1854-74-6Relevant academic research and scientific papers
Hierarchical assembly of helicate-type dinuclear titanium(IV) complexes
Albrecht, Markus,Mirtschin, Sebastian,De Groot, Marita,Janser, Ingo,Runsink, Jan,Raabe, Gerhard,Kogej, Michael,Schalley, Christoph A.,Froehlich, Roland
, p. 10371 - 10387 (2005)
The ligands 4-7-H2 were used in coordination studies with titanium(IV) and gallium(III) ions to obtain dimeric complexes Li 4[(4-7)6Ti2] and Li6[(4/5a) 6Ga2]. The X-ray crystal structures of Li 4[(4)6Ti2], Li4[(5b) 6Ti2], and Li4[(7a)6Ti2] could be obtained. While these complexes are triply lithium-bridged dimers in the solid state, a monomer/dimer equilibrium is observed in solution by NMR spectroscopy and ESI FT-ICR MS. The stability of the dimer is enhanced by high negative charges (Ti(IV) versus Ga(III)) of the monomers, when the carbonyl units are good donors (aldehydes versus ketones and esters), when the solvent does not efficiently solvate the bridging lithium ions (DMSO versus acetone), and when sterical hindrance is minimized (methyl versus primary and secondary carbon substituents). The dimer is thermodynamically favored by enthalpy as well as entropy. ESI FT-ICR mass spectrometry provides detailed insight into the mechanisms with which monomeric triscatecholate complexes as well as single catechol ligands exchange in the dimers. Tandem mass spectrometric experiments in the gas phase show the dimers to decompose either in a symmetric (Ti) or in an unsymmetric (Ga) fashion when collisionally activated. The differences between the Ti and Ga complexes can be attributed to different electronic properties and a charge-controlled reactivity of the ions in the gas phase. The complexes represent an excellent example for hierarchical self-assembly, in which two different noncovalent interactions of well balanced strengths bring together eleven individual components into one well-defined aggregate.
Solvent Dependence of the Monomer–Dimer Equilibrium of Ketone-Substituted Triscatecholate Titanium(IV) Complexes
Kwamen, A. Carel N.,Jenniches, Judith,Oppel, Iris M.,Albrecht, Markus
supporting information, p. 10550 - 10554 (2020/07/24)
Hierarchical helicates based on ketone-substituted titanium(IV)triscatecholates show different monomer-dimer behavior depending on different solvents. The dimerization constants of a whole series of differently alkyl-substituted complexes is analyzed to show that the solvent has a very strong influence on the dimerization. Hereby, effects like solvophobicity/philicity, sterics, electronics of the substituents and weak side-chain—side-chain interactions seem to act in concert.
