Organometallic and coordination compounds with photoemissive and electro-optical properties

Organometallic complexes with luminescent1 and second-order nonlinear optical (NLO) properties2 are of interest as molecular building blocks of composite materials for light emitting systems such as OLED or for electro-optical devices and optical communications. In particular, they can offer additional flexibility, when compared to organic NLO-phores, by introducing electronic charge-transfer transitions between the metal and the ligand, usually at relatively low energy and of relatively high intensity, tunable by virtue of the nature, oxidation state and coordiantion sphere of the metal centre.3 In the last few years, many neutral transition metal complexes have emerged as promising emitters for organic light emitting diodes (OLED).1 Neutral iridium (III) cyclometalated complexes were found of particular interest because they show high phosphorescence quantum yields and long lifetime. Moreover, the wavelength of emitted light can be tuned over a large spectral range by an appropriate choice and combination of ligands. They have been used as active components dispersed in an organic matrix in OLED. In particular the acetylacetonate complexes with various cyclometalated ligands have been deeply studied. Only recently ionic transition metal complexes (iTMC)4 have been used as active layers in electroluminescent devices. Unlike conventional, charge-neutral OLED materials, iTMCs contain mobile counterions that facilitate charge transport through the material and eliminate the need for electron- and hole-injection layers and operate at a low voltage.2 The first reports involving metal complexes were based on Ru(II)5, Os(II)6 and Re(I)7. Only three years ago, cationic Ir(III) cyclometalated complexes have received considerable attention due to the wide range emission color upon ligand selection.8 My PhD thesis is divided in three main sections: 1) Luminescent properties of cationic cyclometallated Ir(III) complexes 2) Second order NLO properties of cyclometallated Ir(III) and Pt(II) organometallic complexes and Zn(II) and lanthanide coordination compounds. 3) Experimental section The first section is dedicated to the preparation and study of the luminescence properties of new cationic Ir(III) cyclometalated complexes with variously substituted 1,10-phenanthrolines such as [Ir(ppy)2(5-X- 1,10- phen)][PF6] (ppy= 2-phenylpyridine, phen= phenanthroline, X= Me, NMe2, NO2, H) and [Ir(ppy)2(4- R’, 7-R’- 1,10- phen)][PF6] (R’= Me and Ph), in order to evidence how the nature, number and position of the phenanthroline substituents tune the luminescence (color of the emission, quantum yield and lifetime) properties. The effect on the emission properties of the substitution of cyclometallated 2-phenylpyridine with more π- delocalized cyclometallated 2-phenylquinoline (pq), 3’-(2-pyridil)- 2,2’:5’,2”-terthiophene (ttpy), 4-5-diphenyl-2-methyl-thiazole (dpmt) and 5- trifluoromethyl-2-(2,4-difluorophenyl)pyridine (dF(CF3)ppy) is also investigated. Preliminary results on the preparation of an OLEC device are given in the case of [Ir(4-5-diphenyl-2-methyl-thiazole)2(5-Methyl-1,10-phenanthroline)][PF6], [Ir(2- phenypyridine)2(5-Methyl-1,10-phenanthroline)][PF6] and [Ir(2- phenyquinoline)2(5-Methyl-1,10-phenanthroline)][PF6]. In the second section the second order NLO properties of the cationic cyclometalated Iridium (III) complexes, described in the first section, are investigated. Then the study is extended to related neutral cyclometallated Ir(III) and Pt(II) complexes. Besides, the role of f electrons on the dipolar and octupolar contributions to the quadratic hyperpolarizability of fluorinated β-diketonates diglyme lanthanide complexes is investigated. Finally, the second order NLO properties of a highly π-delocalized bidentate ligand, dibutyl-(4,5-diazafluorenyl- 9-ilidene-penta-1,3-dienyl)-amine, and related Zn(II) complexes are studied. In the last section, details are given on the synthesis and characterization of all the complexes. This PhD thesis leds to the discovery of new organometallic complexes and coordination compounds appealing as building blocks for molecular materials with both non linear and luminescence properties.