Photoinduced electron transfer in tris(2,2′-bipyridine)ruthenium(ii)-viologen dyads with peptide backbones leading to long-lived charge separation and hydrogen evolution
Bibliographic record
Abstract
Three 5,5'-disubstituted-2,2'-bipyridine ligands tethered to l-Asp-based peptide backbones having pendant viologen-modified branches, i.e., 5-ethoxycarbonyl-5'-(N-G(1)-carbamoyl)-2,2'-bipyridine ((4+)), 5,5'-bis(N-G(1)-carbamoyl)-2,2'-bipyridine ((8+)), and 5,5'-bis(N-G(2)-carbamoyl)-2,2'-bipyridine ((12+)), were prepared, where G(1) = Asp(NHG(3))-NHG(3), G(2) = Asp(NHG(3))-Asp(NHG(3))-NHG(3), and G(3) = -(CH(2))(2)-(+)NC(5)H(4)-C(5)H(4)N(+)-CH(3), i.e., 2-(1'-methyl-4,4'-bipyridinediium-1-yl)ethyl. These were reacted with cis-Ru(bpy)(2)Cl(2) to give three new dyads [Ru(bpy)(2)()](6+) ((6+)), [Ru(bpy)(2)()](10+) ((10+)), and [Ru(bpy)(2)()](14+) ((14+)), respectively, where bpy = 2,2'-bipyridine. All these dyads undergo extremely efficient intramolecular quenching leading to the formation of charge separated (CS) states (Ru(III)-MV(+) ), and display a triple exponential decay due to the presence of three classes of conformers with each exhibiting the individual rate of electron transfer. The lifetimes (contributions) were determined as 12.5 ps (94.2%), 791 ps (4.5%), and 18.3 ns (1.2%) for , 82.2 ps (79.9%), 1.12 ns (12.4%), and 4.60 ns (7.7%) for , and 43.6 ps (71.6%), 593 ps (20.2%), and 3.75 ns (8.1%) for . The forward electron transfer rate constants (k(ET)) for the major components were calculated as k(ET) = 8.3 x 10(10) s(-1) for , k(ET) = 1.2 x 10(10) s(-1) for , and k(ET) = 2.3 x 10(10) s(-1) for . Further, the lifetimes and quantum yields of charge separated states were determined as tau(CS) = 16 +/- 3 ns and Phi(CS) = 0.81 for , tau(CS) = 20 +/- 3 ns and Phi(CS) = 0.92 for , and tau(CS) = 20 +/- 3 ns and Phi(CS) = 0.64 for . The backward electron transfer rate constants (k(BET)) were also determined as 6.3 x 10(7), 5.0 x 10(7), and 5.0 x 10(7) s(-1) for , , and , respectively. From the analysis of electrical conductivity, the major ion-pair adducts in aqueous media were characterized as (PF(6))(5+) (52%) for , (PF(6))(2)(8+) (29%) and (PF(6))(3)(7+) (32%) for , and (PF(6))(3)(11+) (27%) and (PF(6))(4)(10+) (29%) for , at a total complex concentration of 0.04 mM. The present family is found to be the first example of a Ru(bpy)(3)(2+)-MV(2+) system in which three orders of magnitude of difference is achieved between the forward and backward electron transfer rate constants. These dyads were finally combined with a Pt(ii)-based H(2)-evolving catalyst, i.e., cis-diamminedichloroplatinum(ii), to ascertain the applicability of the system towards the visible light-induced water splitting processes.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".