^-·H₂O (2APMO)-designed to feature pseudo-chain structures and grown as centimeter-scale crystals via a facile aqueous-Chemistry (Weinheim an der Bergstrasse, Germany)Designed Metal-Free Quasi-1D Crystals with Giant Birefringence.PMC12089917RS-2024-00442105RS‐2024‐00442105Li YLee JOk KMfalseDesigned Metal-Free Quasi-1D Crystals with Giant Birefringence.Birefringence, a vital property of anisotropic crystals, is indispensable for advanced optical technologies. Quasi-1D structures, with their inherent structural anisotropy, offer fertile ground for discovering materials with exceptional optical anisotropy. In this work, we report four metal-free quasi-1D crystals-(C₅H₆NO)⁺(NO₃)^-(4HPN), (C₅H₆NO)⁺(HC₂O₄)^-(4HPO), (C₄N₃H₆)⁺(NO₃)^-(2APMN), and (C₄N₃H₆)⁺(HC₂O₄)^-·H₂O (2APMO)-designed to feature pseudo-chain structures and grown as centimeter-scale crystals via a facile aqueous-2025-01-01T00:00:00Z2025 May2026-06-01T07:53:32.472Z2026-04-08T10:46:18.645ZS-EPMC120899174019246810.1002/chem.202500849