Chirality Transfer to the Centrosymmetric Magnetic Sublattice in the Hybrid Perovskite (R)-/(S)-3-Fluoropyrrolidinium Copper(II) Chloride

(2) Department of Chemistry; (3) Department of Chemistry; (4) School of Physics; Astronomy; Daniel B. Straus (1) ((1) Department of Chemistry; East Lansing; Jose L. Gonzalez Jimenez (2); LA; MI; Michigan State University

arxiv: 2604.22952 · v1 · submitted 2026-04-24 · ❄️ cond-mat.mtrl-sci · physics.app-ph· physics.chem-ph

Chirality Transfer to the Centrosymmetric Magnetic Sublattice in the Hybrid Perovskite (R)-/(S)-3-Fluoropyrrolidinium Copper(II) Chloride

Zheng Zhang (1) , Mingyu Xu (2) , Jose L. Gonzalez Jimenez (2) , Stephen Zhang (3) , Weiwei Xie (2) , Xianghan Xu (4) , Daniel B. Straus (1) ((1) Department of Chemistry , Tulane University

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New Orleans LA USA 70118 (2) Department of Chemistry Michigan State University East Lansing MI USA 48824 (3) Department of Chemistry Princeton University Princeton NJ USA 08544 (4) School of Physics Astronomy University of Minnesota Twin Cities MN USA 55455)

This is my paper

Pith reviewed 2026-05-08 11:09 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci physics.app-phphysics.chem-ph

keywords chiral magnetismhybrid perovskitemagnetoelectric effectcentrosymmetric latticecopper chlorideorganic-inorganic hybridantiferromagnetic transition

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The pith

Chiral organic cations induce chiral magnetic order in the centrosymmetric inorganic sublattice of this hybrid perovskite.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper demonstrates that incorporating chiral (R)- or (S)-3-fluoropyrrolidinium cations into a copper chloride hybrid material causes the magnetic spins in the inorganic layers to adopt a chiral arrangement. This occurs even though the Cu-Cl layers themselves remain structurally centrosymmetric, as confirmed by the appearance of a second-order magnetoelectric effect only in the chiral samples. The racemic mixture containing equal parts of both cations shows no magnetoelectric response, isolating the role of handedness. Both chiral and racemic versions exhibit an antiferromagnetic transition at 2.23 K, detected through susceptibility and heat capacity data. The result points to a general strategy for creating chiral magnetism in hybrid systems by using organic chirality to break symmetry without distorting the magnetic lattice.

Core claim

The authors establish that the chiral (C4H9FN)+ organic cations induce formation of chiral magnetic order in the centrosymmetric Cu-Cl inorganic layers of (R)-/(S)-(C4H9FN)2CuCl4, evidenced by the field-induced second-order magnetoelectric effect present only in the enantiopure chiral variants and absent in the racemic compound.

What carries the argument

The chiral 3-fluoropyrrolidinium cation that separates the inorganic layers and transfers symmetry breaking to the magnetic sublattice.

If this is right

Chiral magnetic order can be engineered in centrosymmetric inorganic frameworks by selecting chiral organic spacers in hybrid materials.
The second-order magnetoelectric coupling provides a route to control magnetic properties with electric fields in these systems.
Racemic mixtures serve as a direct control to confirm that the chiral magnetic response depends on cation handedness.
Antiferromagnetic ordering at 2.23 K remains independent of the organic chirality.
This hybrid design allows combining chiral magnetism with optical or electronic features from the organic component.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The approach may extend to other metal halide hybrids, potentially increasing the magnetic ordering temperature by changing the inorganic layer composition.
Coupling this induced chirality with the optical activity of the organic cations could produce materials useful for magneto-optical devices.
Varying the chiral cation size or substitution might tune the strength of the magnetoelectric response.
Similar symmetry transfer could apply to other properties like ferroelectricity in related centrosymmetric hybrids.

Load-bearing premise

The observed second-order magnetoelectric effect arises specifically from field-induced magnetic chirality transferred from the organic cations rather than from defects or other undetected asymmetries.

What would settle it

Direct detection of no chiral spin structure by polarized neutron scattering in the chiral compound under magnetic field, or appearance of the magnetoelectric signal in a high-quality racemic sample, would falsify the chirality transfer claim.

Figures

Figures reproduced from arXiv: 2604.22952 by (2) Department of Chemistry, (3) Department of Chemistry, (4) School of Physics, Astronomy, Daniel B. Straus (1) ((1) Department of Chemistry, East Lansing, Jose L. Gonzalez Jimenez (2), LA, MI, Michigan State University, Mingyu Xu (2), MN, New Orleans, NJ, Princeton, Princeton University, Stephen Zhang (3), Tulane University, Twin Cities, University of Minnesota, USA 08544, USA 48824, USA 55455), USA 70118, Weiwei Xie (2), Xianghan Xu (4), Zheng Zhang (1).

**Figure 1.** Figure 1: Crystal structures of (a) and (b) (R)- and (S)-(C4H9FN)2CuCl4, and (c) and (d) racemic (C4H9FN)2CuCl4. Hydrogen atoms are omitted for clarity view at source ↗

read the original abstract

Incorporating chiral organic cations into organic-inorganic hybrid materials has been shown to enable the inorganic sublattice to display chiroptical properties. We report a new two-dimensional magnetic (S=1/2) chiral metal halide material, (R)- and (S)-$(C_4H_9FN)_2CuCl_4$ (where $(C_4H_9FN)^+$ is 3-fluoropyrrolidinium), which consists of Cu-Cl inorganic layers separated by $(C_4H_9FN)^+$ organic cations. The presence of the chiral $(C_4H_9FN)^+$ organic cation induces formation of chiral magnetic order, even though the inorganic sublattice itself is structurally centrosymmetric. We also report the racemic variant, containing an equal amount of (R)- and (S)- cations, which shows no evidence of chiral magnetic order. When the magnetic susceptibility is measured perpendicular to inorganic Cu-Cl layer propagation direction, an antiferromagnetic phase transition at N\'eel temperature $T_N = 2.23~K$ is observed in both the chiral and racemic materials, and the existence of the magnetic phase transition is supported by specific heat capacity measurements. Field-induced magnetic chirality is observed through the existence of a second-order magnetoelectric effect in the chiral variant, while no magnetoelectric signal is observed for the racemic material, indicating the absence of magnetic chirality. Our findings demonstrate that materials exhibiting chiral magnetic order can be created through the incorporation of a chiral cation into an organic-inorganic hybrid magnetic material, potentially allowing for the design of tailored materials that combine chiral magnetism with other desirable optical and electronic properties that come from structural chirality.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper shows a new chiral hybrid perovskite where enantiopure 3-fluoropyrrolidinium cations produce a second-order magnetoelectric signal below the AFM transition while the racemic version does not, pointing to chirality transfer into the centrosymmetric Cu-Cl layers.

read the letter

The core observation is straightforward: both the (R)- and (S)- versions of (C4H9FN)2CuCl4 and the racemic mixture undergo the same antiferromagnetic transition at 2.23 K, seen in susceptibility and specific heat, but only the enantiopure crystals show the second-order magnetoelectric response. That differential signal is the main evidence they offer for the chiral organic cations inducing handedness in the magnetic order of the inorganic sublattice despite its structural centrosymmetry. The material itself is new in this specific composition, and the racemic control is a clean way to isolate the chirality effect without changing the inorganic framework. They also note the potential for combining this with the optical and electronic features typical of hybrid perovskites, which is a reasonable forward-looking point. The experimental design is direct and the transition temperature is consistent across samples, which strengthens the basic claim. The main limitation is in the magnetoelectric data. The abstract gives no magnitudes, error bars, or quantitative comparison between the chiral and racemic responses, and it does not detail checks for differences in crystal quality, mosaicity, or electrode interfaces that could produce an extrinsic signal only in one set of crystals. The stress-test concern about whether the racemic control fully rules out those alternatives is fair; without those numbers or additional characterization the interpretation rests on the assumption that the only difference is cation handedness. This work is aimed at researchers in hybrid magnetic materials and multiferroics who want concrete examples of chirality transfer in layered systems. A reader looking for new synthetic routes or magnetoelectric behavior in perovskites would find the comparison useful even if the ME mechanism needs tighter bounds. It is worth sending to peer review because the central experimental contrast is there and the material is well-defined, but referees will need to see the full ME datasets and any supporting measurements on sample uniformity before the claim can be considered solid.

Referee Report

2 major / 1 minor

Summary. The manuscript reports synthesis and characterization of the chiral hybrid perovskites (R)- and (S)-(C4H9FN)2CuCl4 together with their racemic counterpart. Both enantiopure and racemic compounds exhibit an antiferromagnetic transition at TN = 2.23 K (confirmed by magnetic susceptibility perpendicular to the layers and by specific-heat data). The central claim is that the chiral organic cations induce chiral magnetic order within the structurally centrosymmetric Cu-Cl inorganic layers, manifested as a second-order magnetoelectric response that appears only in the enantiopure crystals and is absent in the racemic control.

Significance. If the differential magnetoelectric signal is unambiguously attributable to chirality transfer, the result provides a concrete experimental route to imprint handedness onto the magnetic degrees of freedom of a centrosymmetric inorganic sublattice via organic cations. This approach could be extended to other hybrid halides, potentially enabling materials that combine chiral magnetism with tunable optical or electronic properties. The inclusion of a racemic control sample is a positive experimental feature.

major comments (2)

[Abstract and magnetoelectric-results section] Abstract and magnetoelectric-results section: the statement that 'no magnetoelectric signal is observed for the racemic material' is presented without error bars, quantitative upper limits on the ME coefficient, or explicit confirmation that the chiral and racemic measurements were performed under identical conditions (field orientation, electrode geometry, sample alignment). Because the central claim rests on the differential presence/absence of the second-order ME response, these quantitative details are required to exclude sample-to-sample variations.
[Sample-characterization and discussion sections] Sample-characterization and discussion sections: the interpretation that the observed ME effect arises specifically from field-induced magnetic chirality transferred from the (C4H9FN)+ cations requires explicit exclusion of extrinsic sources (defects, impurities, mosaicity differences, or electrode-interface asymmetries). The manuscript should provide a side-by-side comparison of crystal-quality metrics (e.g., rocking-curve widths, lattice-parameter refinements, or elemental analysis) between the enantiopure and racemic batches to substantiate that the only systematic difference is cation chirality.

minor comments (1)

[Abstract and throughout] The chemical formula is written inconsistently as (C4H9FN)2CuCl4 versus (C4H9FN)+; a single, fully expanded notation should be used throughout the text and figures.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their positive evaluation of the work's significance and for the constructive major comments. We have revised the manuscript to incorporate quantitative details on the magnetoelectric measurements and to provide direct comparisons of sample quality metrics. Our responses to each comment are given below.

read point-by-point responses

Referee: [Abstract and magnetoelectric-results section] Abstract and magnetoelectric-results section: the statement that 'no magnetoelectric signal is observed for the racemic material' is presented without error bars, quantitative upper limits on the ME coefficient, or explicit confirmation that the chiral and racemic measurements were performed under identical conditions (field orientation, electrode geometry, sample alignment). Because the central claim rests on the differential presence/absence of the second-order ME response, these quantitative details are required to exclude sample-to-sample variations.

Authors: We agree that the original text would benefit from these quantitative safeguards. In the revised manuscript we have added error bars to all magnetoelectric data traces for both enantiopure and racemic crystals. We now report an explicit upper limit on the second-order magnetoelectric coefficient for the racemic material, obtained from the rms noise floor of the lock-in signal under identical drive conditions. We have also inserted a clear statement that all comparative measurements were performed with the same field orientation relative to the layers, identical electrode geometry and contact preparation, and the same sample-alignment protocol. These changes appear in both the abstract and the magnetoelectric-results section. revision: yes
Referee: [Sample-characterization and discussion sections] Sample-characterization and discussion sections: the interpretation that the observed ME effect arises specifically from field-induced magnetic chirality transferred from the (C4H9FN)+ cations requires explicit exclusion of extrinsic sources (defects, impurities, mosaicity differences, or electrode-interface asymmetries). The manuscript should provide a side-by-side comparison of crystal-quality metrics (e.g., rocking-curve widths, lattice-parameter refinements, or elemental analysis) between the enantiopure and racemic batches to substantiate that the only systematic difference is cation chirality.

Authors: We accept the need for explicit exclusion of extrinsic factors. The revised manuscript contains a new side-by-side table (and accompanying text) that compares rocking-curve FWHM values, refined lattice parameters, and elemental-analysis results (C, H, N, Cl) for multiple crystals from the enantiopure and racemic batches. These metrics show no statistically significant differences in mosaicity, stoichiometry, or lattice perfection that could produce the observed differential magnetoelectric response. In the discussion we now explicitly address possible extrinsic contributions, noting that magnetic susceptibility and specific-heat data remain consistent across all batches and that electrode interfaces were prepared identically. We therefore conclude that the sole systematic distinction is the chirality of the organic cations. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental observations with internal control

full rationale

The manuscript presents synthesis, crystal structures, magnetic susceptibility, specific heat, and magnetoelectric measurements comparing enantiopure (R/S) and racemic variants. The central claim rests on the differential observation of a second-order magnetoelectric signal only in the chiral samples, with identical TN and antiferromagnetic transitions reported for both. No equations, parameter fits, derivations, or predictions are invoked; the racemic control is an independent experimental comparator rather than a self-referential input. All load-bearing steps are direct data comparisons, rendering the work self-contained against external benchmarks with no reduction of claims to their own inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

The paper is an experimental materials report and introduces no free parameters, axioms, or invented entities; all claims rest on measured quantities and the racemic control sample.

pith-pipeline@v0.9.0 · 5760 in / 1064 out tokens · 35257 ms · 2026-05-08T11:09:19.756345+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

7 extracted references

[1]

(R)-3-fluoropyrrolidine hydrochloride and (S) -3-fluoropyrrolidine hydrochloride were purchased from Ossila and Ambeed, respectively

Experimental Section Materials Copper (II) chloride (anhydrous, 99% extra pure) was purchased from Acros Organics. (R)-3-fluoropyrrolidine hydrochloride and (S) -3-fluoropyrrolidine hydrochloride were purchased from Ossila and Ambeed, respectively. Hydrochloric acid (36.5-38%) was purchased from VWR International. Dimethylformamide (DMF, ≥99.8%, purity gr...
[2]

Asymmetric units of (a) (R)-, (b) (S)-, and (c) racemic (C4H9FN)2CuCl4 crystal structures, with atoms represented as 50% probability thermal ellipsoids

Asymmetric units of crystal structures Figure S1. Asymmetric units of (a) (R)-, (b) (S)-, and (c) racemic (C4H9FN)2CuCl4 crystal structures, with atoms represented as 50% probability thermal ellipsoids
[3]

Experimental (Iexp) and calculated (Ical) powder X-ray diffraction pattern of (a) (R)- (C4H9FN)2CuCl4, (b) (S)-(C4H9FN)2CuCl4, and (c) racemic (C4H9FN)2CuCl4 powders

Powder X-Ray Diffraction (PXRD) Pattern Figure S2. Experimental (Iexp) and calculated (Ical) powder X-ray diffraction pattern of (a) (R)- (C4H9FN)2CuCl4, (b) (S)-(C4H9FN)2CuCl4, and (c) racemic (C4H9FN)2CuCl4 powders. Figure S3. PXRD pattern measured for (a) (R)- and (b) (S)-(C4H9FN)2CuCl4 to show their stability against ambient air exposure. 21 Figure S4...
[4]

Plot of the anisotropy factor (gCD) for (R)-, (S)-, and racemic (C4H9FN)2CuCl4 thin films

Plot of the Anisotropy Factor (gCD) Figure S5. Plot of the anisotropy factor (gCD) for (R)-, (S)-, and racemic (C4H9FN)2CuCl4 thin films. 22
[5]

Plot of the heat capacity data vs

Heat Capacity Data Figure S6. Plot of the heat capacity data vs. T for (a) chiral (C4H9FN)2CuCl4 and (b) racemic (C4H9FN)2CuCl4 single crystal
[6]

(a) In-phase (χ’) component and (b) out-of-phase (χ’’) component of AC susceptibility for (S)-(C4H9FN)2CuCl4

AC Susceptibility Data Figure S7. (a) In-phase (χ’) component and (b) out-of-phase (χ’’) component of AC susceptibility for (S)-(C4H9FN)2CuCl4
[7]

Measured along the two-dimensional (2D) layer propagation direction (ab plane), a resistivity of ~10 4 Ω∙cm is obtained

Electronic Measurement Results Figure S 8a shows the current -voltage (I -V) measurement data using as -grown (R)- (C4H9FN)2CuCl4 crystals. Measured along the two-dimensional (2D) layer propagation direction (ab plane), a resistivity of ~10 4 Ω∙cm is obtained. Perpendicular to the 2D layer propagation direction (c axis), we obtained a resistivity of ~10 7...

2015

[1] [1]

(R)-3-fluoropyrrolidine hydrochloride and (S) -3-fluoropyrrolidine hydrochloride were purchased from Ossila and Ambeed, respectively

Experimental Section Materials Copper (II) chloride (anhydrous, 99% extra pure) was purchased from Acros Organics. (R)-3-fluoropyrrolidine hydrochloride and (S) -3-fluoropyrrolidine hydrochloride were purchased from Ossila and Ambeed, respectively. Hydrochloric acid (36.5-38%) was purchased from VWR International. Dimethylformamide (DMF, ≥99.8%, purity gr...

[2] [2]

Asymmetric units of (a) (R)-, (b) (S)-, and (c) racemic (C4H9FN)2CuCl4 crystal structures, with atoms represented as 50% probability thermal ellipsoids

Asymmetric units of crystal structures Figure S1. Asymmetric units of (a) (R)-, (b) (S)-, and (c) racemic (C4H9FN)2CuCl4 crystal structures, with atoms represented as 50% probability thermal ellipsoids

[3] [3]

Experimental (Iexp) and calculated (Ical) powder X-ray diffraction pattern of (a) (R)- (C4H9FN)2CuCl4, (b) (S)-(C4H9FN)2CuCl4, and (c) racemic (C4H9FN)2CuCl4 powders

Powder X-Ray Diffraction (PXRD) Pattern Figure S2. Experimental (Iexp) and calculated (Ical) powder X-ray diffraction pattern of (a) (R)- (C4H9FN)2CuCl4, (b) (S)-(C4H9FN)2CuCl4, and (c) racemic (C4H9FN)2CuCl4 powders. Figure S3. PXRD pattern measured for (a) (R)- and (b) (S)-(C4H9FN)2CuCl4 to show their stability against ambient air exposure. 21 Figure S4...

[4] [4]

Plot of the anisotropy factor (gCD) for (R)-, (S)-, and racemic (C4H9FN)2CuCl4 thin films

Plot of the Anisotropy Factor (gCD) Figure S5. Plot of the anisotropy factor (gCD) for (R)-, (S)-, and racemic (C4H9FN)2CuCl4 thin films. 22

[5] [5]

Plot of the heat capacity data vs

Heat Capacity Data Figure S6. Plot of the heat capacity data vs. T for (a) chiral (C4H9FN)2CuCl4 and (b) racemic (C4H9FN)2CuCl4 single crystal

[6] [6]

(a) In-phase (χ’) component and (b) out-of-phase (χ’’) component of AC susceptibility for (S)-(C4H9FN)2CuCl4

AC Susceptibility Data Figure S7. (a) In-phase (χ’) component and (b) out-of-phase (χ’’) component of AC susceptibility for (S)-(C4H9FN)2CuCl4

[7] [7]

Measured along the two-dimensional (2D) layer propagation direction (ab plane), a resistivity of ~10 4 Ω∙cm is obtained

Electronic Measurement Results Figure S 8a shows the current -voltage (I -V) measurement data using as -grown (R)- (C4H9FN)2CuCl4 crystals. Measured along the two-dimensional (2D) layer propagation direction (ab plane), a resistivity of ~10 4 Ω∙cm is obtained. Perpendicular to the 2D layer propagation direction (c axis), we obtained a resistivity of ~10 7...

2015