title: Synthesis of cyclometallated platinum complexes with substituted thienylpyridines and detailed characterization of their luminescence properties.
abstract: Synthesis of various derivatives of 2-(2-thienyl)pyridine via substituted 3-thienyl-1,2,4-triazines is reported. The final step of the synthesis is a transformation of the triazine ring to pyridine in an aza-Diels-Alder-type reaction. The resulting 5-aryl-2-(2-thienyl)pyridines (HL1-HL4) and 5-aryl-2-(2-thienyl)cyclopenteno[c]pyridines (HL5-HL8) (with aryl = phenyl, 4-methoxyphenyl, 2-naphtyl, and 2-thienyl) were used as cyclometallating ligands to prepare a series of eight luminescent platinum complexes of the type [Pt(L)(acac)] (L = cyclometallating ligand, acac = acetylacetonato). X-ray single crystal structures of three complexes of that series, [Pt(L5)(acac)] = [Pt(5-phenyl-2-(2-thienyl)cyclopenteno[c]pyridine)(acac)], [Pt(L6)(acac)] = [Pt(5-(4-methoxy)-2-(2-thienyl)cyclopenteno[c]pyridine)(acac)], and [Pt(L7)(acac)] = [Pt(5-(2-naphtyl)-2-(2-thienyl) cyclopenteno[c]pyridine)(acac)] were determined. Photoluminescence and electronic absorption spectra of the new [Pt(L)(acac)] complexes are reported. For two representative compounds of that series, [Pt(L4)(acac)] and [Pt(L5)(acac)], a detailed photophysical characterization based on highly resolved emission and excitation spectra, as well as on emission decay properties, was carried out. The studies down to low temperature (T = 1.2 K) and up to high magnetic fields (B = 10 T) allowed us to characterize the three individual substates of the emitting triplet state. In particular, it is shown that the lowest triplet states of [Pt(L4)(acac)] and [Pt(L5)(acac)] are largely ligand-centered (LC) of (3)pi pi* character, which experience only weak spin-orbit couplings to higher lying singlet states.
authors.affiliation: Institute of Organic Synthesis, Ural Branch of Russian Academy of Sciences, Kovalevskoy 22, Ekaterinburg, 620219, Russia. dnk@ios.uran.ru
authors.forename: Dmitry N
authors.initials: DN
authors.lastname: Kozhevnikov
authors.forename: Valery N
authors.initials: VN
authors.lastname: Kozhevnikov
authors.forename: Maria M
authors.initials: MM
authors.lastname: Ustinova
authors.forename: Amedeo
authors.initials: A
authors.lastname: Santoro
authors.forename: Duncan W
authors.initials: DW
authors.lastname: Bruce
authors.forename: Burkhard
authors.initials: B
authors.lastname: Koenig
authors.forename: Rafał
authors.initials: R
authors.lastname: Czerwieniec
authors.forename: Tobias
authors.initials: T
authors.lastname: Fischer
authors.forename: Manfred
authors.initials: M
authors.lastname: Zabel
authors.forename: Hartmut
authors.initials: H
authors.lastname: Yersin