Selective synthesis, reactivity and luminescence of unsymmetrical bis-cyclometalated Pt(iv) complexes

Abstract

The degree of MLCT admixture into the 3LC emitting state of unsymmetrical Pt(iv) complexes bearing two different cyclometalated ligands depends on the coordination position of the chromophoric ligand.

Stereoselective Formation of Facial Tris‐Cyclometalated PtIV Complexes: Dual Phosphorescence from Heteroleptic Derivatives

“…The rather short PtÀCb ond distances (range 1.993-2.011 )a re comparable to other Pt-C distances trans to Ni nc yclometalated Pt IV complexes. [13,34]…”

“…The electronic absorption spectra of complexes fac-3 in CH 2 Cl 2 solution at 298 Ks how structured bands ( Figure 3, Ta ble S2, Supporting Information) in the range 300-400nma ttributable to singlet ligand-centered ( 1 LC or 1 p-p*) transitions. [13,14,[34][35][36] The characteristic maximaf rom the individual ligandsc an be identified by comparing the differents pectra,a ppearinga tc a. 363 and3 78 nm (piq), 361 nm (thpy),3 51 and 365 nm (pq) or 314, 326 and3 40 nm (tpy).…”

Strongly Luminescent Pt(IV) Complexes with a Mesoionic N-Heterocyclic Carbene Ligand: Tuning Their Photophysical Properties

“…Although small, the extent of the MLCT contribution to the emissive state has been observed to fluctuate depending on the coordination environment, causing variations in the radiative rates. 21,22,28 Thus, shorter Pt−C bonds from metalated aryls or the presence of suitable π-donor ancillary ligands, e.g., the fluoride ion, result in occupied dπ orbitals with higher energies and greater MLCT admixtures, leading to higher radiative rates. 21 However, a more critical factor that influences the emission properties of cyclometalated Pt(IV) complexes is the presence of thermally accessible ligand-to-metal charge-transfer (LMCT) excited states originating from electronic promotions to dσ* orbitals, which can provide the effective nonradiative deactivation of the emissive excited state.…”

“…In previous contributions, we have shown that several types of Pt­(IV) complexes bearing cyclometalating 2-arylpyridines may exhibit efficient and long-lived luminescence from essentially ligand-centered triplet excited states ( 3 LC) that possess a very low metal-to-ligand charge-transfer (MLCT) admixture. ,,,, These characteristics make them promising candidates for applications that take advantage of relatively long excited-state lifetimes, such as sensing, singlet-oxygen sensitization, or photocatalysis. Although small, the extent of the MLCT contribution to the emissive state has been observed to fluctuate depending on the coordination environment, causing variations in the radiative rates. ,, Thus, shorter Pt–C bonds from metalated aryls or the presence of suitable π-donor ancillary ligands, e.g., the fluoride ion, result in occupied dπ orbitals with higher energies and greater MLCT admixtures, leading to higher radiative rates . However, a more critical factor that influences the emission properties of cyclometalated Pt­(IV) complexes is the presence of thermally accessible ligand-to-metal charge-transfer (LMCT) excited states originating from electronic promotions to dσ* orbitals, which can provide the effective nonradiative deactivation of the emissive excited state.…”

C(sp2)–C(sp2) Reductive Elimination from a Diarylplatinum(II) Complex Induced by a S–S Bond Oxidative Addition at Room Temperature

“…So far, RE reactions have been extensively investigated in platinum complexes for the construction of various bonds. ,− In this regard, much attention has been paid to formation of C­(sp 3 )–C­(sp 3 ) − or C­(sp 2 )–C­(sp 2 ) − bonds from Pt­(IV) complexes which are, generally, thermally or photochemically induced. In contrast, this reaction has been considerably less explored and is less frequent in Pt­(II) chemistry; in fact, diaryl RE reactions from Pt­(II) centers are often endothermic and slow.…”