2794-60-7Relevant academic research and scientific papers
Pyridyldiimine macrocyclic ligands: Influences of template ion, linker length and imine substitution on ligand synthesis, structure and redox properties
Thierer, Laura M.,Wang, Qiuran,Brooks, Sam H.,Cui, Peng,Qi, Jia,Gau, Michael R.,Manor, Brian C.,Carroll, Patrick J.,Tomson, Neil C.
, (2021)
A series of 2,6-diiminopyridine-derived macrocyclic ligands have been synthesized via [2 + 2] condensation around alkaline earth metal triflate salts. The inclusion of a tert-butyl group at the 4-position of the pyridine ring of the macrocyclic synthons results in macrocyclic complexes that are soluble in common organic solvents, thereby enabling a systematic comparison of the physical properties of the complexes by NMR spectroscopy, mass spectrometry, solution-phase UV–Vis spectroscopy, cyclic voltammetry and single-crystal X-ray crystallography. Solid-state structures determined crystallographically demonstrate increased twisting in the ligand, concurrent with either a decrease in ion size or an increase in macrocycle ring size (18, 20, or 22 membered rings). The degree of folding and twisting within the macrocycle can be quantified using parameters derived from the Npyr-M-Npyr bond angle and the relative orientation of the pyridinediimine (PDI) and pyridinedialdimine (PDAI) fragments to each other within the solid state structures. Cyclic voltammetry and UV–Vis spectroscopy were used to compare the relative energies of the imine π* orbital of the redox active PDI and PDAI components in the macrocycle when coordinated to redox inactive metals. Both methods indicate the change from a methyl to hydrogen substitution on the imine carbon lowers the energy of the ligand π* system.
A Novel High-yield Route to Organic Derivatives of Group 2 Metals; X-Ray Structure of 4(py)14>*py (OTf = OSO2CF3) and NMR Spectral Characterisation of (R = SiMe3)
Frankland, Andrew D.,Hitchcock, Peter B.,Lappert, Michael F.,Lawless, Gerard A.
, p. 2435 - 2436 (1994)
Treatment of M(OTf)2 with 2 MOAr or 2 MNR2 (M = Na or K, Ar = C6H2But2-2,6-Me-4; R = SiMe3) in thf at 0 deg C affords 4, (M = Sr 5 or Ba 6), (M = Ca 7 or Sr 8) or 9; the new compounds 1-3 have been characterised by their NMR spectra in pyridine, and the pyridine adduct of 3 also by X-ray diffraction: crystalline 2-OTf)2(μ-OTf)2(μ3-OTf)4(py)14>*py 10 is unique among metal triflates in having three different bonding modes for the -OTf ligand.
Structure of a Hydrated Sulfonatotitanyl(IV) Complex in Aqueous Solution and the Dimethylsulfoxide Solvated Titanyl(IV) Ion in Solution and Solid State
Lundberg, Daniel,Persson, Ingmar
, p. 476 - 487 (2017)
The coordination chemistry of oxotitanium(IV) or titanyl(IV), TiO2+, has been studied in solution by X-ray methods. The titanyl(IV) ion hydrolyzes easily in aqueous systems to solid titanium dioxide as long as it is not stabilized through complexation. In this study the structures of the hydrated bissulfatotitanyl(IV) complex and the dimethylsulfoxide (DMSO) solvated titanyl(IV) ions have been determined. In isolated monomeric titanyl complexes titanium(IV) binds strongly to a doubly bound oxo group at ca. 1.64??, to four ligands in the equatorial plane almost perpendicular to the Ti=O bond at ca. 2.02??, and there is one weakly bound ligand, trans to the Ti=O bond, at ca. 2.22??, for oxygen donor ligands; the O=Ti–Oeq bond angles are 95°–100°. The structure of the DMSO solvated titanyl(IV) ion in the solid state is maintained in DMSO solution.
2,2′-Bis-azonia-cope rearrangements of 2,3-homo-6H-1,4-diazepinium dications
Quast, Helmut,Seidenspinner, Hubert-Matthias,Stawitz, Josef Walter
supporting information, p. 4852 - 4862 (2013/08/23)
The condensation of cis-1,2-cyclopropanediamines with 1,3-dicarbonyl compounds and 1,5-diazapentadienium salts afforded 2,3-homo-1H-1,4-diazepinium salts, which were protonated by very strong acids to yield 2,3-homo-6H-1,4- diazepinium dications. As measures of basicity, the mole fractions of water in trifluoromethanesulfonic acid at half-protonation were determined for 2,3-homo- and 2,3-dihydro-1H-1,4-diazepinium salts. 2,3-Homo-6H-1,4-diazepinium dications underwent 2,2′-bis-azonia-Cope rearrangements, as can be inferred from the product structures, or H/D exchange involving the methylene group of the cyclopropane rings. Apparently, in the Cope rearrangement, this group is interchanged with the methylene group in the seven-membered ring (C-6), which is susceptible to H/D exchange in strong deuteriated acids. Rapid, degenerate, as well as very slow, strongly biased Cope rearrangements have been uncovered in this way. 1H NMR spectra, recorded at elevated temperatures for a solution of the parent dication in trifluoromethanesulfonic acid, reveal broadening of the interchanging 2-H, 3-H and 5-H, 7-H signals and eventually the onset of their coalescence. Surprisingly, the estimated free enthalpy of activation is higher (ΔG?110 °C ≈ 73 ± 2 kJ/mol) than that of 3,4-homotropilidene (ΔG ?110°C = 61 kJ/mol), not lower, as would be expected on the basis of the well-known charge-acceleration of Cope rearrangements. Copyright
Molecular recognition of barbiturates by a metalloreceptor
Doorn, Arie R. van,Rushton, David J.,Straaten-Nijenhuis, Wilma F. van,Verboom, Willem,Reinhoudt, David N.
, p. 421 - 426 (2007/10/02)
Metallomacrocycle 2, possessing an immobilized Lewis-acidic uranyl cation, was synthesized by reaction of aldehyde 9 with 1,2-cis-cyclohexanediamine in the presence of Ba(2+) as a template cation and subsequent transmetallation with UO2(2+).Docking experiments with barbituric acid revealed that a -(CH2)6- spacer between the salen-uranyl and 2,6-diamidopyridine moieties of 2 is optimal.According to 1H-NMR titration experiments, the barbituric acid complex of 2 is up to 2.7 kcal*mol-1 more stable than the complexes with five disubstituted derivatives.The flux of barbbituric acid through a supported liquid membrane is enhanced 3.7 times by carrier 2 mediated transport.
