Abstract Initial efforts to combine a chiral metal–organic framework (MOF), Co(D‐Cam)1/2(bdc)1/2(tmdpy) (D‐Cam=D‐camphoric acid, bdc=1,4‐benzenedicarboxylic acid, tmdpy=4,4′‐trimethylenedipyridine), with peramylated β‐cyclodextrins to investigate whether the use of a MOF can enhance enantioseparations on a cyclodextrin stationary phase are reported. Compared with columns of peramylated β‐cyclodextrin incorporated in a MOF containing sodium chloride, the column of peramylated β‐cyclodextrin+MOF shows excellent selectivity for the recognition of racemates, and higher resolutions are achieved on the peramylated β‐cyclodextrin+MOF stationary phase. Experimental results indicate that the use of Co(D‐Cam)1/2(bdc)1/2(tmdpy) can improve enantioseparations on peramylated β‐cyclodextrins. This is the first report that chiral MOFs can improve enantioseparations on a chiral stationary phase for chromatography.

Chiral metal–organic framework used as stationary phases for capillary electrochromatography

Two novel coordination polymers, [Zn2(CAM)2(Titmb)] (I) and [Zn4Co(OH)2(BTEC)2 (Titmb)2(H2O)2] · 2H2O (II) (H2CAM = camphor acid, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid, and Titmb = 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene), have been hydrothermal prepared and characterized by IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Complex I displays an unusual three-dimensional (3,4,6)-connected network with (4.64.8)2(42.64.89)(62.8)2 topology. Complex II exhibits an interesting heterometallic 3D metal-organic framework. Moreover, the luminescent properties of I have been investigated in the solid state at room temperature.

Abstract In the search of novel potent bioactive compounds, 18 novel camphoric acid-based acylhydrazone compounds 4a–4r were designed and synthesized by the condensation reaction of N-amino camphorimide (3) with substituted benzaldehyde based on camphoric acid as the starting material. The target compounds were characterized by means of Fourier transform infrared (FTIR), 1H nuclear magnetic resonance (NMR), 13C NMR, electrospray ionization-mass spectrometry (ESI-MS), and elemental analysis. The preliminary bioassay showed that the following camphoric acid-based compounds exhibited excellent antifungal activity with an inhibition ratio of 95% against Physalospora piricola at the concentration of 50 μg ml-1: o-bromophenyl acylhydrazone (4f), p-bromophenyl acylhydrazone (4g), p-methoxyphenyl acylhydrazone (4m), and p-hydroxyphenyl acylhydrazone (4p).

The acaricidal activities of (±)-camphor structural analogues against house dust mites were evaluated using the impregnated fabric disc bioassay. The acaricidal effects of camphor and its structural analogues were evaluated against Dermatophagoides farinae and D. pteronyssinus. Based on the LD50 values against D. farinae, (±)-camphor (0.95 µg cm(-2) ) was 38.75 times more effective than N,N-diethyl-m-toluamide (DEET) (36.81 µg cm(-2) ), followed by (+)-camphor (1.41 µg cm(-2) ), (-)-camphor (2.03 µg cm(-2) ) and (1R)-camphor oxime (3.31 µg cm(-2) ) in the impregnated fabric disc bioassay. However, camphor-10-sulfonic acid and camphoric acid had no observable activity against D. farinae or D. pteronyssinus. The acaricidal activities of camphor and its structural analogues against D. pteronyssinus were similar to those against D. farinae. These results indicate that camphor and its structural analogues are suitable for producing acaricidal agents against house dust mites.

Abstract A three‐dimensional (3D) homochiral metal‐organic coordination polymer with a 6‐connected 412.63 topology was synthesized hydrothermally, Cd4(D‐cam)4(bbbm)2 (1) [D‐H2cam = D‐(+)‐camphoric acid and bbbm = 1,1‐(1,4‐butanediyl)bis‐1H‐benzimidazole], which represents the first example of metal‐camphorate coordination polymers constructed from two types of dinuclear cadmium clusters [Cd2(O2C–)4] and a flexible bis(benzimidazole)‐based ligand. The thermal and photoluminescent properties of 1 were investigated.

Co-crystals comprising the active pharmaceutical ingredient 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, C12H10N4, and the chiral co-formers (+)-, (-)- and (rac)-camphoric acid (cam), C10H16O4, have been synthesized. Two different stoichiometries of the API and co-former are obtained, namely 1:1 and 3:2. Crystallization experiments suggest that the 3:2 co-crystal is kinetically favoured over the 1:1 co-crystal. Single-crystal X-ray diffraction analysis of the co-crystals reveals N-H...O hydrogen bonding as the primary driving force for crystallization of the supramolecular structures. The 1:1 co-crystal contains undulating hydrogen-bonded ribbons, in which the chiral cam molecules impart a helical twist. The 3:2 co-crystal contains discrete Z-shaped motifs comprising three molecules of the API and two molecules of cam. The 3:2 co-crystals with (+)-cam, (-)-cam (space group P21) and (rac)-cam (space group P21/n) are isostructural. The enantiomeric co-crystals contain pseudo-symmetry consistent with space group P21/n, and the co-crystal with (rac)-cam represents a solid solution between the co-crystals containing (+)-cam and (-)-cam.

Four complexes were obtained from reaction of uranyl nitrate with (1R,3S)-(+)-camphoric acid under solvo-/hydrothermal conditions with either acetonitrile or N-methyl-2-pyrrolidone (NMP) as the organic component. All complexes crystallize in chiral space groups and are enantiopure species. Complexes [(UO2)4(L)3(OH)2(H2O)4]·3H2O (1) and [(UO2)8K8(L)12(H2O)12]·H2O (2) were obtained in water–acetonitrile in the presence of LiOH or KOH in excess beyond or equal to that simply required to neutralize the acid, respectively. Whereas 1 is a 1D coordination polymer including hydroxide ions resulting from hydrolysis of the uranyl aqua-ion, 2 contains octanuclear uranyl camphorate cages analogous, but for their crystallographic symmetry, to those previously published; these cages are assembled into a 3D framework by bridging potassium ions. The two complexes obtained in water–NMP, [UO2(L)(NMP)] (3) and [(UO2)2Cu(L)3(NMP)2] (4), are devoid both of water molecules and any solvent-derived anions, and they crystallize as 2D assemblies. The sheets in 4, with a thickness of ~14 Å, display a central layer of copper(II) ions surrounded by two layers of uranyl ions. These and previous results suggest that solvo-/hydrothermal conditions using NMP provide a new means of avoiding the formation of uranyl-containing oligomeric or 1D polymeric hydrolysis products which are frequent and often unpredictable outcomes in the synthesis of uranyl–organic assemblies under aqueous conditions, especially in the presence of cosolvents which in themselves are susceptible to hydrolysis. The emission spectrum of compound 3 under excitation at 350 nm displays the usual vibronic fine structure in the ~460–600 nm range, while uranyl luminescence is quenched by Cu(II) cations in complex 4.

Crystal engineering approach has been successfully exploited in designing a new series of supramolecular gelators derived from (1R,3S)-(+)-camphoric acid (CA) and primary amines; facile synthesis o...

It is observed that conglomerate crystallization of achiral precursors yielding racemate metal organic frameworks/coordination polymers (MOFs/CPs) can be driven to absolute homochiral crystallization of the desired enantiomorph by utilizing a suitable chiral induction agent. In a series of crystallization experiments isostructural Zn and Co homochiral CPs (1P, 1M and 2P, 2M) are prepared using the achiral precursors. In the presence of enantiopure camphoric acid, the crystallization process prefers absolute chiral induction over conglomerate formation which is established by single crystal X-ray diffraction and CD spectroscopy.

Syntheses, structures and magnetic properties of one family of 3d–4f chiral metal-organic frameworks (MOFs) based on D(+)-camphoric acid

With the aim of integrating the inherent chirality of ligand and the chirality induced by conformational twists of the asymmetric skeleton of the ligand upon its coordination, (1R,3S)-1,2,2-trimethyl-3-{[5-(2-hydroxy)phenyl-1,3,4-oxadiazol-2-yl]}cyclopentanecarboxylic acid (H2L) was prepared from the acylation reaction of chiral camphoric acid with salicylhydrazide. The reactions of H2L with transition metal ions gave five coordination polymers {[Co(L)(py)2]·DMF}n (1), {[Ni(L)(py)2]·DMF}n (2), [Cu(L)(py)]n (3), [Zn2(L)2(py)2]n (4), and [Cd2(L)2(py)2]n (5). Complexes 1 and 2 show only right-handed helical chains with homochiral helical discrimination by interhelical nonclassic hydrogen bonds C–H···O. However, 3–5 contain right-handed and left-handed helical chains simultaneously, which are arranged alternately and interact with each other by π···π interactions for 3 and by interchain M–O–M linkage for 4 and 5, respectively. The chiralities of these compounds derive from the inherent chirality of the ligand, as well as from the conformational twists of the asymmetric ligand skeleton. The results also reveal the role of different metal ions in the construction of chiral coordination polymers. The fluorescent studies revealed emission bands assigned to intraligand transmission for complexes 1–5.

Synthesis, structure, luminescence and magnetic property of camphorate coordination polymers containing 5,6-dimethylbenzimidazole auxiliary ligand

Solid state solvation is employed to reduce self-absorption, a key loss mechanism in Luminescent Solar Concentrator (LSC) devices. For an example materials system consisting of poly(methylmethacrylate), Camphoric Acid Anhydride, and the laser dye 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7,-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) a substantial shift in DCJTB emission energy of 832.2 cm−1 is observed whilst no decrease in fluorescence quantum yield occurs. When extrapolated to an LSC device a 16.1% relative improvement in efficiency is predicted with a potential for 23.1% when employing stronger dielectric additives. For a range of dicyanomethylene based fluorophores the predicted improvement in LSC efficiency is from 17.5% to 24.4%.

Metal-organic frameworks have large surface area, highly ordered pore structure and good chemical stability. In this study, a porous chiral metal-organic framework InH(D-C10H14O4)2(D-C10H14O4 = D-(+)-camphoric acid) with a left-handed helical channel assembled from D-(+)-camphoric acid was used as chiral stationary phase in GC. InH(D-C10H14O4)2-coated open tubular columns with different inner diameters or lengths were prepared by a dynamic coating method for high-resolution GC separation of various types of organic compounds, including racemates, isomers, alkanes, alcohols, and Grob's test mixture. Their column efficiency, polarity, and selectivity were studied. The experimental results show that the stationary phase has excellent selectivity and also possesses good recognition ability toward these organic compounds, especially for chiral compounds.

A new monomer was prepared from (1R,3S)-(+)-camphoric acid. Novel polyimide and polyimide--clay hybrid composites were developed from one-pot condensation reactions of this monomer and pyromellitic dianhyride. Polyimide-montmorillonite nanocomposites were prepared from solution of polyimide and with different weight percentages (1, 5, 10 wt %) of organo-modified montmorillonite (OM-MMT) using N-methyl-2-pyrrolidone (NMP) as aprotic solvent. The reactive organoclay was formed by using hexadecylpyridinium chloride as a swelling agent for silicate layers of montmorillonite. The polyimide--clay composites films (PI--MMT) were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). All composites were subjected to differential scanning calorimetry measurements for the purpose of examining Tg from all compositions. The clay content significantly influenced the thermal behavior of the polymeric films, such as glass transition and decomposition temperatures of polyimide--clay composites. The glass transition temperatures of the composites were higher than that of the original polyimide. Their thermal decomposition temperatures (Td = temperature at 5% mass loss) were measured via thermogravimetric analysis and showed that the introduction of clay into polymer backbones increased thermal stability. SEM, XRD, and the other conventional techniques were used for structural characterization. Dispersion of the modified clay in the polyimide matrix resulted in nanostructured material containing intercalated polymer between the silicate layers. The morphology and properties of PI nanocomposites greatly depend on the functional groups of the organic modifiers, synthesis procedure, and structure of polyimide because of the chemical reactions and physical interactions involved.

A series of 3D homochiral manganese-lanthanide frameworks have been synthesized based on chiral camphoric acid. In the heterometallic features, D-camphoric acids are unprecedentedly embedded in three coordination modes.

A 3D chiral Co(II) coordination polymer featuring unique self-interpenetrating topology

Inclusion compounds based on metal–organic frameworks (MOFs) have promising practical application in gas storage, separation and fine purification of substances, as well as in catalysis. MOFs are crystalline compounds consisting of metal ions coordinated by bridging organic ligands that form porous structures. The kinetics of the thermal decomposition of the frameworks themselves, namely [Co2(camph)2bpy] and [Co2(asp)2bpy], was investigated (camph and asp are the anions of camphoric and aspartic acids, bpy is the organic amine, 4,4′-bipyridyl). The empty coordination polymer framework based on metal camphorates was thermally (kinetically) less stable than the polymer framework based on metal aspartate. A high kinetic stability of frameworks with aspartic complexes during heating was due to the entropic factor rather than the enthalpic one.

Two homochiral coordination polymers [Mn2(D-cam)2(2-Hpao)4]n (1) and [Co2(D-cam)2(3-abpt)2(H2O)3]n·5nH2O (2) were prepared with D-(+)-camphoric acid, and 1-D complex 1 featured good temperature-independent piezoelectric (6.9 pC N−1) and dielectric properties.