Solvent-dependent fac/mer-isomerization and self-assembly of triply helical complexes bearing a pivot part

Abstract

Tris-chelate metal complexes of unsymmetrical bidentate ligands can form two geometric stereoisomers, facial (fac) and meridional (mer) isomers. Due to their small difference in properties, the highly-selective synthesis of one...

Stereoisomeric coordination polymers based on facial and meridional six-coordinate dysprosium(iii )

“…4 Because of the small differences in their chemical properties, it is challenging to selectively synthesise one of the isolated isomers. 5 Moreover, only a handful of fac/mer isomers of lanthanide complexes have been reported, [6][7][8][9] due to the predominant ionic bonding regimes of the 4f-elements. In addition to chemical challenges, constructing certain coordination environments for lanthanide ions is also of particular interest, especially in the field of single-molecule magnets (SMMs).…”

Electronic insights into aminoquinoline-based PNHN ligands: protonation state dictates geometry while coordination environment dictates N–H acidity and bond strength

“…The synthesis of the complex in acetonitrile led to preliminary isolation of the compound as a dark oily residue even when dried under high vacuum. This residue by 31 P{ 1 H} NMR spectroscopy was shown to be impure due to the appearance of an additional resonance in the NMR spectrum at ∼49 ppm. After re-dissolving in benzene, filtration through Celite, and lyophilization, the isolated free-flowing dark purple powder was then determined to be pure by 31 P{ 1 H} NMR spectroscopy.…”

“…This residue by 31 P{ 1 H} NMR spectroscopy was shown to be impure due to the appearance of an additional resonance in the NMR spectrum at ∼49 ppm. After re-dissolving in benzene, filtration through Celite, and lyophilization, the isolated free-flowing dark purple powder was then determined to be pure by 31 P{ 1 H} NMR spectroscopy. Single crystal XRD of 7 (Fig.…”

“…pK a studies of metal-coordinated secondary amine N-H protons A series of pK a studies were performed to probe the acidity of the coordinated secondary amine in the complexes, using an appropriate base and quantitative, inverse gated decoupled 31 P {gated 1 H} NMR. To make the NMR quantitative, a long relaxation delay time of five seconds was used.…”

“…Fac to mer isomerization of transition metal complexes is not uncommon and has been studied in the literature. [22][23][24][25][26][27][28][29][30][31] As a result of our synthetic investigations, a series of complexes reported herein bearing coordinated secondary amines and their deprotonated analogues were found to be excellent candidates for the determination of the pK a and bond dissociation free energy (BDFE) of their N-H bonds. Upon coordination to a metal, amines with at least one hydrogen generally become more acidic and the N-H BDFE can be lowered.…”