Stereoisomers of Mono-, Di-, and Triruthenium(II) Complexes Containing the Bridging Ligand 1,4,5,8,9,12-Hexaazatriphenylene and Studies of Their Photophysical Properties

Abstract

A combination of synthetic methods involving mononuclear precursors of predetermined chirality {Delta- or Lambda-[Ru(pp)(2)(CO)(2)](2+); pp = 2,2'-bipyridine or 1,10-phenanthroline} and chromatographic techniques has allowed the isolation of the meso (DeltaLambda) and rac (DeltaDelta/LambdaLambda) diastereoisomers of the dinuclear complexes [{Ru(pp)(2)}(2)(&mgr;-HAT)](4+) {HAT = 1,4,5,8,9,12-hexaazatriphenylene}. The enantiomers of the rac forms have been separated, and characterization of all species has been achieved by NMR and CD studies. Additonally, the homochiral (Delta(3)/Lambda(3)) and heterochiral (Delta(2)Lambda/Lambda(2)Delta) diastereoisomers of the trinuclear complexes [{Ru(pp)(2)}(3)(&mgr;-HAT)](6+), and the enantiomers of both forms, have been isolated and identified. Emission studies of all the dinuclear species at room temperature indicate the relative luminescence quantum yields and the emission lifetimes significantly decrease for the meso compared with the rac diastereoisomers. No significant differences were detected at room temperature in the diastereoisomeric forms of the trinuclear compounds. However, in a glass at low temperature (80 K), the luminescence lifetimes of the trinuclear heterochiral diastereoisomer were slightly shorter than those of the homochiral form.

Intervalence Charge Transfer (IVCT) in Ruthenium Dinuclear and Trinuclear Assemblies Containing the Bridging Ligand HAT {1,4,5,8,9,12‐hexaazatriphenylene}

“…Synthesis and stereoisomer separation: The synthetic strategies for the stereoisomerically pure di-{meso (DL) and rac (DD and LL)} and trinuclear {homochiral (D 3 and L 3 ) and heterochiral (D 2 L and L 2 D)} systems have been reported previously, [16,17,37] and were based upon a combination of stereoretentive and chromatographic methodologies. [14,15] Electrochemistry: The electrochemical properties of the stereoisomeric forms [17] of [{Ru(bpy) 2 } 2 (m-hat)] n + and [{Ru-(bpy) 2 } 3 (m-hat)] n + as well as the stereoisomeric mixtures [24,38] of [{Ru(bpy) 2 } 2 (m-hat)] 4 + and [{Ru(bpy) 2 } 3 (m-hat)] 6 + have been reported previously.…”

“…) are given in 6 + have been described previously, [38,39] and in previous work from our laboratory, [16,17] no significant differences were observed in the spectral properties of the diastereosiomers of either of the un-oxidised systems.…”

“…[14][15][16] Mono, di-and trinuclear complexes of HAT have been synthesised, [16][17][18][19][20][21][22][23][24][25][26][27][28] as well as elaborate three-dimensional assemblies such as molecular squares [29] and miAbstract: The IVCT characteristics of the mixed-valence forms of the dinuclear [{Ru(bpy) 2 } 2 (m-hat)] n + and the trinuclear [{Ru(bpy) 2 } 3 (m-hat)]…”

“…The use of these rigid, stereochemically-unambiguous complexes addresses the often neglected stereochemical complexities inherent in such systems, which are known to influence their spectral, electrochemical, photophysical and IVCT properties. [14][15][16][33][34][35][36] The elucidation of the fundamental IVCT properties of these complexes represents a key step in the rational design of higher nuclearity metallosupramolecular systems, in which the intramolecular electron transfer processes may be controlled and ultimately exploited for novel practical applications.…”

STM Imaging of a Heptanuclear Ruthenium(II) Dendrimer, Mono-Add Layer on Graphite

“…Two strategies have been followed to assemble building blocks with the HAT ligand. In the first, two or three [Ru(L) 2 ] 2 units (L 2,2'-bipyridine or 1,10-phenanthroline) (Figure 1b) [3,4] are attatched to the central HAT. The so-formed di-and trinuclear complexes ( Figure 1b, Scheme 1) are luminescent and their interactions with DNA have been investigated.…”