Nucleic Acid Intercalators and Avidin Probes Derived from Luminescent Cyclometalated Iridium(<scp>III</scp>)–Dipyridoquinoxaline and –Dipyridophenazine Complexes

107

We report the synthesis, characterisation, photophysical and electrochemical properties of a series of cationic cyclometallated Ir(III) complexes of general formula [Ir(ppy)(2)(phen)]PF(6) (ppy=2-phenylpyridine, phen=a substituted phenanthroline). A feature of these complexes is that the phen ligands are substituted with one or two 9,9-dihexylfluorenyl substituents to provide extended pi conjugation, for example, the 3-[2-(9,9-dihexylfluorenyl)]phenanthroline and 3,8-bis[2-(9,9-dihexylfluorenyl)]phenanthroline ligands afford complexes 6 and 9, respectively. A single-crystal X-ray diffraction study of a related complex 18 containing the 3,8-bis(4-iodophenyl)phenanthroline ligand, revealed an octahedral coordination of the Ir atom, in which the metallated C atoms of the ppy ligands occupy cis positions. The complexes 6 and 9 displayed reversible oxidation waves in cyclic voltammetric studies (E(ox)(1/2)=+1.18 and +1.20 V, respectively, versus Ag/Ag(+) in CH(2)Cl(2)) assigned to the metal-centred Ir(III)/Ir(IV) couple. The complexes exhibit strong absorption in the UV region in solution spectra, due to spin-allowed ligand-centred (LC) (1)pi-pi* transitions; moderately intense bands occur at approximately 360-390 nm which are red-shifted with increased ligand length. The photoluminescence spectra of all the complexes were characterised by a broad band at lambda(max) approximately 595 nm assigned to a combination of (3)MLCT and (3)pi-->pi* states. The long emission lifetimes (in the microsecond time-scale) are indicative of phosphorescence: the increased ligand conjugation length in complexes 9 and 17 leads to increased lifetimes for the complexes (tau=2.56 and 2.57 micros in MeCN, respectively) compared to monofluorenyl analogues 6 and 15 (tau=1.43 and 1.39 micros, respectively). DFT calculations of the geometries and electronic structures of complexes 6', 9' (for both singlet ground state (S(0)) and triplet first excited (T(1)) states) and 18 have been performed. In the singlet ground state (S(0)) HOMO orbitals in the complexes are spread between the Ir atom and benzene rings of the phenylpyridine ligand, whereas the LUMO is mainly located on the phenanthroline ligand. Analysis of orbital localisations for the first excited (T(1)) state have been performed and compared with spectroscopic data. Spin-coated light-emitting cells (LECs) have been fabricated with the device structures ITO/PEDOT:PSS/Ir complex/Al, or Ba capped with Al (ITO=indium tin oxide, PEDOT=poly(3,4-ethylenedioxythiophene), PSS=poly(styrene) sulfonate). A maximum brightness efficiency of 9 cd A(-1) has been attained at a bias of 9 V for 17 with a Ba/Al cathode. The devices operated in air with no reduction in efficiency after storage for one week in air.

Section: Wwwchemeurjorgmentioning

confidence: 98%

Cationic Bis‐cyclometallated Iridium(III) Phenanthroline Complexes with Pendant Fluorenyl Substituents: Synthesis, Redox, Photophysical Properties and Light‐Emitting Cells

Zeng

Tavaslı

Perepichka

et al. 2008

107

“…[5][6][7]30] This is also caused by steric effects, which modulate DNA binding. Clearly, if L 1 of 4 slots into the narrow minor groove, the octahedral coordination geometry of the complex means that the bulky and elongated dppz ligand will project into the groove wall, which would produce large www.chemeurj.org unfavorable steric interactions.…”

Section: Compared With 1 2 and 3 Complex 4 Displays A Very Differementioning

confidence: 99%

“…[6] This work has also been extended to other d 6 metal ions, with the binding properties of dppz complexes based on Re I , Os II , and Ir III centers all having been described. [7] Related homo-and heterometallic dinuclear intercalators are also known. [8] In contrast, much less work on metal complexes capable of groove binding has been reported.…”

Section: Introductionmentioning

confidence: 99%

Photoactive Ru^II–Polypyridyl Complexes that Display Sequence Selectivity and High‐Affinity Binding to Duplex DNA through Groove Binding

Ghosh

Das

Gill

et al. 2011

The duplex-DNA binding properties of a nonintercalating polypyridyl ruthenium(II) complex that incorporates a linear extended ligand with a catechol moiety has been probed with a variety of photo- and biophysical techniques. These studies reveal that the complex groove binds to DNA sequences biphasically, and displays binding constants equivalent to those of high-affinity metallointercalators. The complex also displays preferential binding to AT-rich sequences. Changes in the structure of the coordinated catechol ligand and the incorporation of intercalating ancillary ligands into the complex were found to modulate both the optical-binding response and binding parameters of the system, which indicates that the catechol moiety plays a crucial role in the observed enhancement to binding affinities.

“…Besides the most conventional and commonly used organic dyes, transitionmetal-complex dyes represent an attractive family of luminescent materials for life science research, because they display many superior physicochemical properties, such as higher photostabilities, larger Stokes shifts, and higher quantum efficiencies. [1] For example, recent studies on luminescent iridiumA C H T U N G T R E N N U N G (III) complexes have found emerging grounds for applications of these dyes in chemosensors, [2] biolabeling, [3,4] live cell staining, [5][6][7][8][9] and in vivo tumor imaging. [10] Secondly, the choice of conjugation chemistry is also important to consider.…”

mentioning

confidence: 98%

Luminescent Peptide Labeling Based on a Histidine‐Binding Iridium(III) Complex for Cell Penetration and Intracellular Targeting Studies

Wang

Jia

Huang

et al. 2011