Spectroscopy, photophysical properties and crystal structures of luminescent diplatinum(I) complexes of bis(diphenylphosphino)methane

Abstract

The reactions of quinoline (quin), 1-methylimidazole (mim), 4-tert-butylpyridine (4But-py) and 2,4,6-trimethylpyridine (tmpy) with [Pt2(dppm)2Cl2] in methanol yielded [Pt2(dppm)(quin)2]2+, [Pt2(dppm)2(mim)2]2+, [Pt2(dppm)2(4But-py)2]2+ and [Pt2(dppm)2(tmpy)Cl]+, respectively. The complexes were isolated as either hexafluorophosphate or perchlorate salts. The crystallographically measured intramolecular Pt-Pt distances are 2.615(1), 2.580(1) and 2.627(2) Å for [Pt2(dppm)2(quin)2]2+, [Pt2(dppm)2(mim)2]2+ and [Pt2(dppm)2(tmpy)Cl]+ respectively, indicating the presence of a single Pt-Pt bond. The 1H and 31P NMR spectra of the complexes have been recorded. Solution UV/VIS spectra of the four new complexes as well as those of [Pt2(dppm)2(PPh3)2][PF 6]2 and [Pt2(dppm)2(py)2][PF6]2 (py = pyridine) were recorded. The lowest-energy absorption band is assigned to a 1(dπ* → dσ*) transition. All of the diplatinum(I) complexes display solid-state luminescence at room temperature and at 77 K with long emission lifetimes.