Tuning the Excimer Emission of Amphiphilic Platinum(II) Complexes Mediated by Phospholipid Vesicles.

Two new amphiphilic platinum(II) complexes, [Pt(2-(4-fluorophenyl)-5-(4-dodecyloxyphenyl)pyridine) (acac)] (Pt-1) and [Pt(2-(4-dodecyloxyphenyl)-5-(thien-2-yl)-c-cyclopentenepyridine) (acac)] (Pt-2), where acac is acetylacetonate, were synthesized and characterized. Apart from conventional phosphorescence of single molecules (ME-monomer emission), complexes Pt-1 and Pt-2 also exhibit excimer emission (EE) when embedded into phospholipid vesicles, that is assigned to emissive Pt-Pt excimers. The EE intensity in vesicular media appeared to depend on the viscosity of the vesicles and the concentration of the embedded complex.

Modulation of Intersystem Crossing Rate by Minor Ligand Modifications in Cyclometalated Platinum(II) Complexes.

Photophysical properties of four new platinum(II) complexes comprising extended ppy (Hppy = 2-phenylpyridine) and thpy (Hthpy = 2-(2'-thienyl)pyridine) cyclometalated ligands and acetylacetonate (acac) are reported. Substitution of the benzene ring of Pt-ppy complexes 1 and 2 with a more electron-rich thiophene of Pt-thpy complexes 3 and 4 leads to narrowing of the HOMO-LUMO gap and thus to a red shift of the lowest energy absorption band and phosphorescence band, as expected for low-energy excited states of the intraligand/metal-to-ligand charge transfer character. However, in addition to these conventional spectral shifts, another, at first unexpected, substitution effect occurs.

Brightly luminescent Pt(II) pincer complexes with a sterically demanding carboranyl-phenylpyridine ligand: a new material class for diverse optoelectronic applications.

A series of three Pt(II) complexes with a doubly cyclometalating terdentate ligand L1, L1H2 = 3,6-bis(p-anizolyl)-2-carboranyl-pyridine, and diethyl sulfide (1), triphenylphosphine (2), and t-butylisonitrile (3) as ancillary ligands were synthesized. X-ray diffraction studies of 1 and 2 show a coordination of the L1 ligand in a C-N-C mode in which the bulky and rigid o-carborane fragment is cyclometalated via a C atom. Importantly, no close intermolecular Pt-Pt contacts occur with this ligand type.

2,2'-Bipyridinyl carboranes as B,N,N-ligands in cyclometallated complexes of platinum(II).

Novel B,N,N-cyclometallated Pt(II) complexes of 2,2'-bipyridin-6-yl carboranes exhibit absorption and emission similar to relative Pt(II) complexes of aromatic C,N,N-ligands: the same transitions but lower intensities. DFT calculations suggest the former emits from the (3)MLCT state while for the latter the mixed (3)ICT-MLCT transitions should be considered.

Phosphorescence vs fluorescence in cyclometalated platinum(II) and iridium(III) complexes of (oligo)thienylpyridines.

Two newly prepared oligothienylpyridines, 5-(2-pyridyl)-5'-dodecyl-2,2'-bithiophene, HL(2), and 5-(2-pyridyl)-5''-dodecyl-2,2':5',2''-ter-thiophene, HL(3), bind to platinum(II) and iridium(III) as N∧C-coordinating ligands, cyclometallating at position C(4) in the thiophene ring adjacent to the pyridine, leaving a chain of either one or two pendent thiophenes. The synthesis of complexes of the form [PtL(n)(acac)] and [Ir(L(n))(2)(acac)] (n = 2 or 3) is described. The absorption and luminescence properties of these four new complexes are compared with the behavior of the known complexes [PtL(1)(acac)] and [Ir(L(1))(2)(acac)] {HL(1) = 2-(2-thienyl)pyridine}, and the profound differences in behavior are interpreted with the aid of time-dependent density functional theory (TD-DFT) calculations.

Synthesis of cyclometallated platinum complexes with substituted thienylpyridines and detailed characterization of their luminescence properties.

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).

A versatile strategy for the synthesis of functionalized 2,2'-bi- and 2,2':6',2' '-terpyridines via their 1,2,4-triazine analogues.

A general synthetic route for the synthesis of functionalized bi- and terpyridines is reported. Functionalized 1,2,4-triazene 4-oxides 7 and 8-obtained from the reaction of hydrazones 1 with pyridine aldehydes and followed by oxidation-are functionalized by introduction of a cyano group via nucleophilic aromatic substitution. The thus-obtained 5-cyano-1,2,4-triazines 9 and 10 undergo facile inverse-electron-demand Diels-Alder reactions with enamines and alkenes to yield functionalized bi- and terpyridines, respectively.