Non-stochastic homochiral helix crystallization: cryptochirality in control?

Vestergren, Marcus; Johansson, Anna; Lennartson, Anders; Håkansson, Mikael

doi:10.1070/mc2004v014n06abeh002009

Cited by 25 publications

(25 citation statements)

References 27 publications

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“…In other words, all batches were essentially enantiopure showing that preferential crystallization had been successful. In contrast to recently published results concerning total spontaneous resolution of a copper(i) coordination helix, [28] a stochastic distribution of L and D crystal batches of 1-3 was found.…”

Section: Resultscontrasting

confidence: 79%

“…Crystallographic data for complexes 2-6. 153 (2) 193 (2) 143 (2) 123 (2) 123 (2) [8,9,[26][27][28] that yield enantiopure crystal batches without stirring. In these cases preferential crystallization is achieved by single-colony growth, a mechanism that also depends on secondary nucleation.…”

Section: Resultsmentioning

confidence: 99%

“…Solutions of enantiopure samples of 1-3 are CD silent owing to rapid racemization in solution, but solid-state CD spectroscopy is a viable option. [27][28][29] Indeed, by grinding a single crystal of L-3 with KBr and pressing a thin disk (the disk preparation is similar to IR spectroscopy, but much less sample is needed and thorough grinding is essential) it is possible to record the CD spectrum of the L enantiomer. The absolute configuration of the crystal was known since diffraction data (including Friedel pairs) could be collected by using the very same crystal before grinding.…”

Section: Resultsmentioning

confidence: 99%

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Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Johansson

Håkansson

2005

Chemistry A European J

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Helical complexes formed between aluminum tris(2,6-diphenylphenoxide) (ATPH) and five different aldehydes have been prepared and structurally characterized by X-ray diffraction. It was found that [Al(OC6H3Ph2)3PhCHO] (2), [Al(OC6H3Ph2)3(4-CH3C6H4CHO)] (3), [Al(OC6H3Ph2)3(4-tBuC6H4CHO)] (4), and [Al(OC6H3Ph2)3(p-CH3OC6H4CHO)] (5) all crystallize as conglomerates, while crystals of [Al(OC6H3Ph2)3(o-CH3OC6H4CHO)] (6) are racemic. Supramolecular CH/pi interactions between molecules in crystals of 2-5 that enable stereochemical information to be mediated in three dimensions have been identified and explain the high frequency of conglomerate formation among ATPH helicates. Since 2-5 are stereochemically labile and thus enantiomerize rapidly in solution, the conglomerates can be resolved by crystallization-induced asymmetric transformation. The determination of the enantiomeric excess (ee) in solid samples of stereochemically labile molecules is not trivial, but solid-state CD spectroscopic data, anomalous dispersion data, and the ee values in alkylation reactions all indicate that preferential crystallization of 2-5 yields an essentially enantiopure product. Thus the preparation of 2-5 constitute new examples of absolute asymmetric synthesis. The helical chirality can be transferred (and thus trapped) to alcohols (with ee values of up to 16%) in crystal-to-crystal reactions with achiral organometallic reagents.

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Section: Resultscontrasting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Johansson

Håkansson

2005

Chemistry A European J

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“…A similar type of helical polymer, containing the repeating tetranuclear unit [Cu 4 Cl 4 (triallylamine) 4 ] ϱ , has also been reported by Hakansson et al [10] The only difference between the two polymers is the pitch of the helix, which differs by ca. 0.4 Å.…”

Section: Description Of the Structuresmentioning

confidence: 69%

Synthesis and Characterisation of a New Cu(O₂CNAllyl₂)₂ Carbamato Complex and an Unusual Polymeric Cu^I Complex [Cu^I₄Cl₄(NHAllyl₂)₄]_n: New Insights into Metal Carbamato Chemistry

et al. 2009

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Transition‐metal N,N‐dialkylcarbamato complexes represent an interesting class of compounds that can be conveniently used as precursors for the controlled formation of inorganic compounds, typically oxides. They can also be used as convenient precursors for chemical grafting of metal oxides on oxide surfaces as well as for the synthesis of inorganic–organic hybrid materials. In this last case, the presence of double bonds on the complex would enable its covalent embedding into a polymer matrix through reaction with suitable monomers. To this aim, we addressed the synthesis of an allyl‐functionalised copper carbamato complex. During the synthesis of the N,N‐diallylcarbamato complex Cu(O2CNAllyl2)2 (Cu1), the formation of the crystalline and unusual polymeric CuI complex [CuI4Cl4(NHAllyl2)4]n (Cu2) was observed. The new compound was characterised by X‐ray single crystal diffraction and FTIR, 1H and 13C NMR spectroscopic analysis. In an attempt to investigate the redox mechanism and the equilibria leading to the formation of the observed unusual CuI polymeric complex, gas chromatography coupled with mass spectrometry (GC–MS) experiments were carried out, which allowed us to identify 3,4‐dimethylpyrrole as the oxidation product of the reaction, leading to the reduction of CuII to CuI.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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“…This implies a stochastic distribution of handedness in experiments in which crystallisation proceeds without seeding, in contrast to recently reported results. [11] Seeding can, of course, be used to predetermine which enantiomorph is formed. The usefulness of solid-state CD spectroscopy as a tool for quantitative ee determination and thus for assessing total spontaneous resolution of the bulk product, [2] has been further demonstrated here.…”

Section: Resultsmentioning

confidence: 99%

Total Spontaneous Resolution of Chiral Covalent Networks from Stereochemically Labile Metal Complexes

Johansson

Håkansson

Jagner

2005

Chemistry A European J

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Stereochemically labile copper and zinc complexes with the N,N'-dimethylethylenediamine ligand (dmeda) have been shown to be promising precursors for the total spontaneous resolution of chiral covalent networks. (N,N')-[Cu(NO3)2(dmeda)]infinity crystallises as a conglomerate and yields either enantiopure (R,R)-1 or enantiopure (S,S)-1. A mixed-valence copper(I/II) complex, [{Cu(II)Br2(dmeda)}3(Cu(I)Br)2]infinity (2), which crystallises as a pair of interpenetrating chiral (10,3)-a nets, is formed from CuBr, CuBr2 and dmeda. One net contains ligands with solely (R,R) configuration and exhibits helices with (P) configuration while the other has solely (S,S)-dmeda ligands and gives rise to a net in which the helices have (M) configuration. The whole crystalline arrangement is racemic, because the interpenetrating chiral nets are of opposite handedness. With zinc chloride (R,S)-[ZnCl(dmeda)2]2[ZnCl4] (3) is obtained, which is a network structure, although not chiral. Total spontaneous resolution of stereochemically labile metal complexes formed from achiral or racemic building blocks is suggested as a viable route for the preparation of covalent chiral networks. Once the absolute structure of the compound has been determined by X-ray crystallography, a quantitative determination of the enantiomeric excess of the bulk product can be undertaken by means of solid-state CD spectroscopy.

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Non-stochastic homochiral helix crystallization: cryptochirality in control?

Cited by 25 publications

References 27 publications

Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Synthesis and Characterisation of a New Cu(O₂CNAllyl₂)₂ Carbamato Complex and an Unusual Polymeric Cu^I Complex [Cu^I₄Cl₄(NHAllyl₂)₄]_n: New Insights into Metal Carbamato Chemistry

Total Spontaneous Resolution of Chiral Covalent Networks from Stereochemically Labile Metal Complexes

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Non-stochastic homochiral helix crystallization: cryptochirality in control?

Cited by 25 publications

References 27 publications

Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Synthesis and Characterisation of a New Cu(O2CNAllyl2)2 Carbamato Complex and an Unusual Polymeric CuI Complex [CuI4Cl4(NHAllyl2)4]n: New Insights into Metal Carbamato Chemistry

Total Spontaneous Resolution of Chiral Covalent Networks from Stereochemically Labile Metal Complexes

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Synthesis and Characterisation of a New Cu(O₂CNAllyl₂)₂ Carbamato Complex and an Unusual Polymeric Cu^I Complex [Cu^I₄Cl₄(NHAllyl₂)₄]_n: New Insights into Metal Carbamato Chemistry