Photochemical ligand ejection from non-sterically promoted Ru(ii)bis(diimine) 4,4′-bi-1,2,3-triazolyl complexes

Welby, Christine E.; Armitage, Georgina K.; Bartley, Harry; Sinopoli, Alessandro; Uppal, Baljinder S.; Elliott, Paul I. P.

doi:10.1039/c3pp50437a

Cited by 30 publications

(41 citation statements)

References 22 publications

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“…These energies can be determined or inferred spectroscopically, electrochemically and computationally and as [Ru(N^N) 3 ] 2+ complexes invariably have a highest occupied molecular orbital of predominantly metallic 4d character, and hence effectively the same ground state, these excited state energies can be readily compared). Work in our laboratory, [26][27][28] and those of others, [29][30][31][32] has shown that complexes containing 1,2,3-triazole rings that lack such steric promotion can also lead to photochemical reactivity, possibly through destabilisation of the 3 MLCT state with respect to the 3 MC state when compared to those states of the archetypal complex [Ru(bpy) 3 ] 2+ . We recently reported the series of complexes [Ru(bpy) 3-n (btz) n ] 2+ (btz = 1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl, n = 1 to 3) 33 in which an increasing number of btz ligands leads to destabilisation of the 1 MLCT bands in the visible absorption spectrum, significantly so for the homoleptic complex [Ru(btz) 3 ] 2+ .…”

Section: Introductionmentioning

confidence: 99%

Photochemistry of [Ru(pytz)(btz)₂]²⁺ and Characterization of a κ¹-btz Ligand-Loss Intermediate

et al. 2016

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We report the synthesis, characterisation and photochemical reactivity of the triazolecontaining complex [Ru(pytz)(btz) 2 ] 2+ (1, pytz = 1-benzyl-4-(pyrid-2-yl)-1,2,3-triazole, btz = 1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl). The UV-visible absorption spectrum of 1 exhibits pytz- and that the T 1 state from a single point triplet state calculation at the S 0 geometry suggests 3 MC character. Optimisation of the T 1 state of the complex starting from the ground state geometry leads to elongation of the two Ru-N(btz) bonds cis to the pytz ligand to 2.539 and 2.544 Å leading to a psuedo 4-coordinate 3 MC state rather than the 3 MLCT state. The work therefore provides additional insights into the photophysical and photochemical properties of ruthenium triazole-containing complexes and their excited state dynamics.2

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Section: Introductionmentioning

confidence: 99%

Photochemistry of [Ru(pytz)(btz)₂]²⁺ and Characterization of a κ¹-btz Ligand-Loss Intermediate

et al. 2016

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“…Due to the magnetically unique nature of each triazole ring environment we propose the identity of this second species to be the solvento complex cis ‐[Os(κ 2 ‐btz) 2 (κ 1 ‐btz)(NCMe)] 2+ ( cis ‐ 3 b ) which is isomeric with trans ‐ 3 b . An intermediate of this type is implicated in the previously reported photolysis of [Ru(bpy) 2 (btz)] 2+ to yield cis ‐[Ru(bpy) 2 (NCCH 3 ) 2 ] 2+ , and many other similar conversions, but where no such species is observed . NMR resonances assigned to a similar intermediate have been observed, albeit at trace levels, during the photolysis of the complex [Ru(bpy) 2 (dmbpy)] 2+ (dmbpy=3,3′‐dimethyl‐2,2′‐bipyridyl) where the photodechelation of the dmbpy ligand is sterically “spring‐loaded” to occur and rechelation is presumably hindered for the same reason.…”

Section: Figurementioning

confidence: 85%

“…In acetonitrile 1 forms both cis ‐ and trans ‐ 2 b whereas in pyridine only trans ‐ 2 a is observed. We would expect the trans isomers to be the more thermodynamically stable based on previous reports . Product formation will depend on the kinetically controlled evolution of the geometry on the excited state potential energy surface but also on the steric demands and therefore accessibility to coordination of the incoming solvent ligand.…”

Section: Figurementioning

confidence: 87%

Labilizing the Photoinert: Extraordinarily Facile Photochemical Ligand Ejection in an [Os(N^N)₃]²⁺ Complex

et al. 2016

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are unambiguously observed and characterised by NMR spectroscopy and mass spectrometry. Kinetically inert d6 complexes of second and third row transition metal elements (e.g. Re(I), Ru(II), Os(II), Ir(III)) have attracted enormous interest due to their attractive photophysical properties that make them potentially amenable to application in lightemitting technologies, [1] dye-sensitised photovoltaics, [2] phosphorescent biological imaging microscopy [3] and solar catalysis.[4] The utility in phosphorescent and electron/energy transfer applications stems from the relatively long-lived triplet metal-to-ligand charge-transfer ( 3 MLCT) states that complexes of these metals exhibit. These can however be deactivated by triplet metal-centred ( 3 MC) states if these are sufficiently close in energy to photoexcited 3 MLCT states [5] and can induce photochemical reactivity such as ligand-loss or isomerisation.[6] For example, photochemical reactivity can be designed into ruthenium(II) complexes; inclusion of steric bulk in the ligand set in order to weaken metal-ligand bonds lowers the 3 MC state making thermal population from 3 MLCT after photoexcitation achievable. This methodology has been exploited in the design of photoinitiated DNA binding complexes with anti-cancer activity. [7] We have recently reported results on the non-sterically promoted photochemical reactivity of the complexes [Ru(bpy)2(btz)] 2+ and [Ru(bpy)(btz)2] 2+ (bpy = 2,2'-bipyridyl).[8]Here, presence of the btz ligand appears to induce a destabilisation of the 3 MLCT state, bringing it into closer energetic proximity to the 3 MC state thereby enabling thermal population of the 3 MC state with consequential photochemical btz ligand ejection in acetonitrile solutions. In the case of the latter of these complexes, this is accompanied by the unprecedented observation of a metastable ligand-loss intermediate, trans-[Ru(bpy)(κ 2 -btz)(κ 1 -btz)(NCCH3)] 2+ , which can be formed quantitatively by photolysis in an NMR tube within minutes and has been crystallographically characterised.[9] The btz ligand has also been observed to induce photochemical decomposition in the iridium(III) complex [Ir(dfptz)2(btz)] + (dfptzH = 4-(2,4-difluorophenyl)triazole) [10] which one would expect to be far more inert due to the typically higher lying 3 MC states associated with the 5d metal centre.These intriguing results led us to explore osmium(II) triazole-based complexes. [Os(N^N)3] 2+ -type complexes are typically highly kinetically inert and require harsh conditions in their synthesis in order to effect ligand exchange. This is due to a large ligand-field splitting yielding high-energy 3 MC states regarded as thermally inaccessible. Consequently these complexes are photochemically stable, avoiding the ligand ejection photochemistry that sometimes afflicts, or can be designed into, Ru(II) analogues. Indeed, for such osmium complexes Meyer noted that "ligand loss photochemistry is either extremely inefficient or nonexistent", [11] a view that has prevailed for s...

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“…2 It is well known that heterocycles containing nitrogen atoms are effective and stable complexing agents with several metal ions such as copper, cobalt, nickel, manganese and iron. 3 The ability of the nitrogen atom to act as a withdrawing atom decreases the repulsion force between adjacent hetero-rings, allowing construction of supramolecular structures with sophisticated architectures.…”

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Mn (II) Complexes Based on Oligopyridines: Structure, Thermal Studies and Optical Band-Gap Determination

Alghool

Slebodnick

2016

Journal of Chemical Research

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Two cationic complexes [Mn(II)(terpy) 2 ]·2(PCP) and [Mn(II)(dipy) 3 ]·2(PCP) (terpy = 2,2':6',2''-terpyridine) (dipy = 2,2-dipyridyl) (PCP = pentacyanopropenide) have been synthesised. Single crystal X-ray diffraction revealed that the PCP ligand acts as a counter ion. The thermal stability of these compounds was investigated. Optical absorption measurements show that the fundamental absorption edge obeys Tauc's relation for the allowed non-direct transition. The optical band gap (Eg) values equal ~2 .7 eV for both complexes.

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Photochemical ligand ejection from non-sterically promoted Ru(ii)bis(diimine) 4,4′-bi-1,2,3-triazolyl complexes

Abstract: Complexes of the form [Ru(diimine)2(btz)](2+) (btz = 1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl) are observed to undergo photochemical ejection of the btz ligand in the absence of any promotion through steric congestion to generate cis-bis(solvent) complexes [Ru(diimine)2(solvent)2](2+).

Cited by 30 publications

References 22 publications

Photochemistry of [Ru(pytz)(btz)₂]²⁺ and Characterization of a κ¹-btz Ligand-Loss Intermediate

Photochemistry of [Ru(pytz)(btz)₂]²⁺ and Characterization of a κ¹-btz Ligand-Loss Intermediate

Labilizing the Photoinert: Extraordinarily Facile Photochemical Ligand Ejection in an [Os(N^N)₃]²⁺ Complex

Mn (II) Complexes Based on Oligopyridines: Structure, Thermal Studies and Optical Band-Gap Determination

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Photochemical ligand ejection from non-sterically promoted Ru(ii)bis(diimine) 4,4′-bi-1,2,3-triazolyl complexes

Abstract: Complexes of the form [Ru(diimine)2(btz)](2+) (btz = 1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl) are observed to undergo photochemical ejection of the btz ligand in the absence of any promotion through steric congestion to generate cis-bis(solvent) complexes [Ru(diimine)2(solvent)2](2+).

Cited by 30 publications

References 22 publications

Photochemistry of [Ru(pytz)(btz)2]2+ and Characterization of a κ1-btz Ligand-Loss Intermediate

Photochemistry of [Ru(pytz)(btz)2]2+ and Characterization of a κ1-btz Ligand-Loss Intermediate

Labilizing the Photoinert: Extraordinarily Facile Photochemical Ligand Ejection in an [Os(N^N)3]2+ Complex

Mn (II) Complexes Based on Oligopyridines: Structure, Thermal Studies and Optical Band-Gap Determination

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Photochemistry of [Ru(pytz)(btz)₂]²⁺ and Characterization of a κ¹-btz Ligand-Loss Intermediate

Photochemistry of [Ru(pytz)(btz)₂]²⁺ and Characterization of a κ¹-btz Ligand-Loss Intermediate

Labilizing the Photoinert: Extraordinarily Facile Photochemical Ligand Ejection in an [Os(N^N)₃]²⁺ Complex