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Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents
Published on: May 28, 2014
Diphosphine Bridge Control of Intramolecular Pt···Pt Association in Dinuclear Pt(II) Complexes with a Dimetalated
Salvador R Marín-González1, Dionisio Poveda1, Delia Bautista2
1Departamento de Química Inorgánica, Facultad de Química, Universidad de Murcia, Campus de Espinardo, 19, Murcia 30100, Spain.
Abstract:
Dinuclear platinum(II) complexes capable of establishing reversible metal-metal interactions constitute attractive platforms for stimuli-responsive luminescent systems. Here, we report a family of diphosphine-bridged complexes of general formula [{Pt(dmtppy)}2(μ-P∧P)] incorporating a dimetalated N∧C∧C ligand derived from 2-(4,4″-dimethyl-[1,1':3',1″-terphenyl]-5'-yl)pyridine, which enables systematic investigation of intramolecular Pt···Pt association. Structural studies reveal that the dppm-bridged derivative (dppm = bis(diphenylphosphino)methane) adopts a stacked conformation featuring a Pt···Pt interaction in solution and in the solid state. In contrast, complexes containing longer diphosphine bridges do not exhibit metallophilic contacts. NMR and electronic spectroscopic studies demonstrate that the dppm complex establishes in solution a solvent- and temperature-dependent equilibrium between open and closed conformations. These conformers give rise to distinct emissive excited states, namely, a structured 3ILCT/MLCT emission associated with the open form and a lower-energy 3MMLCT emission arising from the Pt···Pt-associated species. The interconversion between both structures leads to dual emissions whose relative contributions can be tuned by solvent and temperature. In contrast, complexes containing longer diphosphine bridges display emissions localized on the individual {Pt(dmtppy)} fragments, with solution quantum yields influenced by linker length and flexibility. These results provide clear spectroscopic evidence for reversible intramolecular metallophilic association and highlight diphosphine-bridged architectures as promising platforms for responsive Pt(II) emitters.
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