A synthetic, structural, spectroscopic and DFT study of Re(I), Cu(I), Ru(II) and Ir(III) complexes containing functionalised dipyrido[3,2-a:2',3'-c]phenazine (dppz).

The ligands 11-cyanodipyrido[3,2-a:2',3'-c]phenazine and 2-(11-dipyrido[3,2-a:2',3'-c]phenazine)-5-phenyl-1,3,4-oxadiazole have been coordinated to Re(I), Cu(I), Ru(II) and Ir(III) metal centres. Single-crystal X-ray analyses were performed on fac-chlorotricarbonyl(11-cyanodipyrido[3,2-a:2',3'-c]phenazine)rhenium (C(22)H(9)ClN(5)O(3)Re, a=6.509(5), b=12.403(5), c=13.907(5) A, alpha=96.88(5), beta=92.41(5), gamma=92.13(5) degrees , triclinic, P1, Z=2) and bis-2,2'-bipyridyl(2-(11-dipyrido[3,2-a:2',3'-c]phenazine)-5-phenyl-1,3,4-oxadiazole)ruthenium triflate2 CH(3)CN (C(52)H(36)F(6)N(12)O(8)RuS(2), a=10.601(5), b=12.420(5), c=20.066(5) A, alpha=92.846(5), beta=96.493(5), gamma=103.720(5) degrees , triclinic, P1, Z=2). The ground- and excited-state properties of the ligands and complexes have been investigated with a range of techniques, including electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and excited-state lifetime studies. Spectroscopic, time-resolved and DFT studies reveal that the ligand-centred (LC) transitions and their resultant excited states play an important role in the photophysical properties of the complexes. Evidence for the presence of lower-lying metal-to-ligand charge-transfer transitions is obtained from resonance Raman spectroscopy, but nanosecond transient Raman experiments suggest that once excited, the (3)LC state is populated.

Terpyridine-fused polyaromatic hydrocarbons generated via cyclodehydrogenation and used as ligands in Ru(II) complexes.

A series of novel fused 4'-substituted 2,2' : 6',2''-terpyridine ligands and their ruthenium(II) complexes were prepared. The unusual 4'-substituents comprised 2,3,4,5-pentaphenylbenzene and its tert-butyl derivative (1 and 2) and the products from oxidative cyclodehydrogenation, i.e. polyaromatic fragments consisting of ten or thirteen fused benzene rings (3 and 4). The syntheses of all the ligands are discussed in terms of the demands and limitations of the Scholl reaction. The optical properties of the ligands, along with the single-crystal X-ray structures of 1 and 2, are presented. The latter show that the pentaphenylbenzene and terpyridine appendages of 1 and 2 are perpendicular in the solid state. Despite the inclusion of the large organic chromophore the absorption and emission properties of the Ru(II) bis-terpy complexes (of ligands 1, 2 and 3) were found to be comparable to those of [Ru(terpy)(2)](2+). They are non-emissive at room temperature but emit at 77 K with excited state lifetimes of 11-12 µs.

Photoexcitation in Cu(I) and Re(I) complexes containing substituted dipyrido[3,2-a:2',3'-c]phenazine: a spectroscopic and density functional theoretical study.

Copper(I) and rhenium(I) complexes [Cu(PPh(3))(2)(dppz-11-COOEt)]BF(4), [Cu(PPh(3))(2)(dppz-11-Br)]BF(4), [Re(CO)(3)Cl(dppz-11-COOEt)] and [Re(CO)(3)Cl(dppz-11-Br)] (dppz-11-COOEt = dipyrido-[3,2a:2',3'c]phenazine-11-carboxylic ethyl ester, dppz-11-Br = 11-bromo-dipyrido[3,2a:2',3'c]-phenazine) have been studied using Raman, resonance Raman, and transient resonance Raman (TR(2)) spectroscopy, in conjunction with computational chemistry. DFT (B3LYP) frequency calculations with a 6-31G(d) basis set for the ligands and copper(I) centers and an effective core potential (LANL2DZ) for rhenium in the rhenium(I) complexes show close agreement with the experimental nonresonance Raman spectra. Modes that are phenazine-based, phenanthroline-based, and delocalized across the entire ligand structure were identified. The nature of the absorbing chromophores at 356 nm for ligands and complexes was established using resonance Raman spectroscopy in concert with vibrational assignments from calculations. This analysis reveals that the dominant chromophore for the complexes measured at 356 nm is ligand-centered (LC), except for [Re(CO)(3)Cl(dppz-11-Br)], which appears to have additional chromophores at this wavelength. Calculations on the reduced complexes, undertaken to model the metal-to-ligand charge transfer (MLCT) excited state, show that the reducing electron occupies a ligand MO that is delocalized across the ligand structure. Resonance Raman spectra (lambda(exc) = 514.5 nm) of the reduced rhenium complexes show a similar spectral pattern to that observed in [Re(CO)(3)Cl(dppz)](*-); the measured bands are therefore attributed to ligand radical anion modes. These bands lie at 1583-1593 cm(-1) for [Re(CO)(3)Cl(dppz-11-COOEt)] and 1611 cm(-1) for [Re(CO)(3)Cl(dppz-11-Br)]. The thermally equilibrated excited states are examined using nanosecond-TR(2) spectroscopy (lambda(exc) = 354.7 nm). The TR(2) spectra of the ligands provide spectral signatures for the (3)LC state. A band at 1382 cm(-1) is identified as a marker for the (3)LC states of both ligands. TR(2) spectra of the copper and rhenium complexes of dppz-11-Br show this (3)LC band, but it is not prominent in the spectra of [Cu(PPh(3))(2)(dppz-11-COOEt)](+) and [Re(CO)(3)Cl(dppz-11-COOEt)]. Calculations suggest that the lowest triplet states of both of the rhenium(I) complexes and [Cu(PPh(3))(2)(dppz-11-Br)](+) are metal-to-ligand charge transfer in nature, but the lowest triplet state of [Cu(PPh(3))(2)(dppz-11-COOEt)](+) appears to be LC in character.

Complexes of functionalized dipyrido[3,2-a:2',3'-c]-phenazine: a synthetic, spectroscopic, structural, and density functional theory study.

The ligands 11-bromodipyrido[3,2-a:2',3'-c]phenazine and ethyl dipyrido[3,2-a:2',3'-c]phenazine-11-carboxylate have been prepared and coordinated to ruthenium(II), rhenium(I), and copper(I) metal centers. The electronic effects of substitution of dipyrido[2,3-a:3',2'-c]phenazine (dppz) have been investigated by spectroscopy and electrochemistry, and some photophysical properties have been studied. The crystal structures of [Re(L)(CO)(3)Cl] (L = ethyl dipyrido[3,2-a:2',3'-c]phenazine-11-carboxylate or 11-bromodipyrido[3,2-a:2',3'-c]phenazine) are presented. Density functional theory calculations on the complexes show only small deviations in bond lengths and angles (most bonds within 0.02 Angstroms, most angles within 2 degrees) from the crystallographic data. Furthermore, the vibrational spectra of the strongest Raman and IR bands are predicted to within an average 6 cm(-1) for the complexes [Re(L)(CO)(3)Cl] and [Cu(L)(triphenylphosphine)(2)]BF(4) (in the 1000-1700 cm(-1) region). Spectroscopic and electrochemical evidence suggest that reduction of the complex causes structural changes across the entire dppz ligand. This is unusual as dppz-based ligands typically have electrochemical properties that suggest charge localization with reduction on the phenazine portion of the ligand. The excited-state lifetimes of the complexes have been measured, and they range from ca. 200 ns for the [Ru(L)(2,2'-bipyridine)(2)](PF(6))(2) complexes to over 2 mus for [Cu(11-bromodipyrido[3,2-a:2',3'-c]phenazine)(PPh(3))(2)](BF(4)) at room temperature. The emission spectra suggest that the unusually long-lived excited states of the copper complexes result from metal-to-ligand charge transfer (MLCT) transitions as they are completely quenched in methanol. Electroluminescent films may be fabricated from these compounds; they show MLCT state emission even at low doping levels [<0.1% by weight in poly(vinylcarbazole) polymer matrix].