Studies of κ2- and κ3-tripyridylamine complexes of ruthenium and π-stacking by pyridyls

The reaction of tris(pyridin-2-yl)amine with [CyRuCl2]2 (Cy = p-isopropyltoluene or cymene) in refluxing diglyme led to the formation of cis-[RuCl2{κ2-(2-py)3N}2]·CHCl3 (1a) after recrystallization from chloroform/pentane, or cis-dichloridobis[tris(pyridin-2-yl)amine-κ2N,N']ruthenium(II) dichloromethane disolvate, [RuCl2(C15H12N4)2]·2CH2Cl2 or cis-[RuCl2{κ2-(2-py)3N}2]·2CH2Cl2 (1b). Treatment of 1a with one equivalent of silver(I) hexafluoridoantimonate in dichloromethane gave [RuCl{κ2-(2-py)3N}{κ3-(2-py)3N}][SbF6]·CH2Cl2 (2a). Crystallization of 2a from chloroform provided chlorido[tris(pyridin-2-yl)amine-κ2N,N'][tris(pyridin-2-yl)amine-κ3N,N',N'']ruthenium(II) hexafluoridoantimonate chloroform monosolvate, [RuCl(C15H12N4)2][SbF6]·CHCl3 or [RuCl{κ2-(2-py)3N}{κ3-(2-py)3N}][SbF6]·CHCl3 (2b). Complex 2a reacted with a further equivalent of silver(I) hexafluoridoantimonate to give [Ru{κ3-(2-py)3N}2][SbF6]2 (3). The reaction of (2-py)3N with [CyRuCl2]2 in dichloromethane followed by treatment with excess sodium hexafluoridoantimonate gave the known complex [CyRuCl{κ2-(2-py)3N}][SbF6] (4). Complex 2 is a rare example of a complex containing both κ2- and κ3-(2-py)3N. Intramolecular π-stacking interactions determine the orientation of the free pyridyl in the κ2 complexes. An interesting encapsulation of methylene chloride hydrogen-bonded tetramers was noted in one case.

A Mitochondria-Localized Iridium(III)-Chlorin E6 Conjugate for Synergistic Sonodynamic and Two-Photon Photodynamic Therapy Against Melanoma

While melanoma in its early stages can be successfully treated, the prognosis strongly worsens with an increasing depth of the tumor. Capitalizing on this, there is an urgent need for...

Unravelling the Pathway Complexity in Conformationally Flexible N-Centered Triarylamine Trisamides

Two families of C3 -symmetrical triarylamine-trisamides comprising a triphenylamine- or a tri(pyrid-2-yl)amine core are presented. Both families self-assemble in apolar solvents via cooperative hydrogen-bonding interactions into helical supramolecular polymers as evidenced by a combination of spectroscopic measurements, and corroborated by DFT calculations. The introduction of a stereocenter in the side chains biases the helical sense of the supramolecular polymers formed. Compared to other C3 -symmetrical compounds, a much richer self-assembly landscape is observed. Temperature-dependent spectroscopy measurements highlight the presence of two self-assembled states of opposite handedness. One state is formed at high temperature from a molecularly dissolved solution via a nucleation-elongation mechanism. The second state is formed below room temperature through a sharp transition from the first assembled state. The change in helicity is proposed to be related to a conformational switch of the triarylamine core due to an equilibrium between a 3:0 and a 2:1 conformation. Thus, within a limited temperature window, a small conformational twist results in an assembled state of opposite helicity.