Synthesis, Structure, Optical Properties and Theoretical Studies of Pt(P−P)(CN)₂ with P−P = 1,2‐Bis(diphenylphosphanyl)benzene and 2,2′‐Bis(diphenylphosphanyl)‐1,1′‐binaphthyl − Luminescence from Metal‐to‐Ligand Charge Transfer and Intraligand States

Abstract

The complexes Pt II (P−P)(CN) 2 with P−P = 1,2-bis(diphenylphosphanyl)benzene (dppb) and 2,2Ј-bis(diphenylphosphanyl)-1,1Ј-binaphthyl (binap) were synthesised and characterised by elemental analysis, ESI MS and electronic spectroscopy. The structure of Pt(dppb)(CN) 2 was resolved by single-crystal X-ray diffraction. This compound consists of mononuclear Pt II complexes with an almost planar PtP 2 C 2 coordination. While both complexes are not luminescent in solution, they show an emission in the solid state under ambient conditions. It is suggested that the luminescence of Pt(dppb)(CN) 2 originates from a (Pt II Ǟdppb) metal-to-ligand charge transfer (MLCT) triplet with some dppb intraligand (IL) contribution. This assignment is confirmed by calcula-

Can silver exert a heavy-atom effect in organic ligands? Intraligand phosphorescence of Ag(binap)NO3 with binap=2,2′-bis (diphenylphosphino)-1,1′-binaphthyl under ambient conditions

“…1) shows absorptions at k max = 340 (sh, e = 3400 M À1 cm À1 ), 318 (sh, 6250), 280 (sh, 13,200), 252 (sh, 30,000), 228 (sh, 56,500) and 207 (63,000) nm. The longwavelength portion of this spectrum with both shoulders at 340 and 318 nm shows the same pattern as the spectra of the binap complexes of Pt(II) and Au(I) [21,22]. The emission behavior of these complexes is also almost identical to that of Ag(binap)NO 3 which does not luminesce in solution but exhibits a bright green-yellow emission in the solid state at r.t. Vibrational features of the luminescence spectrum (Fig.…”

“…Since the absorption and emission spectra of Ag(binap)NO 3 are very similar to those of Pt(binap)(CN) 2 [22] and Au 2 Cl 2 binap [21] it is concluded that the lowest and emissive excited state of the silver complex is also of the binap IL type. For the free ligand this phosphorescence occurs only at low temperatures (77 K) [23].…”

“…The binaphthyl moiety exists as an separate chromophore of the binap ligand but still interacts sufficiently with the metal in order to experience the heavy-atom effect. Some Pt(II) and Au(I) binap complexes have been shown to display this ability [21,22]. Finally, it is important to note that the binap IL phosphorescence shows a pronounced vibrational structure which facilitates its identification.…”

“…Silver complexes with bidentate phosphine ligands are quite stable and accessible by simple procedures [19,20]. Moreover, the binap ligand has been shown to be a diagnostic probe for the occurrence of an IL phosphorescence [21,22]. The binaphthyl moiety exists as an separate chromophore of the binap ligand but still interacts sufficiently with the metal in order to experience the heavy-atom effect.…”

Photoluminescence of PtII(cyclooctatetraene)(CN)2 originating from a MLCT triplet

“…For X = CN the LF states should be pushed up to very high energies owing to the large LF strength of cyanide [11]. Accordingly, low-energy IL or MLCT states were expected to determine the photoproperties of Pt II (C 8 H 8 )(CN) 2 in analogy to complexes of the type Pt II (L-L)(CN) 2 with L-L = 1,2-diimine [12] or bidentate phosphine [13].…”