Photoisomerization and thermal isomerization of ruthenium aqua complexes with chloro-substituted asymmetric bidentate ligands

Hirahara, Masanari; Goto, Hiroki; Yamamoto, Rei; Yagi, Masayuki; Umemura, Yasushi

doi:10.1039/c8ra08943d

Cited by 7 publications

(4 citation statements)

References 60 publications

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“…However, the effect of intramolecular hydrogen bonding on photosubstitution reactions has yet to be investigated. We previously reported the photoisomerization of Ru(II) aqua complexes with tridentate ligands and asymmetric bidentate ligands, showing that intramolecular hydrogen bonding played an important role in determining the reversibility of the photoisomerization, as depicted in Figure a. Irreversible photoisomerization was observed from distal -[Ru(tpy)(pynp)OH 2 ] 2+ to the proximal isomer (tpy = 2,2′:6′,2″-terpyridine, pynp = 2-(2′-pyridyl)-1,8-naphthyridine), where intramolecular hydrogen bonding occurs between the aqua ligand and a nitrogen atom on the pendant moiety of the pynp ligand.…”

Section: Introductionmentioning

confidence: 99%

Intramolecular Hydrogen Bonding: A Key Factor Controlling the Photosubstitution of Ruthenium Complexes

et al. 2020

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Photosubstitution reactions of ruthenium complexes with pyrazole ligands, cis-[Ru(bpy)2(pzH)2]2+ (1a), cis-[Ru(bpy)2(pz)(pzH)]+ (1b), and cis-[Ru(bpy)2(pz)2]0 (1c) (pzH = pyrazole, bpy = 2,2′-bipyridine), were investigated. Dicationic complex 1a was deprotonated to 1b using moderate base (pK a = 15.2, MeCN), while the second deprotonation to give 1c required more severe conditions (pK a = 26.9). Monocationic complex 1b possessed an N–H···N-type intramolecular hydrogen bond between the pyrazole and pyrazolate ligands, as corroborated by the solid-state crystal structure. The photosubstitution quantum yield of 1a (Φ = 0.26) was comparable to that of cis-[Ru(bpy)2(pyridine)2]2+ (Φ = 0.24) in acetonitrile solution. In contrast, the photodissociation of a pzH ligand was strongly suppressed by the deprotonation of a pyrazole ligand N–H group. In the presence of 10 000 equiv of 4,4′-dimethylaminopyridine, the quantum yield dropped to ∼2 × 10–6 in acetonitrile. The photosubstitution quantum yield of 1b was even smaller than that of neutral complex 1c, although 1c had a smaller HOMO–LUMO energy gap than monocationic complex 1b. The small quantum yield of 1b was attributed to intramolecular hydrogen bonding between pyrazole and pyrazolate ligands. The apparent rate constants for the photosubstitution of 1b were highly solvent-dependent. The photosubstitution of 1b was suppressed in aprotic solvents, while the reaction was accelerated by 2 orders of magnitude in protic solvents with strong proton donor abilities.

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Section: Introductionmentioning

confidence: 99%

Intramolecular Hydrogen Bonding: A Key Factor Controlling the Photosubstitution of Ruthenium Complexes

et al. 2020

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“…42−44 The introduction of a substituent near the metal center enhances the quantum yields of photoisomerization and allows thermal back isomerization from the distal to proximal isomer. 44 We have reported applications of these stimuliresponsive complexes to artificial photosynthesis, 45−47 stimulus-responsive giant vesicles, 48 host−guest systems. 13 In this work, we focused on the ruthenium complex, proximal-[Ru(C 10 tpy)(C 10 pyqu) OH 2 ] 2+ (proximal-1), that responds to light and thermal stimuli (C 10 tpy = 4′-decyloxy-2,2′:6′,2″-terpyridine and C 10 pyqu = 2-[2′-(6′-decyloxy)pyridyl]quinoline).…”

Section: Introductionmentioning

confidence: 99%

“…We have studied photoresponsive ruthenium aqua complexes with tridentate and asymmetric bidentate ligands. – The introduction of a substituent near the metal center enhances the quantum yields of photoisomerization and allows thermal back isomerization from the distal to proximal isomer . We have reported applications of these stimuli-responsive complexes to artificial photosynthesis, – stimulus-responsive giant vesicles, host–guest systems …”

Section: Introductionmentioning

confidence: 99%

Binding of Stimuli-Responsive Ruthenium Aqua Complexes with 9-Ethylguanine

Maeda,

Tokumoto,

Kojima

et al. 2023

ACS Omega

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Stimuli-responsive ruthenium complexes proximal- and distal-[Ru(C10tpy)(C10pyqu) OH2]2+ (proximal-1 and distal-1; C10tpy = 4′-decyloxy-2,2′:6′,2″-terpyridine and C10pyqu = 2-[2′-(6′-decyloxy)-pyridyl]quinoline) were experimentally studied for adduct formation with a model DNA base. At 303 K, proximal-1 exhibited 1:1 adduct formation with 9-ethylguanine (9-EtG) to yield proximal-[Ru(C10tpy)(C10pyqu)(9-EtG)]2+ (proximal-RuEtG). Rotation of the guanine ligand on the ruthenium center was sterically hindered by the presence of an adjacent quinoline moiety at 303 K. Results from 1H NMR measurements indicated that photoirradiation of a proximal-RuEtG solution caused photoisomerization to distal-RuEtG, whereas heating of proximal-RuEtG caused ligand substitution to proximal-1. The distal isomer of the aqua complex, distal-1, was observed to slowly revert to proximal-1 at 303 K. In the presence of 9-EtG, distal-1 underwent thermal back-isomerization to proximal-1 and adduct formation to distal-RuEtG. Kinetic analysis of 1H NMR measurements showed that adduct formation between proximal-1 and 9-EtG was 8-fold faster than that between distal-1 and 9-EtG. This difference may be attributed to intramolecular hydrogen bonding and steric repulsion between the aqua ligand and the pendant moiety of the bidentate ligand..

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“…[16][17][18] We have studied such systems and have previously reported that thermal back-isomerization can be achieved by introducing steric hindrance near the metal center. 19 The major difference between photoresponsive organic molecules and metal complexes lies in their functionality. In organic photochromic molecular systems, the switchable sites only cause structural changes and have no further functionality.…”

Section: Introductionmentioning

confidence: 99%

A visible-light and temperature responsive host–guest system: the photoisomerization and inclusion complex formation of a ruthenium complex with cyclodextrins

et al. 2022

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Photoisomerization and thermal isomerization of ruthenium aqua complexes with chloro-substituted asymmetric bidentate ligands

Abstract: Introduction of a chloro substituent to the bidentate ligand of ruthenium aqua complexes enhanced photoisomerization and thermal back-isomerization.

Cited by 7 publications

References 60 publications

Intramolecular Hydrogen Bonding: A Key Factor Controlling the Photosubstitution of Ruthenium Complexes

Intramolecular Hydrogen Bonding: A Key Factor Controlling the Photosubstitution of Ruthenium Complexes

Binding of Stimuli-Responsive Ruthenium Aqua Complexes with 9-Ethylguanine

A visible-light and temperature responsive host–guest system: the photoisomerization and inclusion complex formation of a ruthenium complex with cyclodextrins

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