Michel Gruselle

Strong magneto-chiral dichroism in enantiopure chiral ferromagnets

As materials science is moving towards the synthesis, the study and the processing of new materials exhibiting well-defined and complex functions, the synthesis of new multifunctional materials is one of the important challenges. One of these complex physical properties is magneto-chiral dichroism which arises, at second order, from the coexistence of spatial asymmetry and magnetization in a material. Herein we report the first measurement of strong magneto-chiral dichroism in an enantiopure chiral ferromagnet. The ab initio synthesis of the enantiopure chiral ferromagnet is based on an enantioselective self-assembly, where a resolved chiral quaternary ammonium cation imposes the absolute configurations of the metal centres within chromium-manganese two-dimensional oxalate layers. The ferromagnetic interaction between Cr(III) and Mn(II) ions leads to a Curie temperature of 7 K. The magneto-chiral dichroic effect is enhanced by a factor of 17 when entering into the ferromagnetic phase.

Large Magnetization-Induced Second Harmonic Generation in an Enantiopure Chiral Magnet

The absence of centrosymmetry in the enantiopure chiral magnet [N(CH(3))(n-C(3)H(7))(2)(C*H(CH(3))C(2)H(5))][Mn(II)Cr(III)(ox)(3)] allows the observation of bulk second harmonic generation (SHG) in this material. At low temperature, the onset of magnetization gives birth to a magnetization-induced SHG (MSHG) contribution. With an angular shift of 13.1 degrees upon magnetization reversal, the MSHG effects appear to be much larger than the corresponding linear magneto-optical effects. Thanks to the single-crystalline state of the sample, the variation of the signal with the orientation of the magnetic field and/or the angle between the polarization of the incident radiation and the outgoing SHG signal in the paramagnetic and ferromagnetic phases is reproduced and well-understood through the use of a symmetry-based analysis of the nonlinear susceptibility tensor.

Polyfunctional two- (2D) and three- (3D) dimensional oxalate bridged bimetallic magnets

We report major results concerning polyfunctional two- (2D) and three- (3D) dimensional oxalate bridged bimetallic magnets. As a consequence of their specific organisation they are composed of an anionic sub-lattice and a cationic counter-part. These bimetallic polymers can accommodate various counter-cations possessing specific physical properties in addition to the magnetic ones resulting from the interactions between the metallic ions in the anionic sub-lattice. Thus, molecular magnets possessing paramagnetic, conductive and optical properties are presented in this review.

Differentiation of planar chiral enantiomers of 〚Cp*M(2-alkyl-Phenoxo)〛 〚BF4〛 {M = Rh, Ir} by the trisphat anion

Abstract Precursor oxo-dienyl rhodium and iridium complexes 〚(η 5 -Cp*)M(η 5 -2-alkyl-oxodienyl)〛 〚BF 4 〛 ( 2a–c ) were prepared according to literature procedure. Addition of 〚 n -Bu 4 N〛 〚Δ-trisphat〛 ( 6 ) to a CD 2 Cl 2 solution of these chiral derivatives has led to the NMR differentiation of the enantiomers. These results pave the way towards the preparation of enantiomerically pure o -quinone methide complexes.

(Ferrocenylmethyl)trialkyl ammoniums as template cations in optically active two-dimensional oxalate bridged [Cr–Mn] and [Cr–Ni] molecule-based magnets: synthesis and magnetic properties

Abstract A series of (ferrocenylmethyl)trialkyl ammoniums: FcCH2NR3+ with R=CH3 (1), C2H5 (2), n-C3H7 (3), n-C4H9 (4) (X-ray structure provided), n-C5H11 (5) and the planar chiral 1,2-disubstituted Fc(CH3)CH2NBu3+ (6) have been tentatively used as template cation in order to synthesise bidimensional (2D) oxalate bridged molecule-based magnets of general formula {[CrIIIMII(ox)3][FcCH2NR3]}n and{[CrIIIMII(ox)3][Fc(CH3)CH2NBu3]}n (M=Mn2+, Ni2+, ox=C2O42−). These polymeric compounds were obtained only for reactions performed with 2, 3, 4 and 6. Starting from resolved Cr(ox)32−, the networks were prepared in their two enantiomeric forms in the case of {[CrIIINiII(ox)3][FcCH2NBu3]}n ([CrΔ–NiΛ]-4 and [CrΛ–NiΔ]-4) or {[CrIIIMnII(ox)3][FcCH2NBu3]}n ([CrΔ–MnΛ]-4 and [CrΛ–MnΔ]-4)) and characterised by circular dichroism measurements. All these compounds are ferromagnets with a Curie temperature close to 6 K when M=Mn and to 17 K for Ni. While the manganese [Cr–Mn] containing compounds are soft magnets, the [Cr–Ni] networks show coercive force up to 2200 Oe far above those previously reported for these networks.

An Anionic {[MnCo(ox)3]-}n Network with Appropriate Cavities for the Enantioselective Recognition and Resolution of the Hexacoordinated Monocation [Ru(bpy)2(ppy)]+ (bpy = bipyridine, ppy = phenylpyridine)

Partial resolution of the rac-[Ru(bpy)2(ppy)]+ monocation into [Δ-Ru(bpy)2(ppy)]PF6 (1Δ) (ee = 44%) and [Λ-Ru(bpy)2(ppy)]PF6 (1Λ) (ee = 50%) enantiomers was achieved by an unprecedented resolving process which involves the diastereoselective preparation of optically active networks of the type {[Λ-Ru(bpy)2(ppy)][Mn-Λ-Co(ox)3]}n (2Λ) and {[Δ-Ru(bpy)2(ppy)][Mn-Δ-Co(ox)3]}n (2Δ). In these optically active inorganic polymers, the counter-monocation [Ru(bpy)2(ppy)]+ of appropriate configuration occupies the cavities while the excess [Ru(bpy)2(ppy)]+, of opposite configuration, remains in solution and is thus recovered. Anion metathesis of the optically active [Ru(bpy)2(ppy)]PF6 (1Δ) (ee = 44%) and (1Λ) (ee = 50%) with [l-cinchonidinium][Δ-trisphat] [trisphat = tris(tetrachlorobenzenediolato)phosphate(V)] provides the related diastereomers [Δ-Ru(bpy)2(ppy)][Δ-trisphat] (3Δ) (de = 44%) and [Λ-Ru(bpy)2(ppy)][Δ-trisphat] (3Λ) (de = 50%) in 60% yield. Their diastereomeric excesses were assessed by 1H NMR analysis. All products were fully characterized and the absolute configuration was determined by circular dichroism techniques in solution or in the solid state. Additionally the X-ray structure of [Ru(bpy)2(ppy)]PF6 (1) was determined.

Unexpected formation of chiral single crystals of {NH(n-C3H7)3[MnIICrIII(C2O4)3]}, A 2D oxalate-based material

In an attempt to obtain chiral single crystals of a two-dimensional (2D) bimetallic oxalate-based material by enantioselective auto-assembling of Mn2+ and (rac)-[Cr(C2O4)3]3− templated by the optically active complex (+)-(Rp)-[1-CH2(n-C3H7)3-2-CH3(C5H3)Fe(C5H5)]+, we obtained the unexpected 2D network species {NH(n-C3H7)3[MnCr(C2O4)3]}. X-ray diffraction determination of the structure reveals that the complex crystallizes in the enantiomorphous space group P63. The interlayer spacing of 7.93 Å is the lowest found so far for 2D, bimetallic, oxalate-bridged compounds.

Enantiomerically pure quaternary ammonium salts with a chiral alkyl chain N(CH3)(n-C3H7)2(sec-C4H9)I: Synthesis and physical studies†‡

A pair of enantiomerically pure quaternary ammonium salts with a chiral side chain, methyl-(R)-(1-methylpropyl)di(n-propyl)ammonium iodide 1 and methyl-(S)-(1-methylpropyl)di(n-propyl)ammonium iodide 2, and the related racemate, methyl-(rac)-(1-methylpropyl)di(n-propyl)ammonium iodide 3, were synthesized through a reductive alkylation procedure, starting from enantiomerically pure and, also, racemic forms of (rac)-(1-methylpropyl)amine. A spectroscopic chiroptical signature in solution was provided by the Raman optical activity spectra of compounds 1 and 2. The crystallographic structures of 1, 2, and 3 were examined by single crystal X-ray diffraction. 1 crystallizes in the tetragonal space group P4(3)2(1)2 (no. 96), a = b = 12.826 (2) A, c = 17.730 (2) A, V = 2916.9 (5) A(3), Z = 8, Flack coefficient 0.04 (2). 2 crystallizes in the tetragonal space group P4(1)2(1)2 (no. 92), a = b = 12.842 (1) A, c = 17.749 (2) A, V = 2927.0 (5) A(3), Z = 8, Flack coefficient 0.05 (2). The crystal structures and space groups for 1 and 2 are enantiomorphs and the crystallographic investigation confirmed the absolute configuration of the stereocenter in both compounds. 3 crystallizes in the monoclinic space group P2(1)/n(no. 14), a = 8.178 (1) A, b = 14.309 (2) A, c = 12.328 (2) A, beta = 96.811 (6) degrees, V = 1432.4 (2) A(3), Z = 4.

Les cations ammoniums chiraux de type [R1R2R3R4N]+, de nouveaux templates pour les réseaux bimétalliques à pont oxalate

Resume Ce travail decrit l’obtention de nouveaux composes bimetalliques a pont oxalate [R 1 R 2 R 3 R 4 N][MnCr(C 2 O 4 ) 3 ], dont les cations assembleurs sont des ammoniums chiraux de formule [R 1 R 2 R 3 R 4 N] + , pour lesquels R represente un groupement n -alkyle variant de methyle a dodecyle. Pour citer cet article : M. Gruselle et al., C. R. Chimie 6 (2003).

Charge stabilization in cationic anthronyl-substituted alkynes: synthesis, characterization and X-ray molecular structures of M2L6 complexed alkynyl-substituted C10-anthrone [M2L6(μ,η2,η2-R2CCC(OR1)(C13H8O))] (M2L6 Co2(CO)6, MoCoCp(CO)5)

Abstract A series of the novel M 2 L 6 -complexed alkynyl-substituted C10-anthrone derivatives were prepared and fully characterized. Furthermore, the X-ray molecular structures of three complexes belonging to this family were determined with the general formula M 2 L 6 ( μ , η 2 , η 2 -R 3 CCC(OR 1 )(C 13 H 8 O))], M 2 L 6  Co 2 ( CO ) 6 . R 1  CH 3 . R 2  H 5; M 2 L 6  MoCOCp ( CO ) 5 . R 1  CH 3 , R 2  H 7 and M 2 L 6  CO 2 ( CO ) 6 . R 1  CH 3 , R 2  C 6 H 5 8. Addition of HBF 4 to the compounds [MoCoCp(CO) 5 ( μ , η 2 , η 2 -HCCC(OR 1 )(C 13 H 8 O))], R 1 H 6: R 1 CH 1 7, produced the cationic counterpart [MoCOCp(CO) 5 ( μ , η 2 , η 2 -HCCC(C 13 H 8 O))] + BF 4 9 The charge stabilization in this novel carbenium ion possessing an anthrone fragment was investigated and showed that the dinuclear cluster alleviates the positive charge at the C10 carbon center. Further, the reactivity of these carbenium ion towards nucleophiles was also examined.