•An enantiopure molecular cage was used for mediating a chiral photodimerization.•The intrinsically chiral cage demonstrated efficiency in the chiral induction.•External factors play a remarkable role in the supramolecular photochirogenesis.Photochirogenesis through supramolecular assembly provides an intriguing approach to the highly challenging research field of chiral photochemistry. In the present paper, an enantiopure coordination self-assembly cage (cage T) has been employed for mediating the enantiodifferentiating [4 + 4] photocyclodimerization of 2-anthracenecarboxylate (AC) in aqueous medium. The complexing behavior of AC with the cage T has been investigated by UV–vis, circular dichroism and NMR spectral studies. It was found that in aqueous solution, cage T could form both 1:1 and 1:2 host–guest complexes with AC. Photocyclodimerization of AC mediated by cage T were studied at different temperatures and different host/guest ratios. The anti-HT photodimer dominate the photocyclodimerization of AC with cage T. In the presence of an enantiopure cage T, the chiral syn-HT and anti-HH photodimers were produced in moderate enantioselectivity. The enantiodifferentiating mechanism of this supramolecular photochirogenesis system and the effects of external factors are discussed.

In this paper, a water-soluble racemic self-assembled tetrahedral cage [Fe4L6]4− was successfully resolved into their ΔΔΔΔ and ΛΛΛΛ enantiomers by (R)-/(S)-1,1′-bi-2-naphthol. The enantiomeric excess of the resolved Fe(II) cage was 99%.

A novel chiral stationary phase was synthesized by immobilizing heptakis(6-azido-6-deoxy-2,3-di-O-p-chlorophenylcarbamoylated)-β-cyclodextrin onto silica gel surface via Staudinger reaction, and applied in enantiomeric separation of a pair of osmabenzene complexes, {Os[CHC(PPh3)CHC(PPh3)CH](C9H6NO)2}Cl (1), which is the first report for enantioseparation of the chiral-only-at-metal osmabenzene complex till now. The effects of separation conditions including salt additives, organic modifiers, pH values, and column temperature on the retention and resolution of the complex have been investigated in detail. Meanwhile, possible chiral recognition mechanism was presented. Chiral complex 1 was well resolved via semi-preparative chiral HPLC technique under optimization conditions and two pure enantiomers were further characterized by analytical HPLC, NMR spectra and solution circular dichroism (CD) spectra, respectively. Furthermore, absolute configuration of the enantiomer was confirmed by theoretical investigation of CD spectra.Highlights► Synthesis of a novel CD-based CSP with multi-urea linkage via Staudinger reaction. ► Separation of a chiral-only-at-metal osmabenzene complex on MCDP column firstly. ► Effect of chromatographic conditions. ► Configuration of enantiomer determined by theoretical calculation of CD spectra.

Chiral tetrakis(β-diketonate) Ln(III) complexes Δ-[NaLa(d-hfc)4(CH3CN)] (1) and Λ-[NaLa(l-hfc)4 (CH3CN)] (2) (d/l-hfc− = 3-heptafluo-robutylryl-(+)/(−)-camphorate) are a pair of enantiomers and crystallize in the same Sohncke space group (P212121) with dodecahedral (DD) geometry. Typically positive and negative exciton splitting patterns around 320 nm were observed in the solid-state circular dichroism (CD) spectra of complexes 1 and 2, which indicate that their shell configurational chiralities are Δ and Λ, respectively. The apparent bisignate couplets in the solid-state CD spectra of [CsLn(d-hfc)4(H2O)] [Ln = La (3), Yb (5)] and [CsLn(l-hfc)4(H2O)] [Ln = La (4), Yb (6)] show that they are a pair of enantiomers and their absolute configurations are denoted Δ and Λ, respectively. The crystallographic data of 5 reveals that its coordination polyhedron is the square antiprism (SAP) geometry and it undergoes a phase transition from triclinic (α phase, P1) to monoclinic (β phase, C2) upon cooling. The difference between the two phases is brought about by the temperature dependent behaviour of the coordination water molecules, but this did not affect the configurational chirality of the Δ-SAP-[Yb(d-hfc)4]− moiety. Furthermore, time-dependent CD, UV-vis and 19F NMR were applied to study the solution behavior of these complexes. It was found that the chiral-at-metal stability of the three pairs of complexes is different and affected by both the Ln3+ and M+ ion size. The results show that the Cs+ cation can retain the metal center chirality and stablize the structures of [Ln(d/l-hfc)4]− or the dissociated tris(d/l-hfc)Ln(III) species in solution for a longer time than that of the Na+ cation, and it is important that the Cs+ ion successfully lock the configurational chirality around the Yb3+ center of the complex species in solution. This is reasoned by the short Cs+⋯FC, Cs+⋯O–Yb and Cs+⋯Yb3+ interactions observed in the crystal structure of α-5 and further confirmed by the chiral self-assembly of 5 or 6 from [Yb(H2O)(d/l-hfc)3] induced by CsI in a CHCl3 solution.

The effect of chiral metal complexes ([Co(en)3]I3·H2O, cis-[CoBr(NH3)(en)2]Br2, K[Co(edta)]·2H2O and [Ru(phen)3](PF6)2) on the polymer-bound J-aggregates in aqueous mixtures of pesudoisocyanine (PIC) iodine and poly(acrylic acid, sodium)(PAAS) have been studied by UV–vis absorption, circular dichroism (CD) and fluorescence spectra. At low concentration, the PIC monomers could self-assemble to form supermolecules by binding to each of the COO−groups on the polymer chains through electrostatic interactions. After the addition of chiral metal complexes to the formed PIC-PAAS J-aggregates, we found that only the chiral multiple π-conjugated phenanthroline metal complexes could transfer their metal-centered chiral information to the formed J-aggregates. The chiral J-aggregates showed a characteristic induced circular dichroism (ICD) in the visible region of J-band chromophore, and the ICD signals depend on the absolute configuration, concentration of the chiral multiple π-conjugated metal complexes, as well as temperature. More interestingly, the supramolecular chirality of the polymer supported PIC J-aggregates could be memorized even after the addition of an excess opposite chiral complex enantiomers. This is in sharp contrast to the behavior in the high concentrated NaCl induced PIC-J aggregates, in which the optical rotation of a mixture of two enantiomers varies linearly with their ratio.

The present work examines the relationship between the crystal structures and chiroptical properties of four chiral Yb(III) complexes with camphor-derivative β-diketone ligands by means of solid-state circular dichroism (CD) spectroscopy. For the seven-coordinate complexes, [Yb(H2O)(d-hfc)3] (I) and [Yb(H2O)(l-hfc)3] (II) (d/l-hfc− = 3-heptafluorobutyryl-(+)/(−)-camphorate), the Λ- and Δ-diastereomers coexist in their crystals and no apparent bisignate couplets are observed in their solid-state CD spectra. A theoretical study indicates that the ground-state energy difference between the two diastereomers I and II is only 0.913 kcal mol−1, which explains why they could coexist in a crystal environment with the ratio of 1:1. While, eight-coordinate complexes Δ-[Yb(TPPO)2(d-hfc)3]·CHCl3·3C6H12 (III) and Λ-[Yb(TPPO)2(l-hfc)3]·CHCl3·3C6H12 (IV) (TPPO = triphenylphosphine oxide) are enantiopure in the solid-state, and typically negative and positive exciton splitting patterns around 330 nm are observed in their solid-state CD spectra. The solid-state CD spectra of these four complexes are in accordance with their X-ray single-crystal analyses. Besides, their solution CD spectra show that no particular isomer predominates in solution.

Λ- and Δ-enantiomers of cis-[CoBr(NH3)(en)2]Br2 were obtained by absolute asymmetric synthesis. The interactions between the achiral 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and two chiral cationic Co(III) complexes were studied by UV-vis spectroscopy, circular dichroism (CD), fluorescence spectroscopy and atomic force microscopy (AFM). It was found that the cationic Co(III) complexes can induce the formation of chiral porphyrin J-aggregates, that the metal-centered chirality can be transferred to the J-aggregates, and that the chirality was able to be memorized and amplified in the porphyrin J-aggregates. Therefore, this should be a good chiral model for understanding similar processes in physical and biological systems.

The oxalato-bridged dicopper(II) complexes [Cu2(μ-ox)(LRR)2(H2O)2(ClO4)2] (1), [Cu2(μ-ox)(LRR)2(CH3COCH3)2(ClO4)2](1a), [Cu2(μ-ox)(LSS)2(H2O)2(ClO4)2] (2) and [Cu2(μ-ox)(LRR)(LSS)2(CH3COCH3)2(ClO4)2] (3) [LRR = (8R,10R)-(−)-[4,5]-pineno-2,2′-bipyridine, LSS = (8S,10S)-(+)-[4,5]-pineno-2,2′-bipyridine; ox2− = oxalate] were first prepared. A possible mechanism for the formation of the chial dicopper(II) complexes was proposed. Based on elemental analysis, conductance measurement, UV-Vis spectra, CD spectra and X-ray single-crystal diffraction, the oxalato-bridged structures of 1 and 2 were deduced to adopt two Cu(II) ions and the bridged oxalate lying in the nearly same plane. The crystal structures of 1a and 3 reveal that the coordination geometry around each Cu(II) ion is an elongated and distorted octahedron and two axial solvent molecules and two perchlorate ions are anti to each other respectively in both binuclear molecules. The solution CD spectra of 1 and 2 in the visible d-d range show very weak Cotton effects with peaks at 588 and 779 nm, which are approximately of mirror image, suggesting the optical activities may be derived from the vicinal effects of the chiragenic centers at the pinene group of LRR and LSS, respectively. Complex 1 has been characterized by variable-temperature magnetic susceptibility and the data was least-square fitted to the Blenaey-Bowers equation. The exchange integral J was found to be −338.41(4) cm−1 indicating a strong antiferromagnetic interaction between two copper(II) ions.

Eight-coordinate chiral lanthanide complexes [Eu(dbm)3LRR] (1), [Eu(dbm)3LSS] (2) and [Tb(dbm)3LRR] (3) (LRR/LSS = (-)-/(+)-4,5-pineno-2,2′-bipyridine, Hdbm = dibenzoylmethane) were synthesized stereoselectively, which were characterized by UV-vis, CD spectra and X-ray single-crystal diffraction. The mirror-image structure features of complexes 1 and 2 were obtained by combination of the solid-state CD spectra and the crystal structure analysis. After further comparison with the solid-state CD spectra of six-coordinate and seven-coordinate metal complexes containing β-diketone ligands, the CD spectra-absolute configuration correlation rule for the eight-coordinate β-diketonate lanthanide complexes was proposed through the exciton chirality method for the first time. The Δ or Λ absolute configurations of complexes 1–3 with the distorted square antiprism geometry were confirmed by the X-ray single-crystal analysis.

Two sets of diastereomers of pentacoordinate spirophosphoranes separately derived from l-valine (or d-valine) and l-leucine (or d-leucine) were synthesized, isolated, and structurally characterized both in the solid state (X-ray crystallography and solid-state CD spectroscopy) and in the solution (1H NMR). The Λ and Δ absolute configurations of a pair of enantiomers 3a and 4a with distorted trigonal bipyramids (TBPs) geometry are directly determined by X-ray diffraction analysis, respectively. The chiral-at-phosphorus features of the related diastereomers were correlated with their solid-state CD and 1H NMR spectra.(3S,5Λ,8S)-3,8-Di(propan-2-yl)-1,6-dioxa-4,9-diaza-5λ5-phosphaspiro[4.4]-nonane-2,7-dioneC10H19N2O4P[α]D20=-60.3 (c 1.0, DMSO)Absolute configuration: (3S,5Λ,8S)(3S,5Δ,8S)-3,8-Di(propan-2-yl)-1,6-dioxa-4,9-diaza-5λ5-phosphaspiro[4.4]-nonane-2,7-dioneC10H19N2O4P[α]D20=+22.6 (c 1.0, DMSO)Absolute configuration: (3S,5Δ,8S)(3R,5Δ,8R)-3,8-Di(propan-2-yl)-1,6-dioxa-4,9-diaza-5λ5-phosphaspiro[4.4]-nonane-2,7-dioneC10H19N2O4P[α]D20=+60.1 (c 1.0, DMSO)Absolute configuration: (3R,5Δ,8R)(3R,5Λ,8R)-3,8-Di(propan-2-yl)-1,6-dioxa-4,9-diaza-5λ5-phosphaspiro[4.4]-nonane-2,7-dioneC10H19N2O4P[α]D20=-22.6 (c 1.0, DMSO)Absolute configuration: (3R,5Λ,8R)(3S,5Λ,8S)-3,8-Bis(2-methylpropyl)-1,6-dioxa-4,9-diaza-5λ5-phosphaspiro[4.4]-nonane-2,7-dioneC12H23N2O4P[α]D20=-55.7 (c 1.0, acetone)Absolute configuration: (3S,5Λ,8S)(3S,5Δ,8S)-3,8-Bis(2-methylpropyl)-1,6-dioxa-4,9-diaza-5λ5-phosphaspiro[4.4]-nonane-2,7-dioneC12H23N2O4P[α]D20=+31.7 (c 1.0, acetone)Absolute configuration: (3S,5Δ,8S)(3R,5Δ,8R)-3,8-Bis(2-methylpropyl)-1,6-dioxa-4,9-diaza-5λ5-phosphaspiro[4.4]-nonane-2,7-dioneC12H23N2O4P[α]D20=+55.4 (c 1.0, acetone)Absolute configuration: (3R,5Δ,8R)(3R,5Λ,8R)-3,8-Bis(2-methylpropyl)-1,6-dioxa-4,9-diaza-5λ5-phosphaspiro[4.4]-nonane-2,7-dioneC12H23N2O4P[α]D20=-31.9 (c 1.0, acetone)Absolute configuration: (3R,5Λ,8R)

Unsymmetric Schiff base complexes have attracted more attention in recent years due to their diverse effects in catalytic reactions. Due to their high dissymmetry, unsymmetric metallosalen complexes are harder to prepare than symmetric ones. This means that X-ray crystallographic structural determination is sometimes unavailable, so their absolute configurations are determined by circular dichroism (CD) spectroscopy instead. Herein, some quadridentate unsymmetric metallosalen nickel(II) complexes were synthesized and their structures were characterized by CD spectra. An empirical rule for assignment of the absolute configurations of tetra-coordinated pseudo-planar Ni(II) complexes was put forward. Furthermore, a fingerprint was found to judge whether the metallosalen complexes are symmetric or unsymmetric.

Chiral tetrakis(β-diketonate) Ln(III) complexes Δ-[NaLa(d-hfc)4(CH3CN)] (1) and Λ-[NaLa(l-hfc)4 (CH3CN)] (2) (d/l-hfc− = 3-heptafluo-robutylryl-(+)/(−)-camphorate) are a pair of enantiomers and crystallize in the same Sohncke space group (P212121) with dodecahedral (DD) geometry. Typically positive and negative exciton splitting patterns around 320 nm were observed in the solid-state circular dichroism (CD) spectra of complexes 1 and 2, which indicate that their shell configurational chiralities are Δ and Λ, respectively. The apparent bisignate couplets in the solid-state CD spectra of [CsLn(d-hfc)4(H2O)] [Ln = La (3), Yb (5)] and [CsLn(l-hfc)4(H2O)] [Ln = La (4), Yb (6)] show that they are a pair of enantiomers and their absolute configurations are denoted Δ and Λ, respectively. The crystallographic data of 5 reveals that its coordination polyhedron is the square antiprism (SAP) geometry and it undergoes a phase transition from triclinic (α phase, P1) to monoclinic (β phase, C2) upon cooling. The difference between the two phases is brought about by the temperature dependent behaviour of the coordination water molecules, but this did not affect the configurational chirality of the Δ-SAP-[Yb(d-hfc)4]− moiety. Furthermore, time-dependent CD, UV-vis and 19F NMR were applied to study the solution behavior of these complexes. It was found that the chiral-at-metal stability of the three pairs of complexes is different and affected by both the Ln3+ and M+ ion size. The results show that the Cs+ cation can retain the metal center chirality and stablize the structures of [Ln(d/l-hfc)4]− or the dissociated tris(d/l-hfc)Ln(III) species in solution for a longer time than that of the Na+ cation, and it is important that the Cs+ ion successfully lock the configurational chirality around the Yb3+ center of the complex species in solution. This is reasoned by the short Cs+⋯FC, Cs+⋯O–Yb and Cs+⋯Yb3+ interactions observed in the crystal structure of α-5 and further confirmed by the chiral self-assembly of 5 or 6 from [Yb(H2O)(d/l-hfc)3] induced by CsI in a CHCl3 solution.

The effect of chiral metal complexes ([Co(en)3]I3·H2O, cis-[CoBr(NH3)(en)2]Br2, K[Co(edta)]·2H2O and [Ru(phen)3](PF6)2) on the polymer-bound J-aggregates in aqueous mixtures of pesudoisocyanine (PIC) iodine and poly(acrylic acid, sodium)(PAAS) have been studied by UV–vis absorption, circular dichroism (CD) and fluorescence spectra. At low concentration, the PIC monomers could self-assemble to form supermolecules by binding to each of the COO−groups on the polymer chains through electrostatic interactions. After the addition of chiral metal complexes to the formed PIC-PAAS J-aggregates, we found that only the chiral multiple π-conjugated phenanthroline metal complexes could transfer their metal-centered chiral information to the formed J-aggregates. The chiral J-aggregates showed a characteristic induced circular dichroism (ICD) in the visible region of J-band chromophore, and the ICD signals depend on the absolute configuration, concentration of the chiral multiple π-conjugated metal complexes, as well as temperature. More interestingly, the supramolecular chirality of the polymer supported PIC J-aggregates could be memorized even after the addition of an excess opposite chiral complex enantiomers. This is in sharp contrast to the behavior in the high concentrated NaCl induced PIC-J aggregates, in which the optical rotation of a mixture of two enantiomers varies linearly with their ratio.

In this paper, a water-soluble racemic self-assembled tetrahedral cage [Fe4L6]4− was successfully resolved into their ΔΔΔΔ and ΛΛΛΛ enantiomers by (R)-/(S)-1,1′-bi-2-naphthol. The enantiomeric excess of the resolved Fe(II) cage was 99%.