Alcohol Ligands Research Articles

Linear β-amino alcohol catalyst anchored on functionalized magnetite nanoparticles for enantioselective addition of dialkylzinc to aromatic aldehydes.

A linear β-amino alcohol ligand, previously found to be a very efficient catalyst for enantioselective addition of dialkylzinc to aromatic aldehydes, has been anchored on differently functionalized superparamagnetic core–shell magnetite–silica nanoparticles (1a and 1b). Its catalytic activity in the addition of dialkylzinc to aldehydes has been evaluated, leading to promising results, especially in the case of 1b for which the recovery by simple magnetic decantation and reuse was successfully verified.

Synthesis and Crystal Structure of [Benzyl N'-[[2-(hydroxy-kO)phenyl]ethylene]-N-[[2-(hydroxy-kO)phenyl]methylene]-carbamohydrazonothioato-kN,kN']-ethanol-dioxido-uranium

The uranyl compound UO2(L')EtOH (L' = benzyl N-(2-(oxidanyl)benzylidene)-N'-((2-(1-oxidanyl)phenyl)ethylidene) carbamohydrazonothioate) was synthesized and its molecular and crystal structure was determined by X-ray diffraction. The compound crystallizes in the triclinic sp. gr. P$$\bar {1}$$, Z = 2. The coordination geometry about the uranium atom is distorted pentagonal bipyramidal consisting of a UO2O4N2 polyhedron where the oxido ligands occupy axial positions with a symmetric linear structure (O=U=O angle = 179.11(12)°). The pentagonal plane (N2O3) is formed by the dinegative, tetradentate Schiff base ligand (N2O2) and the oxygen atom of the coordinated alcohol ligand. In the complex, the ligand adopts a propeller-like conformation.

Construction of Two High-Nuclear 3d-4d Heterometallic Cluster Organic Frameworks by Introducing a Bifunctional Tripodal Alcohol as a Structure-Directing Agent.

Two unique heterometallic cluster organic frameworks, [Cd4 MnIII 4 MnII 6 (Tri)4 (CH3 COO)14 (μ4 -O)2 (μ3 -O)2 (H2 O)2 ] Cd(H2 O)2 ⋅9 H2 O (1) and Cu[Cd5 Cu6 (Tri)4 (CH3 COO)9 (H2 O)4 ]2 (CH3 COO)3 ⋅24 H2 O (2) (H3 Tri=2-(hydroxymethyl)-2-(pyridine-4-yl)-1,3-propanediol), have been successfully prepared by employing a bifunctional tripodal alcohol ligand as a structure-directing agent. Crystal structure analyses reveal that 1 represents a rare example of frameworks constructed from Cd-Mn heterometallic chains, and 2 is the first heterometallic MOF based on highest-nuclear Cd-Cu heterometallic cluster building blocks. Furthermore, the magnetic properties and gas adsorption abilities of 1 and 2 were systematically studied.

Fe6 clusters of tripodal alcohol ligands: Synthesis, structures and magnetostructural properties

The synthesis, crystal structures, cyclic voltammetric and magnetic characterization of (NEt3H)2[FeIII6Cl6(µ6-O)(thme)4]·3(H2O) (1) (H3thme = trishydroxymethyl ethane) and (NEt3H)2[FeIII6Cl6(µ6-O)(thmp)4]·5.5(H2O) (2) (H3thmp = trishydroxymethyl propane) are reported. Both complexes crystallized in the orthorhombic system and have the space group Pca21. The metallic cores of the complexes comprise of the [(μ6-O)Fe6(μ-O)12] unit. The ligands thme3− and thmp3− adopt the same η2, η2, η2, µ3-bridging mode of the alkoxide oxygen atoms in 1 and 2. Electrochemical studies are consistent with formation of stable quasi-reversible one electron FeII/III redox couples in solution. The fascinating features of the non-covalent supramolecular contacts have been explored and corroborated theoretically by Hirshfeld surface analysis along with electrostatic potential (ESP), deformation density (DD) and ab initio calculations. The interplay of the interactions, (i.e., H⋯O, Cl⋯H and other contacts) give rise to the consolidation of discrete units of 1 and 2 into supramolecular architectures. Variable-temperature and field (H) solid-state direct and alternating current magnetic susceptibility measurements were done on samples of 1 and 2 in the temperature range 1.8–300 K. Analysis of the data confirmed the presence of dominant antiferromagnetic interactions, leading to an S = 0 ground state, and no out of phase ac magnetic susceptibility signals were observed for either cluster, ruling out single-molecule magnet behaviour.

Insights into base-free OsO4-catalyzed aminohydroxylations employing chiral ligands

Attempts to perform the OsO4-catalyzed enantioselective base-free aminohydroxylation of β,β-disubstituted enoates are described. Low yields and racemic products were obtained in the presence of standard chiral ligands, suggesting the occurrence of a “Second Cycle” process due to slow hydrolysis of the amino alcohol product from the Os metal center. Support for this hypothesis was provided by the slightly improved enantioselectivity (60:40 er) obtained with an amino alcohol ligand. Based on density functional theory calculations, it is proposed that the lack of significant enantioselectivity is due to a low-energy (3 + 2) oxo/imido cycloaddition transition state without the chiral ligand in the Second Cycle that outcompetes protonolysis in the First Cycle.

Effect of Regioisomerism on the Efficiency of 1-Phenylpyrrole-Type Atropisomeric Amino Alcohol Ligands in Enantioselective Organometallic Reactions

Syntheses of two regioisomeric series of atropisomeric amino alcohols and a comparative study on their application in the enantio­selective addition of diethylzinc to benzaldehyde are reported. Systematic modification of the electronic and steric properties of the functional groups resulted in highly efficient catalyst ligands in both series. Quantum-chemical calculations agreed well with the experimental results of this first systematic comparative study on regioisomeric ­atropisomeric ligands.

Influence of Background H2O on the Collision-Induced Dissociation Products Generated from [UO2NO3].

Developing a comprehensive understanding of the reactivity of uranium-containing species remains an important goal in areas ranging from the development of nuclear fuel processing methods to studies of the migration and fate of the element in the environment. Electrospray ionization (ESI) is an effective way to generate gas-phase complexes containing uranium for subsequent studies of intrinsic structure and reactivity. Recent experiments by our group have demonstrated that the relatively low levels of residual H2O in a 2-D, linear ion trap (LIT) make it possible to examine fragmentation pathways and reactions not observed in earlier studies conducted with 3-D ion traps (Van Stipdonk et al. J. Am. Soc. Mass Spectrom. 14, 1205-1214, 2003). In the present study, we revisited the dissociation of complexes composed of uranyl nitrate cation [UVIO2(NO3)]+ coordinated by alcohol ligands (methanol and ethanol) using the 2-D LIT. With relatively low levels of background H2O, collision-induced dissociation (CID) of [UVIO2(NO3)]+ primarily creates [UO2(O2)]+ by the ejection of NO. However, CID (using He as collision gas) of [UVIO2(NO3)]+ creates [UO2(H2O)]+ and UO2+ when the 2-D LIT is used with higher levels of background H2O. Based on the results presented here, we propose that product ion spectrum in the previous experiments was the result of a two-step process: initial formation of [UVIO2(O2)]+ followed by rapid exchange of O2 for H2O by ion-molecule reaction. Our experiments illustrate the impact of residual H2O in ion trap instruments on the product ions generated by CID and provide a more accurate description of the intrinsic dissociation pathway for [UVIO2(NO3)]+. Graphical Abstract ᅟ.

Anticancer activities of a β-amino alcohol ligand and nanoparticles of its copper(ii) and zinc(ii) complexes evaluated by experimental and theoretical methods.

2-(2-(2-Hydroxyethylamino)ethylamino)cyclohexanol (HEAC) and copper and zinc complexes, [Cu(HEAC)Cl]Cl (1), [Cu(HEAC)Br]Br (2), [Zn(HEAC)Cl2] (3), were prepared and identified by elemental analysis, FT-IR, UV-Vis, 1H NMR spectroscopy and single-crystal X-ray diffraction. Also nanoparticles of 1–3 were prepared for anticancer studies by ultrasonic irradiation. Particle size and morphology of the nano particles are investigated by PXRD and SEM, respectively. X-ray analysis revealed that the ionic complexes 1 and 2 are isostructural. In the structure of complexes 1 and 2, the metal atom has a CuN2O2X (X: Cl (1), Br (2)) environment with square-pyramidal geometry, containing the tetradentate N2O2-donor HEAC. The bond length of the axial position in the square-pyramidal geometry of 1 and 2 is elongated. Complex 3 has a ZnN2OCl2 environment with trigonal bipyramidal geometry around the zinc atom in which the HEAC acts as mer-N2O-donor. The ability of HEAC and nano particles 1–3 to interact with the nine biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS and Top II) are investigated by docking calculations. For examination of the docking results, the in vitro activities of four compounds against the human leukemia cell line K562 were investigated by evaluation of IC50 values and mode of cell death (apoptosis). The thermodynamic stability of the compounds along with the charge distribution pattern were studied by DFT and NBO analysis, respectively.

Solution behavior and magnetic properties of a novel nonanuclear copper(ii) cluster

A {Cu9} nanocluster was constructed from a new multidentate pyrazole–alcohol ligand and various small sterically-hindering anions. The ESI-MS was for the first time applied to Cu cluster chemistry to detect the solution behaviour and possible assembly mechanism of the {Cu9} cluster. The cluster also exhibited antiferromagnetic behaviour.

New chiral amino alcohol ligands for catalytic enantioselective addition of diethylzincs to aldehydes.

A study aimed at the synthesis and structure optimization of new, efficient, optically active β-amino alcohol ligands with a structure suitable for immobilization on magnetite nanoparticles has been carried out. The optimized homogeneous amino alcohol catalysts 13a and 13b, the chirality of which arises from the Sharpless epoxidation of suitable allyl alcohols, were tested by employing the well-established enantioselective amino alcohol-promoted addition of diethylzinc to benzaldehyde, giving the corresponding benzyl alcohol with nearly quantitative yield and ee = 95%. Then, their broad applicability as chiral catalysts was evaluated by carrying out the same reaction on a family of aldehydes, including variously substituted aromatic ones as well as an aliphatic analogue. The results have confirmed the validity of the fine-tuning process performed on ligands 13a and 13b. In fact, both exhibited excellent catalytic activity as demonstrated by the chemical yields and ee obtained from all the tested aldehydes, almost independent of the position and type of substitution in the aromatic ring.

Convergent (De)Hydrogenative Pathways via a Rhodium α-Hydroxylalkyl Complex

We report the convergent reaction pathways between [RhH(PPh3)4] and POP ketone (1) and alcohol (2) ligands that terminate in the formation of an α-hydroxylalkyl rhodium(I) complex (3), representing two halves of a formal reduction/oxidation pathway between 1 and 2. In the case of hydride transfer to 1, the formation of the α-hydroxylalkyl rhodium(I) complex (3) proceeds via a rare hydrido(η2-carbonyl) complex (4). C–H activation in 2 at the proligand’s central methine position, rather than O–H activation of the hydroxy motif, followed by loss of dihydrogen also generates the α-hydroxylalkyl rhodium(I) complex (3). The validity of the postulated reaction pathways is probed with DFT calculations. The observed reactivity supports α-hydroxylalkyl complexes as competent intermediates in ketone hydrogenation catalyzed by rhodium hydrides and suggest that ligands 1 and 2 may be “noninnocent” coligands in reported hydrogenation catalyst systems in which they are utilized.

Ultralarge 3d/4f Coordination Wheels: From Carboxylate/Amino Alcohol-Supported {Fe4Ln2} to {Fe18Ln6} Rings.

A family of wheel-shaped charge-neutral heterometallic {FeIII4LnIII2}- and {FeIII18MIII6}-type coordination clusters demonstrates the intricate interplay of solvent effects and structure-directing roles of semiflexible bridging ligands. The {Fe4Ln2}-type compounds [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(EtOH), Ln = Dy (1a), Er (1b), Ho (1c); [Fe4Tb2(O2CCMe3)6(N3)4(Htea)4] (1d); [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(CH2Cl2), Ln = Dy (2a), Er (2b); [Fe4Ln2(O2CCMe3)4(N3)6(Htea)4]·2(EtOH)·2(CH2Cl2), Ln = Dy (3a), Er (3b) and the {Fe18M6}-type compounds [Fe18M6(O2CCHMe2)12(Htea)18(tea)6(N3)6]·n(solvent), M = Dy (4, 4a), Gd (5), Tb (6), Ho (7), Sm (8), Eu (9), and Y (10) form in ca. 20–40% yields in direct reaction of trinuclear FeIII pivalate or isobutyrate clusters, lanthanide/yttrium nitrates, and bridging triethanolamine (H3tea) and azide ligands in different solvents: EtOH for the smaller {Fe4Ln2} wheels and MeOH/MeCN or MeOH/EtOH for the larger {Fe18M6} wheels. Single-crystal X-ray diffraction analyses revealed that 1–3 consist of planar centrosymmetric hexanuclear clusters built from FeIII and LnIII ions linked by an array of bridging carboxylate, azide, and aminopolyalcoholato-based ligands into a cyclic structure with a cavity, and with distinct sets of crystal solvents (2 EtOH per formula unit in 1a–c, 2 CH2Cl2 in 2, and 2 EtOH and 2 CH2Cl2 in 3). In 4–10, the largest 3d/4f wheels currently known, nearly linear Fe3 fragments are joined via mononuclear Ln/Y units by a set of isobutyrates and amino alcohol ligands into virtually planar rings. The magnetic properties of 1–10 reveal slow magnetization relaxation for {Fe4Tb2} (1d) and slow relaxation for {Fe4Ho2} (1c), {Fe18Dy6} (4), and {Fe18Tb6} (6).

Dinuclear lanthanide complexes based on amino alcoholate ligands: Structure, magnetic and fluorescent properties

Two binuclear lanthanide complexes [Ln2(hfac)6(HL)2] (LnIII = Dy(1), Tb(2); hfac = hexafluoroacetylacetonate, HL = (R)-2-amino-2-phenylethanol) have been successfully obtained by using amino alcoholate ligand. In two complexes, the Ln(III) ions are bridged by two alkoxido groups from HL ligands, resulting in binuclear complexes. The variable-temperature magnetic susceptibility studies indicate that there exists ferromagnetic interaction between two Ln(III) ions. Frequency dependent out-of-phase signals are observed for complex 1, suggesting SMM type behavior. Complexes 1 and 2 display intensely characteristic luminescent properties.

Magneto-structural correlations in a family of di-alkoxo bridged chromium dimers

A series of di-alkoxo bridged Cr(iii) dimers have been synthesised using pyridine alcohol ligands. The structures fall into four general categories and are of formula: [Cr2(OMe)2(pic)4]·½MeOH·½Et2O (1), [Cr2(hmp)2(pic)2X2] (where X = Cl (2), Br (3)), [Cr2(L)2Cl4(A)2]·2S (where L = hmp, A = H2O and S = Et2O (4); L = hmp, A = pyridine and S = pyridine (5); L = hmp, A = 4-picoline and no S (6); L = hep, A = H2O and S = MeCN (7)), and [Cr(hmp)(hmpH)Cl2]·MeCN (8). Direct current (DC) magnetic susceptibility measurements show relatively weak antiferromagnetic exchange interactions between the Cr(iii) centres with J values <|15| cm-1 in all of the complexes measured. DFT calculations performed on complexes 1-8 reproduce both the sign and strength of the exchange interactions found experimentally, and confirm that the magnitude and sign of the J value is strongly dependent upon the orientation of the dihedral angle formed between the bridging Cr2O2 plane and the O-R vector of the bridging group (θ), and the Cr-O-Cr-O dihedral angle (ψ).

ChemInform Abstract: Asymmetric Henry Reaction Catalyzed by Cu(II)‐Based Chiral Amino Alcohol Complexes with C2‐Symmetry.

Abstract A series of chiral amino alcohol ligands was prepared using commercial amino alcohols and phthalaldehydes. These ligands were used as catalysts in asymmetric Henry reactions in the presence of Cu(II) ions giving good yields (up to 97%) and enantiomeric excesses (ee, up to 98%). The DFT calculations showed the effect of the trans / cis configurations of the Cu-complexes on the origin of enantioselectivity. The easy catalyst preparation, mild reaction conditions, high yields and excellent enantioselectivities make these catalysts suitable for widespread use.

Construction of High-Nuclearity Manganese-Cluster-Organic Frameworks by Using a Tripodal Alcohol Ligand.

Two novel cluster-organic frameworks based on the 12-nuclearity manganese-cluster secondary building unit (SBU), [MnIII4MnII8(L)4(Ac)8(MeO)2(μ5-O)2(H2O)4](Ac)2·16H2O (1) and [MnIII4MnII8(L)4(Ac)8(MeO)2(μ5-O)2(H2O)4](Ac)2·12H2O (2), where Ac = CH3COO- and MeO = CH3O, have been constructed from solvothermal reactions of the 3-nuclearity manganese cluster [Mn3(μ3-O)(Ac)6(py)3](ClO4) (Mn3, where py = pyridine) with a tripodal alcohol ligand containing a 4-pyridyl group. 1 and 2 represent the first examples of metal-organic frameworks containing 12-nuclearity manganese-cluster SBUs. In addition, 1 exhibits an integration of the porosity and magnetic properties from both the framework and cluster in a porous material.

Collision‐induced dissociation of uranyl‐methoxide and uranyl‐ethoxide cations: Formation of UO 2 H + and uranyl‐alkyl product ions

The lower levels of adventitious H2 O in a linear ion trap allow the fragmentation reactions of [UO2 OCH3 ](+) and [UO2 OCH2 CH3 ](+) to be examined in detail. Methanol- and ethanol-coordinated UO2 (2+) -alkoxide precursors were generated by electrospray ionization (ESI). Multiple-stage tandem mass spectrometry (MS(n) ) and collision-induced dissociation (CID) were performed using a linear ion trap mass spectrometer. CID of [UO2 OCH3 (CH3 OH)n ](+) and [UO2 OCH2 CH3 (CH3 CH2 OH)n ](+) , n=3 and 2, causes loss of neutral alcohol ligands, leading ultimately to bare uranyl-alkoxide species. Comparison of 'native' to deuterium-labeled precursors reveals dissociation pathways not previously observed in 3-D ion trap experiments. UO2 H(+) is generated from [UO2 OCH3 ](+) by transfer of H from the methyl group. Variable-energy and variable-time CID experiments suggest that the apparent threshold for production of UO2 H(+) is lower than for UO2 (+) , but the pathway is kinetically less favored for the former than for the latter. CID experiments reveal that [UO2 OCH2 CH3 ](+) dissociates to generate [UO2 CH3 ](+) , a relatively rare species with a U-C bond, and [UO2 (O=CH2 )](+) .

Asymmetric Henry reaction catalyzed by Cu(II)-based chiral amino alcohol complexes with C2-symmetry

A series of chiral amino alcohol ligands was prepared using commercial amino alcohols and phthalaldehydes. These ligands were used as catalysts in asymmetric Henry reactions in the presence of Cu(II) ions giving good yields (up to 97%) and enantiomeric excesses (ee, up to 98%). The DFT calculations showed the effect of the trans/cis configurations of the Cu-complexes on the origin of enantioselectivity. The easy catalyst preparation, mild reaction conditions, high yields and excellent enantioselectivities make these catalysts suitable for widespread use.

Systematic Synthesis of Di‐, Tri‐, and Tetranuclear Homo‐ and Heterometal Complexes Using a Mononuclear Copper Synthon with a Tetradentate Amino Alcohol Ligand

The reaction of Cu(NO3)2·3H2O with an N2O2 tetradentate amino alcohol, N,N‐dibenzyl‐N′,N′‐bis(2‐hydroxyethyl)ethylenediamine (H2L), afforded the mononuclear copper complex [Cu(H2L)(NO3)](NO3) (1), which has been used to construct a series of di‐, tri‐, and tetranuclear homo‐ and heterometallic complexes. Complex 1 dimerized in the presence of NEt3 to form the Cu2 complex [Cu2(HL)2](NO3)2 (2) by the deprotonation of one of the two hydroxy groups in the H2L ligand. The reaction of 1 with Cu(OCOH)2 in the presence of NEt3 afforded the Cu3 complex [Cu3(HL)2(OCOH)2](NO3)2 (5). The metalloligand {Cu(HL)}+ derived from 1 reacted with M(OAc)2 (M = Cu, Co, Zn, Ni) in the absence of NEt3 to form the asymmetric CuM dinuclear complexes [CuM(HL)(OAc)(NO3)2] [M = Cu (3a), Co (3b), Zn (3c), Ni (3d)], whereas in the presence of NEt3 a unit of M(OAc) was captured by two metalloligands to give the bent CuMCu trinuclear complexes [Cu2M(HL)2(OAc)2(NO3)](NO3) [M = Cu (4a), Co (4b), Mn (4c)], which were further transformed into the linear CuMCu trinuclear complexes [Cu3(HL)2{(PhO)2PO2}2](NO3)2 (7a) and [Cu2M(HL)2{(PhO)2PO2}2(MeOH)2](NO3)2 [M = Co (7b), Mn (7c)] with the aid of diphenyl phosphate bridging ligands. When (PhO)PO2(OH) was used as an auxiliary bridging ligand in the reaction of 1 with M(OAc)2 and NEt3, the Cu2M2 tetranuclear complexes [Cu2M2(HL)2{(PhO)PO3}2(NO3)2] [M = Co (8a), Zn (8b)] were synthesized. These results demonstrate that the mononuclear copper synthon with the N2O2 tetradentate amino alcohol ligand {Cu(H2L)}2+ generates the quite useful metalloligand {Cu(HL)}+ by the deprotonation of a hydroxy group, and subsequent reactions lead to the construction of a series of homo‐ and heterometal complexes containing Cu2, CuM (M = Cu, Co, Zn, Ni), bent‐CuMCu (M = Cu, Co, Mn), linear‐CuMCu (M = Cu, Co, Mn), and Cu2M2 (M = Co, Mn) cores in a systematic and selective manner.

Crystal structures of bis-[2-(pyridin-2-yl)phenyl-κ(2) N,C (1)]rhodium(III) complexes containing an aceto-nitrile or monodentate thyminate(1-) ligand.

The crystal structures of bis-[2-(pyridin-2-yl)phen-yl]rhodium(III) complexes with the metal in an octahedral coordination containing chloride and aceto-nitrile ligands, namely (OC-6-42)-aceto-nitrile-chlorido-bis-[2-(pyridin-2-yl)phenyl-κ(2) N,C (1)]rhodium(III), [RhCl(C11H8N)2(CH3CN)] (1), thyminate(1-) and methanol, namely (OC-6-42)-methanol(5-methyl-2,4-dioxo-1,2,3,4-tetrahydro-pyrimidin-1-ido-κN (1))bis-[2-(pyridin-2-yl)phenyl-κ(2) N,C (1)]rhodium(III), [Rh(C11H8N)2(C5H5N2O2)(CH3OH)]·CH3OH·0.5H2O (2), and thy-min-ate(1-) and ethanol, namely (OC-6-42)-ethanol(5-methyl-2,4-dioxo-1,2,3,4-tetra-hydro-pyrimidin-1-ido-κN (1))bis[2-(pyridin-2-yl)phenyl-κ(2) N,C (1)]rhodium(III), [Rh(C11H8N)2(C5H5N2O2)(C2H5OH)]·C2H5OH (3), are reported. The aceto-nitrile complex, 1, is isostructural with the Ir(III) analog. In complexes 2 and 3, the monodeprotonated thyminate (Hthym(-)) ligand coordinates to the Rh(III) atom through the N atom, and the resulting Rh-N(Hthym) bond lengths are relatively long [2.261 (2) and 2.252 (2) Å for 2 and 3, respectively] as compared to the Rh-N bonds in the related thyminate complexes. In each of the crystals of 2 and 3, the complexes are linked via a pair of inter-molecular N-H⋯O hydrogen bonds between neighbouring Hthym(-) ligands, forming an inversion dimer. A strong intra-molecular O-H⋯O hydrogen bond between the thyminate(1-) and alcohol ligands in mutually cis positions to each other is also observed.