Attainment of Pentagonal-Bipyramidal LnIII Complexes from a Planar Pentadentate Ligand

The search for mononuclear lanthanoid-based single-ion magnets (SIMs) has increased the interest in some coordination environments with low coordination numbers, in combination with an axial symmetry, as they could maximize the anisotropy of complexes of oblate lanthanoid ions, such as dysprosium(III). In this sense, the pentagonal–bipyramid geometry can have ground-state doublets with perfect axiality, and therefore such complexes can be good candidates for SIMs. In our particular case, we have used a well-known open planar pentadentate chelating Schiff base ligand as 2,6-bis(1-salicyloylhydrazonoethyl)pyridine) (H4daps) for the synthesis of air-stable pentagonal–bipyramidal LnIII complexes (these being Ln: Dy and Er, oblate and prolate, respectively), in order to compare their structures. Thus, the reaction of H4daps with (CH3)4NOH·5H2O and the corresponding LnCl3·hexahydrate has yielded heptacoordinate [(CH3)4N][LnIII(H2daps)Cl2] complexes, where the tetramethylammonium cation is acting as the counterion of pentagonal–bipyramidal LnIII complexes, which are bearing two chloride atoms in apical positions. As both complexes could be crystallized as single crystals, we can compare their crystal structures, as well as with some other related complexes in the literature, which contain different counterions, trying to see their influence on other properties of the compounds, such as their magnetic behaviorThis research was funded by Spanish Ministerio de Innovación, Ciencia y Universidades grant number [PGC2018 102052-B-C21]S

Taking Advantage of the Coordinative Behavior of a Tridentate Schiff Base Ligand towards Pd2+ and Cu2+

We have explored the suitability of an O,N,N–donor Schiff base (H2SB) for obtaining dinuclear complexes with heavy metal ions such as Cu2+, Zn2+, Ni2+, and Co2+ (borderline acids) as well as Pd2+ and Cd2+ (soft acids). Spectroscopic studies demonstrated that the complexation of H2SB and Cu2+, Zn2+, Ni2+, Co2+, Pd2+, and Cd2+ occurred at a 1:1 stoichiometry. We have found two square planar centers with Pd-N-Pd angles of 93.08(11)° and a Pd–Pd distance of 3.0102(4) Å in Pd2(SB)2·Me2CO. This Pd–Pd distance is 30% shorter than the sum of the van der Waals radii, which is in accordance with a strong palladophilic interaction. Fluorescence studies on H2SB-M2+ interaction showed that H2SB can detect Cu2+ ions in a sample matrix containing various metal ions (hard, soft, or borderline acids) without interference. Determination of binding constants showed that H2SB has a greater affinity for borderline acids than for soft acidsThis research was funded by the Ministerio de Economía y Competitividad of Spain (Ref. CTQ2015-68094-C2-2-R)S

Different Bridging Preferences of Zinc and Palladium in Dimeric Complexes of a Ligand Based on 2-Tosylaminomethylaniline

The 18th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryWe report here the formation of dimeric palladium(II) and zinc(II) complexes of a ligand (H2L) derived from the condensation of 2 tosylaminomethylaniline and 2,3-dihydroxybenzaldehyde.The structures in solution of the corresponding palladium(II) and zinc(II) complexes could be deduced from NMR studies. With the aim of establishing an energy-structure relationship between the two possible linkage isomers (μ-O bridged and μ-N bridged), some theoretical energy calculations have been performe

Imine-tetrahydroquinazoline tautomerism in a tosilated Schiff base

The 14th International Electronic Conference on Synthetic Organic Chemistry session General Organic SynthesisCondensation of the selectively tosilated N-(2-aminobenzyl)-4-methylbenzenesulfonamide with 2-hydroxybenzaldehyde gives rise to (E)-N-(2-(2- hydroxybenzylideneamino)benzyl)-4-methylbenzenesulfonamide in the solid state, as the crystal structure determined shows, and which in solution shows equilibrium between the acyclic imine and 2-(3-tosyl-1,2,3,4-tetrahydroquinazolin-2-yl)pheno

Double imidazolidine condensation in a polynucleating Schiff base

The 14th International Electronic Conference on Synthetic Organic Chemistry session General Organic SynthesisCondensation of pentaethylenehexamine and 3-bromo-5-chlorosalicylaldehyde yielded the bisimidazolidine Schiff base ligand 5,6\'-(1E,1\'E)-(2,2\'-(3,3\'-(ethane-1,2- diyl)bis(2-(3-bromo-5-chloro-2-hydroxyphenyl)imidazolidine-3,1-diyl))bis(ethane- 2,1-diyl))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(2-bromo-4- chlorophenol), H4L. This diimine could be suitably characterised both in the solid state and in solutio

The crystal structure of a compartmental heptadentate ligand

The 13th International Electronic Conference on Synthetic Organic Chemistry session General Organic Synthesis2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine (H3L) was obtained with high purity by Schiff's condensation between 5-bromosalicyaldehyde and triethylenetetramine. Its recrystallisation in methanol yields single crystals suitable for X-ray diffraction studies. H3L crystallises in the monoclinic system, space group P21/c, with a = 21.641(3) Å, b = 11.1217(14) Å, c = 11.4156(15) Å and β = 90.016

Total Hydrolysis of a New Imidazolidine Induced by ZnII

The 18th International Electronic Conference on Synthetic Organic Chemistry session General Organic Synthesis2,2´-(2-(2-hydroxyphenyl)imidazolidin-1,3-diyl)diethanol(H3L) was obtained by condensation between 2-hydroxybenzaldehyde and N,N'-bis(2-hydroxyethyl)ethylenediamine. Its potential ability as NNOOO donor towards ZnII was tested. This study shows that zinc(II) mediates the fast hydrolysis of H3L, yielding the free aldehyde and amine. This latter was crystallographically characterised, showing a supramolecular 1D architecture based on hydrogen bond interaction

H-Bonded Polymerisation of Alternate Δ and Λ Metallohelicates

The 18th International Electronic Conference on Synthetic Organic Chemistry session Polymer and Supramolecular Chemistryhe neutral cadmium(II) complex Cd(HL)2 (H2L = 2-[(1H-imidazol-2-yl)methyleneamino]phenol) is chiral and it can be considered as a simple metallohelicate, with its corresponding Δ and Λ enantiomers. In the solid state, its helixes are hierarchically assembled as a linear polymer, via mutual N-H···O interactions between each two alternating enantiomers, and which also are π-π stacked, so this polymer is based on a by a dimeric repeat unit {Δ,Λ-[Cd(HL)2]2

Synthesis and Characterization of a New Triptycene-Based Tripod

The 18th International Electronic Conference on Synthetic Organic Chemistry session General Organic SynthesisHerein, we report an efficient and facile synthesis of a new triptycene based tripodal ligand containing both imine functionality and phenolic pendant arms. This tripodal unit is a potential building block for constructing novel supramolecular architectures. The newly synthesized 2,6,14-triaminotriptycene derivative, which was characterized by FT-IR, UV−Vis absorption, mass and NMR spectroscopic techniques has interesting properties such as high solubility in common organic solvents and fluorescence emission in THF solution (λ = 550 nm

A heteronuclear ZnGd complex as a potential contrast agent for magnetic resonance imaging

The 20th International Electronic Conference on Synthetic Organic Chemistry session Bioorganic, Medicinal and Natural ProductsA new ligand H3L, with internal compartments for allocating 3d metal ions and external donors to bind 4f ions, was synthesized and completely characterized. Reaction of H3L with zinc(II) and gadolin ium(III) salts allows isolating the heteronuclear complex {[ZnGd(HL)(NO3)(OAc)(CH3OH)](NO3)}∙6H2O (1·6H2O). The ability of 1·6H2O to act as a magnetic resonance imaging (MRI) contrast agent was evaluated and this study shows that both the transversal and longitudinal relaxivities are quite high but the T1/T2 ratio of 7.9 indicates that it could have even greater potential as a T2 contrast agen