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oai:figshare.com:article/34032636 2026-09-30T13:34:07Z category_1 category_915 category_7 category_19 category_24 category_873 portal_63 item_type_6 month_year_09_2026

Fluorine-for-Hydrogen Substitution: A Chemical “Butterfly Effect” on Phase Transition, Dielectric, and Magnetic Behaviors Xiao-Han Lv (22291494) Hong-Jun Chen (9266879) Yin Qian (8966681) Xiao-Zu Wang (2570686) Xiao-Ming Ren (544414) Biophysics Physical Sciences not elsewhere classified Medicine Pharmacology Evolutionary Biology Chemical Sciences not elsewhere classified switchable physical properties structurally identical except planar radical anion macroscopic properties arising identical crystal packing enhances thermal stability b >-</ b designed two salts >- ethyl -< single hydrogen atom mnt )< sub fempyr ][ ni empyr ][ ni compounds undergo two >- methylpyrrolidinium ), 2 –</ sup two compounds >- methylpyrrolidinium >-( 2 transition temperatures transition systems results demonstrate pronounced divergence precise strategy n </ molecular materials magnetic responses increasingly attractive hydrogen substitution fluoroethyl )-< barrier pyrrolidinium Smart molecular materials exhibiting solid–solid phase transitions are increasingly attractive for advanced technological applications due to their switchable physical properties. In this work, we designed two salts, [EMPyr][Ni(mnt)₂] (<b>1-H</b>, [EMPyr]⁺ = <i>N</i>-ethyl-<i>N</i>-methylpyrrolidinium and mnt^2– = maleonitriledithiolate) and [FEMPyr][Ni(mnt)₂] (<b>1-F</b>, [FEMPyr]⁺ = <i>N</i>-(2-fluoroethyl)-<i>N</i>-methylpyrrolidinium), by combining a low-rotational<b>-</b>barrier pyrrolidinium-derived cation with the planar radical anion [Ni(mnt)₂]⁻. These two compounds are structurally identical except for the substitution of a single hydrogen atom by fluorine on the cation. Both compounds undergo two-step solid–solid phase transitions, yielding three mutually isomorphic phases. Remarkably, despite their near-identical crystal packing, fluorination not only enhances thermal stability and raises the phase-transition temperatures but also induces markedly different dielectric and magnetic responses. This pronounced divergence in macroscopic properties arising from a single atomic substitution exemplifies a chemical “butterfly effect” in molecular materials. Our results demonstrate that even minimal chemical modifications can serve as a powerful and precise strategy for tuning structure–property relationships in molecular phase-transition systems. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acs.inorgchem.6c03727.s001 https://figshare.com/articles/journal_contribution/Fluorine-for-Hydrogen_Substitution_A_Chemical_Butterfly_Effect_on_Phase_Transition_Dielectric_and_Magnetic_Behaviors/34032636 CC BY-NC 4.0