Mono- and dinuclear luminescent 1,1′-biisoquinoline gold(I) complexes

Mono- and dinuclear, cationic or neutral gold(I) derivatives [(biisoq)(AuL)]n+ (L = PPh3, n = 1; L = C6F5, n = 0), and [(μ-biisoq)(AuL)2]n+ (biisoq = 1,1′-biisoquinoline; L = PMe3, PPh3, PMePh2, n = 2; L = C6F5, n = 0) have been prepared. Aurophilic interactions and steric requirements of the co-ligand L impose the torsion angle between the two isoquinoline units of the flexible, non-planar 1,1′-biisoquinoline ligand, affording different structures. The X-ray molecular structure of the mononuclear complex with PPh3 confirmed the monodentate mode for the biisoquinoline ligand. In the three X-ray structures solved for dinuclear compounds with bridging biisoquinoline, the torsion angles and the intramolecular gold–gold distances found are, respectively: 65.2° and 3.0739(7) Å for L = PMe3; 80.10° and 3.785 Å for L = C6F5; 95.6° and 4.505 Å for L = PMePh2. All the phosphine derivatives are luminescent at room temperature in the solid state, with emission maxima in the range 390–422 nm, and emit from 370 to 438 nm at 77 K. They are also emissive in CH2Cl2 at 298 K in the range 381–458 nm, whilst they are luminescent at 77 K in the range 382–550 nm. The fluoroaryl derivatives are not emissive.

Graphical abstractLuminescent mono- and dinuclear gold(I) compounds with the helical ligand 1,1′-biisoquinoline have been synthesized, where the N-ligand acts as monodentate or as bridging bidentate.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The 1,1′-biisoquinoline acts as bridging bidentate in dinuclear gold derivatives. ► The ligand acts as monodentate in a mononuclear gold derivative, which is unusual. ► The shortest intramolecular Au–Au distance is 3.0739(7) Å with torsion angle 65.2°. ► Most derivatives are luminescent. ► At 77 K display a dual emission, one shows biisoquinoline vibronic progressions.