trans-Chromophore−Quencher Complexes Based on Ruthenium(II)

Abstract

A series of chromophore−quencher complexes, trans-[Ru(bpy)2(pya)(pyb)] n + (bpy = 2,2‘-bipyridyl; pya, pyb = substituted pyridyl ligands; n = 2−4) have been prepared and characterized. These contain combinations of the electron donor PTZ in py-PTZ (py-PTZ = 10-(4-picolyl)phenothiazine) and the electron acceptors MQ+ (1-methyl-4,4‘-bipyridinium cation), py-AQ (4-((((9,10-anthraquinon-2-yl)carbonyl)amino)methyl)pyridine), and py-MPAA (N-(4-pyridyl)-β-(1-methylpyridinium-3-yl)acrylamide cation), and 4-ethylpyridine (4-Etpy). The asymmetrical complexes (pya ≠ pyb) are synthesized by using the precursor trans-[Ru(bpy)2(DMSO)2](CF3SO3)2·0.5H2O, which is converted into trans-[Ru(bpy)2(py-PTZ)(DMSO)](CF3SO3)2·0.5H2O (1) by reaction with py-PTZ in DMSO/acetone at room temperature. 1 is treated with LiCl in aqueous DMF at 105 °C to prepare trans-[RuCl(bpy)2(py-PTZ)]CF3SO3·H2O (2). 2 is converted into the derivatives trans-[Ru(bpy)2(py-PTZ)(4-Etpy)](PF6)2·0.5H2O (5), trans-[Ru(bpy)2(py-PTZ)(MQ+)](PF6)3 (7), trans-[Ru(bpy)2(py-PTZ)(py-AQ)](PF6)2·H2O (9), and trans-[Ru(bpy)2(py-PTZ)(py-MPAA)](PF6)3·H2O (11) by chloride abstraction at room temperature in the presence of 4-Etpy, [MQ](PF6), py-AQ, and [py-MPAA](PF6), respectively. The salts trans-[Ru(bpy)2(4-Etpy)(MQ+)](PF6)3·H2O (6), trans-[Ru(bpy)2(4-Etpy)(py-AQ)](PF6)2 (8), and trans-[Ru(bpy)2(4-Etpy)(py-MPAA)](PF6)3 (10) are synthesized by chloride abstraction from trans-[RuCl(bpy)2(4-Etpy)]PF6·H2O in the presence of [MQ](PF6), py-AQ, or [py-MPAA](PF6). The symmetrical complexes trans-[Ru(bpy)2(MQ+)2](PF6)4·3H2O (3) and trans-[Ru(bpy)2(py-PTZ)2](PF6)2·H2O (4) are synthesized by reaction of trans-[Ru(bpy)2(H2O)2](CF3SO3)2 with an excess of the appropriate ligand in DMF at 100 °C. Visible light irradiation of these complexes at room temperature leads to photochemical decomposition. At lower temperatures (<200 K), emission typical of RuIII−bpy•- (and RuIII−MQ•) MLCT states is observed. The appearance of a thermally activated decay pathway above 150 K signals the presence of a crossing to a photochemically reactive ligand-field state. As a result, significant formation of redox-separated states by electron transfer is not observed for the redox triads trans-[Ru(bpy)2(py-PTZ)(X)] n + (X = py-AQ, n = 2; X = py-MPAA or MQ+, n = 3). Nonetheless, the results obtained have important implications for the stereochemical design of Ru(II)-based chromophore−quencher complexes.

Ruthenium(II/III) bipyridine complexes incorporating thiol-based imine functions

“…The ligand L can act as both a sand a p-donor in contrast to the s-donor but Since the discovery of important photo-redox activities p-acceptor nature of bipyridine molecule. Herein we report of ruthenium complexes incorporating 2,29-bipyridine ligthe synthesis of a group of new ruthenium-bipyridine and, there has been continuous research activity in the complexes having a RuN S chromophore, their spectro- 5 direction of developing new ruthenium-bipyridine comscopic and electrochemical properties and the electronic plexes with the perspective of tuning the redox and structure of the trivalent congener. To the best of our photophysical functions of this class of complexes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Vectorial Electron Transfer in Donor–Photosensitizer–Acceptor Triads Based on Novel Bis‐tridentate Ruthenium Polypyridyl Complexes

“…[21] As an alternative approach the trans-[RuA C H T U N G T R E N N U N G (bpy) 2 (py) 2 ] 2 + (py = pyridine) motif has been used, but it unfortunately also suffers from a short room-temperature excited-state lifetime and, additionally, poor photostability. [22] Recently, our group has detailed the rational development [23,24] and facile synthesis [25,26] of a new class of Ru II bistridentate photosensitizers, based on Ru II bis-2,6-di(quinolin-8-yl)pyridine ([RuA C H T U N G T R E N N U N G (dqp) 2 ] 2 + ). An almost perfect octahedral coordination sphere, with short and equal Ru-N dis-A C H T U N G T R E N N U N G tances, and consequently a strong ligand field is created through the use of six-membered chelates leading to photophysical properties similar to those of [RuA C H T U N G T R E N N U N G (bpy) 3 ] 2 + .…”

Ruthenium(II) complexes containing 2,9-dimethyl-1,10-phenanthroline and 4,4′-dimethyl-2,2′-bipyridine as ancillary ligands: synthesis, characterization and DNA-binding

“…The interaction of polypyridyl ruthenium complexes with DNA has attracted considerable attention in recent decades, in the hope of developing novel probes of DNA structure or new therapeutic agents [6][7][8][9]. Ruthenium polypyridyl complexes have been the subject of considerable research interest owing to their unique photophysical, photochemical, and redox properties [10,11]. The binding mode of the parent complex [Ru(phen) 3 ] 2+ (phen = 1,10-phenanthroline) is still ambiguous [12,13].…”

“…Besides the above mentioned factors, ancillary ligands play an important role in DNA-binding behaviors of complexes. To explore the effect of the ancillary ligand on DNA-binding properties, two new complexes [Ru(dmp) 2 (ipbp)] 2+ (1) and [Ru(dmb) 2 (ipbp)] 2+ (2) (dmp = 2,9-dimethyl-1,10-phenanthroline, ipbp = 3-(1H-Imidazo [4,5-f] [1,10]phenanthrolin-2-yl)-4H-1-banzopyran-2-one, dmb = 4,4 0 -dimethyl-2,2 0 -bipyridine, Scheme 1) were synthesized and characterized by elemental analysis, FAB-MS, ES-MS, and 1 H NMR. The DNA-binding properties of complexes 1 and 2 were investigated by absorption titration, thermal denaturation, and viscosity measurements.…”