Academic literature on the topic 'Flexible amide ligands'

Five novel polyoxometalates-based metal–organic complexes constructed from different types of polyanions and flexible bis-pyrazine–bis-amide ligands with different spacer lengths have been hydrothermally synthesized and structurally characterized.

Two new two-dimensional copper(II) coordination polymers, [Cu(L)(BDC)]_H2O (1) and [Cu2(L)0:5(SIP)(OH)(H2O)] 2H2O (2) [L=N;N0-bis(3-pyridylamide)-1,6-hexane, H2BDC=1,3- benzenedicarboxylic acid, H3SIP=5-sulfoisophthalic acid (3,5-dicarboxybenzenesulfonic acid)], have been synthesized hydrothermally by self-assembly of the flexible bis-pyridyl-bis-amide ligand L and the aromatic polycarboxylate ligands H2BDC or H3SIP. X-Ray diffraction analysis reveals that complex 1 displays a metal-organic coordination layer with a binodal (3,5)-connected {42.67.8}{42.6} topology, in which the L ligands adopt a m2-bridging mode (via ligation of the pyridyl nitrogen atoms). Complex 2 also exhibits a layered network based on tetranuclear copper clusters [Cu4(μ3-OH)2(H2O)2(O2C-)4], L ligands and SIP anions, showing a binodal (4,8)-connected network with {414.610.84}{44.62} topology, in which the L ligands adopt a μ6-bridging coordination mode (via ligation of the pyridyl nitrogen and carbonyl oxygen atoms). Adjacent layers in 1 and 2 are further linked by hydrogen bonding interactions to form three-dimensional supramolecular frameworks. The electrochemical behavior of the two complexes in bulk-modified carbon paste electrodes has been investigated

N-anilinoethylamides are a class of melatoninergic agents with the aniline portion mimicking the indole ring of the natural ligand and the ethylamide chain reproducing that of melatonin. The simplest compound in this class, N-{2-[(3-methoxyphenyl)methylamino]ethyl}acetamide (UCM793), has nanomolar binding affinity for MT1 and MT2 membrane receptors. To explore the effect of chain conformation on receptor binding, a methyl group was inserted on the methylene alpha or beta to the amide nitrogen and conformational equilibria were investigated by NMR spectroscopy and molecular dynamics simulations. Receptor affinity was conserved only for the beta-methyl derivative, which also showed significant stereoselectivity, with the (S) enantiomer being the eutomer. Molecular dynamics simulations, validated by NMR spectroscopy, showed that the beta-methyl group affects the conformational preferences of the ethylamide chain. Docking into the receptor crystal structure provides a rationale for the observed chiral recognition, suggesting that the (S)-beta-methyl group favors the conformation that better fits the receptor binding site.

Using an flexible amide-type tripodal ligand N , N ′, N ″-tris(3-pyridyl)-1,3,5-benzenetricarboxamide (L) and 1,4-benzenedicarboxylic acid ( H 2 bdc ), a three-dimensional copper(II) metal-organic framework (MOF) formulated as [ Cu ( bdc )( L )]n has been hydrothermally synthesized and structurally characterized by IR, elemental, X-ray single-crystal diffraction and thermal analysis. The complex crystallizes in the triclinic, space group P - 1, a = 8.891(2) Å, b = 11.760(2) Å, c = 15.348(3) Å, α = 96.73(3)°, β = 105.96(3)°, γ = 106.47(3)°, V = 1446.2(5) Å3, Mr = 666.10, Dc = 1.530 g/cm3, Z = 2, F(000) = 682, GOOF = 1.0560, μ(MoKα) = 0.817 mm-1, R = 0.0366 and wR = 0.0885. The structural analyses reveal that the title compound consists of one Cu ( II ) atom, two halves of bdc, and one L ligand. Each Cu ( II ) atom is linked by two bdc ligands and three L ligands to form a three-dimensional network. In addition, the electrochemical behavior of title compound has been studied. CCDC No. 990526.

The synthesis of amide-based molecules, possessing pre-organized structures, has received significant attention due to their potential applications as molecular receptors and as components of nanomaterials. In this study, four extended tetraamide ligands incorporating ethylene and propylene spacers, namely 1,2-bis[N,N′-6-(3-pyridylmethylamido)pyridyl-2-carboxyamido]ethane (L1), 1,2-bis[N,N′-6-(4-pyridylmethylamido)pyridyl-2-carboxyamido]ethane (L2), 1,2-bis[N,N′-6-(3-pyridylmethylamido)pyridyl-2-carboxyamido]propane (L3) and 1,2-bis[N,N′-6-(4-pyridylmethylamido)pyridyl-2-carboxyamido]propane (L4), were successfully synthesized. Further, reaction of L2 and L4, incorporating pendant 4-pyridyl donors as the metal coordinating sites, with cadmium salts, produced two close-packed one-dimensional coordination polymers, {[Cd3(L2)4(H2O)10](NO3)6·12H2O·CH3OH}n and {[Cd(SO4)(L4)(H2O)2]·4H2O·CH3OH}n. X-ray crystallography reveals that the flexible tetraamide ligands fold upon themselves in the coordination polymer structure. As a consequence, the anion pocket in {[Cd(SO4)(L4)(H2O)2]·4H2O·CH3OH}n incorporating the ligand with the propylene spacer was blocked from encapsulating charge-balancing anions, which were involved in bridging the di-cadmium units. Interestingly, a strong interaction between the 2,6-pyridine dicarboxamide moiety with the nitrate anions was found in {[Cd3(L2)4(H2O)10](NO3)6·12H2O·CH3OH}n, showing potential for materials made from these ligands to serve as anion receptors.

This thesis provides an account of the synthesis and study of fifteen amide-containing polypyridyl ligands, eleven of which are new compounds. These ligands all possess at least one amide moiety, potentially capable of anion binding and one or more pendant pyridyl donor groups as the metal coordinating sites. A further evolution over previously reported compounds is that a majority of the amide compounds incorporate a pre-organised amide component that will constitute the anion binding region. The alkyl and phenyl spacers were utilised to confer flexibility to these compounds and to extend the spacing between the anion binding moiety and the pendant metal complexing groups. The compounds investigated in this work are divided into three categories; (i) unsymmetrical monoamide ligands that possess one amide functional group, one ester protected carboxylate and one external donor pyridyl moiety; (ii) symmetrical flexible amide ligands that possess two or more internal amide groups and two external pyridyl metal coordinating sites, and; (iii) symmetrical amide bridging ligands that incorporate two di-2-pyridylmethylamine chelating motifs. The coordination chemistry and metallo-supramolecular chemistry of these ligands was investigated with a range of late transition metals including cadmium(II), copper(II), cobalt(II), silver(I), zinc(II) and palladium(II). Palladium(II) precursors, with a selection of monodentate or bidentate chelating ancillary blocking ligands, were utilised to form discrete mono- and dinuclear assemblies with a view to investigating anion complexation in solution. Other transition metal precursors were studied with a focus on the synthesis of coordination polymers that display anion coordinating pockets. Reaction of the monoamide ligands containing a pendant 3-pyridyl group with copper salts led to the formation of five very similar discrete planar and cleft-containing [Cu₂L₂] dinuclear metallo-macrocyclic complexes. The monoamide compounds, lacking a methylene spacer between the amide and the pendant pyridyl ring, form near planar [Cu₂L₂] dinuclear metallo-macrocyclic complexes; meanwhile introduction of a CH₂ spacer, by using a more flexible ligand, results in the formation of cleft-containing complexes. Reaction of the more flexible ligand with copper perchlorate results in a cleft-containing complex whereby encapsulation of a perchlorate anion in the cavity is stabilised by anion-π interactions. The flexible monoamide ligand with a pendant 4-pyridyl group forms 1-D coordination polymers based on a similar dinuclear metallo-macrocycle building block motif. Reaction of a related ligand with cadmium(II) nitrate and copper(II) acetate led to a formation of two 2-D coordination polymers, both prepared via a solvothermal approach. The 2-D coordination polymer obtained with cadmium(II) nitrate has small oval channels with the oxygen atoms of the nitrate anions and ligands lining the channels. This contrasts with the 2-D coordination polymer obtained with copper(II) acetate which is close-packed in the solid-state. In a similar manner to studies on the monoamide ligands, the symmetrical flexible diamide ligands and tetraamide ligands were used to form discrete complexes and metallo-macrocyclic containing coordination polymers. Two mononuclear Pd(II) supramolecular cages were obtained from the reaction of flexible diamide ligand with pendant 3-pyridyl groups, while a mixture of Pd(II) supramolecular isomers was obtained with the analogue of this ligand. A crystal structure of a mononuclear palladium(II) complex showed specific anion interactions between the pre-organised NH donors and hexafluorophosphate anions in the solid-state. Similar interactions were observed in the majority of the coordination polymers obtained with the flexible diamide and tetraamide ligands. In the crystal structures of three isostructural dinuclear metallo-macrocycle based coordination polymers containing the diamide ligand with pendant 3-pyridyl groups, the pre-organised NH donors are hydrogen bonded to the counterions, including nitrate and perchlorate. In addition to this interaction, the structures were stabilised by π-stacking interactions between the pendant pyridine groups and pyridyl cores. Reaction of the flexible diamide ligand containing pendant 4-pyridyl groups with cadmium(II) and zinc(II) nitrate provided access to two isostructural and isomorphous 1-D coordination polymers, while slow evaporation with cadmium(II) perchlorate gave 2-D coordination polymer. Reaction of the set of flexible tetraamide ligands containing pendant 4-pyridyl groups gave two coordination polymers that adopt semi-helical and close-packed structures in the solid-state. Only one coordination polymer was able to be obtained with the tetraamide ligands with pendant 3-pyridyl groups. The coordination chemistry of the chelating amide ligands with silver(I), cadmium(II) and palladium(II) salts were also studied and these ligands found to act as a bis(bidentate) ditopic bridge to connect two metal ions. This study has revealed that the monoamide or unsymmetrical amide ligands in combination with copper(II) salts can form discrete anion cages potentially capable of interacting with anions via hydrogen bonding and anion-π interactions. The symmetrical and flexible diamide ligands also show potential to interact with anions in the solid-state and may be used for the development of materials suitable for anion separation or sequestration and also as design elements of anion binding moieties for sensors. Unfortunately, the incorporation of more flexible amide ligands into metallo-supramolecular assemblies was not shown to increase the ‘size’ of the anion pocket of the assemblies but, due to the additional flexibility, results in the formation of more close-packed structures. It is also shown that self-association may limit the applicability of the tetraamide ligands to bind with either cations or anions in solution. The preliminary anion competition studies have shown that the coordination compounds derived from L5 and L6 tend to precipitate salts of either sulfate or, more likely based on the Hofmeister series, perchlorate anions under competitive conditions. All compounds obtained in this work were characterised by a combination of ¹H and ¹³C NMR spectroscopy, IR spectroscopy, mass spectrometry, elemental analysis and X-ray crystallography. Simultaneous Thermal Analysis (STA) and Powder Diffraction X-ray Diffraction (PXRD) results for selected compounds are also described. In this thesis, crystal structures of seven ligands and twenty nine novel coordination compounds are described.
Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2012

博士
中原大學
化學研究所
105
In this dissertation, the syntheses, structures and properties of coordination polymers based on the flexible bis-pyridyl-bis-amide and/or tetracarboxylate ligands, have been extensively discussed and summarized basically in five parts. Part I: The contribution of flexible bis-pyridyl-bis-amide (bpba) ligands, which are also known as versatile ligands possessing various active coordination atoms (N and O) and different flexible –CH2– skeletons, is significant in the construction of coordination polymers. In this Highlight, structures of the different dimensional networks based on the flexible bpba ligands with or without participation of auxiliary polycarboxylate ligands are discussed, along with an overview of the preparations and conformations of the ligands. Part II: Two pairs of Hg(II) supramolecular isomers, [HgBr2(GAG-L1)]∞ [L1 = N,N-di(3-pyridyl)adipoamide], 1, and [HgBr2(AAA-L1)]∞, 2, and [HgI2(GAG-L1)]∞, 3, and [HgI2(AAA-L1)]∞, 4, have been successfully synthesized by various methods, and structurally characterized by single crystal X-ray crystallography. Complex 1 forms a one-dimensional (1D) meso-helical chain, 2 and 4 exhibit normal 1D helical chains, while 3 displays a 1D sinusoidal chain. The L1 ligands in 1 and 3 display GAG trans syn-syn conformation, while those in 2 and 4 adopt the AAA trans syn-syn conformation. In addition, complexes 1 and 3 can be irreversibly transformed to 2 and 4, respectively, under simple heating or hydrothermal condition. Moreover, complex 1 exhibits intense violet-blue photoluminescence in the solid state, whereas 2 and 3 display weak broad emissions in the blue-green region and 4 shows undetectable emission intensity. Part III: By utilizing the flexible ligands, bis(3,5-dicarboxyphenyl)adipoamide, H4L6; bis(N-pyrid-3-ylmethyl)adipoamide, L4; and bis(N-pyrid-3-ylmethyl) suberoamide, L5, four coordination polymers of the types {[M(L6)0.5(L4)(H2O)2]H2O}n (M = Co, 5; Ni, 6) and {[M2(L6)(L5)2(H2O)4]3H2O}n (M = Co, 7; Ni, 8) have been hydrothermally synthesized and structurally characterized by the single crystal X-ray diffraction. Complexes 5 - 8 are topologically identical coordination polymers having the moganite type 2-fold interpenetrating 4,4-connected 3D net. Additionally, both Co(II) complexes are thermochromic and exhibit the reversible structural transformation on dehydration/rehydration followed by the color change but Ni(II) complexes are unable to show such behavior. All four complexes display good photo-degradation performance and the Co(II) complexes show slightly higher efficiencies than the Ni(II) ones. Part IV: By using a new flexible tetracarboxylic acid, bis(3,5-dicarboxyphenyl) adipoamide, H4L6, and its isomer, bis(2,5-dicarboxyphenyl)adipoamide, H4L7, three Mg(II) coordination polymers, [Mg2(L6)(H2O)2]2EtOH3H2O, 9, [Mg2(L6)(H2O)8], 10, and [Mg2(L7)(H2O)6].H2O, 11, have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Complexes 9 and 10 are the solvent ratio dependent hydrothermally stable products. The tetracarboxylate ligand of complex 9 adopts a unique 8-nonadentate bonding mode, resulting in a three-dimensional (3D) 5-connected uninodal (44.66)-pcu-5-Pmna net, whereas those of 10 and 11 display the 4-tetradentate and 6-hexadentate bonding modes, forming a 1D linear chain and a 3,6-connected 2-nodal 3D net having {4.62}2{42.610.83}-rtl topology, respectively. Complex 9 shows a series of structural transformations on heating up to 200 oC and almost reversible structural transformation when the activated products were immersed in the mixture of ethanol and water or on hydrothermal. Likewise, complex 10 exhibits reversible structural transformation on heating/hydrothermal while 11 exhibits the irreversible structural transformations. All three complexes exhibit blue light emissions and that of complex 11 is much more intense. Part V: By applying three flexible ligands, bis(3,5-dicarboxyphenyl) adipoamide, H4L6; N,N’-bis(3-pyridyl)sebacoamide, L2 and N,N’-bis(3-pyridyl)dodecanedipoamide, L3; four new coordination polymers: [Co(L6)0.5(H2O)3]H2O, 12; [Co(L6)0.5(L2)(H2O)]4H2O, 13; [Cd(L6)(H2O)2]2EtOH3H2O, 14 and [HgI2(L3)]∞, 15; have been hydrothermally synthesized and structurally characterized by the single crystal X-ray diffraction. Complex 12 forms the 2D looped like structure with (4.62)2(42.62.82) topology, while 13 possesses a 2,4,4-connected-3-nodal 2D net with the new topology {42.82.102}{42.84}2{4}2. Further, complex 14 possesses a three-dimensional (3D) 5-connected uninodal (44.66)-pcu net, whereas 15 displays a 1D linear chain. Moreover, the thermal properties of complexes 12-13 were investigated.

碩士
中原大學
化學研究所
106
Three Cd(II) coordination polymers constructed from flexible bis-pyridyl-bis-amide ligands and dicarboxylic acids with different flexibility, {[Cd(L1)(SA)]．5H2O．CH3OH}n, (L1 = N,N’-di(3-pyridyl)adipoamide ; H2SA = suberic acid), 1, {[Cd(L1)(AA)]．2H2O}n, (H2AA = adipic acid), 2, {[Cd(L2)(SA)]．5H2O．3H2O }n, (L2 = N,N’-di(3-pyridyl)suberoamide), 3, were synthesized by hydrothermal reactions. These complexes were structurally characterized by using single-crystal X-ray diffraction and churactized by using powder X-ray diffraction, Elemental Analyzer and IR spectra. Complexes 1 and 2 and 3 are 2D layers with the sql topologys. Luminiscent and thermal propertties are also discussed.

碩士
中原大學
化學研究所
105
A series of divalent coordination polymers constructed from N,N’-di(3-pyridyl)suberoamide (L1), N,N’-di(4-pyridyl)suberoamide (L2), N,N’-di(3-pyridyl)adipamide (L3) and angular polycarboxylaic ligands, including {[Cd(L1)(2,6-PDC)]·5H2O}n (2,6-H2PDC = 2,6-pyridinedicarboxylic acid), 1, {[Cd(L2)(2,6-PDC)]·2.5H2O}n, 2, {[Cd(L1)1.5(1,2,3-HBTC]·2H2O}n (1,2,3-H3BTC = 1,2,3-benzenetricarboxylic acid), 3, [Ni(L2)(1,3-PDA)(H2O)2]n (1,3-PDA = 1,3-phenylenediacetic acid), 4, [Co(L2)(1,3-PDA)(H2O)2]n, 5, [Co(L1)(5-NH2-IPA)]n (5-NH2-H2IPA = 5-aminoisophthalic acid), 6, {[Co(L2)0.5(5-NH-IPA)(H2O)2]．2H2O}n, 7, [Co(L1)(5-NO2-IPA)(H2O)]n (5-NO2-H2IPA = 5-aminoisophthalic acid), 8, [Co(L1)1.5(1,4-NDC)(H2O)]n (1,4-H2NDC = 1,4-naphthalenedicarboxylic acid), 9, [Co3(L1)1.5(1,4-NDC)3(EtOH)]n, 10, {[Co(L2)1.5(1,4-NDC)]．H2O }n, 11, {[Co(L2)0.5(1,4-NDC)]·(EtOH)}n, 12, {[Ni(L2)1.5(1,4-NDC)]．H2O }n, 13, and [Co(L3)( 1,3,5-HBTC) (H2O)]n (1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid), 14, have been synthesized by hydrothermal reactions. Their structures have been determined by single-crystal X-ray diffraction analyses and characterized by powder X-ray diffraction and thermal gravimetric analysis. Complexes 1, 4, 5, 6, 8 and 9 are 2D layers with the sql topology and 2 and 14 form 1D looped chains, while 3 exhibits a 3D framework with a new (65.8) topology that shows a (1 + 4) self-penetration, and 7 displays a 2D network with a new (63)(65.8) topology. Complex 10 exhibits a 3D framework with a new (48.66.8) topology that shows a (1 + 2) self-penetration, and 11 and 13 display 5-fold interpenetrated 3D frameworks with the bnn topology, while 12 displays a 2-fold interpenetrated 3D framework with the pcu topology. While complexes 4 and 9 show structural reproducibility toward water, complexes 9 and 10 display irreversible structural transformation upon solvent exchange. Moreover, complexes 4 and 5 show catalytic effect on the photodegradation.