Solid-state CD Spectra Research Articles

Induced chirality at the surface: fixation of a dynamic M/P invertible helical Co3 complex on SiO2.

Dynamic M/P invertible helicity was successfully induced at a SiO2 surface immobilized with a dynamic helical trinuclear cobalt complex, [LCo3(NHMe2)6](OTf)3, using chiral ((R) or (S))-1-phenylethylamine. Solid-state CD spectra and theoretical calculations suggested that the fixation of the M/P helical complex on the surface via coordination interactions was the key factor of the induced chirality at the surface.

The Research of G-Motif Construction and Chirality in Deoxyguanosine Monophosphate Nucleotide Complexes.

A detailed understanding of the mismatched base-pairing interactions in DNA will help reveal genetic diseases and provide a theoretical basis for the development of targeted drugs. Here, we utilized mononucleotide fragment to simulate mismatch DNA interactions in a local hydrophobic microenvironment. The bipyridyl-type bridging ligands were employed as a mild stabilizer to stabilize the GG mismatch containing complexes, allowing mismatch to be visualized based on X-ray crystallography. Five single crystals of 2′-deoxyguanosine–5′–monophosphate (dGMP) metal complexes were designed and obtained via the process of self-assembly. Crystallographic studies clearly reveal the details of the supramolecular interaction between mononucleotides and guest intercalators. A novel guanine–guanine base mismatch pattern with unusual (high anti)–(high anti) type of arrangement around the glycosidic angle conformations was successfully constructed. The solution state 1H–NMR, ESI–MS spectrum studies, and UV titration experiments emphasize the robustness of this g–motif in solution. Additionally, we combined the methods of single-crystal and solution-, solid-state CD spectrum together to discuss the chirality of the complexes. The complexes containing the g–motif structure, which reduces the energy of the system, following the solid-state CD signals, generally move in the long-wave direction. These results provided a new mismatched base pairing, that is g–motif. The interaction mode and full characterizations of g–motif will contribute to the study of the mismatched DNA interaction.

Lanthanide clusters of phenanthroline containing a pyridine-pyrazole based ligand: magnetism and cell imaging.

In this contribution, we report the synthesis, characterization and luminescence-magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+ and Tb3+) using a new pyridine-pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. The unorthodox N-rich ligand forms isostructural trinuclear lanthanide complexes with a topology that closely resembles two interdigitating hairpins. The clusters crystallize in chiral space groups and also exhibit chirality for bulk samples, which were further confirmed using solid state CD spectra. Magnetic studies on the complexes reveal their interesting features while the Gd cluster shows a significant cryogenic magnetic cooling behaviour with a moderately high magnetic entropy change of -23.42 J kg-1 K-1 at 7 T and 2 K. On the other hand, Eu and Tb complexes exhibit interesting fluorescence properties. The compounds were subsequently used as fluorescent probes for the imaging of human breast adenocarcinoma (MCF7) cells. Live cell confocal microscopy images show that the complexes penetrate beyond the usual cytoplasm region and can be useful in imaging the nucleus region of MCF7 cells.

Chiral 3D Coordination Polymers Consisting of Achiral Terpyridyl Precursors: from Spontaneous Resolution to Enantioenriched Induction.

A pair of enantiomers of three-dimensional (3D) chiral coordination polymers (CCPs) were successfully constructed by using achiral components 4,2':6',4''-terpyridyl precursors and Cu2+ through spontaneous resolution (1 a). By utilising feeding controlled chiral-templated induction and chiral auxiliary behaviour of optically pure camphor sulfonate (CSA), the enantioenriched (1 b-P and 1 b-M) and CSA captured (1 c-P and 1 c-M) CCPs were successfully synthesised, respectively. The chiral information of the corresponding products was confirmed by X-ray single crystal diffraction and solid-state CD spectra. Meanwhile, the formation processes of 1 b-P and 1 b-M were monitored through solution CD spectra, UV/Vis spectra and ESI-TOF MS. Based on these results, a reasonable chiral-templated induction mechanism of forming 1 b-P and 1 b-M was proposed.

Transition-metal(ii) complexes with a tripodal hexadentate ligand, 1,1,1-tris[2-aza-3-(imidazol-4-yl)prop-2-enyl]ethane, exhibiting incomplete total or absolute spontaneous resolution

Crystal structures and solid-state CD spectra of the compounds, [M(H3L)]Cl(ClO4) (M = Mn, Fe, Co, Ni and Zn) were examined.

Designing Multifunctional MOFs Using the Inorganic Motif [Cu3(μ3-OH)(μ-Pyz)] as an SBU and Their Properties

In a continuation of our interest in pyrazole-based multifunctional metal–organic frameworks (MOFs), we report herein the construction of a series of Cu(II) MOFs using pyrazole and various 5-substituted isophthalic acids. The central theme is to generate MOFs using the crystal engineering strategy of spacer and node; however, for the node we have introduced a well-known inorganic motif, a [Cu3(μ3-OH)(μ-Pyz)3] unit. The appearance of the SBU in five MOFs confirms the robustness and reproducibility of the motif with some interesting structures of various dimensionality ranging from 1D helical and 2D herringbone grid to a complex 3D framework. The deployment of bent acids brings chirality via helicity in the system, as further confirmed by solid-state CD spectra. A detailed investigation of the porous MOFs reveals their importance as zeolite analogues for environment remediation. MOF-1–MOF-5 show some interesting photodegradation of harmful organic dyes. MOF-4 and MOF-5 show impressive selective CO2 gas sorption properties. Furthermore, magnetic properties associated with the trinuclear and hexanuclear SBUs of MOF-1 and MOF-3–MOF-5 have also been investigated.

A pair of novel 4-connected homochiral coordination polymers based on proline-tetrazole ligand

A pair of novel 2D homochiral coordination polymers based on proline-tetrazole ligand, namely [Cd((S)-PTZ)2]n (1-L) and [Zn((S)-PTZ)2]n (2-L), were obtained and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, solid-state CD spectra, single-crystal X-ray crystallography and powder X-ray diffraction. The compounds 1-L and 2-L display 4-connected net and SHG response.

Molecular geometry and optical activity of helically chiral N-nitrosamines derived from 1,2,3,4-tetrahydro- and 1,2,3,4,7,8,9,10-octahydro-1,10-phenanthroline

X-ray crystallographic analysis of the title N-nitrosamines revealed that they assume helical conformations in the solid state. Nitrosamines 1b and 2b were resolved by inclusion crystallization with optically active diols (TADDOLs). The absolute configuration of the guest molecules in the complexes 1b·3b and 2b·3b was assigned as M. The optical activity of the resolved compounds is manifested by their solid state CD spectra, which showed relatively strong Cotton effects in the region of the nitrosamine n–π∗ transition. Theoretical calculations of the electronic and CD spectra performed by classic ab initio methods predicted the correct Cotton effect signs of 1b and 2b.

Coordination Driven Self-Assembly in Co(II) Coordination Polymers Displaying Unprecedented Topology, Water Cluster, Chirality, and Spin-Canted Magnetic Behavior

The present work reports facile synthesis, full characterization, and architectural diversity of seven Co(II) coordination polymers, namely, [{Co(H2MBP)2(12-CDA)}·CH3OH]∞ (1), [{Co(H2MBP)(12-CDA)(H2O)}]∞ (2), [{Co0.5(H2MBP)(14-CDA)0.5}·(H2O)2.5]∞ (3), [{Co(H2MBP)(14-CDA)(H2O)2}]∞ (4), [{Co(H2MBP)(13-ADA)0.5}]∞ (5), [{Co(H2MBP)2(135-CTA)(H2O)}(H2O)3.5]∞ (6), and [{Co2(μ2O)(H2MBP)3(1245-CHA)}(H2O)12]∞ (7), derived from a 4,4′-methylene bispyrazole (H2MBP) ligand and various flexible dicarboxylate coligands. The type of alicyclic flexible carboxylate coligand used in the synthesis and its coordination to the metal center play a key role in controlling the dimensionality and topology of the frameworks. Topological analysis of the simplified nets reveals that 1 and 3 possess a 4-connected sql topology, 2 features a 3-connected uninodal hcb topology, 5 contains a 3D cds topology, and 7 possesses an unprecedented new 3D topology. Interestingly, a well-resolved 1D water chain is found within 3 and the presence of a heptanuclear water cluster assisted via a free carboxylate group is observed in 6. Chirality associated with 5 has been supported by solid-state CD spectra, and variable-temperature magnetic studies indicate that 7 exhibits canted magnetic coupling between the carboxylate bridged Co(II) ions.

Spontaneous resolution upon crystallization of allenyl-bis-phosphine oxides.

The first example of 'spontaneous resolution by crystallization' in allene chemistry, by means of crystal structures and solid state CD spectra of the R and S enantiomers, is presented. These allenes are prepared by the simple reaction of Ph2PCl with o-nitro functionalized propargyl alcohols.

Synthesis, structure and characterization of three different dimension inorganic–organic hybrid vanadates: [Co2(mIM)5(H2O)2]V4O12, [Ni2(mIM)7(H2O)]V4O12·H2O and [Cd(eIM)2(H2O)]V2O6

Three novel inorganic–organic hybrid vanadates [Co2(mIM)5(H2O)2]V4O12 (1), [Ni2(mIM)7(H2O)]V4O12·H2O (2) and [Cd(eIM)2(H2O)]V2O6 (3) (mIM = 1-methylimidazole, eIM = 1-ethylimidazole) with different dimension structures were prepared by a hydrothermal synthetic approach. The distinct dimensions of the hybrid vanadate architectures can be affected by changing the reactant molar ratio, ligands and temperature. All three compounds were fully characterized by single crystal XRD, EA, TGA, XPS, IR and UV/Vis diffuse reflectance spectroscopy. Compound 1 exhibits an interesting 3D chiral framework which was prepared without any chiral source species. Compound 2 shows an interesting 2D folded structure and compound 3 presents a ladder-shaped 1D chain configuration. The solid-state CD spectrum of crystal 1 reveals strong Cotton effects between 200–375 nm and confirms the chiral characteristics of compound 1.

Variety of Crystal Structures of Chiral Schiff Base Lu(III)-Ni(II)/ Cu(II)/Zn(II) and the Related Complexes

New mononuclear [Cu2(L1)2(H2O)]2H2O・CH3OH] (cyCu)2, multinuclear [Cu2(L1)2K2][Ni(CN)4] (cyCuKNi), and dinuclear Ni(L1)Lu(NO3)3 (cyLuNi), Cu(L1)Lu(NO3)3 (cyLuCu) and Zn(L1)Lu[(NO3)2CH3COO]CH3OH (cyLuZn) complexes incorporating chiral Schiff base ligands were prepared and characterized by various techniques such as solid-state CD spectra, diffuse reflectance electronic spectra, IR spectra, and single crystal X-ray diffraction analysis. Crystal structures were also compared with previous ones, namely [Cu(L2)](H2O) (diCu), Cu(L1)Gd(NO3)3 (cyGdCu). Interestingly, determined crystal structures exhibited drastically different structural characteristics as regards coordination numbers, crystalline solvents, features and strain condition, nevertheless with little modification in 3d metal substitution and/or modified organic ligands. In this paper, comparison of common components of structures will be discussed systematically.

Spontaneous resolution of polyoxometalate-based inorganic-organic hybrids driven by solvent and common ion.

Three single-sided, triol-functionalized Anderson POM hybrids were successfully synthesized. With suitable solvents and the effect driven by common-ion synergy, enantiopure crystals were obtained when the spontaneous resolution of enantiomers occurred upon crystallization. The chirality of POM-organic hybrids was confirmed by single-crystal X-ray diffraction and solid-state CD spectrum. A reversible, spontaneous resolution process for POM-based inorganic-organic hybrids was observed in this work.

Chiral and achiral helical coordination polymers of zinc and cadmium from achiral 2,6-bis(imidazol-1-yl)pyridine: Solvent effect and spontaneous resolution

Four 2D helical coordination polymers (CPs) (1–4) were synthesized using achiral 2,6-bis (imidazol-1-yl)pyridine (pyim2) ligand with metal nitrates (metal = zinc and cadmium), which showed that variation in the solvent condition leads to difference in geometry around the central metal ion and results in chiral/achiral behaviour of these CPs. By using (pyim2), [trans-Zn(pyim2)2(NO3)2]n (1) was obtained by unary solvent (MeOH), while [trans- Cd(pyim2)2(NO3)2] n (2) was formed under binary solvent mixtures (DMF/MeOH). On the other hand, in ternary solvent mixture (DMF/MeOH/H2O) it resulted into an achiral {[trans-Zn(pyim2)2(H2O)2] ·(NO3)2}n (3) and homochiral {[cis-Cd(pyim2)2(H2O)2] ·(NO3)2}n (4) coordination polymer, respectively. The homochiral behaviour of the coordination polymer (4) was further studied by solid state CD spectra and also its optical behaviour was analyzed by polarimetry.

Development and Validation of a Method for the Analysis of Paroxetine HCl by Circular Dichroism

A simple, rapid, and sensitive method for the analysis of paroxetine, in tablets as well as the pure drug, by circular dichroism is described. The method was validated for repeatability, linearity, limit of detection, limit of quantification, and recovery according to the International Conference on Harmonization guidelines. Excellent results were obtained, within the globally accepted validation reference values, particularly taking into account the low concentration levels investigated. This is the first report of the quantitation of paroxetine, a chiral drug, without previous separation of the analyte. Additionally, the solid state CD spectrum of PXT was obtained.

VARIETY OF STRUCTURES OF BINUCLEAR CHIRAL SCHIFF BASE CE(III)/PR(III)/LU(III)-NI(II)/CU(II)/ZN(II) COMPLEXE

We have prepared and characterized several 3d-4f (Ni(II), Cu(II) and Zn(II) transition metal ions and Ce(III), Pr(III), and Lu(III) lanthanide metal ions) complexes incorpolating chiral Schiff base ligands (abbreviated as CeNi , CeCu , CeZn , PrNi , PrCu , PrZn , LuNi , LuCu , and LuZn , respectively). Solid-state CD spectra and diffuse reflectance electronic spectra exhibited reasonable shift by combination of 3d and 4f ions at charge-transfer region. Magnetic features (antiferromagnetic interactions, if any) also exhibited substitution of 3d-4f ions of siamagnetic or paramagnetic spin numbers. Interestingly, determined crystal structures of some of them exhibited different structural chacters about coordination numbers, crystalline solvents, and dimetic (or bridging) features nevertheless of 3d-4f metal substituion in identical organic ligands.

Magnetic and ferroelectric properties of a chiral cyano-bridged Pr(III)-Cr(III) complex

Abstract A novel chiral cyanide-bridged Pr(III)-Cr(III) bimetallic complex, [Pr(DMSO)4(H2O)3Cr(CN)6] (1) (DMSO = dimethylsulfoxide) has been prepared and characterized by single-crystal X-ray diffraction, IR, elemental analysis and solid-state CD spectra. Complex 1 crystallizes in the monoclinic with chiral space group P21 and displays as a dinuclear molecule. The solid-state CD spectra confirm the chiral nature of complex 1. Magnetic studies indicate ferromagnetic interactions between Pr(III) and Cr(III) ions. Ferroelectric measurements reveal that complex 1 exhibits ferroelectric features representing electric hysteresis loops at room temperature with remanent polarizations of 0.111 μC/cm2 and coercive electric fields of 4.13 kV/cm.

Anion and pH induced spontaneous resolution of Δ- and Λ-[M(H2Biim)3]SO4 (M = Ru2+, Co2+, Ni2+, Mn2+, Fe2+, and Zn2+) enantiomers

The homochiral self-assembly of [M(H2biim)3]SO4 (M2+ = Ru, 1; Co, 2; Ni, 3; Mn, 4; Fe, 5; and Zn, 6; H2biim = 2,2′-biimidazole) complexes have been systematically observed. For complexes 1 and 2, the spontaneous resolution processes not only depend on the counter anion but are also impacted by the pH value of the reaction solution. The enantiomers Δ-1 and Λ-1, and Δ-2 and Λ-2 were isolated in acidic conditions, while rac-1 and rac-2·5H2O were obtained in neutral conditions, respectively. For complexes 3–6, however, the spontaneous resolution processes are independent on the pH value of the reaction solution. Single crystal X-ray diffraction analysis reveals the enantiomers Δ and Λ are homochiral (10,3)-b three-dimensional networks constructed by the hydrogen bonds between the sulfate and H2biim ligand, whereas rac-1 assembles into (6,3) two-dimensional layers (see CrystEngComm, 2009, 11, 1114–1121) and rac-2 into one-dimensional chains. The data observed here seem to suggest that the hydrogen bonding modes between the sulfate and H2biim ligand play a crucial role in spontaneous resolution of the enantiomers. Furthermore, the solid state CD spectra and powder XRD patterns were also used to diagnose the obtained complexes.

A chiral tetranuclear copper(II) complex based on a new Schiff-base ligand: Synthesis, structure, magnetic property and CD spectra

New chiral Schiff-base ligand l-H2vap, derived from the condensation of o-vanillin and l-2-amino-3-phenyl-1-propanol, reacts with Cu(Ac)2·H2O and Gd(NO3)3·6H2O in the presence of triethylamine to produce a chiral tetranuclear complex l-[Cu4(Hvap)2(vap)2(MeOH)2](NO3)2·MeOH (1). The single-crystal X-ray diffraction analyses reveal that complex 1 crystallizes in the chiral monoclinic space group P21 with Z = 2. Four copper(II) atoms are held together by two alkoxide μ3-O2 − atoms and two phenoxide μ2-O2 − atoms from four individual ligands to form a boat-shaped {Cu4O4} unit. The solid-state CD spectra confirm the chiral nature of complex 1. Magnetic studies indicate that there are strong antiferromagnetic interactions between the adjacent copper(II) ions in complex 1.

Environmental Dependence of Artifact CD Peaks of Chiral Schiff Base 3d-4f Complexes in Soft Mater PMMA Matrix

Four chiral Schiff base binuclear 3d-4f complexes (NdNi, NdCu, GdNi, and GdCu) have been prepared and characterized by means of electronic and CD spectra, IR spectra, magnetic measurements, and X-ray crystallography (NdNi). A so-called artifact peak of solid state CD spectra, which was characteristic of oriented molecules without free molecular rotation, appeared at about 470 nm. Magnetic data of the complexes in the solid state (powder) and in PMMA cast films or solutions indicated that only GdCu preserved molecular structures in various matrixes of soft maters. For the first time, we have used the changes of intensity of artifact CD peaks to detect properties of environmental (media solid state (KBr pellets), PMMA cast films, concentration dependence of PMMA in acetone solutions, and pure acetone solution) for chiral 3d-4f complexes (GdCu). Rigid matrix keeping anisotropic orientation exhibited a decrease in the intensity of the artifact CD peak toward negative values. The present results suggest that solid state artifact CD peaks can be affected by environmental viscosity of a soft mater matrix.