Supramolecular dyad derived from a buckybowl series of O2N2-donor naphthodiaza-crowns coordinated to C60: photophysical,NMR and theoretical studies

Supramolecular complexation of C₆₀ with L¹-L⁵ were studied in toluene, chloroform and 1,2-dichlorobenzene solvents using UV–vis, fluorescence, ¹H, ¹³C NMR spectroscopy as well as density functional theory (DFT) calculations. The Job’s plot of continuous variation method established 1:1 stoichiometry for L¹-L⁵/C₆₀. Binding constants (K) calculated for L¹-L⁵/C₆₀ were also determined employing UV–vis and fluorescence spectroscopy. Both steady-state and time-resolved fluorescence spectroscopic surveys showed remarkable fluorescence quenching phenomenon for L¹-L⁵ in the presence of C₆₀ which was primarily attributed to involvement of a static process. The observed fluorescence quenching in L¹–L⁵ was described in terms of both π–π and n–π interactions of the naphthalene moieties and the nitrogen donor groups on the aza-crown macrocyclic ligands with C₆₀, respectively. Moreover, DFT calculations using B₃LYP/6-31G* basis set confirmed on the aforesaid π–π interaction of naphthalene groups on the aza-crowns with C₆₀. The DFT calculations also established significant distributions of charge between C₆₀ and L¹-L⁵ in according to the electronic structure and geometry of L¹-L⁵/C₆₀, very similar to phthalocycnine/C₆₀ systems.     

Synthetic Ionophores. Part 20: Synthesis and Ionophore Character of 2-Aminothiophenol and 1,3-/1,4-Phenylene Based Silver Selective Receptors

Nucleophilic displacements of 1,3- and 1,4-bis(bromomethyl)benzenes with 2-aminothiophenol provide 1,3- and 1,4- bis(2-aminophenylthiomethyl)benzenes 3 and 11 which undergo intermolecular cyclodehydrochlorination with thiodiglycolyl dichloride and isophthaloyl dichloride to give respectively 6, 8 and 12,13. The diamine 3 and its N,N'-dibenzyl derivative 4 with pyridine-2,6-dicarbonyl dichloride give 7 and 5, respectively. The extraction and transport behaviour of these receptors have been determined towards alkali (Li⁺, Na⁺, K⁺),alkaline earth (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺), Tl⁺, Ag⁺ and Pb²⁺ picrates.The participation of various ligating sites in binding have been evaluated through ¹³ NMR studies. The acyclic receptors 3, 4 and 11 show higher Ag⁺ selectivity than the cyclic analogs 6 and 12. In the case of acyclic receptor 3 the organisation induced by the 1,3-phenylene spacer and 2-aminophenylthio units and its flexibility generates optimal binding and selectivity towards Ag⁺. However, in cyclicreceptors 3 and 12 though the three thioether unitsare better organised, the inward placement of the NH_amide units restricts the entry of Ag⁺ into the cavity and lowers both the order of binding and selectivity. The lack of binding ability in 7due to an intramolecular NH_amide–-N_py H-bond isrestored in the N-benzyl derivative 5.     

A highly selective fluorescent chemosensor for successive detection of Fe3+ and CN− in pure water

A water-soluble fluorescent chemosensor (D) based on 1, 8-naphthalimide derivative has been designed and synthesised as a new fluorescent sensor for successive detection of Fe³⁺ and CN^?. Fluorescence measurements show that chemosensor D has excellent fluorescent-specific selectivity and high sensitivity for Fe³⁺ over many other metal ions in pure water. Moreover, the complex of D and Fe³⁺ (D–Fe³⁺) displayed high sensitivity for CN^? over many other anions in the same medium. Even more important, the recognition of the sensor D for Fe³⁺ and D–Fe³⁺ complex for CN^- could be used successfully in pure water. The test strips based on D and D–Fe³⁺ exhibited good selectivity to Fe³⁺ and CN,^- respectively, we believe the test strips could serve as convenient and efficient Fe³⁺ and CN^? test kits.     

Synthesis,spectral characterization,and evaluation of antimicrobial activity of O,O′-alkanediyl S-(N-phthalimidomethyl) dithiophosphates and zinc bis(O,O′-alkanediyl) dithiophosphates

The synthesis of novel dithiophosphate derivatives has been achieved. Two O,O′-alkanediyl S-(N-phthalimidomethyl) dithiophosphates and two Zinc bis(O,O′-alkanediyl) dithiophosphates are synthesized by an easy and facile chemical synthetic route. Zinc bis[O,O′-(2-methylpentane-2,4-diyl) dithiophosphate] L¹, Zinc bis[O,O′-(2-ethylhexane-1,3-diyl) dithiophosphate] L², O,O′-(2-methylpentane-2,4-diyl) S-(N-phthalimidomethyl) dithiophosphate L³ and O,O′-(2-ethylhexane-1,3-diyl) S-(N-phthalimidomethyl) dithiophosphate L⁴ are synthesized from the respective ammonium salts. Compounds L¹, L², L³, and L⁴ are characterized by (CHN) elemental analysis, ESI mass, FT-IR, ¹H, ¹³C, and ³¹P NMR techniques. The crystal structure of ammonium O,O′-(2-methylpentane-2,4-diyl) dithiophosphate is discussed. L¹, L², L³, and L⁴ were evaluated for antimicrobial activity. It was found that the phthalimide derivatives L³ and L⁴ showed much better antifungal potential against some species of fungus. The Zinc dithiophosphates L¹ and L² showed good antibacterial activity against Bacillus cereus and Escherichia coli.     

Bis(naphthol)-based fluorescent chemoprobe for cesium cation and its immobilisation on silica nanoparticle as a high selective adsorbent

Abstract

A bis(naphthol)-based cation receptor 1 has been synthesised by three steps of synthetic procedure. The spectroscopic properties of 1 upon addition of various metal ions were investigated by UV–vis absorption and fluorescence spectroscopy. As a result, the absorption of 1 was linearly decreased as a function of concentration of added Cs⁺. Also, 1 exhibited dramatic fluorescence quenching effect upon exposure to caesium cation. Contrastively, no significant quenching effect was observed upon addition of other metal ions such as Na⁺, K⁺, Rb⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ni²⁺ and Zn²⁺. It was found that 1 formed a 1:1 complex with Cs⁺ by Job’s plot. Furthermore, we also prepared 1-functionalised silica nanoparticle (SiO₂-1) as an adsorbent for Cs⁺. SiO₂-1 showed a great capacity for selective removal of caesium ion from aqueous solution as well as from tap water. Thus, it is potentially useful for the detection and removal of caesium cation from environmental and biological fluids polluted by nuclear radiation and nuclear waste.     

Theoretical study on structures and stability of HC2P isomers

 The structures and isomerization pathways of various HC₂P isomers in both singlet and triplet states are investigated at the B3LYP/6-311G(d,p), QCISD/6-311G(d,p) (for isomers only) and single-point CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) levels. At the CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) level, the lowest-lying isomer is a linear HCCP structure ³ 1 in the ³∑⁻ state. The second low-lying isomer has a CPC ring with exocyclic CH bonding ¹ 5 in a singlet state at 10.5 kcal/mol. The following third and fourth low-lying isomers are a singlet bent HCCP structure ¹ 1 at 20.9 kcal/mol and a bent singlet HPCC structure ¹ 3 at 35.8 kcal/mol, respectively. Investigation of the HC₂P potential-energy surface indicates that in addition to the experimentally known isomer ³ 1, the other isomers ¹ 1, ¹ 3 and ¹ 5 also have considerable kinetic stability and may thus be observable. However, the singlet and triplet bent isomers HCPC ¹ 2 and ³ 2 as well as the triplet bent isomer HPCC ³ 3 are not only high-lying but are also kinetically unstable, in sharp contrast to the situation of the analogous HCNC and HNCC species that are both kinetically stable and that have been observed experimentally. Furthermore, the reactivity of various HC₂P isomers towards oxygen atoms is briefly discussed. The results presented here may be useful for future identification of the completely unknown yet kinetically stable HC₂P isomers ¹ 1, ¹ 3 and ¹ 5 either in the laboratory or in interstellar space. Received: 5 November 2000 / Accepted: 25 November 2001 / Published online: 8 April 2002     

Different conjugated system Cd(II)/Hg(II) Schiff base complexes: syntheses,supramolecular metal−organic frameworks,luminescent properties and DFT study

A series of different conjugated systems of 2D/3D supramolecular metal-organic frameworks (SMOFs) are constructed by C/O?H?Cl hydrogen bonds and π?π interactions. These complexes, [HgL¹Cl₂] (1), [HgL²Cl₂] (2), [HgL³Cl₂] (3), [CdL⁴Cl₄]₂ (4), and [CdL⁵Cl₂(CH₃OH)] (5), have been synthesized and characterized by single-crystal X–ray diffraction, ¹H NMR, FT–IR, and EA. The X-ray diffraction analyses reveal that 1 features a 3D supramolecular framework with {4⁴·6⁶} topology structure, while 2, 3, and 5 exhibit 3D 6-connected {4¹²·6³} topology structures. Complex 4 shows a two-dimensional layer with 4⁴ topology structure. Based on these varied structures caused by different conjugated system, the emission maximum wavelengths of 1–5 can be tuned in a large range of 492–587 nm. Both electron-donating ability and the conjugated system in general can support λ_em shift to red direction. In order to have better understanding of electronic transitions of the complexes, a time-dependent DFT study has been performed. The enhancement of the fluorescence intensities for the complexes compared to the ligands indicates potential to serve as photoactive materials.     

Synthesis,structure and isomerism of “three-bridge” exo-nido-osmacarborane clusters

The reaction of OsCl₂(PPh₃)₃ with [nido-7-R¹-8-R²-C₂B₉H₁₀]K⁺ produced a series of new exo-nido-osmacarborane complexes exo-nido-5,6,10-[Cl(Ph₃P)₂Os]-5,6,10-(-H)₃-10-H-7-R¹-8-R²-7,8-C₂B₉H₆ (1: R¹ = R² = H; 2: R¹ = R² = Me; 3: R¹ = R² = PhCH₂; 4: R¹ + R² = 1,2-C₆H₄(CH₂)₂; 5: R¹ = H, R² = Me) in which the osmium-containing group is linked to the nido-carborane ligand through three two-electron three-center bonds. Compounds 1—5 are formed as mixtures of symmetric (a) and asymmetric (b) isomers; pure symmetric isomers 2a and 4a were isolated by fractional crystallization, and the mixture of isomers 3a, was quantitatively separated into individual compounds 3a and 3b by column chromatography on silica gel. Detailed analysis of the ³¹P{¹H}, ¹H, ¹¹B NMR spectra of 1a,b—5a,b and 2D ¹H-¹H{¹¹B} and ¹¹B{¹H}-¹¹B{¹H} NMR spectra of 3a and 3b was performed. The structures of isomers 2a and 4a were confirmed by an X-ray diffraction study. According to the NMR and X-ray diffraction data, the isomerism of exo-nido-complexes 1a,b—5a,b is actually the cis—trans-isomerism of ligand arrangement in the octahedral coordination of the Os atom.     

1,2-Bis-[(5-methyl/chloro/nitro)-2-1H-benzimidazolyl]-1,2-ethanediols and their PdCl2 complexes

1,2-Bis-[(5-methyl)-2-1H-benzimidazolyl]- (L ¹), 1,2-bis-[(5-chloro)-2-1H-benzimidazolyl]- (L ²), 1,2-bis-[(5-nitro)-2-1H-benzimidazolyl]-1,2-ethanediol (L ³) and their PdCl₂ complexes were synthesized and characterized by elemental analysis, molar conductivity, i.r. and ¹H-n.m.r. spectra. The benzene ring substituents lead to a decrease in melting point. The methyl group reduces the solubility and the acidity of L ¹ and Pd(L ¹)Cl₂, whereas the Cl and NO₂ groups increase the solubility and the acidity of L ², L ³, Pd(L ²)Cl₂ and Pd(L ³)Cl₂. In Pd(L ¹)Cl₂ and Pd(L ²)Cl₂ complexes, the ligands act as a bidentate through two nitrogen atoms. In Pd(L ³)Cl₂, ligand coordination occurs through one OH group oxygen atom and one of the benzimidazole nitrogen atoms.     

Double-armed and tetra-armed cyclen-based cryptands

Double-armed and tetra-armed cyclen-based cryptands (1a–1d and 2) that bridge two aromatic rings by diethyleneoxy and triethyleneoxy units were prepared. The CSI-MS of 1:1 mixtures ([Ag⁺]/[ligand]) indicated that these new cryptands form 1:1 complexes with Ag⁺. The log K values for the interaction between Ag⁺ and 2 was greater than those of 1a–1d, double-armed cyclens (3a–3c and 4), and tetra-armed cyclen (5). The Ag⁺-ion-induced ¹H NMR spectral changes suggest that the Ag⁺–π interactions of the Ag⁺ complexes with the cryptands (1a–1d and 2) are stronger than those in Ag⁺/double-armed and tetra-armed cyclens. To visualise the Ag⁺?π interactions, the isosurfaces of the LUMO and HOMOs of the Ag⁺ complexes were calculated at the B3LYP/3–21G(*) theoretical level. The LUMO of the Ag⁺ ion is distorted by interaction with the HOMOs of the aromatic side arms. The calculations reveal Ag⁺?π interactions between the Ag⁺ ion and the aromatic side arms, and these are shown graphically.     

Exploiting Complementary Second-sphere Effects in Supramolecular Coordination Solids

In the design of extended supramolecular solids, reliable synthons are a valuable commodity. This work concerns the complementary second-sphere coordination interactions between a highly preorganized hexasulphonated ligand, L, and aquated metal ions. Four second-sphere inclusion complexes [M(H²O)⁶]² L ·(S)³ (M/S: Mg/acetone, 1; Zn/acetone, 2, Mg/dioxane, 3; Zn/dioxane, 4) and three extended networks {[(M(H²O)³)²(L)]·(H²O)^14.5}^∞ (M=Cr, 5; Fe, 6; Al, 7) have been structurally characterized by X-ray crystallography. The second-sphere effects on the stabilization of the primary coordination sphere are illustrated by TGA experiments. In these assemblies, the potential of a new supramolecular synthon is illustrated, that being the complementary hydrogen-bonding interaction between cis-aquo ligands and sulphonate oxygen atoms.     

A criterion for the confluence of two seams of conical intersection in triatomic molecules

It is shown that the cross product t ^{I J} (R _x )≡g ^{I J} (R _x )×h ^{I J} (R _x ), where g _τ ^{I J} (R)=(c ^I (R _x )−c ^J (c ^I (R _x )+c ^J (R _x )), h _τ ^{I J} (R)=c ^I (R _x )^† c ^J (R _x ), τ is an internal nuclear coordinate, the c ^I (R) satisfy [H(R)−E _I (R)]c ^I (R)=0 and H(R) is the electronic Hamiltonian matrix, is a unique property of a conical intersection at R _x . t ^{I J} (R _x )=0 when R _x is located at the intersection of two (or more) seams of conical intersection. This criterion for an intersection of two seams of conical intersection has important implications for algorithms that seek to locate such points. Here it␣is␣used to analyze the trifurcation of a generic C_2v ^2S+1 A−^2S+1 B seam of conical intersection, analogous to those recently found in AlH₂ and CH₂. Received: 31 July 1997 / Accepted: 27 August 1997     

Zinc(II) and mercury(II) complexes with Schiff bases: syntheses,spectral, and structural characterization

Schiff bases o-vanilidene-1-aminobenzene (HL¹) and o-vanilidene-2-methyl-1-aminobenzene (HL²) lead to the formation of mono- and bis-[(Cl)Zn(L¹)] (1), [(Cl)Zn(L²)] (2), [(Cl)Hg(L¹)] (3), [(Cl)Hg(L²)] (4), [Zn(L¹)₂] (5), [Zn(L²)₂] (6), [Hg(L¹)₂] (7), and [Hg(L²)₂] (8) complexes by reactions of zinc(II) and mercury(II) chlorides in different mole ratio(s). Complexes 1–8 have been characterized by elemental analyses (Zn, Hg, C, H, Cl, and N), melting point and spectral (IR, ¹H-NMR), PXRD, molar conductivity measurement, and TGA. Conductivity measurements suggest non-electrolytes. Structural compositions have been assigned by mass spectral studies. Four-coordinate geometry may be assigned to these complexes tentatively. Structural study reveals that in 1–4 two metal centers are held together by two bridged (μ₂-Cl) chlorides, whereas 5–8 contain two bidentate Schiff-base ligands around one metal-producing monomers.     

Synthesis of mixed-ligand complexes of VO2+ and VO3+ incorporating hydrazone, 1,10-phenanthroline and 8-hydroxyquinoline

2-Aminobenzoylhydrazide (abh) reacts with equimolar amounts of either [V^IVO(acac)₂] or [V^IVO(bzac)₂] (where acac^? and bzac^? are the monoanionic forms of acetylacetone (Hacac) and benzoylacetone (Hbzac), respectively) in the presence of equimolar amounts of 1,10-phenanthroline (phen) to form the octahedral mixed-ligand complexes [V^IVO(L¹)(phen)] (1) and [V^IVO(L²)(phen)] (2), where (L¹)^2? and (L²)^2? are the dianionic forms of the 2-aminobenzoylhydrazone of acetylacetone (H₂L¹) and benzoylacetone (H₂L²). Upon substituting phen by 8-hydroxyquinoline (Hhq), pentavalent [V^VO(L¹)(hq)] (3) and [V^VO(L²)(hq)] (4) complexes were instead obtained. In the crystal structures of 3 and 4, the hydrazone ligands coordinate to the vanadium center through the enolic-O, one imine-N and amide-O in a mer geometry. The amine and the second imine nitrogen form intramolecular hydrogen bonds. Complexes 1 and 2 display quasi-reversible one-electron oxidation peaks near +0.60 V, while the pentavalent 3 and 4 exhibit quasi-reversible one-electron reduction peaks near ?0.18 V versus Ag/AgCl in CH₂Cl₂ solution. EPR spectroscopic studies on 1 and 2 suggest that the unpaired electron is present in the d_xy orbital. DFT studies for 3 indicate that the d_xy orbital of vanadium is the main contributor to the LUMO.     

Unusual Formation of a β-linked Disaccharide in a Nis Glycosylation

Abstract

The N-halosuccinimide glycosylation is a highly selective reaction that leads to trans-configured 1-alkoxy-2-halo-glycosides (halo = bromo, iodo).²³ As an exception to the generally observed exclusive formation of α-linked glycosides in such reactions,² we obtained a 3 / 1 mixture of α- and β-disaccharide 6 and 7, when we treated the silylated glycal 4 with NIS (N-iodosuccinimide) and the glycoside 5.⁴ The similarly protected arabino glycal 9, on the other hand, gave exclusively the expected α-linked saccharide 11, when treated with NIS and the alcohol component 10.⁵ Silylated glycals 4 and 9 were obtained from L-digitoxal 1 ⁶ and L-rhamnal 8 ⁷ by treatment with tert-butyldiphenylchlorosilane⁸ and tert-butyldimethylchlorosilane,⁹ respectively. In both cases the 3-O-silylated derivatives formed in high yields. Only in case of the ribo-configuration minor amounts of a 4-O-silylated product 3 were identified.     

Construction of acetate-bridged dicopper(II) hybrid organic–inorganic networks with calix[4]arene-derived nitrogenous ligands

The reactions of mono-, bis- and tetrapicolyl-p-tert-butylcalix[4]arene derivatives functionalised in the phenolic positions (L ¹ –L ⁴ ) with copper(II) acetate resulted in the formation of discrete complexes or extended coordination polymers. The centrosymmetric dimer [Cu₂(μ-O₂CCH₃)₄(L ¹ )₂] 1, obtained with monodentate L ¹ , has square pyramidal coordination around the copper centres and a cone conformer of monopicolyl-calix[4]arene acting as an axial ligand, with a molecule of acetonitrile hosted within its cavity. The potentially bidentate L ² acts as a monodentate ligand, affording the complex [Cu₂(μ-O₂CCH₃)₄(L ² )₂] 2, which based on spectroscopic and combustion analysis data has a similar coordination sphere around Cu(II). Compound L ³ bridges two dicopper units in the coordination polymer [Cu₂(μ-O₂CCH₃)₄(μ-L ³ )] _n 3, with the calixarene hosting a molecule of tetrahydrofuran. Finally, compound L ⁴ reacts with 4 equivalents of copper(II) acetate, presumably generating a two-dimensional coordination polymer formulated as [{Cu₂(μ-O₂CCH₃)₄}₂(L ⁴ )] 4.     

Synthesis of the [<Superscript>2</Superscript>H,<Superscript>15</Superscript>N]-labeled antiviral drug “triazavirine”

Selective methods for the incorporation of stable isotopes ¹⁵N and ²H into the structure of antiviral medicine “triazavirine” 1 were developed. The synthesized isotopically modified “triazavirine” 1– ² H ₃ , ¹⁵ N ₃ contained the labeled atoms in both the azole and the azine rings. ¹³C and ¹⁵N NMR spectra of the isotope-containing sample 1– ² H ₃ , ¹⁵ N ₃ were thoroughly analyzed.     

A series of Keggin-based AgI-belt/cycle structures constructed from 5-phenyl-1H-tetrazole and its derivative through Ag–N and Ag–C bonds

Three Keggin-based compounds containing Ag^I belts and cycles constructed from 5-phenyl-1H-tetrazole (L¹) and its derivative 5-m-tolyl-1H-tetrazole (L²), [Ag₉L¹₅(PW^VW^VI₁₁O₄₀)]·H₂O (1), [Ag₁₁L¹₆(H₂O)₂(SiMo^VMo^VI₁₁O₄₀)] (2) and [Ag₁₀L²₈(HPMo₁₂O₄₀)]·H₂O (3), have been synthesized under hydrothermal conditions and characterized by IR spectra and single crystal X-ray diffraction. Compound 1 shows a channel-like 3-D metal-organic framework with Keggin anions in channels. Adjacent layers of 2 share the same anions to construct a 3-D framework. Compound 3 has a 2-D metal-organic layer containing Ag^I cycles. Adjacent layers link through sharing Ag–N bonds and a channel-like 3-D framework is formed. Electrochemical and photocatalytic properties of 1–3 have been studied. The experimental results show that 1–3 have excellent catalytic performance for reduction of nitrite and bromate and also have photocatalytic properties for degradation of MB and RhB.     

Trigonal (-3) symmetry octahedral lanthanide(III) complexes of zwitterionic tripodal ligands: luminescence and magnetism

Sandwich coordination complexes, [Ln^III(H₃L)₂]X₃?solvents, of Tb(III), Eu(III), Dy(III), Ho(III) and Er(III) were prepared with two new zwitterionic ester-substituted tripodal amine ligands, tris((2-hydroxy-5-n-butyl benzoate)aminoethyl)-amine (H₃L¹) and tris((2-hydroxy-5-methyl benzoate)aminoethyl)-amine (H₃L²). These ligands were synthesised by condensation of the appropriately substituted salicylaldehyde with tris(2-aminoethyl)amine (tren) followed by in situ reduction of the tris-imine to tris-amine. Subsequent 2:1 reaction with lanthanide(III) ions yields [Ln^III(H₃L)₂]X₃?solvents (L = L¹, L²; X = Cl^?, NO₃^?; solvents = MeOH or H₂O). All complexes were characterised by microanalysis, infrared spectroscopy, high resolution mass spectrometry and solid-state photoluminescence measurements. The crystal structures of [Tb^III(H₃L¹)₂]Cl₃·6MeOH, [Dy(H₃L¹)₂]Cl₃·6MeOH, [Eu^III(H₃L¹)₂]Cl₃·6MeOH and [Tb^III(H₃L¹)₂](NO₃)₃ reveal high-crystallographic ?3 symmetry at the O₆-coordinated octahedral lanthanide(III) ions and that the tripodal ligands are bound in zwitterionic form: the protons from the phenolic oxygens have migrated to the amino nitrogens. Photoluminescence measurements indicate various degrees of energy transfer of the ligand chromophore to the lanthanide ions, as both ligand and lanthanide emission features are observed. Despite the high-crystallographic symmetry and the likely small transverse magnetic anisotropy of the complexes, no evidence of slow relaxation of the magnetisation, characteristic of a single-molecule magnet, was observed for [Tb^III(H₃L¹)₂]Cl₃·MeOH·3H₂O, [Dy^III(H₃L¹)₂]Cl₃·6H₂O, [Ho^III(H₃L¹)₂](NO₃)₃·2H₂O, [Er^III(H₃L¹)₂]·H₂O and [Tb^III(H₃L¹)₂](NO₃)₃ down to 2.0 K.     

Synthesis,coordination properties and DFT studies of novel trans-disubstituted hexaaza-macrocycles containing pyridine and/or ethyldioxolane arms

Abstract

Novel trans-disubstituted hexaaza-macrocyclic ligands L¹ and L² were successfully prepared by the alkylation of the trans secondary amines presented in L with pyridine and ethyldioxolane groups, respectively. The coordination properties of compounds L¹ and L² towards different transition, post-transition and lanthanoid metal ions were explored. Colorless crystals of [NaL¹]I and L^2´Br₂, suitable for X-ray diffraction, were obtained by slow evaporation of an acetonitrile solution of compounds L¹ or L², showing an anti conformation between the methyl groups and the pendant arms in trans positions. The [ML¹]ⁿ⁺ (M?=?Ni²⁺, Cu²⁺, Zn²⁺) systems were investigated by DFT calculations (B3LYP model).