Abstract
Herein we report the synthesis of a stimuli-responsive binuclear Au(I) complex based on the 1,5-bis(p-tolyl)-3,7-bis(pyridine-2-yl)-1,5-diaza-3,7-diphosphacyclooctane ligand, which is a novel template for the design of luminescent metal complexes. In the solid state, the complex obtained gives three different crystalline phases, which were characterized by XRD analysis. It was also found that the crystalline phases can be reversibly interconverted by recrystallization or solvent vapour treatment. The emission of these phases varies in the 500–535 nm range. Quite unexpectedly, the emission energy of these phases is mostly determined by the non-covalent interactions of the solvent molecules with the ligand environment, which have nearly no effect on the Au–Au interactions in the chromophoric centre. The complex obtained demonstrates thermo/solvatochromism to display greenish emission in a DCM matrix and blue emission in an acetone matrix at 77 K, in contrast to the blue emission of the phase containing a DCM molecule and greenish-yellow emission of the acetone solvate in a crystal cell at room temperature. The potentially important role of co-crystallized solvent molecules in the ligand-based emission of the complex obtained is supported by DFT calculations.
Highlights
The cyclic aminomethylphosphines in common and 1,5diaza-3,7-diphoshpacyclooctanes in particular are convenient templates for the targeted design of AuIJI) luminescent complexes due to easy functionalization of the framework at the heteroatoms of the cycle and their ability to vary framework conformation.[10]
In the crystal phase of (1c, one of the solvent molecules is disposed outside the “basket” whereas the other sits in the cavity but the distances between acetone and coordinated chlorides and between acetone and a phenyl ring are substantially longer (3.280 and 3.365 Å, respectively) than those in 1b and no contacts between acetone oxygen and the PNNP protons were found
The results of model DFT calculations, which take into account local interactions of an isolated complex molecule with the solvents found in the solid state, support the ligand-based mechanism of emission and point to the potentially important role of solvent molecules co-crystallized with the complex in the 1b and 1c phases
Summary
The cyclic aminomethylphosphines in common and 1,5diaza-3,7-diphoshpacyclooctanes in particular are convenient templates for the targeted design of AuIJI) luminescent complexes due to easy functionalization of the framework at the heteroatoms of the cycle and their ability to vary framework conformation.[10]. The complex obtained shows a clear dependence of the luminescence properties on the nature of co-crystallized solvent (dichloromethane, acetone) and structure of the crystalline phases.
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