Project Title

Digold bis(amidine) complexes upon insertion into NH···N' hydrogen bonds: Synthesis, structures, and molecular dynamics in solution

Presenters

Academic department under which the project should be listed

CSM - Chemistry and Biochemistry

Faculty Sponsor Name

Michael Stollenz

Abstract (300 words maximum)

Group 11 metal centers that are embedded in polydentate ligand scaffolds have attracted considerable interest within in the past decade, since they facilitate closed-shell metal MI···MI (d10···d10) interactions (M = Cu, Ag, Au). The extraordinary luminescence properties of these multinuclear clusters result in potential applications not only for nanoelectronics, but they also serve as powerful building blocks in organic light-emitting devices/diodes (OLEDs).

Our concept is based on a series of the new polydentate bis(amidine) ligands L1–5H2 with a sterically protected flexible backbone. It has been recently demonstrated that L1H2 undergoes with mesitylcopper a clean conversion into a neutral, homoleptic, and helically-bent tetranuclear complex [L12Cu4], that dimerizes into the unique octanuclear cluster [L14Cu8]. The goal of this project is to explore the coordination chemistry of ligands LH2, that are capable of providing two additional donor sites, with regard to the formation of new unusual homo- and heteronuclear coinage metal clusters. Herein, we describe a convenient straightforward synthetic sequence in three steps for the new ligands L2–5H2. Moreover, the molecular structures of L3H2 and L5H2, determined by X-ray crystallography, are presented. They feature a remarkable network of intra- and intermolecular hydrogen bonds in the solid state. Both bis(amidine) ligands react with [(Me2S)AuCl] to yield the dichloro-digold complexes [L3H2(AuCl)2] and [L5H2(AuCl)2]. X-ray crystallography reveals that two AuCl fragments insert into the two intramolecular NH···N' hydrogen bonds of L3H2 to form NH···Cl–Au–N' hydrogen bridges in [L3H2(AuCl)2]. For L5H2, a rearrangement of inter- and intramolecular NH···N' hydrogen bonds with concomitant AuCl insertion results in a similar structure for [L5H2(AuCl)2]. The molecular dynamic behavior of [L3H2(AuCl)2] in solution, monitored by variable-temperature 1H NMR spectroscopy, is also discussed.

Project Type

Poster

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Digold bis(amidine) complexes upon insertion into NH···N' hydrogen bonds: Synthesis, structures, and molecular dynamics in solution

Group 11 metal centers that are embedded in polydentate ligand scaffolds have attracted considerable interest within in the past decade, since they facilitate closed-shell metal MI···MI (d10···d10) interactions (M = Cu, Ag, Au). The extraordinary luminescence properties of these multinuclear clusters result in potential applications not only for nanoelectronics, but they also serve as powerful building blocks in organic light-emitting devices/diodes (OLEDs).

Our concept is based on a series of the new polydentate bis(amidine) ligands L1–5H2 with a sterically protected flexible backbone. It has been recently demonstrated that L1H2 undergoes with mesitylcopper a clean conversion into a neutral, homoleptic, and helically-bent tetranuclear complex [L12Cu4], that dimerizes into the unique octanuclear cluster [L14Cu8]. The goal of this project is to explore the coordination chemistry of ligands LH2, that are capable of providing two additional donor sites, with regard to the formation of new unusual homo- and heteronuclear coinage metal clusters. Herein, we describe a convenient straightforward synthetic sequence in three steps for the new ligands L2–5H2. Moreover, the molecular structures of L3H2 and L5H2, determined by X-ray crystallography, are presented. They feature a remarkable network of intra- and intermolecular hydrogen bonds in the solid state. Both bis(amidine) ligands react with [(Me2S)AuCl] to yield the dichloro-digold complexes [L3H2(AuCl)2] and [L5H2(AuCl)2]. X-ray crystallography reveals that two AuCl fragments insert into the two intramolecular NH···N' hydrogen bonds of L3H2 to form NH···Cl–Au–N' hydrogen bridges in [L3H2(AuCl)2]. For L5H2, a rearrangement of inter- and intramolecular NH···N' hydrogen bonds with concomitant AuCl insertion results in a similar structure for [L5H2(AuCl)2]. The molecular dynamic behavior of [L3H2(AuCl)2] in solution, monitored by variable-temperature 1H NMR spectroscopy, is also discussed.